- Email: [email protected]
A MEMS-BASED MICRO-BIOPSY ACTUATOR FOR CAPSULAR ENDOSCOPE USING LIGA PROCESS
A MEMS-BASED MICRO-BIOPSY ACTUATOR FOR CAPSULAR ENDOSCOPE USING LIGA PROCESS Sunkil Park*, Kyo-in Koo*, Gil-sub Kim*, HyunMin Choi*, Myeong-Jun Jung*, Seoung Min Bang**, Si Young Song**, and Dongil "Dan" Cho*, 1 *
School of Electrical Engineering and Computer Science, ASRI, NBSRC, ISRC, NAVRC, Seoul National University, Korea **Department of Internal Medicine, Yonsei University College of Medicine, Korea
Abstract: This paper presents a LiGA (German acronym for LIthografie, Galvanoformung, Abformung) based micro biopsy actuator for the capsular endoscope. The proposed fabricated actuator aims to extract sample tissues inside small gastric intestines, that cannot be reached by conventional biopsy. The actuator size is 10 mm in diameter and 1.8 mm in length. The mechanism is of a slider-crank type. The actuator consists of trigger, rotational module, and micro biopsy tool. The core components are fabricated using the LiGA process, for overcoming the limitations in accuracy of conventional precision machining. Copyright © 2006 IFAC Keywords: Capsular endoscope, actuator, LiGA, biopsy, x-ray
1. Introduction It is becoming increasingly common to find research relating to capsular endoscopes replacing conventional wire endoscopes. PillCam (GivenImaging, Israel), OMOM (Jinshan, China), and Endo Capsule (Olympus, Japan) were commercialized in July of 2001, March of 2005 and October of 2005, respectively. MiRO was developed by the Intelligent Microsystem Center (Seoul, Korea) in March of 2005. In addition, Norika3 (RFsystems, Japan) and SmartPill (Smartpill, US) are developing similar products. These capsular endoscopes can transfer 1
To whom correspondence should be addressed: [email protected]; + (82) 2- 880-8371, Fax +82-2-877-9304 Seoul National University, San 56-1, Shinlim-dong, Kwanak-gu, Seoul, 151-742, Korea
images in all gastro-intestines and cause little discomfort to patients when swallowing the capsules. Conventional wire endoscopes, are characteristic of continuous discomfort and limited diagnostic scope. Even though capsular endoscopes have these advantages over conventional wire endoscopes, they are not expected to completely replace conventional wire endoscopes, because of their single function as an image transport. In this paper, a MEMS (Microelectromechanical Systems) based micro biopsy actuator is developed for the multi-function capsular endoscope. This actuator was designed for integration with a capsular endoscope. To overcome the limitation of conventional precision machining, the actuator was fabricated using the LiGA (German acronym for LIthografie, Galvanoformung, Abformung) process.
20
2. Mechanism and design The MiRO has a diameter of 10 mm and height of 26 mm. A space of diameter 10 mm and height 2 mm is permitted for a micro biopsy actuator, because of other components of the capsular endoscope such as CCD camera, image transport module, telemetry system, and battery. The actuator (diameter 10 mm and height 1.8 mm) was designed and fabricated using the LiGA process, which is smaller than the space permitted. A Si micro spike was developed as a micro biopsy tool without an actuator (Byun, et al., 2005). The design of the Si micro spike is applied to a biopsy component of the actuator. The slider-crank mechanism was utilized for spike actuating, as shown in Fig. 1. The actuating force is stored at a torsional spring (Diameter 0.14 mm). The spring triggering is performed by a melting polymer string. The polymer string is melted by allowing current to heat the SMA (Shape Alloy Memory), which coils the polymer string. Then, the micro spike strokes the target tissue. All the dimensions of the actuator’s components and specification data are extracted from preliminary research (Byun, et al., 2005).
mechanism is used in a variety of machines, when there is a need to convert rotary motion into stroke motion and vice versa. The desired crank motion is developed using the following inverse kinematical relationships, from the desired slider motion in Cartesian space (all notations are specified in Fig. 2.):
Fig. 2. The stroke motion components schematic ⎡ x (t )2 + r 2 + l 2 ⎤ ⎥ ϕ = cos−1 ⎢⎢ 1 ⎥ ⎢⎣ (2x 1 (t ) r ) ⎥⎦
(1)
Where as illustrated in Fig. 2, x1 (t ) =1 +r −x (t ) , In addition, from Fig. 2, the Cartesian position of the slider can be expressed as: ⎛ ⎞ ⎛r 2 ⎞ x (t ) = r ⎜⎜⎜1 − cos(ϕ) + ⎜⎜ ⎟⎟⎟ sin2(ϕ)⎟⎟⎟ ⎜⎝ 2l ⎠⎟ ⎜⎝ ⎠⎟
(1)
(2)
(2)
Differentiating with respect to time results in the following:
⎛dx d ϕ ⎞⎟ dx dϕ = ⎜⎜ ⎟⎟ = J dt dt ⎝⎜ d ϕ dt ⎠ ⎡⎛ 2 ⎞ ⎤ Where, J = dx = r sinϕ + ⎢⎜⎜r ⎟⎟ sin(2ϕ)⎥ ⎟ ⎢ ⎥ ⎜ ⎟ dϕ ⎣⎢⎝ 2l ⎠ ⎦⎥
(3) Fig. 1. Schematics of tissue sampling mechanism of micro biopsy actuator (Top view, before actuation (1), actuation mode (2), Bottom view, after actuation (3)) 3. Modelling In order to make the back and forth motion, with approximately 2.5 mm distance, the slider-crank mechanism (Nagchaudhuri, 2005) was applied. This
(3)
2 2 ⎡ 2 ⎤ Thus, d ϕ = J −1 ⎢ d x − d J d ϕ ⎥ 2 2 ⎢ dt dt ⎥⎦⎥ dt ⎣⎢ dt
⎡ d 2 x ⎛d ϕ ⎞2 ⎧⎪ ⎫ ⎛ r ⎞⎟ ⎪⎤⎥ ⎪ ⎢ ⎜ ⎟ ⎪ ⎜ ⎢ dt 2 − ⎜⎝⎜ dt ⎠⎟⎟ ⎪⎨r cos (ϕ) + ⎝⎜⎜ l ⎠⎟⎟ cos (2ϕ)⎪⎬⎥ ⎪⎦⎥ ⎩⎪ ⎭ ⎢ =⎣ ⎡ ⎤ ⎛ r 2 ⎞⎟ ⎢r sin (ϕ) + ⎜⎜ ⎟ sin (2ϕ)⎥ ⎢ ⎥ ⎜⎝ 2l ⎠⎟⎟ ⎣⎢ ⎦⎥
(4)
To carry out the computer simulation, the following parameter values are chosen: Crank radius, r = 2.15 mm, connecting rod length, l =3.4 mm. The simulations results (Fig. 3 and 4) demonstrate that the maximum slider stroke is approximately 4.48 mm.
21
PMER P-LA 900PM photoresist is coated on the deposited seed layer with 1000 rpm, 35 s using spin coater. The PMER photoresist is uniformly deposited with 27 µm thickness. The wafer is exposed and developed sequentially. Gold electroplating is performed to manufacture the X-ray absorber structure.
(a) Polyimide film, wafer bonding
Fig. 3. The simulated position of the slider (Cartesian) for the first crank cycle (1st cycle)
(b) Seed (Ti/Au) depo. and PR pattering
(c) Au electroplating
(d) PR strip, release
Si Wafer
Dry PR
Polyimide film
Photo resist
Gold
Fig. 5. Process flow of x-ray mask fabrication using polyimide film
Fig. 4. The simulated velocity of the slider for the first crank cycle (1st cycle) 4. Fabrication of micro biopsy actuator To integrate the actuator to the permitted space (diameter 10 mm and height 2 mm), the actuator component cannot be fabricated by conventional precision machining. Therefore, the LiGA process is applied to making precise dimension fabrication with fine sidewall roughness and high aspect ratio structure. The recent development of the LIGA process, which consists of x-ray lithography, electroplating and electromoulding, has led to the high-volume fabrication of various plastic MEMS components. DXRL (Deep x-ray lithography), the first step in the LIGA process, is considered an important process step, because it determines the quality and accuracy of the final product. In addition, DXRL can provide a final product several millimeters high, with an aspect ratio exceeding 100:1. 4.1. Fabrication of X-ray mask A polyimide film of thickness 125 µm is bonded on the wafer using dry photoreist, and then the Ti /Au (300 Å / 1500 Å) seed layer is deposited by a metal sputter on the polyimide film for electroplating. TOK
4.2. X-ray exposure & electromolding process The LiGA process flow is presented in Fig. 6. A PMMA bonded on a titanium substrate is irradiated using the fabricated X-ray mask. The irradiated PMMA is developed at room temperature with a specific organic developer, commonly known as GG developer (2-(2-butoxy-ethox) ethanol 60%, Morpholine 20%, Ethanolamine 5%, DI water 15%). Nickel electroplating is performed on the developed PMMA mold. Finally, the core components are fabricated by removing the mould parts, as shown in Fig. 7 (Kim, et al., 2005; Moon, et al., 2005). Irradiation is performed at the PLS (Pohang Accelerator Laboratory) in Pohang, Korea. It operates at 2.5 GeV with an electron current between 110 and 190 mA. Among many beam lines, the 9C1 beam line is equipped with the 250 µm Be filters and a 50 µm polyimide filter. The distance in air from the polyimide filter to the exposure vacuum jig is 18 cm. The theoretical calculation of the critical wavelength is 2.0 Å at the end of the beam line. The x-ray beam size was 180ⅹ15 mm2, the PMMA samples were irradiated under a scanning velocity of 3 cms-1. For fast and effective development of irradiated polymer samples, the bottom dose of the sample must be greater than 4 kJcm-3. In addition, the maximum dose under the membrane must be less than 20 kJcm-3. For making the components of the micro biopsy actuator, the PMMA as an x-ray photoresist is exposed to 4.0 kJcm-3 of bottom dose.
22
5. Experiment & Analysis of micro biopsy actuator Figure 8 presents the assembled micro biopsy actuator. First, for triggering the micro biopsy actuator, the SMA of diameter 0.0015" is connected to a 3 V button cell battery. Then, the spring fixation pin mounting torsional spring is rotated 180 ° anticlockwise, for readying tissue samples. A spring fixation pin is then fixed with polymer wire of diameter 0.1 mm. When the power switch is turned on, the spring is rotated clockwise 180° and the micro biopsy tool moves back and forth. The micro biopsy actuator is tested with the force measurement system, when the micro biopsy tool moves forward. Figure 9 presents the experimental setting which consists of a load-cell with a strain gauge, spring fixation pin, indicator, XYZ stage, and notebook connected with a serial (RS-232) port indicator. Figure 10 presents the measured force when the spike moves forward. The measured force is 0.66 N, which is greater than the tissue penetration force of 0.22 N. The tissue penetration force is extracted from the preliminary tissue sampling experiment with micro biopsy tools (Byun, et. al., 2005).
Fig. 6. LiGA process flow (X-ray exposure diagram (1), electromolding process (2))
2 .8
mm
mm
5. 1
5 mm
Fig. 8. Photograph of assembled actuator of diameter 10 mm using components fabricated by the LiGA process (1) Load-cell 4.1 mm
m 5m 2.8 mm
4 .2
(2)
(3)
Fig. 7. FE-SEM photograph of fabricated actuator components using LiGA process (Top view, micro spike (1), connecting bar (2), spring fixation pin (3))
Actuator
Battery
Fig. 9. Setup photograph for force measurement with load-cell, indicator, and PCB
23
Fig. 10. Graph of measured force of micro biopsy actuator with load-cell
Kim, J.T and C.G, Choi, "Absorber embedded x-ray mask for high aspect ratio polymeric optical components," IOP Journal of Micromechanics and Microengineering, vol. 15, pp. 615-619, Jan 2005 Moon, S.J and S.S, Lee, "A novel fabrication method of a microneedle array using inclined deep x-ray exposure," IOP Journal of Micromechanics and Microengineering, vol. 15, pp. 903-911, Mar 2005. Park, S.K., A.R. Lee, M.J. Jeong, H. M. Choi, S.Y. Song, S.M. Bang, S. J. Paik, J. M. Lim, D.Y. Jeon, S.K. Lee, C.N. Chu, and D.I. Cho, "A Disposable MEMS-Based Micro-Biopsy Catheter for the Minimally Invasive Tissue Sampling," IEEE/RSJ International Conference on Intelligent Robots and Systems, Edmonton, Alberta, Canada, Aug. 2-6, 2005.
6. Conclusion In this paper, a micro biopsy actuator for capsular endoscope integration, is presented. This actuator has a diameter 10 mm and height 1.8 mm. The core components are fabricated using the LiGA process to overcome the limitations of conventional precision machining. It reliably performs with a 3 V button cell battery. The tissue biopsy experiment is currently being performed using a pig’s small intestine ex vivo, with the fabricated micro biopsy actuator. 7. Acknowledgment This research has been supported by the Intelligent Microsystem Center(IMC;http://www.microsystem. re.kr), which carries out one of the 21st century's Frontier R&D Projects sponsored by the Korea Ministry Of Commerce, Industry and Energy, by a grant of the Korea Health 21 R&D Project, Ministry of Health & Welfare, Republic of Korea (A05-0251B20604-05N1-00010A), by the SRC/ERC program of MOST/KOSEF (Grant # R11-2000-075-01001-0), and the Pohang Accelerator Laboratory (PAL; http://pls.postech.ac.kr ) REFERENCES Byun, S.W., J.M. Lim, S.J. Paik, A.R. Lee, K.I. Koo, S.K. Park, J.H. Park, B.D. Choi, J.M. Seo, K.A. Kim, H. Chung, S.Y. Song, D.Y. Jeon, S.S. Lee, and D. I. Cho, "Novel Barbed Micro-Spikes for Micro-Scale Biopsy," IOP Journal of Micromechanics and Microengineering, vol. 15, no. 6, pp. 1279-1284, 2005 Nagchaudhuri, A, "MECHATRONIC REDESIGN OF SLIDER CRANK MECHANISM, "Proceedings of IMECE2002 ASME International Mechanical Engineering Congress & Exposition, IMECE2002-32482, New Orleans, Louisiana, November 17-22, 2002
24
School of Electrical Engineering and Computer Science, ASRI, NBSRC, ISRC, NAVRC, Seoul National University, Korea **Department of Internal Medicine, Yonsei University College of Medicine, Korea
Abstract: This paper presents a LiGA (German acronym for LIthografie, Galvanoformung, Abformung) based micro biopsy actuator for the capsular endoscope. The proposed fabricated actuator aims to extract sample tissues inside small gastric intestines, that cannot be reached by conventional biopsy. The actuator size is 10 mm in diameter and 1.8 mm in length. The mechanism is of a slider-crank type. The actuator consists of trigger, rotational module, and micro biopsy tool. The core components are fabricated using the LiGA process, for overcoming the limitations in accuracy of conventional precision machining. Copyright © 2006 IFAC Keywords: Capsular endoscope, actuator, LiGA, biopsy, x-ray
1. Introduction It is becoming increasingly common to find research relating to capsular endoscopes replacing conventional wire endoscopes. PillCam (GivenImaging, Israel), OMOM (Jinshan, China), and Endo Capsule (Olympus, Japan) were commercialized in July of 2001, March of 2005 and October of 2005, respectively. MiRO was developed by the Intelligent Microsystem Center (Seoul, Korea) in March of 2005. In addition, Norika3 (RFsystems, Japan) and SmartPill (Smartpill, US) are developing similar products. These capsular endoscopes can transfer 1
To whom correspondence should be addressed: [email protected]; + (82) 2- 880-8371, Fax +82-2-877-9304 Seoul National University, San 56-1, Shinlim-dong, Kwanak-gu, Seoul, 151-742, Korea
images in all gastro-intestines and cause little discomfort to patients when swallowing the capsules. Conventional wire endoscopes, are characteristic of continuous discomfort and limited diagnostic scope. Even though capsular endoscopes have these advantages over conventional wire endoscopes, they are not expected to completely replace conventional wire endoscopes, because of their single function as an image transport. In this paper, a MEMS (Microelectromechanical Systems) based micro biopsy actuator is developed for the multi-function capsular endoscope. This actuator was designed for integration with a capsular endoscope. To overcome the limitation of conventional precision machining, the actuator was fabricated using the LiGA (German acronym for LIthografie, Galvanoformung, Abformung) process.
20
2. Mechanism and design The MiRO has a diameter of 10 mm and height of 26 mm. A space of diameter 10 mm and height 2 mm is permitted for a micro biopsy actuator, because of other components of the capsular endoscope such as CCD camera, image transport module, telemetry system, and battery. The actuator (diameter 10 mm and height 1.8 mm) was designed and fabricated using the LiGA process, which is smaller than the space permitted. A Si micro spike was developed as a micro biopsy tool without an actuator (Byun, et al., 2005). The design of the Si micro spike is applied to a biopsy component of the actuator. The slider-crank mechanism was utilized for spike actuating, as shown in Fig. 1. The actuating force is stored at a torsional spring (Diameter 0.14 mm). The spring triggering is performed by a melting polymer string. The polymer string is melted by allowing current to heat the SMA (Shape Alloy Memory), which coils the polymer string. Then, the micro spike strokes the target tissue. All the dimensions of the actuator’s components and specification data are extracted from preliminary research (Byun, et al., 2005).
mechanism is used in a variety of machines, when there is a need to convert rotary motion into stroke motion and vice versa. The desired crank motion is developed using the following inverse kinematical relationships, from the desired slider motion in Cartesian space (all notations are specified in Fig. 2.):
Fig. 2. The stroke motion components schematic ⎡ x (t )2 + r 2 + l 2 ⎤ ⎥ ϕ = cos−1 ⎢⎢ 1 ⎥ ⎢⎣ (2x 1 (t ) r ) ⎥⎦
(1)
Where as illustrated in Fig. 2, x1 (t ) =1 +r −x (t ) , In addition, from Fig. 2, the Cartesian position of the slider can be expressed as: ⎛ ⎞ ⎛r 2 ⎞ x (t ) = r ⎜⎜⎜1 − cos(ϕ) + ⎜⎜ ⎟⎟⎟ sin2(ϕ)⎟⎟⎟ ⎜⎝ 2l ⎠⎟ ⎜⎝ ⎠⎟
(1)
(2)
(2)
Differentiating with respect to time results in the following:
⎛dx d ϕ ⎞⎟ dx dϕ = ⎜⎜ ⎟⎟ = J dt dt ⎝⎜ d ϕ dt ⎠ ⎡⎛ 2 ⎞ ⎤ Where, J = dx = r sinϕ + ⎢⎜⎜r ⎟⎟ sin(2ϕ)⎥ ⎟ ⎢ ⎥ ⎜ ⎟ dϕ ⎣⎢⎝ 2l ⎠ ⎦⎥
(3) Fig. 1. Schematics of tissue sampling mechanism of micro biopsy actuator (Top view, before actuation (1), actuation mode (2), Bottom view, after actuation (3)) 3. Modelling In order to make the back and forth motion, with approximately 2.5 mm distance, the slider-crank mechanism (Nagchaudhuri, 2005) was applied. This
(3)
2 2 ⎡ 2 ⎤ Thus, d ϕ = J −1 ⎢ d x − d J d ϕ ⎥ 2 2 ⎢ dt dt ⎥⎦⎥ dt ⎣⎢ dt
⎡ d 2 x ⎛d ϕ ⎞2 ⎧⎪ ⎫ ⎛ r ⎞⎟ ⎪⎤⎥ ⎪ ⎢ ⎜ ⎟ ⎪ ⎜ ⎢ dt 2 − ⎜⎝⎜ dt ⎠⎟⎟ ⎪⎨r cos (ϕ) + ⎝⎜⎜ l ⎠⎟⎟ cos (2ϕ)⎪⎬⎥ ⎪⎦⎥ ⎩⎪ ⎭ ⎢ =⎣ ⎡ ⎤ ⎛ r 2 ⎞⎟ ⎢r sin (ϕ) + ⎜⎜ ⎟ sin (2ϕ)⎥ ⎢ ⎥ ⎜⎝ 2l ⎠⎟⎟ ⎣⎢ ⎦⎥
(4)
To carry out the computer simulation, the following parameter values are chosen: Crank radius, r = 2.15 mm, connecting rod length, l =3.4 mm. The simulations results (Fig. 3 and 4) demonstrate that the maximum slider stroke is approximately 4.48 mm.
21
PMER P-LA 900PM photoresist is coated on the deposited seed layer with 1000 rpm, 35 s using spin coater. The PMER photoresist is uniformly deposited with 27 µm thickness. The wafer is exposed and developed sequentially. Gold electroplating is performed to manufacture the X-ray absorber structure.
(a) Polyimide film, wafer bonding
Fig. 3. The simulated position of the slider (Cartesian) for the first crank cycle (1st cycle)
(b) Seed (Ti/Au) depo. and PR pattering
(c) Au electroplating
(d) PR strip, release
Si Wafer
Dry PR
Polyimide film
Photo resist
Gold
Fig. 5. Process flow of x-ray mask fabrication using polyimide film
Fig. 4. The simulated velocity of the slider for the first crank cycle (1st cycle) 4. Fabrication of micro biopsy actuator To integrate the actuator to the permitted space (diameter 10 mm and height 2 mm), the actuator component cannot be fabricated by conventional precision machining. Therefore, the LiGA process is applied to making precise dimension fabrication with fine sidewall roughness and high aspect ratio structure. The recent development of the LIGA process, which consists of x-ray lithography, electroplating and electromoulding, has led to the high-volume fabrication of various plastic MEMS components. DXRL (Deep x-ray lithography), the first step in the LIGA process, is considered an important process step, because it determines the quality and accuracy of the final product. In addition, DXRL can provide a final product several millimeters high, with an aspect ratio exceeding 100:1. 4.1. Fabrication of X-ray mask A polyimide film of thickness 125 µm is bonded on the wafer using dry photoreist, and then the Ti /Au (300 Å / 1500 Å) seed layer is deposited by a metal sputter on the polyimide film for electroplating. TOK
4.2. X-ray exposure & electromolding process The LiGA process flow is presented in Fig. 6. A PMMA bonded on a titanium substrate is irradiated using the fabricated X-ray mask. The irradiated PMMA is developed at room temperature with a specific organic developer, commonly known as GG developer (2-(2-butoxy-ethox) ethanol 60%, Morpholine 20%, Ethanolamine 5%, DI water 15%). Nickel electroplating is performed on the developed PMMA mold. Finally, the core components are fabricated by removing the mould parts, as shown in Fig. 7 (Kim, et al., 2005; Moon, et al., 2005). Irradiation is performed at the PLS (Pohang Accelerator Laboratory) in Pohang, Korea. It operates at 2.5 GeV with an electron current between 110 and 190 mA. Among many beam lines, the 9C1 beam line is equipped with the 250 µm Be filters and a 50 µm polyimide filter. The distance in air from the polyimide filter to the exposure vacuum jig is 18 cm. The theoretical calculation of the critical wavelength is 2.0 Å at the end of the beam line. The x-ray beam size was 180ⅹ15 mm2, the PMMA samples were irradiated under a scanning velocity of 3 cms-1. For fast and effective development of irradiated polymer samples, the bottom dose of the sample must be greater than 4 kJcm-3. In addition, the maximum dose under the membrane must be less than 20 kJcm-3. For making the components of the micro biopsy actuator, the PMMA as an x-ray photoresist is exposed to 4.0 kJcm-3 of bottom dose.
22
5. Experiment & Analysis of micro biopsy actuator Figure 8 presents the assembled micro biopsy actuator. First, for triggering the micro biopsy actuator, the SMA of diameter 0.0015" is connected to a 3 V button cell battery. Then, the spring fixation pin mounting torsional spring is rotated 180 ° anticlockwise, for readying tissue samples. A spring fixation pin is then fixed with polymer wire of diameter 0.1 mm. When the power switch is turned on, the spring is rotated clockwise 180° and the micro biopsy tool moves back and forth. The micro biopsy actuator is tested with the force measurement system, when the micro biopsy tool moves forward. Figure 9 presents the experimental setting which consists of a load-cell with a strain gauge, spring fixation pin, indicator, XYZ stage, and notebook connected with a serial (RS-232) port indicator. Figure 10 presents the measured force when the spike moves forward. The measured force is 0.66 N, which is greater than the tissue penetration force of 0.22 N. The tissue penetration force is extracted from the preliminary tissue sampling experiment with micro biopsy tools (Byun, et. al., 2005).
Fig. 6. LiGA process flow (X-ray exposure diagram (1), electromolding process (2))
2 .8
mm
mm
5. 1
5 mm
Fig. 8. Photograph of assembled actuator of diameter 10 mm using components fabricated by the LiGA process (1) Load-cell 4.1 mm
m 5m 2.8 mm
4 .2
(2)
(3)
Fig. 7. FE-SEM photograph of fabricated actuator components using LiGA process (Top view, micro spike (1), connecting bar (2), spring fixation pin (3))
Actuator
Battery
Fig. 9. Setup photograph for force measurement with load-cell, indicator, and PCB
23
Fig. 10. Graph of measured force of micro biopsy actuator with load-cell
Kim, J.T and C.G, Choi, "Absorber embedded x-ray mask for high aspect ratio polymeric optical components," IOP Journal of Micromechanics and Microengineering, vol. 15, pp. 615-619, Jan 2005 Moon, S.J and S.S, Lee, "A novel fabrication method of a microneedle array using inclined deep x-ray exposure," IOP Journal of Micromechanics and Microengineering, vol. 15, pp. 903-911, Mar 2005. Park, S.K., A.R. Lee, M.J. Jeong, H. M. Choi, S.Y. Song, S.M. Bang, S. J. Paik, J. M. Lim, D.Y. Jeon, S.K. Lee, C.N. Chu, and D.I. Cho, "A Disposable MEMS-Based Micro-Biopsy Catheter for the Minimally Invasive Tissue Sampling," IEEE/RSJ International Conference on Intelligent Robots and Systems, Edmonton, Alberta, Canada, Aug. 2-6, 2005.
6. Conclusion In this paper, a micro biopsy actuator for capsular endoscope integration, is presented. This actuator has a diameter 10 mm and height 1.8 mm. The core components are fabricated using the LiGA process to overcome the limitations of conventional precision machining. It reliably performs with a 3 V button cell battery. The tissue biopsy experiment is currently being performed using a pig’s small intestine ex vivo, with the fabricated micro biopsy actuator. 7. Acknowledgment This research has been supported by the Intelligent Microsystem Center(IMC;http://www.microsystem. re.kr), which carries out one of the 21st century's Frontier R&D Projects sponsored by the Korea Ministry Of Commerce, Industry and Energy, by a grant of the Korea Health 21 R&D Project, Ministry of Health & Welfare, Republic of Korea (A05-0251B20604-05N1-00010A), by the SRC/ERC program of MOST/KOSEF (Grant # R11-2000-075-01001-0), and the Pohang Accelerator Laboratory (PAL; http://pls.postech.ac.kr ) REFERENCES Byun, S.W., J.M. Lim, S.J. Paik, A.R. Lee, K.I. Koo, S.K. Park, J.H. Park, B.D. Choi, J.M. Seo, K.A. Kim, H. Chung, S.Y. Song, D.Y. Jeon, S.S. Lee, and D. I. Cho, "Novel Barbed Micro-Spikes for Micro-Scale Biopsy," IOP Journal of Micromechanics and Microengineering, vol. 15, no. 6, pp. 1279-1284, 2005 Nagchaudhuri, A, "MECHATRONIC REDESIGN OF SLIDER CRANK MECHANISM, "Proceedings of IMECE2002 ASME International Mechanical Engineering Congress & Exposition, IMECE2002-32482, New Orleans, Louisiana, November 17-22, 2002
24