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Facile and low-cost synthesis of flexible nano-generators based on polymeric and porous aerogel materials
Current Applied Physics xxx (xxxx) xxx–xxx
Contents lists available at ScienceDirect
Current Applied Physics journal homepage: www.elsevier.com/locate/cap
Facile and low-cost synthesis of flexible nano-generators based on polymeric and porous aerogel materials Morteza Beyranvand, Ahmad Gholizadeh∗ School of Physics, Damghan University (DU), Damghan, Iran
A R T I C LE I N FO
A B S T R A C T
Keywords: Triboelectric nanogenerator Porous aerogel material Polymeric materials Triboelectricity
Triboelectric nano-generators (TE-NGs) can be utilized as a power supply for wireless systems, sensors, and operators. In this paper, new flexible TE-NGs that use sodium carboxymethyl cellulose (CMC), poly dimethyl siloxane (PDMS), polyvinylidene fluoride (PVDF), poly (4,4′-oxydiphenylene-pyromellitimide) (KAPTON) films and also sugar as a piezoelectric material were developed and are reported. Also, the outputs of NGs made by linear power under a periodic pressure of ~ 0.2 MPa at a frequency of 3 Hz showed that the highest output of NGs are related to PDMS–KATTON, PDMS, PVDF–KAPTON, PVDF, CMC NGs, respectively. It has been also observed that NGs connected in series to each other have a higher output than paralleled NGs so that their voltages increase at higher frequencies. Besides, a significant point is that the NGs are made in a low-cost, affordable, and environmentally-friendly route, which is a superior characteristic with respect to the rest of the NGs.
1. Introduction With global warming and rising energy crisis, trying to access the green and renewable energy sources is one of the critical challenges [1,2]. Photovoltaics, thermal electricity, and electromagnetic induction are the technologies that are used well for energy harvesting [3–5]. However, the size of systems and devices that they sometimes are being used in inaccessible environments, it's getting smaller every day and the use of conventional batteries will not any help because of the larger size of the battery than the size of the nano-scale. Also, sensors or systems which can be used for medical applications are placed inside the body or for example, in military applications need to hide or put them in dust, rain, wet or dark. So one of the most important and main challenges is the issue of feeding these devices. Energy harvesting from mechanical vibrations which are routinely day today and at all hours of the day in our environment, and converting these vibrations into electricity has been one of the goals of nanotechnology. Hence the design and synthesis of multi-purpose self-powered systems with small size, high sensitivity and much lower power consumption such as triboelectric and piezoelectric NGs which can absorb energy efficiently from the natural environment and convert it into electrical energy, have been very much considered [3]. Triboelectric nano-generators (TE-NG) can be used as a power supply for wireless systems, sensors, and operators, which operate in a different area as medical, military, and
∗
environmental issues. The structure of these NGs consists of two layers, including TE materials and a separator in the middle of it as well as suitable electrodes for the transfer of charges to the external circuit. After the contact and intermittent separation of these two layers, due to movements of mechanical environments, including wares of water, wind or body movements, resident electrical charges are generated by electrostatic induction and from one substance to another are transferred. In 2006, the first NG consist of a ZnO nano-wire, was designed by Wang and Sang [6]. The force produced by probe tip of atomic force microscope (AFM) acts on a ZnO nanowire and distorts the nanowire. ZnO piezoelectric property creates an electrical field in the direction of the force applied to the nanowire. The small potential output obtained by the nano-wire has a sharp peak with a maximum of 6 mV and shows the negative amount with respect to the bottom of nanowire. When AFM tip is at the starting point of contact with nanowire, due to the presence of a reverse-biased Schottky junction, there is no potential output for the output of the NGs. The potential output in NGs, only time is generated that AFM tip with the compressed side of the nanowire is in contact [7]. Improving the prototype output power of a direct current NGs, was made by eliminating the use of AFM to create the mechanical movement inside nanowires [5]. These NGs were designed in 2007 by Wang et al. [8]. In these NGs, zigzag-shaped metal electrode is used instead of
Corresponding author. E-mail addresses: [email protected], [email protected] (A. Gholizadeh).
https://doi.org/10.1016/j.cap.2019.11.009 Received 10 August 2019; Received in revised form 25 October 2019; Accepted 11 November 2019 1567-1739/ © 2019 Korean Physical Society. Published by Elsevier B.V. All rights reserved.
Please cite this article as: Morteza Beyranvand and Ahmad Gholizadeh, Current Applied Physics, https://doi.org/10.1016/j.cap.2019.11.009
Current Applied Physics xxx (xxxx) xxx–xxx
M. Beyranvand and A. Gholizadeh
using the AFM. The zigzag-shaped electrode that placed above the nanowires is similar to the AFMs but made from platinum-coated silicon wafer. The potential output value created with dimension 6 mm2 is about 10 mV. An innovative approach for access to AC NGs is using the ZnO nanowire arrays that their two ends are partially placed on electrodes [9,10]. In this NG, which was designed by Xu in 2010, a low frequency and alternating mechanical shock on the surface of the upper electrode is applied and generates an alternating pulse at the outlet of NG. In this NG, using polymer material PMMA, which surrounds the nanowires, the stability and mechanical hardness of the whole machine increases, and a short circuit between the substrate and electrode, is prevented. Zhang et al. [11], produced electricity from mechanical energy created by putting the TE-NG structure on the shoe floor when walking. The synthesis process starts by creating a pattern from the PDMS layer. Zhang et al. [12], studied on the synthesis of biosensors for blood sugar regulation. The structure of their NGs was such that were attached to the person's clothing, where the mechanical energy generated by the movement of the individual clothes led to the production of electricity for feeding biomass sensor [11–13]. In this paper, synthesis of the triboelectric NGs based on the materials CMC, KAPTON, PVDF, PDMS as well as sugar used as a piezoelectric material have been investigated. Proper placements of these layers consist of flexible porous polymers, and incorporation of appropriate and efficient materials can lead to many potential applications. This work also presents a simple, environmentally friendly, and cost-effective method to synthesis the flexible TE-NGs.
the previous section. To prepare the NG based on the porous CMC/ PDMS aerogel film, first, the PDMS solution was prepared from a prepolymer PDMS, pharmaceutical agent, and Ethyl acetate with a ratio 10:1:20. Then, compressed CMC aerogel was dipped into a PDMS solution. A well-drained aerogel film was placed under the hood for 2.45 h to evaporate the solvent and then held at 100 °C for 1.30 h. The CMC/PDMS aerogel film was spin-coated on both sides with a mixture of the pre-polymer PDMS and the drug agent (no solvent) with a ratio of 10:1. The sample was again kept at 100 °C for 1.15 h. After that, PDMS/ (CMC/PDMS)/PDMS film (1 cm × 1 cm in area × 220 μm thickness) was cut. Finally, aluminum foil was used on both sides of three-layer film to obtain a NGs. Schematic illustration for the preparation of the sample is shown in Fig. 1(c). The detailed information on the preparation of other types of aerogel films can be found below.
2. Experimental
Here, the synthesis process of the compressed CMC film is similar to the previous section 2.2. To prepare the PVDF/CMC–PVDF/PVDF NG, first, DMF (15 cc) was slowly added to acetone (10 cc), and then PVDF (4.5 g) was slowly added to the mixture of the DMF-acetone and thereafter wait for 1.3 h until the solution PVDF-DMF-acetone ultimately be gelatinous. The compressed CMC aerogel film was dipped into the PVDF-DMF-acetone solution using a vacuum-assisted liquid filling method to enable the solution to penetrate the inner pores. The aerogel completely coated for 30min was placed underneath the hood to evaporate the solvent. The CMC-PVDF aerogel film was spin-coated on both sides with a mixture of the pre-polymer PVDF-DMF. The PVDF/ CMC-PVDF/PVDF film was cut into pieces (1 cm × 1 cm in area × 220 μm thickness). After that, the aluminum foil is used on both sides of the three-layer film to make the NG, as shown in Fig. 1(e).
2.4. Step-by-step preparation of aluminum foil/KAPTON/PDMS/CMCPDMS/PDMS/aluminum foil NG Here, the synthesis process of the compressed CMC and PDMS/ (CMC/PDMS)/PDMS films is similar to previous sections 2.2 and 2.3, respectively. Then, the PDMS/(CMC/PDMS)/PDMS was spin-coated on the one side with a KAPTON layer. After that, the aluminum foil is used on both sides of the four-layer film to obtain the NG, as shown in Fig. 1(d). 2.5. Step-by-step preparation of aluminum foil/PVDF/CMC–PVDF/PVDF/ aluminum foil NG
2.1. Materials Sodium carboxymethyl cellulose (CMC), polydimethyl siloxane (PDMS), polyvinylidene fluoride (PVDF), dimethylformamide (DMF), poly (4,4′-oxydiphenylene-pyromellitimide) (KAPTON), benzoic acid, ethyl acetate were purchased from Sigma-Aldrich. Here, we introduced a new method for synthesis of CMC, CMC-PDMS, and CMC-PVDF aerogel films. 2.2. Step–by–step preparation of the aluminum foil/CMC/aluminum foil NG To prepare the compressed CMC film, first 0.5 g CMC was mixed with a solution containing 0.1 g sugar and 40 cc deionized water and then wait at least 45 min until CMC and sugar are completely dissolved in water. Besides, in another beaker, 3.25 g benzoic acid was poured on 20 cc alcohols and then remains 5 min until thoroughly mixing. Finally, alcohol-benzoic acid solution added slowly to carboxymethyl cellulosesugar-water. Then, a circular white mass appears in the solution obtained from carboxymethyl cellulose-deionized water-benzoic acid-alcohol. Ultimately, obtained solution set initially for 10 h under the IR light with distance 20 cm, until thoroughly water has evaporated, then it takes a gelatinous form and after that, it poured into pre-embedded molds and placed it in the oven for 4 h at 180 °C. Then, the almost dried gelation material was pressed to reduce its pores and strengthen it. Finally, it placed in the oven again up to 8 h at 100 °C until completely benzoic acid removed from the material to prepare the porous aerogel film. The synthesis process of the porous aerogel film is shown in Fig. 1(a). Aluminum foil is used on both sides of the CMC layer to obtain NGs, as shown in Fig. 1(b).
2.6. Step–by–step preparation of aluminum foil/KAPTON/PVDF/ CMCPVDF/PVDF/aluminum foil NG Here, the synthesis process of the compressed CMC and PVDF/CMCPVDF/PVDF films is similar to previous sections 2.2 and 2.5, respectively. To prepare the KAPTON/PVDF/CMC-PVDF/PVDF, the PVDF/ CMC-PVDF/PVDF film was spin-coated on the one side with a KAPTON layer and then aluminum foil was placed on both sides of the four-layer film to obtain the NG as shown in Fig. 1(f). 2.7. Characterization of the NGs Field-Emission Scanning Electron Microscope (FE–SEM, MIRA3 model; TESCAN) was used to measure and display the porosity of the synthesized aerogel NGs. The electrical output data of the NGs were recorded using an I–V Meter Device. Schematic illustration showing the electrical setup for the measurement of the electrical output data of the NGs is in Fig. 2. 3. Results and discussion
2.3. Step-by-step preparation of aluminum foil/PDMS/CMC-PDMS/ PDMS/aluminum foil NG
Fig. 3 shows the microstructure of CMC, CMC-PVDF, and CMCPDMS aerogel films. Although the CMC aerogel film has been prepared
Here, the synthesis process of the compressed CMC film is similar to 2
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Fig. 1. (a) The synthesis process of the porous aerogel film. Schematic illustration for the preparation of NG (b) Aluminum Foil/CMC/Aluminum Foil, (c) Aluminum Foil/PDMS/CMC-PDMS/PDMS/Aluminum Foil, (d) Aluminum Foil/KAPTON/PDMS/CMC-PDMS/PDMS/Aluminum Foil, (e) Aluminum Foil/PVDF/CMC-PVDF/ PVDF/Aluminum Foil, (f) Aluminum Foil/KAPTON/PVDF/CMC-PVDF/PVDF/Aluminum Foil NG.
PVDF–DMF–acetone almost covers the pores after the in-deep and spincoat process. Similarly, as shown in Fig. 3(c), the porous CMC film can significantly facilitate the absorption of the PDMS ethyl acetate/prepolymer solution and PDMS, thereby leading to a complete coating on the porous surface of the compressed CMC aerogel. Fig. 4 shows the low output of a compact NG based on Aluminum Foil/porous CMC Film/Aluminum Foil film without an air gap under periodic stress of 0.2 Mpa at a frequency 3 Hz prepared under the room temperature ambient conditions. For the Aluminum Foil/Porous CMC film/Aluminum Foil NG with dimensions 1 cm × 1 cm × 220 μm, the average value of the open-circuit voltage (Voc) generated from a single NG and two similar NGs that are connected in series is about 0.75 V and
under the room temperature ambient conditions introduced in section 3.2, it includes a highly porous structure with interconnected pores, as shown in Fig. 3(a). The porosity of the other CMC aerogel films reported in Ref. [12] is more than our CMC aerogel film, which can be attributed to different synthesis methods. They prepared CMC aerogel film after a freeze-drying process, followed by placement the CMC solution in a dry ice–acetone solution at −78 °C. Although the porosity of our CMC aerogel film is low, the synthesis process of the CMC aerogel film includes a simple and low-cost. So, using this aerogel is the easiest way to absorb the ethyl acetate/pre-polymer PDMS and acetone solution-DMF/ PVDF polymer solution. As shown in Fig. 3(b), the porosity of the CMC aerogel film decreases a lot to the fact that the solution
Fig. 2. Schematic illustration showing the electrical setup for the measurement of electrical output data of the NGs. 3
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Fig. 4. The electrical output (Voc) for a single NG and combined NGs based on layers Aluminum Foil/Porous CMC film/Aluminum Foil film by connecting two NGs in series.
1.45 V. It is better to know these outputs are also much smaller than the other studied NGs but acceptable only for the CMC aerogel film that has no active polymer materials such as PDMS or PVDF. However, the Voc of our CMC aerogel film is lower than that reported in Refs. [12,13], which can be attributed to the lower porosity originated from the different synthesis method as observed in FE-SEM images. This lower porosity is due to the building the aerogels in the room temperature ambient conditions. That is, we have not used devices such as freezedrying or autoclave to synthesis our NGs [12,13]. It should also be noted that this is the first time a piezoelectric compound (sugar) and a CMC polymeric material has been taken to make a NGs. Fig. 5 shows the electric outputs (Voc and Isc) for all single NGs prepared in the room temperature ambient conditions without an air gap under a periodic pressure of 0.2 MPa at a frequency of 3 Hz, for a NG with a dimension of 1 cm × 1 cm × 220 μm. Fig. 6 shows a comparison of the outputs (Voc and Isc) for the single NGs and connected in parallel and series. As can be seen in histogram plots of Voc and Isc shown in Fig. 6a and b, the lowest output is belonging to CMC film. But the reason why the output of the porous CMC film is less than the rest is that no other polymer materials are used as an active material. Fig. 7 shows the electric outputs (Voc and Isc) of all NGs connected in series and parallel, prepared in the room temperature ambient conditions without an air gap under a periodic pressure of 0.2 MPa at a frequency of 3 Hz, for a NG with a dimension of 1 cm × 1 cm × 220 μm. The output of the NG made with the PDMS material is larger than the NG made with the PVDF material. Since the CMC-PDMS film is placed inside the oven, the ability to the flexibility of PDMS material is more than CMC-PVDF. While the action taken for PDMS is not suitable for the PVDF, because the PVDF is rapidly dried at room temperature but if then it is placed under the heat of the oven similar to CMC-PDMS film, the layers are arched and separated, so it loses its flexibility. To measure the current, if two NGs are connected in parallel, their outputs follow the superposition theorem. That is, if the positive charges are placed on positive charges and the negative charges are placed on negative charges, the output is equal to the sum of the outputs. But if two NGs are connected in series, the positive charges are placed on negative charges and output will be reduced so that it will neutralize each other. To measure the voltage, if two NGs are connected in series, their outputs will increase, while for parallel connecting, outputs will be reduced. Besides, if two NGs with the same output are connected in series, the output current will remain constant, and the output voltage will be the sum of the individual voltages. While if two NGs with the same output are connected in parallel, the output voltage will remain constant, and the output current will be the sum of the individual currents. It should be noted that if the output of the two NGs is not the same, for example, when the NGs are connected in parallel, NG having the lower current will weaken the current of other NG with higher current. Our results of Voc and Isc show the relatively good outputs
Fig. 3. FE-SEM images of porous aerogel films prepared under the room temperature ambient conditions at different magnifications; (a) CMC (b) CMCPVDF (c) CMC-PDMS.
4
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Fig. 6. Comparison of the values of Voc and Isc of an arrangement of (a), (b) the single TE-NGs and connected in, (c) series and (d) parallel for (1) porous CMC film, (2) PVDF/porous CMC film–PVDF/PVDF, (3) PVDF/porous CMC film–PVDF/PVDF/KAPTON, (4) PDMS/porous CMC film–PDMS/PDMS, (5) PDMS/porous CMC film–PDMS/PDMS/KAPTON.
NGs in series together. While, in piezoelectric NGs, for example, both negative and positive charges are generated on the plates. According to previous studies [15,16], we know that selecting polymeric materials with different abilities in obtaining or losing electrons leads to better outputs. Finally, we have tested the values of the voltage and current outputs under following four experiments. First; it is still a few months that goes through the synthesis of NGs, and it was observed that the NGs continued to contain the output that is about the same output as before. Hence, keeping NGs in normal environmental conditions does not cause any disruption in NGs. Second; we placed some NGs under different temperature conditions (including temperatures of 100 °C and 150 °C as well as low temperature). It is found that TE-NGs are more active under high temperatures due to the presence of their polymer materials and also contain higher output. But the polymeric materials are gradually losing their activity at low temperatures, and as a result, their output is reduced. Third; the values of Voc and Isc for TE-NGs were measured at various frequencies, and we also observed that at the higher frequency, the current output is also increased. Besides, these TE-NGs uniformly pressurized over their surface, the output voltage considerable and more can be given to us [17]. Fourth; Other electrodes, such as copper foil was tested to replace the aluminum foil and it was found that the conductivity of copper foil is much more than aluminum foil, which results better output of NGs.
Fig. 5. The electric outputs (Voc and Isc) generated by various single compact NGs under a compressive stress of 0.2 MPa at a frequency of 3 Hz. Various compact NGs fabricated using (a) PDMS/porous CMC film–PDMS/PDMS, (b) PDMS/porous CMC film–PDMS/PDMS/KAPTON, (c) PVDF/porous CMC film–PVDF/PVDF (d) PVDF/porous CMC film–PVDF/PVDF/KAPTON.
(depending on the conditions of their synthesis under the room temperature ambient condition), while these values are lower than those one reported in Refs. [12–14]. However, it can be attributed to the method of preparing our samples under room temperature ambient conditions. It results in lower porosity with respect to that than prepared by ultra-advanced devices such as freeze-drying [12,13]. Although the low output is perhaps a disadvantage, we able to prepare it at the lowest cost and at laboratory room temperature, and the devices which it is also found in every laboratory. So when aerogel film is made at laboratory room temperature, because the holes are limited and the polymer solution is less in the porosity, or rather, then the cavities have a lower absorption capacity. Since these polymer materials contain charges, the NG made in the room temperature ambient conditions carries fewer charges than the NG prepared by the ultra-advanced devices such as freeze-drying. The other advantage of these NGs with respect to the other NGs such as piezoelectric NGs is that the negative and positive charges place on two separated electrodes, which makes it easy to connect the several
4. Conclusion In this paper, the synthesis of a lightweight, flexible, and cost-effective TE-NGs, switching the selection of the materials along with the composition of sugar, which is a piezoelectric material, have been investigated. Here, we have proposed a simple and clear production process for the production of high quality and low-cost energy facilities which are flexible for various applications such as automatically turn on active sensors and electronic devices. Then, the morphology, and voltage and current outputs of the different TE-NGs have been compared to the previous reports. The results show that selecting materials with different abilities in obtaining or losing electrons leads to a better output. Therefore, some materials tend to lose electrons (positive triboelectric) due to their capabilities and their manufacturing conditions, while some other materials tend to absorb electrons (negative 5
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voltage and current also significantly increased. We hope that this research will bring new hopes in the field of flexible energy absorbent materials that the importance and demand for which is increasing. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgment The financial support of the Iran National Science Foundation (INSF) under Grant number 95806516 is acknowledged. References [1] J. Holdren, Sustainability and energy, Science 315 (2007) 737. [2] V.S. Arunachalam, L. Elizabeth, Fleischer, Harnessing materials for energy, MRS Bull. 33 (4) (2008). [3] N. Seung, J.-S.-S. Cha, M.-K. Seong, J.-K. Hyun, J.-P. Young, K. Sang-Woo, M.K. Jong, Sound-Driven piezoelectric nanowire-based nano-generators, Adv. Mater. 22 (2010) 4726–4730. [4] M.S. Dresselhaus, G. Chen, M.Y. Tang, R.G. Yang, H. Lee, D.Z. Wang, Z.F. Ren, J.P. Fleurial, P. Gogna, New directions for low-dimensional thermoelectric materials, Adv. Mater. 19 (8) (2007) 1043–1053. [5] X.D.S. Wang, H. J, J. Liu, Z.L. Wang, Direct-current nano-generator driven by ultrasonic, Science 316 (2007) 102–105. [6] M.S. Dresselhaus, G. Chen, M.Y. Tang, R.G. Yang, H. Lee, D.Z. Wang, Z.F. Ren, J.P. Fleurial, P. Gogna, New directions for low-dimensional thermoelectric materials, Adv. Mater. 19 (8) (2007) 1043–1053. [7] Z.L. Wang, Piezoelectric nano-generators based on zinc oxide nanowire arrays, Science 312 (2006) 242–245. [8] X. Sheng, Q. Yong, X. Chen, W. Yaguang, Y. Rusen, W. Zhong Lin, Self-powered nanowire devices, Nat. Nanotechnol. 5 (2010) 366–373. [9] D. Choi, M.Y. Choi, W.M. Choi, H.J. Shin, H.K. Park, J.S. Seo, J. Park, S.J. Chae, Y.H. Lee, S.W. Kim, J.Y. Choi, S.Y. Lee, J.M. Kim, Fully rollable transparent nanogenerators based on graphene electrodes, Adv. Mater. 22 (2010) 2187–2192. [10] T.-C. Hou, Y. Yang, H. Zhang, J. Chen, L.-J. Chen, Z.L. Wang, Triboelectric nanogenerator built inside shoe insole for harvesting walking energy, Nano Energy 2 (5) (2013) 62-856. [11] H. Zhang, Y. Yang, T.-C. Hou, Y. Su, C. Hu, Z.L. Wang, Triboelectric nano-generator built inside clothes for self-powered glucose biosensor, Nano Energy 2 (5) (2013) 24-1019. [12] T. Yanfeng, Z. Qifeng, C. Bo, Ma Zhenqiang, G. Shaoqin, A new class of flexible nanogenerators consisting of porous aerogel films driven by mechanoradicals, Adv. Nano Energy 38 (2017) 401–411. [13] Z. Qifeng, C. Zhiyong, M. Zhenqiang, G. Shaoqin, Cellulose nanofibril/reduced graphene oxide/carbon nanotube hybrid aerogels for highly flexible and all-solidstate supercapacitors, ACS Appl. Mater. Interfaces 7 (2015) 3263–3271. [14] S. Masato, M. Youhei, H. Shigeo, S. Yusuke, Y. Katsuhiro, Sh Shigetaka, Triboelectricity in polymers: effects of the ionic nature of carbon–carbon bonds in the polymer main chain on charge due to yield of mechano-anions produced by heterogeneous scission of the carbon–carbon bond by mechanical fracture, J. Electrost. 62 (2004) 35–50. [15] K. Asano, Y. Higashiyama, K. Yatsuzuka, K. Yamanaka, The behavior of emitted charge cloud from an axisymmetric ion-flow anemometer. Industry Applications Society Annual Meeting, J. Electrost. 37 (1996) 39–52. [16] D. Davies, Charge generation on dielectric surfaces, J. Phys. D Appl. Phys. 2 (11) (1969) 1533. [17] F.-R. Fan, Z.-Q. Tian, Z.L. Wang, Flexible triboelectric generator, Nano Energy 1 (2) (2012) 34-328.
Fig. 7. The electric outputs (Voc and Isc) generated by various series and parallel compact NGs under a compressive stress of 0.2 MPa at a frequency of 3 Hz. (a) PDMS/porous CMC film–PDMS/PDMS, (b) PDMS/porous CMC film–PDMS/PDMS/KAPTON, (c) PVDF/porous CMC film–PVDF/PVDF (d) PVDF/porous CMC film–PVDF/PVDF/KAPTON.
triboelectric materials). Therefore, materials must be selected to the highest differences in terms of triboelectric properties. It was noted that it is possible to use a series of the synthesis processes and operations on the surface to increase friction between the surfaces. It was also observed with increasing the pressure and the frequency, the values of
6
Contents lists available at ScienceDirect
Current Applied Physics journal homepage: www.elsevier.com/locate/cap
Facile and low-cost synthesis of flexible nano-generators based on polymeric and porous aerogel materials Morteza Beyranvand, Ahmad Gholizadeh∗ School of Physics, Damghan University (DU), Damghan, Iran
A R T I C LE I N FO
A B S T R A C T
Keywords: Triboelectric nanogenerator Porous aerogel material Polymeric materials Triboelectricity
Triboelectric nano-generators (TE-NGs) can be utilized as a power supply for wireless systems, sensors, and operators. In this paper, new flexible TE-NGs that use sodium carboxymethyl cellulose (CMC), poly dimethyl siloxane (PDMS), polyvinylidene fluoride (PVDF), poly (4,4′-oxydiphenylene-pyromellitimide) (KAPTON) films and also sugar as a piezoelectric material were developed and are reported. Also, the outputs of NGs made by linear power under a periodic pressure of ~ 0.2 MPa at a frequency of 3 Hz showed that the highest output of NGs are related to PDMS–KATTON, PDMS, PVDF–KAPTON, PVDF, CMC NGs, respectively. It has been also observed that NGs connected in series to each other have a higher output than paralleled NGs so that their voltages increase at higher frequencies. Besides, a significant point is that the NGs are made in a low-cost, affordable, and environmentally-friendly route, which is a superior characteristic with respect to the rest of the NGs.
1. Introduction With global warming and rising energy crisis, trying to access the green and renewable energy sources is one of the critical challenges [1,2]. Photovoltaics, thermal electricity, and electromagnetic induction are the technologies that are used well for energy harvesting [3–5]. However, the size of systems and devices that they sometimes are being used in inaccessible environments, it's getting smaller every day and the use of conventional batteries will not any help because of the larger size of the battery than the size of the nano-scale. Also, sensors or systems which can be used for medical applications are placed inside the body or for example, in military applications need to hide or put them in dust, rain, wet or dark. So one of the most important and main challenges is the issue of feeding these devices. Energy harvesting from mechanical vibrations which are routinely day today and at all hours of the day in our environment, and converting these vibrations into electricity has been one of the goals of nanotechnology. Hence the design and synthesis of multi-purpose self-powered systems with small size, high sensitivity and much lower power consumption such as triboelectric and piezoelectric NGs which can absorb energy efficiently from the natural environment and convert it into electrical energy, have been very much considered [3]. Triboelectric nano-generators (TE-NG) can be used as a power supply for wireless systems, sensors, and operators, which operate in a different area as medical, military, and
∗
environmental issues. The structure of these NGs consists of two layers, including TE materials and a separator in the middle of it as well as suitable electrodes for the transfer of charges to the external circuit. After the contact and intermittent separation of these two layers, due to movements of mechanical environments, including wares of water, wind or body movements, resident electrical charges are generated by electrostatic induction and from one substance to another are transferred. In 2006, the first NG consist of a ZnO nano-wire, was designed by Wang and Sang [6]. The force produced by probe tip of atomic force microscope (AFM) acts on a ZnO nanowire and distorts the nanowire. ZnO piezoelectric property creates an electrical field in the direction of the force applied to the nanowire. The small potential output obtained by the nano-wire has a sharp peak with a maximum of 6 mV and shows the negative amount with respect to the bottom of nanowire. When AFM tip is at the starting point of contact with nanowire, due to the presence of a reverse-biased Schottky junction, there is no potential output for the output of the NGs. The potential output in NGs, only time is generated that AFM tip with the compressed side of the nanowire is in contact [7]. Improving the prototype output power of a direct current NGs, was made by eliminating the use of AFM to create the mechanical movement inside nanowires [5]. These NGs were designed in 2007 by Wang et al. [8]. In these NGs, zigzag-shaped metal electrode is used instead of
Corresponding author. E-mail addresses: [email protected], [email protected] (A. Gholizadeh).
https://doi.org/10.1016/j.cap.2019.11.009 Received 10 August 2019; Received in revised form 25 October 2019; Accepted 11 November 2019 1567-1739/ © 2019 Korean Physical Society. Published by Elsevier B.V. All rights reserved.
Please cite this article as: Morteza Beyranvand and Ahmad Gholizadeh, Current Applied Physics, https://doi.org/10.1016/j.cap.2019.11.009
Current Applied Physics xxx (xxxx) xxx–xxx
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using the AFM. The zigzag-shaped electrode that placed above the nanowires is similar to the AFMs but made from platinum-coated silicon wafer. The potential output value created with dimension 6 mm2 is about 10 mV. An innovative approach for access to AC NGs is using the ZnO nanowire arrays that their two ends are partially placed on electrodes [9,10]. In this NG, which was designed by Xu in 2010, a low frequency and alternating mechanical shock on the surface of the upper electrode is applied and generates an alternating pulse at the outlet of NG. In this NG, using polymer material PMMA, which surrounds the nanowires, the stability and mechanical hardness of the whole machine increases, and a short circuit between the substrate and electrode, is prevented. Zhang et al. [11], produced electricity from mechanical energy created by putting the TE-NG structure on the shoe floor when walking. The synthesis process starts by creating a pattern from the PDMS layer. Zhang et al. [12], studied on the synthesis of biosensors for blood sugar regulation. The structure of their NGs was such that were attached to the person's clothing, where the mechanical energy generated by the movement of the individual clothes led to the production of electricity for feeding biomass sensor [11–13]. In this paper, synthesis of the triboelectric NGs based on the materials CMC, KAPTON, PVDF, PDMS as well as sugar used as a piezoelectric material have been investigated. Proper placements of these layers consist of flexible porous polymers, and incorporation of appropriate and efficient materials can lead to many potential applications. This work also presents a simple, environmentally friendly, and cost-effective method to synthesis the flexible TE-NGs.
the previous section. To prepare the NG based on the porous CMC/ PDMS aerogel film, first, the PDMS solution was prepared from a prepolymer PDMS, pharmaceutical agent, and Ethyl acetate with a ratio 10:1:20. Then, compressed CMC aerogel was dipped into a PDMS solution. A well-drained aerogel film was placed under the hood for 2.45 h to evaporate the solvent and then held at 100 °C for 1.30 h. The CMC/PDMS aerogel film was spin-coated on both sides with a mixture of the pre-polymer PDMS and the drug agent (no solvent) with a ratio of 10:1. The sample was again kept at 100 °C for 1.15 h. After that, PDMS/ (CMC/PDMS)/PDMS film (1 cm × 1 cm in area × 220 μm thickness) was cut. Finally, aluminum foil was used on both sides of three-layer film to obtain a NGs. Schematic illustration for the preparation of the sample is shown in Fig. 1(c). The detailed information on the preparation of other types of aerogel films can be found below.
2. Experimental
Here, the synthesis process of the compressed CMC film is similar to the previous section 2.2. To prepare the PVDF/CMC–PVDF/PVDF NG, first, DMF (15 cc) was slowly added to acetone (10 cc), and then PVDF (4.5 g) was slowly added to the mixture of the DMF-acetone and thereafter wait for 1.3 h until the solution PVDF-DMF-acetone ultimately be gelatinous. The compressed CMC aerogel film was dipped into the PVDF-DMF-acetone solution using a vacuum-assisted liquid filling method to enable the solution to penetrate the inner pores. The aerogel completely coated for 30min was placed underneath the hood to evaporate the solvent. The CMC-PVDF aerogel film was spin-coated on both sides with a mixture of the pre-polymer PVDF-DMF. The PVDF/ CMC-PVDF/PVDF film was cut into pieces (1 cm × 1 cm in area × 220 μm thickness). After that, the aluminum foil is used on both sides of the three-layer film to make the NG, as shown in Fig. 1(e).
2.4. Step-by-step preparation of aluminum foil/KAPTON/PDMS/CMCPDMS/PDMS/aluminum foil NG Here, the synthesis process of the compressed CMC and PDMS/ (CMC/PDMS)/PDMS films is similar to previous sections 2.2 and 2.3, respectively. Then, the PDMS/(CMC/PDMS)/PDMS was spin-coated on the one side with a KAPTON layer. After that, the aluminum foil is used on both sides of the four-layer film to obtain the NG, as shown in Fig. 1(d). 2.5. Step-by-step preparation of aluminum foil/PVDF/CMC–PVDF/PVDF/ aluminum foil NG
2.1. Materials Sodium carboxymethyl cellulose (CMC), polydimethyl siloxane (PDMS), polyvinylidene fluoride (PVDF), dimethylformamide (DMF), poly (4,4′-oxydiphenylene-pyromellitimide) (KAPTON), benzoic acid, ethyl acetate were purchased from Sigma-Aldrich. Here, we introduced a new method for synthesis of CMC, CMC-PDMS, and CMC-PVDF aerogel films. 2.2. Step–by–step preparation of the aluminum foil/CMC/aluminum foil NG To prepare the compressed CMC film, first 0.5 g CMC was mixed with a solution containing 0.1 g sugar and 40 cc deionized water and then wait at least 45 min until CMC and sugar are completely dissolved in water. Besides, in another beaker, 3.25 g benzoic acid was poured on 20 cc alcohols and then remains 5 min until thoroughly mixing. Finally, alcohol-benzoic acid solution added slowly to carboxymethyl cellulosesugar-water. Then, a circular white mass appears in the solution obtained from carboxymethyl cellulose-deionized water-benzoic acid-alcohol. Ultimately, obtained solution set initially for 10 h under the IR light with distance 20 cm, until thoroughly water has evaporated, then it takes a gelatinous form and after that, it poured into pre-embedded molds and placed it in the oven for 4 h at 180 °C. Then, the almost dried gelation material was pressed to reduce its pores and strengthen it. Finally, it placed in the oven again up to 8 h at 100 °C until completely benzoic acid removed from the material to prepare the porous aerogel film. The synthesis process of the porous aerogel film is shown in Fig. 1(a). Aluminum foil is used on both sides of the CMC layer to obtain NGs, as shown in Fig. 1(b).
2.6. Step–by–step preparation of aluminum foil/KAPTON/PVDF/ CMCPVDF/PVDF/aluminum foil NG Here, the synthesis process of the compressed CMC and PVDF/CMCPVDF/PVDF films is similar to previous sections 2.2 and 2.5, respectively. To prepare the KAPTON/PVDF/CMC-PVDF/PVDF, the PVDF/ CMC-PVDF/PVDF film was spin-coated on the one side with a KAPTON layer and then aluminum foil was placed on both sides of the four-layer film to obtain the NG as shown in Fig. 1(f). 2.7. Characterization of the NGs Field-Emission Scanning Electron Microscope (FE–SEM, MIRA3 model; TESCAN) was used to measure and display the porosity of the synthesized aerogel NGs. The electrical output data of the NGs were recorded using an I–V Meter Device. Schematic illustration showing the electrical setup for the measurement of the electrical output data of the NGs is in Fig. 2. 3. Results and discussion
2.3. Step-by-step preparation of aluminum foil/PDMS/CMC-PDMS/ PDMS/aluminum foil NG
Fig. 3 shows the microstructure of CMC, CMC-PVDF, and CMCPDMS aerogel films. Although the CMC aerogel film has been prepared
Here, the synthesis process of the compressed CMC film is similar to 2
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Fig. 1. (a) The synthesis process of the porous aerogel film. Schematic illustration for the preparation of NG (b) Aluminum Foil/CMC/Aluminum Foil, (c) Aluminum Foil/PDMS/CMC-PDMS/PDMS/Aluminum Foil, (d) Aluminum Foil/KAPTON/PDMS/CMC-PDMS/PDMS/Aluminum Foil, (e) Aluminum Foil/PVDF/CMC-PVDF/ PVDF/Aluminum Foil, (f) Aluminum Foil/KAPTON/PVDF/CMC-PVDF/PVDF/Aluminum Foil NG.
PVDF–DMF–acetone almost covers the pores after the in-deep and spincoat process. Similarly, as shown in Fig. 3(c), the porous CMC film can significantly facilitate the absorption of the PDMS ethyl acetate/prepolymer solution and PDMS, thereby leading to a complete coating on the porous surface of the compressed CMC aerogel. Fig. 4 shows the low output of a compact NG based on Aluminum Foil/porous CMC Film/Aluminum Foil film without an air gap under periodic stress of 0.2 Mpa at a frequency 3 Hz prepared under the room temperature ambient conditions. For the Aluminum Foil/Porous CMC film/Aluminum Foil NG with dimensions 1 cm × 1 cm × 220 μm, the average value of the open-circuit voltage (Voc) generated from a single NG and two similar NGs that are connected in series is about 0.75 V and
under the room temperature ambient conditions introduced in section 3.2, it includes a highly porous structure with interconnected pores, as shown in Fig. 3(a). The porosity of the other CMC aerogel films reported in Ref. [12] is more than our CMC aerogel film, which can be attributed to different synthesis methods. They prepared CMC aerogel film after a freeze-drying process, followed by placement the CMC solution in a dry ice–acetone solution at −78 °C. Although the porosity of our CMC aerogel film is low, the synthesis process of the CMC aerogel film includes a simple and low-cost. So, using this aerogel is the easiest way to absorb the ethyl acetate/pre-polymer PDMS and acetone solution-DMF/ PVDF polymer solution. As shown in Fig. 3(b), the porosity of the CMC aerogel film decreases a lot to the fact that the solution
Fig. 2. Schematic illustration showing the electrical setup for the measurement of electrical output data of the NGs. 3
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Fig. 4. The electrical output (Voc) for a single NG and combined NGs based on layers Aluminum Foil/Porous CMC film/Aluminum Foil film by connecting two NGs in series.
1.45 V. It is better to know these outputs are also much smaller than the other studied NGs but acceptable only for the CMC aerogel film that has no active polymer materials such as PDMS or PVDF. However, the Voc of our CMC aerogel film is lower than that reported in Refs. [12,13], which can be attributed to the lower porosity originated from the different synthesis method as observed in FE-SEM images. This lower porosity is due to the building the aerogels in the room temperature ambient conditions. That is, we have not used devices such as freezedrying or autoclave to synthesis our NGs [12,13]. It should also be noted that this is the first time a piezoelectric compound (sugar) and a CMC polymeric material has been taken to make a NGs. Fig. 5 shows the electric outputs (Voc and Isc) for all single NGs prepared in the room temperature ambient conditions without an air gap under a periodic pressure of 0.2 MPa at a frequency of 3 Hz, for a NG with a dimension of 1 cm × 1 cm × 220 μm. Fig. 6 shows a comparison of the outputs (Voc and Isc) for the single NGs and connected in parallel and series. As can be seen in histogram plots of Voc and Isc shown in Fig. 6a and b, the lowest output is belonging to CMC film. But the reason why the output of the porous CMC film is less than the rest is that no other polymer materials are used as an active material. Fig. 7 shows the electric outputs (Voc and Isc) of all NGs connected in series and parallel, prepared in the room temperature ambient conditions without an air gap under a periodic pressure of 0.2 MPa at a frequency of 3 Hz, for a NG with a dimension of 1 cm × 1 cm × 220 μm. The output of the NG made with the PDMS material is larger than the NG made with the PVDF material. Since the CMC-PDMS film is placed inside the oven, the ability to the flexibility of PDMS material is more than CMC-PVDF. While the action taken for PDMS is not suitable for the PVDF, because the PVDF is rapidly dried at room temperature but if then it is placed under the heat of the oven similar to CMC-PDMS film, the layers are arched and separated, so it loses its flexibility. To measure the current, if two NGs are connected in parallel, their outputs follow the superposition theorem. That is, if the positive charges are placed on positive charges and the negative charges are placed on negative charges, the output is equal to the sum of the outputs. But if two NGs are connected in series, the positive charges are placed on negative charges and output will be reduced so that it will neutralize each other. To measure the voltage, if two NGs are connected in series, their outputs will increase, while for parallel connecting, outputs will be reduced. Besides, if two NGs with the same output are connected in series, the output current will remain constant, and the output voltage will be the sum of the individual voltages. While if two NGs with the same output are connected in parallel, the output voltage will remain constant, and the output current will be the sum of the individual currents. It should be noted that if the output of the two NGs is not the same, for example, when the NGs are connected in parallel, NG having the lower current will weaken the current of other NG with higher current. Our results of Voc and Isc show the relatively good outputs
Fig. 3. FE-SEM images of porous aerogel films prepared under the room temperature ambient conditions at different magnifications; (a) CMC (b) CMCPVDF (c) CMC-PDMS.
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Fig. 6. Comparison of the values of Voc and Isc of an arrangement of (a), (b) the single TE-NGs and connected in, (c) series and (d) parallel for (1) porous CMC film, (2) PVDF/porous CMC film–PVDF/PVDF, (3) PVDF/porous CMC film–PVDF/PVDF/KAPTON, (4) PDMS/porous CMC film–PDMS/PDMS, (5) PDMS/porous CMC film–PDMS/PDMS/KAPTON.
NGs in series together. While, in piezoelectric NGs, for example, both negative and positive charges are generated on the plates. According to previous studies [15,16], we know that selecting polymeric materials with different abilities in obtaining or losing electrons leads to better outputs. Finally, we have tested the values of the voltage and current outputs under following four experiments. First; it is still a few months that goes through the synthesis of NGs, and it was observed that the NGs continued to contain the output that is about the same output as before. Hence, keeping NGs in normal environmental conditions does not cause any disruption in NGs. Second; we placed some NGs under different temperature conditions (including temperatures of 100 °C and 150 °C as well as low temperature). It is found that TE-NGs are more active under high temperatures due to the presence of their polymer materials and also contain higher output. But the polymeric materials are gradually losing their activity at low temperatures, and as a result, their output is reduced. Third; the values of Voc and Isc for TE-NGs were measured at various frequencies, and we also observed that at the higher frequency, the current output is also increased. Besides, these TE-NGs uniformly pressurized over their surface, the output voltage considerable and more can be given to us [17]. Fourth; Other electrodes, such as copper foil was tested to replace the aluminum foil and it was found that the conductivity of copper foil is much more than aluminum foil, which results better output of NGs.
Fig. 5. The electric outputs (Voc and Isc) generated by various single compact NGs under a compressive stress of 0.2 MPa at a frequency of 3 Hz. Various compact NGs fabricated using (a) PDMS/porous CMC film–PDMS/PDMS, (b) PDMS/porous CMC film–PDMS/PDMS/KAPTON, (c) PVDF/porous CMC film–PVDF/PVDF (d) PVDF/porous CMC film–PVDF/PVDF/KAPTON.
(depending on the conditions of their synthesis under the room temperature ambient condition), while these values are lower than those one reported in Refs. [12–14]. However, it can be attributed to the method of preparing our samples under room temperature ambient conditions. It results in lower porosity with respect to that than prepared by ultra-advanced devices such as freeze-drying [12,13]. Although the low output is perhaps a disadvantage, we able to prepare it at the lowest cost and at laboratory room temperature, and the devices which it is also found in every laboratory. So when aerogel film is made at laboratory room temperature, because the holes are limited and the polymer solution is less in the porosity, or rather, then the cavities have a lower absorption capacity. Since these polymer materials contain charges, the NG made in the room temperature ambient conditions carries fewer charges than the NG prepared by the ultra-advanced devices such as freeze-drying. The other advantage of these NGs with respect to the other NGs such as piezoelectric NGs is that the negative and positive charges place on two separated electrodes, which makes it easy to connect the several
4. Conclusion In this paper, the synthesis of a lightweight, flexible, and cost-effective TE-NGs, switching the selection of the materials along with the composition of sugar, which is a piezoelectric material, have been investigated. Here, we have proposed a simple and clear production process for the production of high quality and low-cost energy facilities which are flexible for various applications such as automatically turn on active sensors and electronic devices. Then, the morphology, and voltage and current outputs of the different TE-NGs have been compared to the previous reports. The results show that selecting materials with different abilities in obtaining or losing electrons leads to a better output. Therefore, some materials tend to lose electrons (positive triboelectric) due to their capabilities and their manufacturing conditions, while some other materials tend to absorb electrons (negative 5
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voltage and current also significantly increased. We hope that this research will bring new hopes in the field of flexible energy absorbent materials that the importance and demand for which is increasing. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgment The financial support of the Iran National Science Foundation (INSF) under Grant number 95806516 is acknowledged. References [1] J. Holdren, Sustainability and energy, Science 315 (2007) 737. [2] V.S. Arunachalam, L. Elizabeth, Fleischer, Harnessing materials for energy, MRS Bull. 33 (4) (2008). [3] N. Seung, J.-S.-S. Cha, M.-K. Seong, J.-K. Hyun, J.-P. Young, K. Sang-Woo, M.K. Jong, Sound-Driven piezoelectric nanowire-based nano-generators, Adv. Mater. 22 (2010) 4726–4730. [4] M.S. Dresselhaus, G. Chen, M.Y. Tang, R.G. Yang, H. Lee, D.Z. Wang, Z.F. Ren, J.P. Fleurial, P. Gogna, New directions for low-dimensional thermoelectric materials, Adv. Mater. 19 (8) (2007) 1043–1053. [5] X.D.S. Wang, H. J, J. Liu, Z.L. Wang, Direct-current nano-generator driven by ultrasonic, Science 316 (2007) 102–105. [6] M.S. Dresselhaus, G. Chen, M.Y. Tang, R.G. Yang, H. Lee, D.Z. Wang, Z.F. Ren, J.P. Fleurial, P. Gogna, New directions for low-dimensional thermoelectric materials, Adv. Mater. 19 (8) (2007) 1043–1053. [7] Z.L. Wang, Piezoelectric nano-generators based on zinc oxide nanowire arrays, Science 312 (2006) 242–245. [8] X. Sheng, Q. Yong, X. Chen, W. Yaguang, Y. Rusen, W. Zhong Lin, Self-powered nanowire devices, Nat. Nanotechnol. 5 (2010) 366–373. [9] D. Choi, M.Y. Choi, W.M. Choi, H.J. Shin, H.K. Park, J.S. Seo, J. Park, S.J. Chae, Y.H. Lee, S.W. Kim, J.Y. Choi, S.Y. Lee, J.M. Kim, Fully rollable transparent nanogenerators based on graphene electrodes, Adv. Mater. 22 (2010) 2187–2192. [10] T.-C. Hou, Y. Yang, H. Zhang, J. Chen, L.-J. Chen, Z.L. Wang, Triboelectric nanogenerator built inside shoe insole for harvesting walking energy, Nano Energy 2 (5) (2013) 62-856. [11] H. Zhang, Y. Yang, T.-C. Hou, Y. Su, C. Hu, Z.L. Wang, Triboelectric nano-generator built inside clothes for self-powered glucose biosensor, Nano Energy 2 (5) (2013) 24-1019. [12] T. Yanfeng, Z. Qifeng, C. Bo, Ma Zhenqiang, G. Shaoqin, A new class of flexible nanogenerators consisting of porous aerogel films driven by mechanoradicals, Adv. Nano Energy 38 (2017) 401–411. [13] Z. Qifeng, C. Zhiyong, M. Zhenqiang, G. Shaoqin, Cellulose nanofibril/reduced graphene oxide/carbon nanotube hybrid aerogels for highly flexible and all-solidstate supercapacitors, ACS Appl. Mater. Interfaces 7 (2015) 3263–3271. [14] S. Masato, M. Youhei, H. Shigeo, S. Yusuke, Y. Katsuhiro, Sh Shigetaka, Triboelectricity in polymers: effects of the ionic nature of carbon–carbon bonds in the polymer main chain on charge due to yield of mechano-anions produced by heterogeneous scission of the carbon–carbon bond by mechanical fracture, J. Electrost. 62 (2004) 35–50. [15] K. Asano, Y. Higashiyama, K. Yatsuzuka, K. Yamanaka, The behavior of emitted charge cloud from an axisymmetric ion-flow anemometer. Industry Applications Society Annual Meeting, J. Electrost. 37 (1996) 39–52. [16] D. Davies, Charge generation on dielectric surfaces, J. Phys. D Appl. Phys. 2 (11) (1969) 1533. [17] F.-R. Fan, Z.-Q. Tian, Z.L. Wang, Flexible triboelectric generator, Nano Energy 1 (2) (2012) 34-328.
Fig. 7. The electric outputs (Voc and Isc) generated by various series and parallel compact NGs under a compressive stress of 0.2 MPa at a frequency of 3 Hz. (a) PDMS/porous CMC film–PDMS/PDMS, (b) PDMS/porous CMC film–PDMS/PDMS/KAPTON, (c) PVDF/porous CMC film–PVDF/PVDF (d) PVDF/porous CMC film–PVDF/PVDF/KAPTON.
triboelectric materials). Therefore, materials must be selected to the highest differences in terms of triboelectric properties. It was noted that it is possible to use a series of the synthesis processes and operations on the surface to increase friction between the surfaces. It was also observed with increasing the pressure and the frequency, the values of
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