Recent trends in mechanical micropumps and their applications: A review

Mechatronics 60 (2019) 34–55

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Review

Recent trends in mechanical micropumps and their applications: A review S. Mohith∗, P. Navin Karanth, S.M. Kulkarni Department of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal, P.O. Srinivasnagar, Mangalore 575025, India

a r t i c l e

i n f o

a b s t r a c t

Keywords: Microfluidics MEMS Micropump Drug delivery system LOC μTAS

In recent years micropump technology has gained considerable importance and has become the highlighted area of research particularly for microfluidic applications. The driving force towards the development of micropump technology has been the integration of pumping systems into microfluidic devices to fulfill the need for accurate delivery of fluids. The present review brings out the recent research and development in the field of micropump technology with an emphasis on mechanical micropump. This review highlights the complete history and descriptions of different mechanical micropump design, actuation principles, materials and performance/operating parameters with relevant schematic diagrams. A comparative study with quantitative and graphical data has been presented to address the potential advantages and disadvantages of the different actuation schemes of mechanical micropump with the emphasis on flow rate and back pressure developed. Factors such as actuator type, operating parameters, diaphragm materials, and flow rectification mechanisms and their effect on micropump performance are addressed in detail. This study also highlights the requirements and applications of micropump in different fields such as biomedical, drug delivery, thermal management, fuel cells, etc.

1. Introduction

microfluidics which has led to the development of different varieties of microfluidic devices like micropumps, micro-mixers, micro-valves, micro-filters, micro-reactors, and micro-separators [3,5] for distinctive applications. Considering the requirement of microfluidic systems to handle fluid at micro to the nanoscale, researchers and scientists have realized the need of a pumping system which can deliver a minute quantity of fluid at a required pressure sufficient enough to make the fluid flow through the microfluidic system. This need has resulted in the development of different micropumps with different actuation principles and fabrication technologies. Micropump is a device which can transfer or deliver the working fluid (liquid or gas) at accurate volume from a reservoir to target. The potential advantages of the micropump include the precise delivery of fluid in microliters to milliliters per second or per minute, the flexibility of integration with different electromechanical systems with effective space reduction [6–8,12]. The essential components of miniaturized pumping system include miniaturized pump (micropump), reservoir of fluid to be pumped, flow sensor for flow measurement, signal conditioner unit and a controller for the flow parameters as shown in Fig. 1. Micropumps incorporated in microfluidic systems should possess sufficient flow control, a wide range of flow rate, lower power consumption, and high back pressure [9,10]. Different approaches to the development of micropumps are available in literature since their introduction in the late 1970s. Fig. 2 represents the significant ones carried out between 1970s and 1990s. The micropump concept developed by Spencer et al. [13] was the first ever

The rapid growth of sub-millimeter and microscale engineering in recent years has resulted in the development of miniaturized systems and devices. Miniaturization mainly focuses on reducing the size of the system with reduced cost and improved performance. A miniaturized device has the advantage of higher speed, lower price, portability, use of disposable materials, lower sample volume, low energy requirements, etc. [1]. The potential advantage of miniaturization has motivated many researchers to develop miniaturized systems which can handle the fluids and liquids at the microscale to the nanoscale range. This motivation has led to the development of microfluidics through an integrated approach incorporating micro-scale engineering and fluid mechanics. Microfluidics mainly deals with manipulation and analysis of the small volume of fluids or liquids. Microfluidic devices are class of miniaturized pumping systems which can pump, mix, monitor and control the minute volume of the fluids [4]. Microfluidics proved to be very efficient in fields like chemistry, medical, biology, molecular analysis, biodefence, molecular biology, microelectronics, pharmaceuticals, and automobile engineering. Typical applications of microfluidic systems include chemical analysis, biological and chemical sensing, drug delivery, molecular separation, electronic cooling and for environmental monitoring. Precision control systems for automotive, aerospace and machine tool industries also incorporate the microfluidic systems in their application [2,3,5]. Many researchers have contributed significantly into

∗

Corresponding author. E-mail addresses: [email protected] (S. Mohith), [email protected] (P.N. Karanth), [email protected] (S.M. Kulkarni).

https://doi.org/10.1016/j.mechatronics.2019.04.009 Received 5 November 2018; Received in revised form 27 February 2019; Accepted 27 April 2019 Available online 9 May 2019 0957-4158/© 2019 Elsevier Ltd. All rights reserved.

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Mechatronics 60 (2019) 34–55

plications [9]. Capable of delivering fluid at micro-nano scale mainly through microchannels, micropumps have gained considerable significance in chemical/biological analysis system in the form of μTAS (Micro Total Analysis System) which intends to reduce the quantities of samples and reagents used in the analysis within limited time and reduced manual intervention. DNA analysis, genomics, proteomics, amplification, sequencing or synthesis of nucleic acids, drug discovery, clinical diagnosis, environmental and food analysis etc. are some of the application areas of μTAS which incorporates effective pumping mechanisms which can deliver fluids from picoliters to microliters. Factors like fluid viscosity, pH value, chemical stability, corrosion temperature are considered to be significant in the design of micropumps for analysis systems [6,28–30]. Fig. 3 highlights the most common applications and timeline of establishment of micropump in different domain. Micropumps find application in space explorations too for assisting the propulsion of mini/microsatellites or space crafts. The reduced size and weight of the micropump technology allow them to integrate with the satellites easily. Since the working medium for propulsion is in gaseous form, larger stroke volumes are required to pump the gases at a pressure sufficient enough to lift the load of the satellites/spacecraft [31–33]. Micropumps have also served the purpose of continuous heat dissipation in space-constrained electronics through single-phase or two-phase cooling. Capable of delivering liquids or air through the microchannels, micropumps are effectively used in cooling application resulting in enhanced performance of electronic devices. Since the flow of fluid associated with the heat sink is through channels, fluid at higher pressures are required which can reduce the temperature gradient resulting in dissipation of a large amount of heat [34–37]. Fuel cells which convert chemical energy into electrical energy either in the form of a proton exchange fuel cell (PEMFC) or direct methanol fuel cell (DMFC) employ miniaturized pumps to a greater extent. Application of micropump fuel mainly focuses on the accurate delivery of liquid fuel (methanol) [38–40].

Fig. 1. Schematic of miniaturized pumping system.

attempt which incorporated a piezoelectric actuator with active valves to achieve a flow rate of 19 μcc/V at a pressure of 1 mm-Hg/V. This was later extended by Van Lintel et al. [18] with the introduction of passive check valves resulting in an optimal flow of 0.008 ml/min at an input voltage of 100 V at 1 Hz frequency. An improvised concept of micropump was presented by Stemme and Stemme [23] with the valveless configuration by the use of the nozzle/diffuser which achieved an optimal flow rate of 16 ml/min with a back pressure of 19.6 kPa at 20 V, 100 Hz. Above researchers marked the beginning of micropump development which built a strong foundation for many researchers to come up with improvised concepts with different geometry, actuation mechanism and fabrication technologies for various applications. The early stage of micropump development was for delivery/dispensing therapeutic drugs. Micropumps developed between the years 1978 and 1988 were mainly intended to deliver insulin for maintaining the blood sugar level in diabetic patients [14–17]. Further, medical conditions like bone infection, cancer, and tumors have employed micropumps for drug delivery into cancerous cells and bloodstreams [22,27]. Precise metering and distribution of drugs at the required rate is an essential aspect of micropump used for drug delivery/dosing ap-

Fig. 2. History of micropump development [20,21,24–26]. 35

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Mechatronics 60 (2019) 34–55

Fig. 3. Timeline of establishment of micropump applications in different domains.

Fig. 4. Classification of micropump.

Fig. 4 shows the broad classification of micropumps. Micropumps fall under two categories, (1) Mechanical micropumps which are characterized by the presence of moving mechanical parts like an oscillating diaphragm or a rotor which exerts pressure on the working fluid for pumping. (2) Non-mechanical micropumps which convert the non-mechanical energy into kinetic energy which is utilized to pump

the fluid. Mechanical micropumps also termed as displacement micropumps which develop a pulsating flow due to their periodic nature. Further, displacement pumps fall under reciprocating/oscillating type which incorporates an oscillating diaphragm or reciprocating piston and rotary type with vanes or gears. Most of the micropumps reported are of diaphragm/membrane type where oscillation of thin 36

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Mechatronics 60 (2019) 34–55

2. Mechanical (displacement type) micropumps

diaphragm/membrane driven by an actuator causes the flow of fluid [6–10]. A pulsating flow occurs as a result of the oscillating nature of the mechanical micropumps. Centrifugal type micropump is also a kind of mechanical pump with limited miniaturization due to lower effectiveness at lower Reynolds’s number [6]. The non-mechanical micropumps involve direct interaction with the working fluid through electrical, magnetic or chemical means [6,9,11]. Hence, non-mechanical micropumps deliver a continuous flow of fluids. Thus non-mechanical micropumps are also termed as continuous micropumps. Inspired by the widespread applications of micropumps in different domains, an attempt is made to review the recent work that has been carried by the researchers in the field of mechanical micropump. Extensive review on various aspects of micropump technology has been presented by Laser and Santiago [6], Tsai and Sui [7], Iverson and Garimella [8] and Nisar et al. [9]. The present review focuses on the recent advancements in the field of mechanical micropumps over the past decade (2008–2018). The earlier sections of this review emphasized on the works that have been carried out in the late ’90s to drive the readers into the concept of micropump with the highlight on the history of the micropump development and establishment of micropump applications in different domains. The preceding sections emphasize on the state of the art technologies implemented in the area of mechanical micropumps in recent years. Throughout the study, the maximum measured flow rates (Qmax) and differential pressures (Δpmax) of the micropumps signify the parameters for performance evaluation. Apart from performance parameters the present review highlights the evolution of different actuation schemes, operating parameters, design/material aspects and fabrication processes.

Mechanical micropumps utilize reciprocating diaphragm actuated by a physical actuator for pumping the fluid. The general construction of the mechanical/displacement pump consists of a pumping chamber, flexible diaphragm, an actuator, Inlet and outlet [12]. Fig. 5 represents the schematic working of mechanical micropump. Oscillation or reciprocation of the membrane/diaphragm in a mechanical micropump occurs through a physical actuator which generates the necessary pressure difference required for pumping the fluid. The oscillation of the diaphragm causes increased chamber volume which in turn leads to a decrease in the pressure inside the pumping chamber. This pressure drop causes the fluid to flow from the high-pressure reservoir to the pumping chamber which corresponds to supply mode. The flexing of the diaphragm in the opposite direction leads to an increase in the chamber pressure due to decreased chamber volume. Thus, it leads to the outflow of the fluid from the chamber through the outlet which corresponds to pumping mode. Flow rectification of the fluid in mechanical micropumps can be achieved either through microvalves (check valves, ball valves, etc.) or by static geometry valves such as nozzle/diffusers (valveless micropump). Fig. 6 illustrates the schematic working of both valve and valveless micropump. Micropump incorporates two types of microvalves namely passive or active valves [7–9]. Active Valves operates with an actuator which directs the opening and closing of the valve during suction and delivery whereas passive valves operate by the pressure difference between the inlet and outlet generated due to the oscillation of the diaphragm. A valveless micropump does not involve check valves

Fig. 5. Schematic showing working principle of mechanical micropump.

Fig. 6. Schematic illustration of micropump with (a) valves (b) valveless. 37

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Fig. 7. Roadmap of mechanical micropump development.

instead incorporates static nozzle/diffuser which performs the functions of valves. During the supply mode, the inlet element to acts as a diffuser which offers lower rectification thus a significant amount of fluid gets transported through the inlet into the chamber. At the same time, the outlet element acts as a nozzle with higher rectification and minimizes the reverse flow of fluid pumped in the previous cycle. The reverse phenomena occur during the pumping mode where the outlet acts as a diffuser and inlet as the nozzle. As a result, a larger volume of fluid flows out of the chamber through the outlet with a minor portion of the flow through the inlet nozzle [6–10]. Since the introduction of micropump by Spencer et al. [13], many researchers have contributed to the development of micropump technology. Majority of the works reported on micropumps are of mechanical/displacement type with different actuation principles. The primary emphasis of research on mechanical micropump has been an improvisation of performance to have higher flow rates and pressure with the ability to have accurate control of flow. Fig. 7 represents the roadmap towards the development of micropump from the early 1970s to the present. It is evident that mechanical micropump development has traveled a long way in adopting different actuation mechanisms, flow rectification valves, design/materials, and fabrication processes. Tables 1–7 highlight the summary of key features of recently reported mechanical micropumps with the emphasis on micropump actuators, material/fabrication, flow rectification mechanisms, optimal performance parameters such as flow rate and pressure, optimal operating parameters and geometrical features. These tables also highlight the fabrication process employed for each of the reported micropump with different colors. The subsequent parts of the review bring out the detailed descriptions of the recent contributions towards mechanical micropump technology.

magnetic, electrostatic, shape memory alloy (SMA), thermo-pneumatic, phase change, ionic conductive polymer film (ICPF), dielectric elastomer film (DEF) are some of the actuations implemented in mechanical micropumps (Fig. 8). Piezoelectric drivers are one of the most common forms of micropump actuation reported by many researchers (Table 1). Fig. 8(a) represents the schematic of the working principle of piezoelectric actuated micropump. The piezoelectric material is bonded on to a thin flexible diaphragm which when subjected to an AC voltage undergoes bending due to the conversion of electrical energy into mechanical strain [41–43]. The mechanical strain thus induced flexes the diaphragm leading to pressure variation inside the pump chamber. This pressure variation, in turn, results in inflow and outflow of the fluid to be pumped. The performance of piezo-actuated micropump mainly depends on stroke volume governed by the mechanical strain produced. The polarization limit of the material and the applied voltage determines the mechanical strain thus controlling the flow rate of the micropump [6]. The high-performance piezoelectric materials such as PZT-5A and PZT-5H [52,53] have strain coefficients of -171 C/N, -274 C/N d31 strain constants and 374 C/N, 574 C/N d33 strain constants. Most of the Piezo micropumps reported have implemented piezo actuators in the form of a circular disc with the range of diameter (8–30 mm) and thickness (0.06– 0.215 mm) [45–56,59–63]. Other form of piezo actuator having rectangular cross section (20 × 40 mm) [61] and square-shaped (5.5 × 5.5 mm, 4 × 4 mm, 8 × 8 mm) [62,65] piezo plate, multi-layered piezo stack actuator [56] are also reported for micropump actuation. Most of the piezo actuators reported for micropump actuation are readily available in the form of discs or plates (Murata Technologies, Ariose Electronics Taiwan, Sunny Tech Electronics Co. Ltd, APC Int Ltd, USA, etc.) and some of the actuators are made in-house through powder hot pressing [57], screen printing [58] and dry powder deposition processes [62]. Fig. 8(b) represents the schematic of electromagnetic actuated micropump. Magnetic/electromagnetic micropump works on the principle of generation of repulsive and attractive forces between the permanent

3. Mechanical micropump drivers/actuators The actuation principles implemented for mechanical micropump involve electrical, thermal or magnetic energy. Piezoelectric, electro38

S. Mohith, P.N. Karanth and S.M. Kulkarni

Table 1 Mechanical micropump with piezoelectric actuation [67].

39

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Table 2 Mechanical micropump with electromagnetic actuation.

Table 3 Mechanical micropump with thermopneumatic actuation.

Table 4 Mechanical micropump with phase change actuation [106].

magnet and drive coil on the application of electric current through the drive coil which in turn oscillates the diaphragm or membrane [68– 70]. The micro-drive coils for electromagnetic actuation are of materials like Copper, Chromium employing fabrication processes such as electron beam evaporation [71]; electroplating [77] PCB based technology [78] on a glass substrate. The permanent magnets used are of Neodymium magnet (NdFeB) [71,76] which are either attached or embedded into the flexible diaphragm. Table 2 represents the summary of recent works on electromagnetic actuated micropump.

The thermopneumatic and phase change actuation of the micropump works on the same principle except for the medium used for actuation. Fig. 8(c) and (d) show the schematic of thermopneumatic and phase change micropump. Continuous thermal expansion and contraction of air or phase changing material in the secondary chamber exert pressure on to the diaphragm surface causing it to deflect [85–87,99,100]. Phase change actuation employs materials such as paraffin, perfluro compounds which undergoes a phase transition when subjected to heating cycle [101–104]. The source of heat generation is through micro heater

40

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Mechatronics 60 (2019) 34–55

Table 5 Mechanical micropump with shape memory alloy actuation/magnetic shape memory alloy actuation [112,115].

Table 6 Mechanical micropump with electrostatic actuation [121,122,124,125].

Table 7 Mechanical micropump with electro active polymer actuation [136,137].

made of Chromium/Gold (Cr/Au) [88], Platinum/Chromium (Pt/Cr) [95] deposited on to glass substrate through Electron Beam Evaporation. Materials like methyl perfluoropropyl ether undergo a phase transition at a normal skin temperature of the human body. Thus such materials can be utilized as a source of actuation for skin contact actuated micropumps for medical applications [104]. Tables 3 and 4 summarize the different concepts of thermopneumatic and phase change micropump. The actuation of micropump through the shape memory alloy (SMA) employs either thermal or magnetic source. These materials can undergo a solid phase transition between the austenitic phase at high temperature and the martensitic phase at low temperature. This phenomenon of phase transition is reversible which allows it to remember its original shape and regain it. Mechanical strain developed during this phase transition results in deformation of the micropump membrane [107–110]. Thus fluid flow occurs due to the change in pump chamber volume as shown in Fig. 8(e). Ni/Ti is the most common form of SMA materials used in micropump actuation which undergoes the phase transition be-

tween 49 and 55 °C [111]. Ni/T Ni–Mn–Ga is another class of magnetic SMA which undergoes deformation in the presence of a magnetic field [113,114]. Table 5 represents the critical features of SMA actuated micropump. The electrostatic micropump utilizes the force of attraction and repulsion generated between the electrodes which actuate a flexible diaphragm as shown in Fig. 8(f). Upon application of electric potential across the electrodes attached to the membrane and pump body, the generated electrostatic force causes the diaphragm to flex causing a change in chamber volume (increased) and pressure (decreased) resulting in the flow of fluid inside the chamber [116–118]. Thus pulsating flow is achieved because of continuous change in diaphragm momentum due to the applied voltage. The electrodes usually employ of Chromium/Gold Chromium (Cr/Au/Cr) [120], Boron (B) [123], Aluminum (Al) by sputtering, deep reactive ion etching (DRIE). Amount of fluid delivered by electrostatic actuated micropump mainly depends on the diaphragm deflection which is governed by the electrostatic force generated which in 41

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Fig. 8. Mechanical micropumps with different actuation schemes. (a) Piezoelectric actuator (b) Electromagnetic actuator (c) Thermopneumatic actuator (d) Phase change actuation (e) Shape memory alloy (SMA) Actuator (f) Electrostatic actuator (g) Electro active polymers (EAP) Actuator.

turn is dependent on applied electric potential. Table 6 highlights the key features of electrostatic micropump. Electro-active polymer (EPA) is another class of material used for micropump actuation which undergoes deformation in the presence of electric field. The schematic of the micropump actuation with EPA is as shown in Fig. 8(g). EPA actuator consists of polymer membrane sandwiched between flexible compliant electrodes. When subjected to an external electric field across the electrodes, these polymer films experiences a compressive electrostatic force which leads to horizontal expansion wrapping in the direction of the restricted surface. Thus causing deformation of diaphragm bonded on to its surface [126–131]. Deformation of the diaphragm causes variation of pump chamber volume and pressure leading to inflow and outflow of the fluid. Ionic conductive polymer film (ICPF) and dielectric elastomer (DEA) are the two types of EPA reported for micropump actuation. ICPF actuated micropump reported to use Nafion (0.18– 0.6 mm thickness) as an actuator coated with a conductive surface of Gold, Silver or Platinum. The DEA for micropump includes materials like Acrylic elastomers (0.33–0.5 mm thickness) (VHB 4910 from 3 M, USA). Table 7 presents the highlight of recent works of ICPF micropump and DEA micropumps.

rectification of the fluid occurs through microvalves at the inlet and the outlets which convert the non-directional flow to a directional flow. The selection of flow rectification methods mainly depends on factors such as closing pressure, response type, micropump efficiency, material compatibility, etc. [5,140].Check valves and static geometry valves (nozzle/diffusers) serves the purpose of providing directionality to the working fluid. Most of the literatures available on mechanical micropumps have implemented check valves, ball valves which are found to have dynamic characteristics. The check valves or flap valves are usually of rectangular cross-section (cantilever type) or circular cross-section (bridge type) made of materials like Silicon (Si), Glass or Polydimethylsiloxane (PDMS) [63,77,141]. Fig. 9 represents the schematic of the microvalves used in mechanical micropumps. The check valves reported for micropumps are either passive type which operate based on the pressure variation inside the chamber [56,63,79] or active type which are driven through piezoelectric [13,142,143], electrostatic [119,123,144], phase change [101,103,105] and other drivers. Ball valves are also found to be an excellent candidate for flow rectification in micropump application [77,80]. Tables 8 and 9 summarize the different types of microvalves incorporated in the recent micropump. The second category of flow rectification mechanism employed in mechanical micropumps involves static geometry nozzle/diffusers which do not include any moving parts. Micropumps with such static geometrical arrangement of flow rectification are termed as valveless

4. Micropump valves The flow rectification principle at the inlet and outlet of the pump chamber significantly influence its performance. Usually, the flow 42

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Fig. 9. Flow rectification mechanisms employed in mechanical micropump.

Table 8 Geometrical and performance features of active valve. Active valves First author

Year

Ref. no.

Valve type

Valve actuation

Valve material

Micropump actuation

Geometry (mm3 )

Flow Rate (ml/min)

Pressure (kPa)

R Bode´n S. Lee S. Svensson R Boden H. Kim

2008 2009 2010 2014 2015

[101] [119] [103] [105] [123]

Check Valve Check Valve Check Valve Check Valve Check Valve

Phase Change Electrostatic Phase Change Phase Change Electrostatic

– Pyraline SS Polyamide Pyraline

Phase Change Electrostatic Phase Change Phase Change Electrostatic

– – – – 2 × 2 × 0.003

0.001 0.29 0.0063 0.0012 4

5000 7.3 9000 2000 12.8

Table 9 Geometrical and performance features of passive valve. Passive valves with rectangular cross section First author

Year

Ref. no.

Valve type

Valve Material

Micropump actuation

Valve geometry (mm3 )

Flow rate (ml/min)

Pressure (kPa)

Park J.Ni T. T. Nguyen E. Shoji

2013 2014 2008 2016

[56] [79] [132] [135]

Check Valve Check Valve Check Valve Check Valve

SS PDMS PDMS Silicone Rubber

Piezoelectric Electromagnetic ICPF ICPF

1.24 × 2.37 × 0.12 0.35 × 0.16 × 0.06 3 × 2 × 0.5 0.5

3.7 0.00026 0.76 0.3

14 0.55 1.5 —

Passive valves with circular cross section First author

Year

Ref. no.

Valve Type

Valve material

Micropump actuation

Valve diameter (mm)

Valve thickness (mm)

Flow rate (ml/min)

Pressure (kPa)

H. K. Ma

2015

[63]

Check valve

PDMS

Piezoelectric

5.8

0.3

6.21

0.2

Ball diameter (mm)

Flow rate (ml/min)

Pressure (kPa)

13.2 29.4

0.25 1.5

Ball Type Check Valve First author

Year

Ref. no.

Valve type

Valve material

Micropump actuation

M. T. Ke A. H. Sima

2012 2015

[77] [80]

Ball valve Ball valve

Glass-SS Glass-SS

Electromagnetic 2 Electromagnetic 2

5. Micropump chamber configuration

micropumps. The performance of such nozzles/diffusers mainly depends on the inlet/outlet dimensions, channel length and the channel angle (Fig. 9) [145,146]. Most of the valveless micropumps have incorporated Flat and Conical types of nozzles/diffusers. Table 10 represents the complete descriptions of the flat and conical nozzle/diffuser implemented in the recent micropump study. The static behavior of the nozzle/diffuser is advantageous in overcoming the problems of wear and fatigue failure that exits in check valves.

Fig. 10 schematically represents the different chamber configurations of the mechanical micropump. Most of the mechanical micropumps reported are of single chamber type. The first mechanical micropump developed by Spencer et al. [13] incorporated a single chamber configuration. Fig 8(a)–(g) illustrates the working principle of the single chamber micropump with different actuation. The micropump proposed 43

S. Mohith, P.N. Karanth and S.M. Kulkarni

Table 10 Geometrical and performance features of nozzle/diffuser (valveless). Conical nozzle/diffuser First author

Year

Ref. no.

Valve material

Micropump Actuation

Inlet diameter (mm)

Outlet diameter (mm)

Channel length (mm)

Channel angle

Flow rate (ml/min)

Pressure (kPa)

P Verma H. Kang

2009 2016

[49] [64]

Si PMMA

Piezoelecrtric Piezoelecrtric

0.53 0.53

– 1.18

5.3 4.7

10 10°

2.4 9.1

0.743 –

Flat nozzle/diffuser (trapezoidal)

44

First author

Year

Ref. no.

Valve material

Micropump actuation

Inlet width (mm)

Outlet width (mm)

Channel length (mm)

Channel angle

Flow rate (ml/min)

Pressure (kPa)

Hwang Wang W. Zhang L. Y. Tseng Y. Wei S. Singh R. Kanth Zhou C Zhi Y. J. Chang P. Kawun N Kumar M. M. Said R. R. Gidde L. J. Yang M. Ochoa P. S. Chee J. Santos M. Ghazali

2008 2008 2013 2013 2014 2015 2011 2011 2012 2013 2016 2016 2017 2018 2011 2012 2016 2010 2017

[45] [46] [57] [58] [59] [60] [66] [74] [76] [78] [81] [82] [83] [84] [93] [94] [96] [134] [139]

Si Si LTCC Si EP PDMS PMMA PDMS PMMA PDMS PDMS PDMS Si PDMS PDMS Glass PDMS PMMA PMMA

Piezoelectric Piezoelectric Piezoelectric Piezoelectric Piezoelectric Piezoelectric Piezoelectric Electromagnetic Electromagnetic Electromagnetic Electromagnetic Electromagnetic Electromagnetic Electromagnetic Thermopneumatic Thermopneumatic Thermopneumatic ICPF DEA

0.19 0.1 0.9 0.8 2 0.1 – 0.1 0.1 0.15 0.086 0.12 0.05 0.1 0.01 0.2 – 1 0.2

0.35 0.15 – – – – – 0.5 0.25 – 0.216 – 0.4 – 6 – – 2 –

0.08 2.5 5 3.1 10 1.5 6 1.6 2.3 1.5 0.949 1.5 1.35 1.1 – 28 10 10 1.5

6 8 – 10 15 10 7 10 – 11.3 10 10 15 9 8 12 20 5.72 14

0.037 1.5 0.63 1.2 0.038 0.02 0.497 0.3196 0.13 0.47 0.135 0.336 0.0066 0.441 1.25 × 10−5 0.10205 1.25 × 10−5 0.0082 0.0212

– 7.7 1.55 5.3 10 0.22 4.93 0.931 – – 0.245 0.441 – 0.35 1 × 10−5 5.86 – – –

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Fig. 10. Chamber configuration of mechanical micropump.

by Van De Pol et al. [19] adopted the new concept of the peristaltic chamber with three chambers in a series built on a Si wafer with piezoelectric actuation. The arrangement of actuators in peristaltic micropump is such that the diaphragm flexes in particular sequence one after the other leading to the flow of fluid from one chamber to other as shown in Fig 10(d). Peristaltic micropumps with piezoelectric drivers [57], electromagnetic driver [75], thermopneumatic [89–91], phase change Driver [101–103], shape memory alloy [110] [111] and electrostatic [119,120] are reported. Works of literature on double chamber parallel configuration [45,54,72] of the micropump are also available which effectively enhances the performance of micropump concerning fluid delivery. The highlights of mechanical micropump performance with different chamber configurations are presented in Tables 1–7.

are some of the non-planar configurations implemented in mechanical micropumps to a limited extent. The optimization studies on diaphragms effectively involve finite element analysis particularly for understanding the frequency response when subjected to different actuation forces. With such approaches, the diaphragm geometry can be optimized to have an efficient micropump operation. Commercial FEM packages like Ansys, Comsol, etc. are found to be useful in this regard [54,56,61]. 7. Micropump materials and fabrication process The early stage of micropump fabrication was purely based on silicon micromachining as seen in Spencer et al. [13]. As observed from the literature, mechanical micropump technology extensively utilizes Silicon - Glass based micromachining processes for fabrication. Some of the common microfabrication processes involve photolithography, anisotropic etching, surface micromachining and bulk micromachining of Si [147]. High fabrication costs together with the cost of materials, the time consumed adds on to the disadvantages even though microfabrication yields better properties. Improvement in precision fabrication techniques has led to the use of polymer-based materials like PMMA, PDMS, PLLA, PC, etc. in micropump fabrication. Polymeric materials like PDMS can be easily molded by conventional casting technique or spin coating to form the different components such as the chamber body, diaphragm and microfluidic components [60,73] [79,88– 90,95–97]. Micropumps fabricated with materials like PMMA, PLLA through micro CNC machining [47,63,64,132,138], CO2 based LASER cutting and engraving processes [66,75,80] are also observed in the recent works. Reduced material cost, improved material compatibility, and strength, reduction in the cost of fabrication are some of the advantages features found in the use of polymer-based materials with conventional machining and fabrication processes. Fig. 12 represents the schematic of fabrication technologies employed in mechanical micropump.

6. Diaphragm materials and design A diaphragm is a force applying surface, which undergoes periodic oscillation due to the excitation from the actuator. Since the pumping volume depends on the deflection of the diaphragm, the design and material selection significantly influence the micropump performance. Most of the micropumps reported have implemented the flexible flat planar structure of the diaphragms/membranes with different thickness and material properties to have optimum pumping. Table 11 represents the commonly used diaphragm material, their mechanical properties, and thickness range. A lower value of Young’s modulus and higher reversible strain of the diaphragm material is a primary requirement which results in higher deflection of the membrane leading to a more significant flow rate [5]. Fig. 11 represents some of the diaphragm designs incorporated in mechanical micropumps. The planar dimensions of diaphragm decide the overall size of the micropump since it has to accommodate the whole planar surface of the diaphragm. Other planar configuration of the diaphragm with flexural hinges can effectively enhance diaphragm deflection to increase the swept volume [64]. Corrugated diaphragms, bossed diaphragms 45

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Table 11 Material properties of different diaphragm materials. Material

Actuation principle adopted

Thickness (mm)

Young’s modulus (GPa)

Poisson’s ratio

Density (Kg/m3 )

Glass PDMS

Piezoelectric Piezoelectric Electrostatic Electromagnetic Thermopneumatic Phase change Piezoelectric Piezoelectric Piezoelectric Phase change Piezoelectric Electrostatic Thermopneumatic Phase change Piezoelectric Electromagnetic ICPF DEA

0.2 0.011–0.4

62.75 0.00075–0.0015

0.2 0.45–0.5

2540 965–1030

0.1 0.1–0.2 0.01–0.1

160–169 0.5 NR

0.27 - 0.3 – 0.3

2300 – 7900

0.15–0.25 0.00015 - 0.003

10.3 1130

0.33 –

8.4–8.73 –

0.3–0.5

–

0.47

1200

0.18 - 0.6 0.56

0.35–0.61 –

– –

2500 –

Si Electropolymer SS Brass Polyamide

Rubber Nafion Acrylic elastomer

Fig. 11. Commonly used diaphragm designs in mechanical micropump.

Fig. 12. Schematic of mechanical micropump fabrication processes.

46

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8. Discussion

actuation. The phase change type and ICPF actuator were found to have relatively lower actuation voltage when compared with other types of actuation. Piezoelectric actuation resulted in higher floweret whereas phase change type actuated micropump was able to pump the fluid against higher back pressure. In spite of the comparison made between different actuation mechanisms of mechanical micropump, obtaining the desired flow and maintaining the safety mainly depends on the optimization of micropump parameters. Well established numerical modeling and simulations and experimental approaches would lead to an optimized configuration of micropump delivering efficient design and performance. The highlighted features of different mechanical micropumps drivers are summarized below (Fig. 8).

The yearlong research in the field of microfluidics has resulted in the establishment of effective microscale pumping mechanisms. Various types of pumping mechanisms by many researchers have effectively fulfilled the need of microscale flow as seen from the previous sections. Following sections elaborates the factors affecting the mechanical micropump performance. 8.1. Actuator/driver type and operation parameters The performance of mechanical micropump with the emphasis on flow rate and pressure development significantly depends on the type of actuator used. Since the mechanical micropumps consist of an oscillating diaphragm, the deflection of the diaphragm determines the swept volume which in turn depends on the driver configuration. Fig. 13 and Fig. 14 compares the performance of recently reported actuation schemes of the mechanical micropump in terms of flow rate and back pressure. Among all the actuation principles, the flow rate was found to be increasing with the increase in actuation voltage and frequency. The resonating frequency of the diaphragm determines the optimal flow. As evident from Tables 1 to 7, Piezoelectric, electromagnetic and thermopneumatic actuators are reported extensively for micropump

• Piezoelectric actuation: Piezoelectric actuators are one of the earliest and most commonly used drivers for mechanical micropump. Higher actuation forces coupled with faster response are the key features of piezoelectric actuators. Typical actuation voltage of piezo actuator varies between 1 and 320 V and frequency response of about 50 kHz. The precise control of volume flow from micropump could be achieved with proper control of input voltage to the piezo actuator which in turn controls the diaphragm deflection. Circular piezoelectric drivers are found to have a deflection of about 7–13 μm for a voltage range of

Fig. 13. Comparison of (a) flow rate (b) back pressure achieved with different actuation of micropump included in Table 1. 47

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Fig. 14. Range of (a) flow rate and (b) back pressure (c) voltage (d) frequency of operation for mechanical micropumps with different actuation principles.

30–200 V [45,48,56,66]. Materials processing and difficulty in the attachment on to the diaphragm are major disadvantages associated with piezoelectric actuators [8,44]. • Electromagnetic actuation: Electromagnetic actuators offer the advantage of higher membrane deflection since they can generate higher force. The other benefits include low voltage actuation, short response time [44,70]. These actuators have actuation voltage, current ranging between 0.7–10 V and 0.2–7.8 A with driving frequency ranging between 1 and 720 Hz. PDMS diaphragm with electromagnetic actuation is found to have deflection range of 1.8–110 μm when supplied with 0.2–1 A of current [71,73,76–78,82–83]. Electromagnetic actuation offers disadvantages of higher power consumption and heat dissipation along with the difficulties associated with the integration of magnets and drive coils into the micropump assembly [44,73]. • Thermopneumatic/Phase change actuation: With the thermopneumatic/phase change actuation higher flow rate could be achieved because of its ability to induce high pressure resulting in higher membrane deflection at lower actuation voltages. From the literature, it is evident that the thermopneumatic actuation for micropump has optimal operating parameters of 4–11 V at 1– 4 Hz whereas phase change actuation has a range of 1.8–12.5 V, 0.21–60 Hz. Diaphragm deflection of about 60–70 μm is achievable with these actuators at 6–7.5 V. The major drawback which limits the application of thermopneumatic/phase change actuation is that they have reduced response time especially during the cooling process and low frequency of operation. In addition to this, phase change actuation has a limitation on materials used as a medium for actuation [87,100]. • Shape memory alloy Actuation: SMA as an actuator in micropump has the advantages of high force to volume ratio, high damping capacity, stress and strain recovery upon heating and

cooling, chemical resistance, biocompatibility. Unpredictable deformation behavior due to temperature sensitivity, high power consumption, a poor cooling rate at high-frequency operations are some of the disadvantages associated with SMA actuators [108,109]. • Electrostatic actuation: Small scale integration with high frequency (1–17 kHz) operation is easily achievable with Electrostatic actuation. Also, these actuators consume less power, a lower voltage (100–160 V) and have a faster response. Lower displacement range limits the performance of micropump with electrostatic actuation leading to lower flow rate [118,119]. • Electroactive polymers: EPA actuators have the advantage of large deformability and faster response but have poor repeatability which affects the micropump performance. ICPF actuation has the lowest range of actuation voltage which ranges between 2 and 5 V and frequency of 0.5–3 Hz. Difficulties in the fabrication of ICPF limits its application in micropump actuation. DEA actuators require very high voltage for actuation which is a major disadvantage when used as the source of actuation for micropump. The typical range of DEA actuation voltage is between 3000 and 4200 V and frequency response of 0.5–8 Hz. 8.2. Valve parameters The performance of flow rectification mechanism at the inlet and outlet is critical in the operation of micropump. Tables 8–10 present the complete description of different flow rectification mechanisms of the mechanical micropump. The active dynamic geometry microvalves require an additional synchronized actuation scheme according to the oscillation of the pump diaphragm. The integration of the actuator in addition to the micropump actuator and extra energy consumed limits the application of active valves. Passive dynamic geometry check 48

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valves do not require additional actuator and can be used effectively for high-frequency operation. Since most check valves reported are of flap type, design and material property of such valve play a vital role in the dynamic operation. The check valves are designed to have a natural frequency higher than the pump operating frequency [56]. Fabrication of flap valves incorporates materials like PDMS, Pyriline, and Silicone rubber which offer low stiffness and higher flexibility to valve opening and closing. A rectangular flap valve with a dimension of 3 × 2 × 0.5 mm3 was found to have a deflection of 0.112 mm at 0.5 kPa pressure [132]. Dynamic geometry valves are capable of withstanding higher back pressure as it offers a barrier to reverse flow. But the dynamic behavior of the microvalves leads to wear, fatigue failure in the long run. Stiction of valves on to the valve seat due to the adhesion force can also affect the performance of the microvalve [8]. A passive PDMS check valve of 0.35 × 0.16 × 0.06 mm3 was fund to have a critical opening pressure of 1 kPa up to which no flow was observed in the forward direction [79]. Thus the pressure variation must be above the critical opening pressure of the valve to have significant flow through the outlet. Ball valves are equally competitive enough to offer better flow rectification and unidirectional flow, but the integration of ball valves into the microfluidic system is a complex process. Static geometry fluid channels particularly nozzles/diffusers are found to be effective in achieving flow rectification. The absence of moving structures is advantageous mainly when the pumping fluid contains particulate matters like cells, drug particles, DNA samples, etc. [6]. The amount of flow rectification of the nozzle/diffusers mainly depends on geometrical features like the inlet/outlet dimensions, the angle of divergence and the channel length. Singh et al. [61] and Gidde et al. [84] simulated the performance of nozzle/diffuser considering with different geometries of nozzle/diffuser and concluded that lower divergence angle of nozzle/diffuser resulted in lower rectification efficiency leading to increased flow rate with an increase in divergence angle. A higher value of divergence angle causes flow separation resulting in a reduced flow rate. Observation on channel length revealed that the lower channel length had lower flow rate due to lesser geometric variation between nozzle/diffuser whereas the higher value of channel length resulted in increased pressure drop with reduced flow rate. The throat width also had a significant effect on micropump performance. A lower throat width had a lesser flow rate due to the choking effect. The flow rate was also found to be low for a higher value of throat width due to lower rectification efficiency. Nozzle/diffuser with the divergence angle of 10°, a channel length of 1.5 mm and throat size of 0.1 mm was implemented in micropump proposed by Singh et al. [61] which was able to pump 0.02 ml/min of DI water with a back pressure of 0.22 kPa. The micropump proposed by Gidde et al. [84] had optimal nozzle/diffuser geometry of 10° divergence angle, a channel length of 1.1 mm and neck width of 0.125 mm with the optimal flow rate of 0.441 ml/min and pressure of 0.35 kPa.

of piezoelectric actuated micropump by Ma et al. [63] revealed that the micropump was able to pump 1.35 ml/min and 1.12 ml/min of water with a chamber depth of 1 and 1.5 mm, respectively having same chamber diameter of 10 mm. Employment of multiple chamber configurations in the mechanical micropump can also enhance the performance to a greater extent. The double chamber combination of micropump proposed by Zhou et al. [72] with electromagnetic actuation was able to deliver 0.02773 ml/min of working fluid which was superior when compared with the flow rate of 0.01961 ml/min from a single chamber micropump at 0.3 A of the input current. Similarly double chamber piezo-actuated micropump proposed by Guo et al. [54] outperformed the performance of single chamber pump by a factor of almost 1.3 with flow rate of 0.1517 ml/min (double chamber) and 0.115 ml/min (single chamber) when actuated at 110 V. Multistage peristaltic chamber configuration was found to be effective in enhancing the flow rate of the micropump. A peristaltic electrostatic micropump was developed by Kim et al. [123] with one, two and nine numbers of chambers. This particular micropump achieved a flow rate of 2.1 ml/min (at 14 kHz), 3 ml/min (at 14 kHz), 4 ml/min (at 17 kHz) against back pressure of 2 kPa, 4.5 kPa and 12.8 kPa respectively corresponding to 1, 2 and 9 chamber configuration when actuated at ±100 V. Though multi-chamber enhances the performance of the micropump, limitations occurs as a result of fabrication complexities, space and size aspects. 8.4. Micropump diaphragm The swept volume of the diaphragm is a function of diaphragm deflection which determines the amount of fluid pumped. Factors like diaphragm designs, materials, geometry, and type of loading play a vital role in assessing the performance of the micropump. Most of the mechanical micropumps reported have implemented a flat planar flexible membrane with a circular or rectangular cross-section. Maximum deflection occurs when the diaphragm is made to oscillate at resonance. The resonance frequency of the diaphragm is determined by the material property and stiffness values which in turn depends on the geometric features like the thickness, cross-sectional area. The deflection of diaphragm tends to decrease with increase in the thickness of the membrane due to increased resistance to bending [61]. However, diaphragm thickness cannot reduce beyond a certain limit due to the problems arising from self-sagging and stiction of the diaphragm surface. Water flow rate of 2.87 ml/min was achieved by Ma et al. [64] with Polyethylene Terephthalate diaphragm of 0.15 mm thickness actuated through piezoelectric disc which was superior when compared with a flow rate of 2.21 ml/min achieved with 0.10 mm thickness diaphragm of the same material at about 25 Hz. Further reduction of diaphragm thickness to 0.05 mm resulted in a reduced flow rate of 1.15 ml/min at 10 Hz. This reduction in the flow rate was due to the smaller thickness of the diaphragm leads to the problem of adhesion between the diaphragm surface and the chamber wall. A similar effect was also observed in the micropump proposed by Kawun et al. [81] where the flow rate dropped from a value of 0.0971–0.076 ml/min when the thickness of the PDMS diaphragm reduced from 0.570–0.180 mm. Selection of material for mechanical micropump majorly depends on the frequency of vibration which often depends on the driving mechanism. The application materials PDMS, Parylene, Silicone Rubber, Latex Rubber, etc. are found to be effective in the low-frequency range which has a lower modulus and tends to offer higher deflection. For drivers associated with higher frequency, higher stiffness diaphragms made of materials like stainless steel, copper, Si, glass, etc. are preferred which offer higher force and faster mechanical response [8]. Apart from geometry and material selection enhancement of diaphragm deflection can be achieved through implementation of the addition of design features like flexures, corrugations/grooves, slots, bossed structures which reduces the stiffness of the diaphragm to a greater extent [148–152]. The change in the loading position of the

8.3. Chamber configuration Since the performance of mechanical micropump greatly depends on chamber configuration, well-established chamber design and optimization can lead to performance enhancement of the micropump. Chamber diameter and height are the two critical geometrical factors which affect the performance of mechanical micropump. The flow rate increases with chamber height up to specific value due to the reduction in the flow losses. Beyond a threshold value, the flow rate decreases with increase in chamber volume due to higher damping of the fluid accommodated inside the chamber. Thus prevents the complete transfer of energy from oscillating diaphragm into the fluid. An increase in the chamber diameter also enhances the flow rate due to increase swept volume of the membrane, but limitations are put on chamber diameter so that micropump can be easily accommodated into microfluidic systems considering their constraints on space and size [61,84]. Experimental investigation 49

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diaphragm also has a significant role in deflection enhancement. Conventionally most micropump diaphragms are loaded centrally, i.e., the actuation force on the diaphragm acts in the central region. Shabanian et al. [153,154] proved a new concept of actuating the membrane circumferentially through piezo rings resulting in deflection of about 0.25 mm with PVC diaphragm (0.1 mm thick and 22 mm diameter) which outperformed the deflection of 0.024 mm of the same diaphragm loaded centrally through conventional bimorph method.

delivery, Intravenous delivery, Transdermal delivery, Cell-based drug delivery therapy, Metronomic drug delivery, Intraocular drug delivery, Intracochlear drug delivery needs efficient mechanical micropump for accurate dosing and delivery of liquid-based drugs [156–158]. Micropumps for drug delivery do not require high flow rate instead of precise metering, small dose and back pressure independent flow are critical aspects. 9.2. Lab on chip (LOC)/micro total analysis systems (μTAS)

8.5. Micropump material

Lab on Chip or Micro Total Analysis Systems is a class of miniaturized devices built on to a single chip mainly used for biological or chemical analysis, Drug Discovery [159]. The functioning of LOC devices depends significantly on moving fluids to perform their function. Micropumps are effectively used in LOC or μTAS because of its ability to precisely control and deliver different types of liquid at the required pressure. The primary purpose of micropump in μTAS is to control the flow of fluids like the blood sample, DNA samples, chemicals, etc. through microchannels. Micropumps for LOC applications should possess the capability to reduce sample size or reagent quantities and incorporates low-cost disposable materials in addition to precise control and delivery of a wide range of flow and pressure. An analysis system needs a full autonomous micropump capable of operating without human intervention with the intention of avoiding the contamination while handling chemical/biological fluids. Zhang and Eitel [57], Wang et al. [73], Ha et al. [91], Landari et al. [98] have justified their work on mechanical micropump for LOC/μTAS applications.

Compatibility of micropump materials with the operating environment is of primary concern particularly in the field of biological, chemical and electronic applications. Selection of material also influences the type of fabrication process to be adopted in micropump fabrication. Since the operating fluids are continuously in contact with the diaphragm and pump body, chemical stability and biocompatibility of micropump materials are more critical in chemical analysis and biomedical applications. Thermal stability of the micropump material is also an important factor which has to be taken care where the micropump materials undergo heating and cooling cycles particularly with micropumps with thermopneumatic, phase change, SMA actuation which inherits an inbuilt heater or application involving electronic cooling. An extensive report on the use of micromachined Silicon-Glass reported for micropump fabrications which are found to have higher geometrical precision, superior fatigue strength and wear properties. In spite of such advantageous features, the high cost of manufacture, elaborate manufacturing process, and limited material choice has led the way to find alternative materials for micropumps. The recent trend has shown the use of polymer-based materials as an alternative for conventional silicon-based materials due to considerable advancements in the fabrication technology of precision components. Polymer-based materials like PDMS, PMMA, PLLA, etc. have gained significant emphasis on micropump technology due to their superior strength, enhanced structural properties and stability. Additionally, these materials are inexpensive, disposable and are competitive enough to be used in mass production.

9.3. DNA hybridization DNA hybridization provides a sensitive, specific and rapid detection of target nucleic acids in a sample thus providing an early test for detection and identification of pathogens in clinical samples [160–162]. Micropumps can efficiently serve the purpose of delivering the DNA samples and driving them through a microchannel of the device either by flow through hybridization (on directional flow) or shuttle flow hybridization (multi-channel flow) [161]. Chia et al. [92], Ullakko et al. [113] suggested the use of their work on micropump for DNA hybridization and profiling. Accurate delivery of DNA sample with reduced sample size or reagents together with biocompatibility and compactness are the primary requirement of micropump for DNA hybridization. The bidirectional flow capability of peristaltic micropumps is useful in back and forth movement of biological samples which is also one the requirement this particular application [8].

9. Applications of the mechanical micropump The capability to deliver the fluid at a precise volume together with the possibility of integration with other subsystems lead to the use of mechanical micropump in the number of applications. Selection of micropump for a particular application mainly depends on the working environment and pumping requirement. A detailed discussion on the recent applications of mechanical micropump irrespective of the actuation schemes is presented in this particular section.

9.4. Thermal management and electronic cooling The need for continuous heat dissipation in space-constrained electronics has led to the use of mechanical micropumps for pumping the coolants into the liquid/air cooled heat sinks. The primary purpose of the liquid/air-cooled heat sink is to reduce the temperature gradient by dissipating a large amount of heat. Considering the need of higher heat transfer and overcoming the pressure drop occurring due to the flow of liquid through the fins or microchannels, the micropump must be capable of delivering fluid at high pressure and overcome pressure drop across the channels [8,163–165]. Also, emphasis must be diverted towards a compact design of the micropump together with adequate thermal stability to facilitate the integration of micropump inside the electronic gadgets.

9.1. Controlled drug delivery/dosing systems The early stage of micropump developed began with the intention of assisting the accurate delivery of insulin in diabetic patients [13]. Rapid growth in the microfabrication technology integrated with electronic control systems resulted in the development of full-fledged insulin delivery systems. Such systems can monitor the glucose level of the patient and deliver the insulin through an efficient micropump according to the need of the patient [9,155]. The motivation for the delivery and dosing of a wide variety of drugs for different medical conditions has originated from the research on micropump for insulin delivery. Micropumps play a vital role in drug delivery or dosing systems which deliver precise volume and concentration of drug from the reservoir to the target zone. Stabilization of drug concentration, localized delivery, reduction of dosage, etc. are some of the advantages of using micropump in drug delivery systems. Researchers like Yang N Kumar et al. [80], Mousoulis et al. [104], and Wei and Guo [133] have proposed their work on mechanical micropump for drug delivery applications. The concept of Therapeutics

9.5. Fuel cells Fuel cells are miniaturized devices which convert chemical energy into electrical energy hence they are used as a source of electric power sources. Micropumps are found to be effective in delivering the fuel 50

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required for generating the electric power particularly in Direct Methanol Fuel Cell (DMFC) [166–167]. Since methanol serves the purpose of the fuel in DMFC, Hwang [51] and Park et al. [56] reported piezo-actuated micropump which can deliver methanol at the required rate. Micropumps for DMFC application are expected to have lower energy consumption with compact size.

Therefore these polymers may be used as thin film actuators for micropump. Shape Memory Alloy polymers (PTFE, PU, Poly-caprolactone, EVA + nitrile rubber, PE, Poly-cyclooctene); Magnetic composite polymers may also be possible novel actuators for micropump actuation [179,180]. Most of the conventional mechanical micropumps incorporate centrally loaded oscillating diaphragm with actuation load applied at the central region. On the other hand, the higher stroke of the diaphragm is possible to achieve when actuated away from the central region, i.e., circumferentially as reported by Shabanian et al. [153]. This, in turn, increases the volume flow rate of mechanical micropump. Replacement of flat diaphragm with the slotted, corrugated or flexural hinged diaphragm can also lead to larger diaphragm deflection leading to higher volume stroke. Implementation of static geometry valves such as nozzle/diffuser in mechanical micropump has proved to be advantageous over conventional check valves both in terms of fabrication and dynamic operation. In spite of such advantages features, the backflow occurring during the pump operation reduces the overall performance of the micropump. This disadvantage opens up space for implementation of static geometry check valves like tesla valve which allows fluid flow in a single direction eliminating the problems of backflow associated with nozzle/diffusers [181,182]. In addition, there is also a need for the establishment of feasible, low-cost manufacturing techniques for mass production of the micropump as a product for the commercial market.

9.6. Gas chromatography (GC) Gas Chromatography is one of the techniques used for the analysis of complex gaseous mixtures particularly in medical diagnosis, environmental monitoring and forensic science [168,169]. A GC uses a narrow flow tube called column through which different chemical constituents of the sample pass through at different rates. Micropumps can serve the purpose of control, and accurate delivery and flow of gases. The compressibility of the gases is a significant challenge in handling gases. The micropump for GC must be capable enough to address the problems arising from the compressibility. Chemical stability is also an important consideration as the gases are in contact with pump body. Kim et al. [123] proposed an electrostatic micropump for gas chromatography. 10. Future perspectives for development of mechanical micropump In the global scenario, the microfluidic pump is gaining considerable significance due to the increased need for micro pumping systems in life science, health care devices, pharmaceuticals, electronic gadgets, etc. The market for micropump is expanding globally in developed American and European countries and developing countries like China, India. The compound annual growth rate (CAGR) for the micropump market is expected to be at around 19.4% from 2017 to 2023 [170]. In spite of high demand and contribution from the number of researchers, commercialization of the mechanical micropump technology has not matured to a greater extent. Though extensive technical data are available, selection of micropump with suitable actuation principle and its performance enhancement to meet the application requirement poses a significant challenge to the researchers. An attempt is made to address some of the factors which could improve the performance of the mechanical micropump. The authors believe some of the factors mentioned above could motivate researchers contribution to mechanical micropump development. Since the major players for micropump technology being the pharmaceutical and medical devices companies, there is a vast scope for the development of mechanical micropump technology into a compact, wearable, disposable device with the implementation of superior actuation mechanism and materials. Thus there is a need to focus on the application of biocompatible materials which can ease the use of micropump technology even for bio-implants [98,171–173]. The recent trend shows extensive utilization of materials like PDDA (Poly diallyldimethylammonium chloride), PDMS (Polydimethylsiloxane), SU-8 (epoxy-based negative photoresist), PMMA (Polymethylmethacrylate), etc. which have excellent biocompatibility characteristics [7]. The actuation scheme majorly decides the micropump performance; there has been a continuous effort in the implementation of new actuation principles for performance enhancement. Over the years, conventional piezoelectric actuators with PZT (Lead Zirconate Titanate) have seen extensive utilization for micropump actuation. Though PZT has superior response features, the presence of Lead makes it toxic thus causing a threat to the environment, particularly in biomedical applications [174]. Therefore the future works on mechanical micropump may focus on the use of lead-free piezoelectric materials like BaTiO3 (BT), BiNaTiO3 (BNT), BiKTiO3 (BKT) and other polymeric piezoelectric materials like PVDF, Parylene, ZnO/SU8, etc. [175,176]. Electroactive polymers such as Polysiloxanes, Polyurethanes Polyacrylates Polyesters perfluorinated sulfonic acid have a higher strain coefficient [177,178].

11. Concluding remarks The need for micro pumping systems in microfluidic devices and significant contributions from many researchers led to the rapid growth of micropump technology after the 1970s. In this regard, an attempt is made to understand the most recent works that have been carried out in the field of micropump technology with the emphasis on mechanical micropumps. Overall, this review extracts some of the major factors such as actuation schemes, size, operating parameters, flow rectification principle, material/fabrication techniques which affect the mechanical micropump performance. This review will benefit the existing and new researchers who are intended to work on micropump development. The following conclusions are drawn which highlight the recent trends towards mechanical micropump development. • Mechanical displacement type micropump has evolved significantly with more emphasis on the implementation of different types of actuation rather than component change. Displacement type micropumps are characterized by lower power requirement except for those involving thermal or magnetic actuation. Most of the mechanical micropumps reported have incorporated piezoelectric, electromagnetic actuation principle whose performance parameters are relatively superior compared to other actuation schemes. Ionic conductive polymers based actuation appears to be the new promising approach towards the micropump actuation because of its ability to deliver fluid flow at low voltage. • Most of the mechanical micropumps reported have implemented either check valves or nozzle/diffusers (valveless) for achieving flow rectification. Comparing the Performance of micropump in terms of flow and pressure produced, micropump with check valves outperforms the valveless configuration. The problems associated with the fabrication and integration of check valves has diverted towards the application of nozzle/diffusers at the expense of a slight reduction in performance. • Change in the chamber configuration also enhances the performance of the micropump. Double chamber and peristaltic chamber configuration of the micropump showed a better performance than the single chamber configuration. Applications involving the 51

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restriction on space can incorporate a single chamber configuration of the micropumps • Materials with lower modulus like PDMS, Silicone rubber; Parylene, etc. are used as diaphragm materials to have enhanced deflection resulting in a higher volumetric stroke. Implementation of geometrical features like slots, corrugation, flexural hinges can also improve the diaphragm deflection when compared to conventional flat diaphragms. Researchers have also suggested circumferential loading for the membrane which leads to improvement in the diaphragm deflection due to bending effect. • Though most of the micropump structures utilized materials like Si, Glass, etc., the recent trend towards the use of polymer-based materials like PDMS, PMMA, plastic, etc., has been witnessed because of its lower cost, enhanced strength, ease of fabrication. Emphasis has also been diverted towards material compatibility to justify application of micropump particularly for biomedical, chemic/biological analysis where biocompatibility, thermal and chemical stability is of vital importance. Other than conventional microfabrication techniques, researches have also proposed fabrication processes like CNC milling, Laser cutting/engraving for micropump fabrication which is as competitive as that of microfabrication techniques. • As observed by the author, there has been an increased need for micropump technology in microfluidics particularly in the application like biomedical, drug delivery, total analysis systems, biological/chemical analysis, thermal management, Fuel cells, etc.

[21] Judy JW, Tamagawa T, Polla DL. Surface-machined micromechanical membrane pump. In: Proceedings of the IEEE micro electro mechanical systems. IEEE; 1991. p. 182–6. [22] Dash AK, Suryanarayanan R. An implantable dosage form for the treatment of bone infections. Pharm Res 1992;9(8):993–1002. [23] Stemme E, Stemme G. A valveless diffuser/nozzle-based fluid pump. Sensors and Actuators A: physical 1993;39(2):159–67. [24] Guo S, Nakamura T, Fukuda T, Oguro K. Design and experiments of micro pump using ICPF actuator. In: Proceedings of the MHS’96 proceedings of the seventh international symposium on micro machine and human science; 1996. p. 235–40. [25] Zhang W, Ahn CH. A bidirectional magnetic micropump on a silicon wafer. In: Technical digest solid state sensor and actuator workshop; 1996. p. 94–7. [26] Benard WL, Kahn H, Heuer AH, Huff MA. A titanium-nickel shape-memory alloy actuated micropump. In: Proceedings of international solid state sensors and actuators conference (Transducers’ 97), 1; 1997. p. 361–4. [27] Dash AK, Cudworth GC. Therapeutic applications of implantable drug delivery systems. J Pharmacol Toxicol Methods 1998;40(1):1–12. [28] Li PCH. Microfluidic lab-on-a-chip for chemical and biological analysis and discovery. CRC press; 2005. [29] Tüdos AJ, Besselink GAJ, Schasfoort RBM. Trends in miniaturized total analysis systems for point-of-care testing in clinical chemistry. Lab Chip 2001;1(2):83– 95. [30] Reyes DR, Iossifidis D, Auroux P-A, Manz A. Micro total analysis systems. 1. Introduction, theory, and technology. Anal Chem 2002;74(12):2623–36. [31] Roux F, Fruman D, Gibek I, Dugue F, Billard J-Y, Bonafos B. Development of a micropump for hydrazine propulsion systems. In: Proceedings of the 37th joint propulsion conference and exhibit; 2001. p. 3831. no. July. [32] Xiong J, Zhou Z, Ye X, Wang X, Feng Y, Li Y. A colloid micro-thruster system. Microelectron Eng 2002;61–62(2002):1031–7. [33] Krpoun R, Shea HR. Integrated out-of-plane nanoelectrospray thruster arrays for spacecraft propulsion. J Micromech Microeng 2009;19(4). [34] Darabi J, Ekula K. Development of a chip-integrated micro cooling device. Microelectron J 2003;34(11):1067–74. [35] Singhal V, Garimella SV, Raman A. Microscale pumping technologies for microchannel cooling systems. Appl Mech Rev 2004;57(3):191. [36] Garimella SV, Singhal V, Liu D. On-chip thermal management with microchannel heat sinks and integrated micropumps. Proc IEEE 2006;94(8):1534–48. [37] Sung MK, Mudawar I. Single-phase and two-phase hybrid cooling schemes for high-heat-flux thermal management of defense electronics. In: Proceedings of the 2008 11th intersociety conference on thermal and thermomechanical phenomena in electronic systems. I-THERM; 2008. p. 121–31. [38] Luharuka R, Wu CF, Hesketh PJ. Design, fabrication, and testing of a near constant pressure fuel delivery system for miniature fuel cells. Sens Actuators A Phys 2004;112(2–3):187–95. [39] Zhang T, Wang QM. Valveless piezoelectric micropump for fuel delivery in direct methanol fuel cell (DMFC) devices. J Power Sources 2005;140(1):72– 80. [40] Yang X, Zhou Z, Cho H, Luo X. Study on a PZT-actuated diaphragm pump for air supply for micro fuel cells. Sens Actuators A Phys 2006;130–131:531–6 no. SPEC. ISS.. [41] Aksel E, Jones JL. Advances in lead-free piezoelectric materials for sensors and actuators. Sensors 2010;10(3):1935–54. [42] Muralt P, Polcawich RG, Trolier-McKinstry S. Piezoelectric thin films for sensors, actuators, and energy harvesting. MRS Bull 2009;34(September):658–64. [43] Minase J, Lu TF, Cazzolato B, Grainger S. A review, supported by experimental results, of voltage, charge and capacitor insertion method for driving piezoelectric actuators. Precis Eng 2010;34(4):692–700. [44] Dong S. Review on piezoelectric, ultrasonic, and magnetoelectric actuators. J Adv Dielectr 2012;02(01):1230001. [45] Hwang IH, Lee SK, Shin SM, Lee YG, Lee JH. Flow characterization of valveless micropump using driving equivalent moment: theory and experiments. Microfluid Nanofluidics 2008;5(6):795–807. [46] Wang W, Zhang Y, Tian L, Chen X, Liu X. Piezoelectric diffuser/nozzle micropump with double pump chambers. Front Mech Eng China 2008;3(4):449–53. [47] Kim HH, Park DH, Ryu BH, Lim KJ. Design and modeling of piezoelectric pump for microfluid devices. Ferroelectrics 2009;378(1):92–100. [48] Dau VT, Dinh TX, Sugiyama S. A MEMS-based silicon micropump with intersecting channels and integrated hotwires. J Micromech Microeng 2009;19(12). [49] Verma P, Chatterjee D, Nagarajan T. Design and development of a modular valveless micropump on a printed circuit board for integrated electronic cooling. Proc Inst Mech Eng Part C J Mech Eng Sci 2009;223(4):953–63. [50] Wang SS, Huang XY, Yang C. Valveless micropump with acoustically featured pumping chamber. Microfluid Nanofluidics 2010;8(4):549–55. [51] Hwang JY, et al. Periodic fuel supply to a micro-DMFC using a piezoelectric linear actuator. J Micromech Microeng 2010;20(8):0–7. [52] Luo Y, Lu M, Cui T. A polymer-based bidirectional micropump driven by a PZT bimorph. Microsyst Technol 2011;17(3):403–9. [53] Choi A, Vatanabe SL, De Lima CR, Silva ECN. Computational and experimental characterization of a low-cost piezoelectric valveless diaphragm pump. J Intell Mater Syst Struct 2012;23(1):53–63. [54] Guo L, Yan W, Xu Y, Chen Y. Valveless piezoelectric micropump of parallel double chambers. Int J Precis Eng Manuf 2012;13(5):771–6. [55] Guan YF, Shen MG, Han LL. Simulations and experiment analysis of a piezoelectric micropump. Appl Mech Mater 2012;229–231:1688–92. [56] Park J-H, Seo M-Y, Ham Y-B, Yun S-N, Kim D-I. A study on high-output piezoelectric micropumps for application in DMFC. J Electroceramics 2012;30(1–2):102–7.

Conflict of interest The author(s) declared no conflicts of interest with respect to the authorship and publication of this article. Reference [1] Iwai H, Wong H. The road to miniaturization. Phys World 2005;18(9):40–4. [2] Whitesides GM. The origins and the future of microfluidics. Nature 2006;442(7101):368–73. [3] Lei KF. Microfluidic systems for diagnostic applications: a review. J Lab Autom 2012;17(5):330–47. [4] Sackmann EK, Fulton AL, Beebe DJ. The present and future role of microfluidics in biomedical research. Nature 2014;507(7491):181–9. [5] Zhang C, Xing D, Li Y. Micropumps, microvalves, and micromixers within PCR microfluidic chips: advances and trends. Biotechnol Adv 2007;25(5):483–514. [6] Laser DJ, Santiago JG. A review of micropumps. J Micromech Microeng 2004;14(6). [7] Tsai NC, Sue CY. Review of MEMS-based drug delivery and dosing systems. Sens Actuators A Phys 2007;134(2):555–64. [8] Iverson BD, Garimella SV. Recent advances in microscale pumping technologies: a review and evaluation. Microfluid Nanofluidics 2008;5(2):145–74. [9] Nisar A, Afzulpurkar N, Mahaisavariya B, Tuantranont A. MEMS-based micropumps in drug delivery and biomedical applications. Sens Actuators, B Chem. 2008;130(2):917–42. [10] Ashraf MW, Tayyaba S, Afzulpurkar N. Micro Electromechanical Systems (MEMS) based microfluidic devices for biomedical applications. Int J Mol Sci 2011;12(6):3648–704. [11] Zhou C, Zhang H, Li Z, Wang W. Chemistry pumps: a review of chemically powered micropumps. Lab Chip 2016;16(10):1797–811. [12] Wang YN, Fu LM. Micropumps and biomedical applications – a review. Microelectron Eng 2018;195:121–38. [13] Spencer WJ, Corbett WT, Dominguez LR, Shafer BD. An electronically controlled piezoelectric insulin pump and valves. IEEE Trans Sonics Ultrason. 1978;25(3):153–6. [14] Sefton MV, Lusher HM, Firth SR, Waher MU. Controlled release micropump for insulin administration. Ann Biomed Eng 1979;7(3–4):329–43. [15] Clemens AH. Programmable open-loop micropump insulin delivery system. Diabetes Care 1980;3(2):359–61. [16] Sefton MV, Burns KJ. Controlled release micropumping of insulin at variable rates. Ind Eng Chem Prod Res Dev 1981;20(1):1–5. [17] Sefton MV. Implantable micropump for insulin delivery. Adv Chem Ser 2009;199:511–22. [18] Van Lintel HTG, Van De Pol FCM, Bouwstra S. A piezoelectric micropump based on micromachining silicon. Sens Actuators A Phys 1988;15:153–67. [19] Van De Pol FCM, Van Lintel HTG, Elwenspoek M, Fluitman JHJ. A thermopneumatic micropump based on micro-engineering techniques. Sens Actuators A Phys 1990;21(1–3):198–202. [20] Smits JG. Piezoelectric micropump with three valves working peristaltically. Sens Actuators A Phys 1990;21(1–3):203–6. 52

S. Mohith, P.N. Karanth and S.M. Kulkarni

Mechatronics 60 (2019) 34–55

[57] Zhang W, Eitel RE. An integrated multilayer ceramic piezoelectric micropump for microfluidic systems. J Intell Mater Syst Struct 2013;24(13):1637–46. [58] Tseng LY, Yang AS, Lee CY, Cheng CH. Investigation of a piezoelectric valveless micropump with an integrated stainless-steel diffuser/nozzle bulge-piece design. Smart Mater Struct 2013;22(8). [59] Wei Y, Torah R, Yang K, Beeby S, Tudor J. A novel fabrication process to realise a valveless micropump on a flexible substrate. In: Proceedings of the 2013 transducers & eurosensors XXVII: the 17th international conference on solid-state sensors, actuators and microsystems (TRANSDUCERS & EUROSENSORS XXVII), 025034; 2013. p. 1079–82. [60] Pečar B, Možek M, Resnik D, Dolžan T, Vrtačnik D, Križaj D. Piezoelectric peristaltic micropump with a single actuator. J Micromech Microeng 2014;24(10):105010. [61] Singh S, Kumar N, George D, Sen AK. Analytical modeling, simulations and experimental studies of a PZT actuated planar valveless PDMS micropump. Sens Actuators A Phys 2015;225:81–94. [62] Cheng CH, Yang AS, Lin CJ, Huang WJ. Characteristic studies of a novel piezoelectric impedance micropump. Microsyst Technol 2017;23(6):1709–17. [63] Ma HK, Luo WF, Lin JY. Development of a piezoelectric micropump with novel separable design for medical applications. Sens Actuators A Phys 2015;236:57–66. [64] Ma HK, Chen RH, Yu NS, Hsu YH. A miniature circular pump with a piezoelectric bimorph and a disposable chamber for biomedical applications. Sens Actuators A Phys 2016;251:108–18. [65] Aggarwal S, Paul BE, DasGupta A, Chatterjee D. Experimental characterization of piezoelectrically actuated micromachined silicon valveless micropump. Microfluid Nanofluidics 2017;21(1):1–11. [66] Kant R, Singh D, Bhattacharya S. Digitally controlled portable micropump for transport of live micro-organisms. Sens Actuators A Phys 2017;265:138–51. [67] Munas FR, et al. Development of PZT actuated valveless micropump. Sensors (Switzerland) 2018;18(5). [68] Pan T, McDonald SJ, Kai EM, Ziaie B. A magnetically driven PDMS micropump with ball check-valves. J Micromech Microeng 2005;15(5):1021–6. [69] McDonald S, Pan T, Ziaie B. A magnetically driven PDMS micropump with microball valves. In: Proceedings of the 26th annual international conference of the IEEE engineering in medicine and biology society, 1; 2004. p. 2650–3. [70] Chang HT, Lee CY, Wen CY. Design and modeling of electromagnetic actuator in mems-based valveless impedance pump. Microsyst Technol 2007;13(11–12):1615–22. [71] Lee CY, Chang HT, Wen CY. A MEMS-based valveless impedance pump utilizing electromagnetic actuation. J. Micromech Microeng 2008;18(3). [72] Zhou Y, Amirouche F, Chen L. Design and characterization of a magnetically driven valveless micropump for drug delivery. J. Med. Device. 2009;3(2):027553. [73] Wang YH, Tsai YW, Tsai CH, Lee C-Y, Fu L-M. Design and analysis of impedance pumps utilizing electromagnetic actuation. Sensors 2010;10(4):4040–52. [74] Zhou Y, Amirouche F. An electromagnetically-actuated all-pdms valveless micropump for drug delivery. Micromachines 2011;2(3):345–55. [75] Shen M, Dovat L, Gijs MAM. Magnetic active-valve micropump actuated by a rotating magnetic assembly. Sens Actuators B Chem. 2011;154(1):52–8. [76] Zhi C, Shinshi T, Uehara M. A micro pump driven by a thin film permanent magnet. J Adv Mech Des Syst Manuf 2012;6(7):1180–9. [77] Ke MT, Zhong JH, Lee CY. Electromagnetically-actuated reciprocating pump for high-flow-rate microfluidic applications. Sensors (Switzerland) 2012;12(10):13075–87. [78] Chang YJ, Chung YW, Chou TA, Huang MF. Valve-less diaphragm micropump with electromagnetic actuation. Adv Mater Res 2013;647:929–34. [79] Ni J, Wang B, Chang S, Lin Q. An integrated planar magnetic micropump. Microelectron Eng 2014;117:35–40. [80] Sima AH, Salari A, Shafii MB. Low-cost reciprocating electromagnetic-based micropump for high-flow rate applications. J Micro/Nanolithography MEMS MOEMS 2015;14(3):035003. [81] Kawun P, Leahy S, Lai Y. A thin PDMS nozzle/diffuser micropump for biomedical applications. Sens Actuators A Phys 2016;249:149–54. [82] Kumar N, George D, Sajeesh P, Manivannan PV, Sen AK. Development of a solenoid actuated planar valveless micropump with single and multiple inlet-outlet arrangements. J. Micromech Microeng 2016;26(7). [83] Said MM, Yunas J, Bais B, Hamzah AA, Majlis BY. Hybrid polymer composite membrane for electromagnetic (EM) valveless micropump. J Micromech Microeng 2017;27(7):075027. [84] Gidde RR, Pawar PM, Ronge BP, Dhamgaye VP. Design optimization of an electromagnetic actuation based valveless micropump for drug delivery application. Microsyst Technol 2019;25(2):509–19. [85] Kim JH, Na KH, Kang CJ, Jeon D, Kim YS. A disposable thermopneumatic-actuated microvalve stacked with PDMS layers and ITO-coated glass. Microelectron Eng 2004;73–74:864–9. [86] Mamanee W, Tuantranont A, Afzulpurkar NV, Porntheerapat N, Rahong S, Wisitsoraat A. PDMS based thermopnuematic peristaltic micropump for microfluidic systems. J Phys Conf Ser 2006;34(1):564–9. [87] Nguyen N-T, Wereley ST, Shaegh SAM. Fundamentals and applications of microfluidics. Artech house; 2019. [88] Lin T-Y, Ou Y-C, Yang L-J. A thermopneumatic valveless micropump with PDMS-based nozzle/diffuser structure for microfluidic system. In: Proceedings of the ASME 2008 first international conference on micro/nanoscale heat transfer; 2008. p. 293–6. [89] Liao H-H, Yang Y-J. Fabrication and characterization of thermo-pneumatic peristaltic micropumps. Nanotech 2008;3:296–9. [90] Yang YJ, Liao HH. Development and characterization of thermopneumatic peristaltic micropumps. J Micromech Microeng 2009;19(2).

[91] Ha SM, Cho W, Ahn Y. Disposable thermo-pneumatic micropump for bio lab-on-a-chip application. Microelectron Eng 2009;86(4–6):1337–9. [92] Chia BT, Liao HH, Yang YJ. A novel thermo-pneumatic peristaltic micropump with low temperature elevation on working fluid. Sens Actuators A Phys 2011;165(1):86–93. [93] Yang LJ, Lin TY. A PDMS-based thermo-pneumatic micropump with Parylene inner walls. Microelectron Eng 2011;88(8):1894–7. [94] Ochoa M, Ziaie B. A fermentation-powered thermopneumatic pump for biomedical applications. Lab Chip 2012;12(20):4044–8. [95] Chee PS, Minjal MN, Leow PL, Ali MSM. Wireless powered thermo-pneumatic micropump using frequency-controlled heater. Sens Actuators A Phys 2015;233:1–8. [96] Liu B, Sun J, Li D, Zhe J, Oh KW. A high flow rate thermal bubble-driven micropump with induction heating. Microfluid Nanofluidics 2016;20(11):1–9. [97] Hamid NA, Majlis BY, Yunas J, Syafeeza AR, Wong YC, Ibrahim M. A stack bonded thermo-pneumatic micro-pump utilizing.pdf. Microsyst Technol 2017;23:4037–43. [98] Hamid NA, Burhanuddin YM, Jumril Y, Syafeeza AR, Wong YC, Ibrahim M. A stack bonded thermo-pneumatic micro-pump utilizing polyimide based actuator membrane for biomedical applications. Microsystem Technologies 2017;23(9):4037–43. [99] Bardaweela HK, Andersonb MJ, Weissa LW, Richardsa RF, Richards CD. Characterization and modeling of the dynamic behavior of a liquid–vapor phase change actuator. Sens Actuators A Phys 2008;149(2):284–91. [100] Ogden S, Klintberg L, Thornell G, Hjort K, Bode´n R. Review on miniaturized paraffin phase change actuators, valves, and pumps. Microfluid. Nanofluidics 2013;17(1):53–71. [101] Bodén R, Hjort K, Schweitz JÅ, Simu U. A metallic micropump for high-pressure microfluidics. J Micromech Microeng 2008;18(11). [102] Yoo JC, La GS, Kang CJ, Kim YS. Microfabricated polydimethylsiloxane microfluidic system including micropump and microvalve for integrated biosensor. Curr Appl Phys 2008;8(6):692–5. [103] Svensson S, Sharma G, Ogden S, Hjort K, Klintberg L. High-pressure peristaltic membrane micropump with temperature control. J Microelectromech Syst 2010;19(6):1462–9. [104] Mousoulis C, Ochoa M, Papageorgiou D, Ziaie B. A skin-contact-actuated micropump for transdermal drug delivery. IEEE Trans Biomed Eng 2011;58(5):1492–8. [105] Boden R, Ogden S, Hjort K. Microdispenser with continuous flow and selectable target volume for microfluidic high-pressure applications. J Microelectromech Syst 2013;23(2):452–8. [106] Huang C, Tsou C. The implementation of a thermal bubble actuated microfluidic chip with microvalve, micropump and micromixer. Sensors Actuators, A Phys. 2014;210:147–56. [107] Makino E, Mitsuya T, Shibata T. Fabrication of TiNi shape memory micropump. Sensors Actuators, A Phys. 2001;88(3):256–62. [108] Zainal MA, Sahlan S, Mohamed Ali MS. Micromachined shape-memory-alloy microactuators and their application in biomedical devices. Micromach. 2015;6(7):879–901. [109] Fu Y, Du H, Huang W, Zhang S, Hu M. TiNi-based thin films in MEMS applications: a review. Sens Actuators A Phys 2004;112(2–3):395–408. [110] Guo S, Sun X, Ishii K, Guo J. SMA actuator-based novel type of peristaltic micropump. In: Proceedings of the 2008 IEEE international conference on information and automation. ICIA 2008; 2008. p. 1620–5. [111] Sun X, Hao Y, Guo S, Ye X, Yan X. The development of a new type of compound peristaltic micropump. In: Proceedings of the 2008 IEEE international conference on robotics and biomimetics, ROBIO 2008; 2008. p. 698–702. [112] Sassa F, Al-Zain Y, Ginoza T, Miyazaki S, Suzuki H. Miniaturized shape memory alloy pumps for stepping microfluidic transport. Sens Actuators B Chem 2012;165(1):157–63. [113] Ullakko K, Wendell L, Smith A, Müllner P, Hampikian G. A magnetic shape memory micropump: contact-free, and compatible with PCR and human DNA profiling. Smart Mater Struct 2012;21(11). [114] Smith AR, Saren A, Järvinen J, Ullakko K. Characterization of a high-resolution solid-state micropump that can be integrated into microfluidic systems. Microfluid Nanofluid 2015;18(5–6):1255–63. [115] Saren A, Smith AR, Ullakko K. Integratable magnetic shape memory micropump for high-pressure, precision microfluidic applications. Microfluid Nanofluid 2018;22(4). [116] MacHauf A, Nemirovsky Y, Dinnar U. A membrane micropump electrostatically actuated across the working fluid. J Micromech Microeng 2005;15(12):2309–16. [117] Sam J, Kumar J, Tetteh EA, Braineard EP. A study of why electrostatic actuation is preferred and a simulation of an electrostatically actuated cantilever beam for mems applications. Int J Eng Sci Emerg Technol 2014;6(5):441–6. [118] Conrad H, Schenk H, Kaiser B, Langa S, Gaudet M, Schimmanz K, Stolz1 M, Lenz M. A small-gap electrostatic micro-actuator for large deflections. Nat Commun 2015;6:1–7. [119] Lee S, Yee SY, Besharatian A, Kim H, Bernal LP, Najafi K. Adaptive gas pumping by controlled timing of active microvalves in peristaltic micropumps. In: Proceedings of the international solid-state sensors, actuators and microsystems conference. IEEE; 2009. p. 2294–7. [120] Lee KS, Kim B, Shannon MA. Development of a peristaltic gas micropump with a single chamber and multiple electrodes. J Micromech Microeng 2013;23(9). [121] Gao J, Guo D, Santhanam S, Fedder GK. Large stroke electrostatic actuated PDMS-on-silicon micro-pump. In: Proceedings of the 2015 transducers – 2015 18th international conference on solid-state sensors, actuators and microsystems (TRANSDUCERS); 2015. p. 117–20. [122] Jeong S-Y, Cho C, Hong P, Lee D, Kim B. Peristaltic micropump with multi-electrodes using electrostatic force. Adv Mater Res 2015;1125:571–6.

53

S. Mohith, P.N. Karanth and S.M. Kulkarni

Mechatronics 60 (2019) 34–55

[123] Kim H, Washabaugh PD, Bernal LP, Najafi K, Astle AA. An integrated electrostatic peristaltic 18-stage gas micropump with active microvalves. J Microelectromech Syst 2014;24(1):192–206. [124] Lee I, Hong P, Cho C, Lee B, Chun K, Kim B. Four-electrode micropump with peristaltic motion. Sens Actuators A Phys 2016;245:19–25. [125] Uhlig S, et al. Electrostatically driven in-plane silicon micropump for modular configuration. Micromachines 2018;9(4):190. [126] Uchida M, Xu C, Le Guilly M, Taya M. Design of nafion actuator with enhanced displacement. In: Proceedings of the smart structures and materials 2002: electroactive polymer actuators and devices (EAPAD), 4695; 2002. p. 57–67. [127] Guo S, Asaka K. Polymer-based new type of micropump for bio-medical application. In: Proceedings of the 2003 IEEE international conference on robotics and automation; 2004. p. 1830–5. [128] Pak JJ, Kima J, Oha SW, Sona JH, Chob SH, Leec S-K, Parkd J-Y, Kimd B. Fabrication of ionic-polymer-metal-composite (IPMC) micropump using a commercial Nafion. In: Proceedings of the smart structures and materials 2004: electroactive polymer actuators and devices, 5385; 2004. p. 272. [129] Loverich JJ, Kanno I, Kotera H. Concepts for a new class of all-polymer micropumps. Lab Chip 2006;6(9):1147–54. [130] O’Halloran A, O’Malley F, McHugh P. A review on dielectric elastomer actuators, technology, applications, and challenges. J Appl Phys 2008;104(7). [131] Rosset S, Niklaus M, Dubois P, Shea HR. Large-stroke dielectric elastomer actuators with ion-implanted electrodes. J Microelectromech Syst 2009;18(6):1300–8. [132] Nguyen TT, Goob NS, Nguyenc VK, Yood Y, Park S. Design, fabrication, and experimental characterization of a flap valve IPMC micropump with a flexibly supported diaphragm.pdf. Sens Actuators A Phys 2008;141(2):640–8. [133] Wei W, Guo S. A novel PDMS diaphragm micropump based on ICPF actuator. In: Proceedings of the 2010 IEEE international conference on robotics and biomimetics, 2010; 2010. p. 1577–83. [134] Santos J, Lopes B, Branco PJC. Ionic polymer-metal composite material as a diaphragm for micropump devices. Sens Actuators A Phys 2010;161(1–2):225–33. [135] Shoji E. Fabrication of a diaphragm micropump system utilizing the ionomer-based polymer actuator. Sensors Actuators B Chem 2016;237:660–5. [136] Pang X, Li B, Xia D, Jing S. Application of dielectric elastomer planar actuators in a micropump chip. In: Proceedings of the 2009 4th IEEE conference on industrial electronics and applications, ICIEA 2009, 1; 2009. p. 1199–202. [137] Li B, Chen H, Wu J, Zhu Z, Xia D, Jing S. Design and fabrication of a microfluidic chip driven by dielectric elastomers. In: Proceedings of the second international conference on smart materials and nanotechnology in engineering, 7493; 2009. p. 74935S. [138] Chee PS, Che KM, Sultan M, Ali M. Soft dielectric elastomer actuator for micropump application. In: 2016 IEEE 29th International Conference on Micro Electro Mechanical Systems (MEMS); 2016. p. 561–4. IEEE. [139] Mohd Ghazali FA, Mah CK, AbuZaiter A, Chee PS, Mohamed Ali MS. Soft dielectric elastomer actuator micropump. Sens Actuators A Phys 2017;263:276–84. [140] Au AK, Lai H, Utela BR, Folch A. Microvalves and micropumps for BioMEMS. Micromachines 2011;2(2):179–220. [141] Walczak R, Adamski K, Lizanets D. Inkjet 3D printed check microvalve. J Micromech Microeng 2017;27(4). [142] Zhang D, Lv J, Jiang Y, Chen H, Fu J. A piezoelectric microvalve with a flexure-hinged driving frame and microfabricated silicon sealing pair. Mechatronics 2014;24(5):511–18. [143] Bonhoeffer B, Boldrini M, Boiger G, Kwade A, Juhnke M. Experimental characterization and simulation of a piezo-actuated micro dispensing valve. J Fluids Eng 2017;139(5):051105. [144] Yildirim E, Arikan MAS, Külah H. A normally closed electrostatic parylene microvalve for micro total analysis systems. Sens Actuators A Phys 2012;181:81–6. [145] Wang J, Aw KC, McDaid A, Sharma RN. Comprehensive investigation of diffuser/nozzle element at low Reynolds number aimed at valveless pump design. Int J Appl Mech 2015;07(04):1550058. [146] Yuan S-qi, Yang S, He X-h, Deng Z-d, Cai S-c. Design and experimental study of a novel three-way diffuser/nozzle elements employed in valveless piezoelectric micropumps. J Brazilian Soc Mech Sci Eng 2014;37(1):221–30. [147] Kim BJ, Meng E. Review of polymer MEMS micromachining. J Micromech Microeng 2015;26(1). [148] Xua T, Zhaoa L, Jianga Z, Guoa X, Dinga J, Xiangb W, Zhao Y. A high sensitive pressure sensor with the novel bossed diaphragm combined with peninsula-island structure. Sens Actuators A Phys 2016;244:66–76. [149] Zhu J, Wang M, Chen L, Ni X, Ni H. An optical fiber Fabry–Perot pressure sensor using corrugated diaphragm and angle polished fiber. Opt Fiber Technol 2017;34(1):42–6. [150] Roopa R, Karanth PN, Kulkarni SM. Effect of flexure hinge geometry on central deflection of piezo actuated diaphragm for micropump. In: Proceedings of the IEEE international conference on power, control, signals and instrumentation engineering (ICPCSI) 2017, 1; 2018. p. 2636–8. [151] Azizollah Ganji B, Babaei Sedaghat S, Roncaglia A, Belsito L. Design and fabrication of high performance condenser microphone using C-slotted diaphragm. Microsyst Technol 2018;24(7):3133–40. [152] Roopa R, Navin Karanth P, Kulkarni SM. Design, fabrication and experimental studies of compliant flexure diaphragm for micro pump. Int J Eng Technol 2018;7(2.21):66. [153] Shabanian A, Goldschmidtboeing F, Vilches S, Phan H-H, Bhat Kashekodi A, Rajaeipour P, Woias P. A novel piezo actuated high stroke membrane for micropumps. Microelectron Eng 2016;158(March):26–9.

[154] Shabanian A, Goldschmidtboeing F, Gowda HGB, Dhananjaya CC, Woias P. The deformable valve pump (DVP). In: Proceedings of the TRANSDUCERS 2017 – 19th international conference on solid-state sensors, actuators and microsystems (TRANSDUCERS); 2017. p. 1777–80. [155] Jean-louis S. Evolution of diabetes insulin delivery devices. J Diabetes Sci Technol 2010;4(3):505–13. [156] Ainslie KM, Desai TA. Microfabricated implants for applications in therapeutic delivery, tissue engineering, and biosensing. Lab Chip 2008;8(11):1864–78. [157] Van Der Maaden K, Jiskoot W, Bouwstra J. Microneedle technologies for (trans)dermal drug and vaccine delivery. J Control Release 2012;161(2):645–55. [158] Mahnama A, Nourbakhsh A, Ghorbaniasl G. A survey on the applications of implantable micropump systems in drug delivery. Curr Drug Deliv 2014;11(1):123–31. [159] Oh KW. Lab-on-chip (LOC) devices and microfluidics for biomedical applications. MEMS Biomed Appl 2012:150–71. [160] Weng X, Jiang H, Li D. Microfluidic DNA hybridization assays. Microfluid Nanofluidics 2011;11(4):367–83. [161] Saidur MR, Aziz ARA, Basirun WJ. Recent advances in DNA-based electrochemical biosensors for heavy metal ion detection: a review. Biosens Bioelectron 2017;90:125–39 November 2016. [162] Huang S, Li C, Lin B, Qin J. Microvalve and micropump controlled shuttle flow microfluidic device for rapid DNA hybridization. Lab Chip 2010;10(21):2925–31. [163] Wen CY, Yeh SJ, Leong KP, Kuo WS, Lin H. Application of a valveless impedance pump in a liquid cooling system. IEEE Trans Compon Packag Manuf Technol 2013;3(5):783–91. [164] Duan B, Guo T, Luo M, Luo X. A mechanical micropump for electronic cooling. In: Proceedings of the 19th international conference on solid-state sensors, actuators and microsystems (TRANSDUCERS); 2014. p. 1038–42. [165] Hsieh SS, Hsu YF, Wang ML. A microspray-based cooling system for high powered LEDs. Energy Convers Manag 2014;78:338–46. [166] Zhao TS, Chen R, Yang WW, Xu C. Small direct methanol fuel cells with passive supply of reactants. J Power Sources 2009;191(2):185–202. [167] Ong BC, Kamarudin SK, Basri S. Direct liquid fuel cells: a review. Int J Hydrogen Energy 2017;42(15):10142–57. [168] Hsieh HC, Kim H. A miniature closed-loop gas chromatography system. Lab Chip 2016;16(6):1002–12. [169] Al-Rubaye AF, Hameed IH, Kadhim MJ. A review: uses of gas chromatography-mass spectrometry (GC-MS) technique for analysis of bioactive natural compounds of some plants. Int J Toxicol Pharmacol Res 2017;9(01). [170] www.market research future.com, “Micro pump market research report – forecast to 2023,”(2018), [online].Avilable: https://www.marketresearchfuture. com/reports/micro-pump-market-13002018. [Accessed 1 Feb 2019] [171] Cobo A, Sheybani R, Tu H, Meng E. A wireless implantable micropump for chronic drug infusion against cancer. Sens Actuators A Phys 2016;239:18–25. [172] Johnson DG, Borkholder DA. Towards an implantable, low flow micropump that uses no power in the blocked-flow state. Micromachines 2016;7(6). [173] Humayun FM, Santos A, Altamirano JC, Ribeiro R, Gonzalez R, de la Rosa A, Shih J, Pang C, Jiang SC, Calvillo P, Huculak J, Zimmerman J. Implantable micropump for drug delivery in patients with diabetic macular edema. Transl Vis Sci Technol 2014;3(6):5. [174] Ibn-Mohammed T, Koh SCL, Reaney IM, Sinclair DC, Mustapha KB, Acquaye A, Wang D. Are lead-free piezoelectrics more environmentally friendly? MRS Commun 2017;7(1):1–7. [175] Panda PK, Sahoo B. PZT to lead free piezo ceramics: a review. Ferroelectrics 2015;474(1):128–43. [176] Ramadan KS, Sameoto D, Evoy S. A review of piezoelectric polymers as functional materials for electromechanical transducers. Smart Mater Struct 2014;23(3). [177] Bahramzadeh Y, Shahinpoor M. A review of ionic polymeric soft actuators and sensors. Soft Robot 2013;1(1):38–52. [178] Opris DM. Polar elastomers as novel materials for electromechanical actuator applications. Adv Mater 2018;30(5):1–23. [179] Mohd Jani J, Leary M, Subic A, Gibson MA. A review of shape memory alloy research, applications and opportunities. Mater Des 2014;56:1078–113. [180] Gray BL. A review of magnetic composite polymers applied to microfluidic devices. J Electrochem Soc 2014;161(2):B3173–83. [181] Thompson SM, Paudel BJ, Jamal T, Walters DK. Numerical Investigation of Multistaged Tesla Valves. J Fluids Eng 2014;136(8):081102. [182] de Vries SF, Florea D, Homburg FGA, Frijns AJH. Design and operation of a Tesla– type valve for pulsating heat pipes. Int J Heat Mass Transf 2017;105:1–11.

Mohith S. received his B.E. (Bachelors in Engineering) degree in Mechanical Engineering in the year 2013 and M.Tech. (Master of Technology) Degree in Machine Design in the year 2015 from Visvesvaraya Technological University (VTU), Karnataka. He is currently a Research Scholar in the Department of Mechanical Engineering, National Institute of Technology Karnataka where his research focus is on the development of valveless micropump. His area of interest includes MEMS, Microfluidic Devices, Biomedical Devices, Mechatronics, Product Design and Development.

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S. Mohith, P.N. Karanth and S.M. Kulkarni

Mechatronics 60 (2019) 34–55

Navin Karanth P. is an Assistant Professor in the Department of Mechanical Engineering at National Institute of Technology Karnataka, Surathkal. He received his Ph.D. degree from the NITK Surathkal, Mechanical Engineering department in the field of Mechatronics during the year 2012. He received his M.Tech. Degree from NITK Surathkal, in 2001 and B.Tech. from the MIT Manipal, in 1997. He has industrial experience of more than two years and teaching experience of more than 15 years. He is a life member of ISTE and Indian Society of Heat and Mass Transfer. His current research interests are into mechatronic systems and microsystems.

S. M. Kulkarni is currently working as a professor in the Department of Mechanical Engineering in National Institute of Technology Karnataka. Earlier he completed his graduation from Mysore University, Post-graduation from Bharathiar University and Ph.D. degree from Indian Institute of Science, Bangalore. He has also received Sir Vithal N. Chandavarkar Award for Best Ph.D. thesis. He has about 30 years of experience in teaching and has published 49 journal papers, 70 conference papers. His professional activities include peer reviewing of the article in journals like JOM, JOMA etc. He is actively involved in the development of curriculum for engineering education at various deemed universities. His teaching and research interests are Mechatronics, MEMS, Product Development and Materials.

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