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The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published. The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.

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The International Journal Of Engineering And Science (IJES) ||Volume||3 ||Issue|| 4||Pages|| 55-58||2014|| ISSN(e): 2319 – 1813 ISSN(p): 2319 – 1805 www.theijes.com The IJES Page 55 Design and Simulation of Electrothermally Activated Bidirectional Microtweezer Using PMMA for Biomedical Applications 1, Ritu Devi , 2, Vineet Bansal , 3, Dinesh Kumar 1, Ambala College of Engineering and Applied Research, Ambala 133101 2, Indian Institute of Technology, Mumbai 3, Department of Electronic Science, Kurukshetra University, Kurukshetra ------------------------------------------------------ABSTRACT---------------------------------------------------- The design and simulation of PMMA (Polymethylmethacrylate) microtweezer that can be used for the manipulation of biological species in solution with minimal desired interactions is done using COMSOL Multiphysics 4.2a. The electro thermally activated polymer bimorph microtweezer consists of two “hot-and- cold-arm” actuators with gold (Au) layer of 1 um thick on both sides of the actuator to provide bidirectional operation i.e. capable of producing displacement in two directions as a single device. It provides the total inward displacement of 11.38 µm and total outward displacement of 8.06 µm with applied potential of 1 volt. KEYWORDS: MEMS electrothermal actuation, bidirectional microtweezer, polymethylmethacrylate, gold ----------------------------------------------------------------------------------------------------------------- Date of Submission: 06 March 2014 Date of Publication: 05 April 2014 ---------------------------------------------------------------------------------------------------------------- I. INTRODUCTION In MEMS, microtweezers have great importance because of their vast application area. Applications of microtweezer ranges from micro manipulation i.e. manipulation of micro components to cell manipulation. There are different kinds of microtweezers depending upon the principle of actuation used such as piezoelectric, electrostatic, electrothermal and electromagnetic1 . Thermal actuation is mostly used as compared to other actuation mechanism because it provides larger forces and easier control. Thermal actuators are based on the principle of joule heating and thermal expansion 2, 3 .The substance that has higher coefficient of thermal expansion (CTE) provides larger displacement. CTE of polymers is larger as compare to semiconductors and metals4 . So, polymers provide larger displacement than semiconductors and metals. There are some other advantages of polymers over semiconductors and metals. These are lower stiffness, transparency, better biocompatibility, lower material cost and easier fabrication by mass replication technology5 . Like SU-8, PMMA is also a non conducting polymer. For making electrothermal devices it must be electrically conducting. This can be done by depositing a metal layer on its surface6 .Microtweezers developed using polymers provide larger displacement and gentle handling force that is ideally suitable for biological applications1 . PMMA (polymethyl methacrylate) is sustainable, environment friendly, has small Young’ modulus and high thermal expansion coefficient which makes it suitable for electrothermal application. Electrothermal actuators using PMMA requires less power for producing same displacement as compared to polysilicon electrothermal actuator4 . II. DESIGN AND SIMULATION In this paper a polymeric microtweezer designed using PMMA that can provide in-plane bidirectional operation. This design is based on two lateral thermal bimorph actuators7 with total length of microtweezer is 250 µm and initial tip opening of 30 µm. A gold layer of 1 µm thick is considered on inner side of narrow arm and outer side of wide arm that acts as heaters. The properties of PMMA and gold are listed in Table 1.
Design And Simulation Of Electrothermally... www.theijes.com The IJES Page 56 Table 1 Properties of PMMA and Gold It has four anchors out of which anchor A1 and A4 are connected to outer layer of gold while anchor A2 and A3 are connected to inner layer. Any one from anchors A1 and A2 is supplied with potential of 1 volt depending upon the direction of operation either inward or outward and A4 and A3 are connected to ground. Structure of microtweezer is shown in Figure 1. The design is simulated in MEMS module of COMSOL Multiphysics 4.2a. Figure 1 Geometrical representation electrothermal microtweezer III. RESULTS AND DISCUSSIONS This microrweezer provides bidirectional operation as single device depending upon the potential applied to either anchor A1 or anchor A2. When potential is applied to anchor A1, microtweezer gives converging displacement of 11.38 µm as shown in Figure.2. Figures 3 and 4 show the stress and temperature distribution for inward displacement of microtweezer, respectively. Figure 2 Total inward displacement in microtweezer Figure 3 Stress distributions for inward deflection of microtweezer Properties PMMA Gold Co-efficient of thermal expansion 70x10-6 per K 14.2x10-6 per K Thermal conductivity 0.19W/mK 317 W/mK Heat capacity 1420 J/Kg K 129 J/Kg K Density 1190 Kg/ m3 19300 Kg/m3 Young’s modulus 3x109 Pa 70x109 Pa Electrical conductivity 1x10-19 s/m 4.6x106 s/m Poisson ratio 0.4 0.44 Relative permittivity 3 ---
Design And Simulation Of Electrothermally... www.theijes.com The IJES Page 57 When the potential of 1 volt is applied at anchor A2 then, the microtweezer provides diverging displacement of 8.0613 µm as shown in Figure 5. The stress and temperature distributions for outward deflection of microtweezer are shown in Figures 6 and 7, respectively. Figure 4 Temperature distributions for inward deflection of microtweezer Figure 5 Total outward displacement in microtweezer Figure 6 Stress distribution for diverging displacement Figure 7 Temperature distributions for diverging displacement
Design And Simulation Of Electrothermally... www.theijes.com The IJES Page 58 The variations in inward and outward displacement of microtweezer with applied potential are graphically shown in igure 8. Figure 8 Inward and outward displacement with applied potential IV. CONCLUSIONS Most of microtweezers provide either converging displacement or diverging displacement but the device designed in this paper provides both i.e converging as well as diverging displacement which increases range of its deflection up to 46 µm. It can be used as a microtweezer for handling biological samples as PMMA being a biocompatible material. V. ACKNOWLEDGEMENT The authors are thankful to NPMASS for funding this activity and setting up a Design Center for research in MEMS/NEMS at Electronic Science Department, Kurukshetra University. VI. REFERENCES [1] R. Voicu, R. Muller, L. Eftime, “Design Optimization for an Electro-Thermally Actuated Polymeric Microgripper”, DTIP of MEMS and MEOMS, 9-11 April 2008. [2] TimothyMoulton, G.K. Ananthasuresh, “Micromechanical devices with embedded electro-thermal-compliant actuation”, Sensors and Actuators A 90, 38-48 (2001). [3] Roberto Venditti, Jacky S H Lee, Yu Sun and Dongqing Li, “An in-plane, bi-directional electrothermal MEMS actuator”, Journal of Micromechanics and Microengineering, vol. 16, 2067–2070 (2007). [4] V. Vidyaa , G. Arumaikkannu, “Hybrid Design of a Polymeric Electrothermal Actuator for Microgripper”, International Journal of Mechanical and Industrial Engineering (IJMIE), Volume-1, Issue-2, 31-35 (2011). [5] Susumu Sugiyama, Satoshi Amaya and Dzung Viet Dao, “Development of polymer MEMS process technology as an approach to a sustainable production system”, Advances in Natural Sciences: Nanoscience and Nanotechnology, vol. 3, 1-7 (2012). [6] Dan Sameoto, See-Ho Tsang, M. Parameswaran, “Polymer MEMS processing for multi-user applications” Sensors and Actuators A 134, 457-464 (2007). [7] J K Luo, A J Flewitt, S M Spearing, N A Fleck and W I Milne, “Comparison of microtweezers based on three lateral thermal actuator configurations”, Journal of Micromechnics and Microengineering, vol.- 15, 1294–1302 (2005).

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I03401055058

  • 1. The International Journal Of Engineering And Science (IJES) ||Volume||3 ||Issue|| 4||Pages|| 55-58||2014|| ISSN(e): 2319 – 1813 ISSN(p): 2319 – 1805 www.theijes.com The IJES Page 55 Design and Simulation of Electrothermally Activated Bidirectional Microtweezer Using PMMA for Biomedical Applications 1, Ritu Devi , 2, Vineet Bansal , 3, Dinesh Kumar 1, Ambala College of Engineering and Applied Research, Ambala 133101 2, Indian Institute of Technology, Mumbai 3, Department of Electronic Science, Kurukshetra University, Kurukshetra ------------------------------------------------------ABSTRACT---------------------------------------------------- The design and simulation of PMMA (Polymethylmethacrylate) microtweezer that can be used for the manipulation of biological species in solution with minimal desired interactions is done using COMSOL Multiphysics 4.2a. The electro thermally activated polymer bimorph microtweezer consists of two “hot-and- cold-arm” actuators with gold (Au) layer of 1 um thick on both sides of the actuator to provide bidirectional operation i.e. capable of producing displacement in two directions as a single device. It provides the total inward displacement of 11.38 µm and total outward displacement of 8.06 µm with applied potential of 1 volt. KEYWORDS: MEMS electrothermal actuation, bidirectional microtweezer, polymethylmethacrylate, gold ----------------------------------------------------------------------------------------------------------------- Date of Submission: 06 March 2014 Date of Publication: 05 April 2014 ---------------------------------------------------------------------------------------------------------------- I. INTRODUCTION In MEMS, microtweezers have great importance because of their vast application area. Applications of microtweezer ranges from micro manipulation i.e. manipulation of micro components to cell manipulation. There are different kinds of microtweezers depending upon the principle of actuation used such as piezoelectric, electrostatic, electrothermal and electromagnetic1 . Thermal actuation is mostly used as compared to other actuation mechanism because it provides larger forces and easier control. Thermal actuators are based on the principle of joule heating and thermal expansion 2, 3 .The substance that has higher coefficient of thermal expansion (CTE) provides larger displacement. CTE of polymers is larger as compare to semiconductors and metals4 . So, polymers provide larger displacement than semiconductors and metals. There are some other advantages of polymers over semiconductors and metals. These are lower stiffness, transparency, better biocompatibility, lower material cost and easier fabrication by mass replication technology5 . Like SU-8, PMMA is also a non conducting polymer. For making electrothermal devices it must be electrically conducting. This can be done by depositing a metal layer on its surface6 .Microtweezers developed using polymers provide larger displacement and gentle handling force that is ideally suitable for biological applications1 . PMMA (polymethyl methacrylate) is sustainable, environment friendly, has small Young’ modulus and high thermal expansion coefficient which makes it suitable for electrothermal application. Electrothermal actuators using PMMA requires less power for producing same displacement as compared to polysilicon electrothermal actuator4 . II. DESIGN AND SIMULATION In this paper a polymeric microtweezer designed using PMMA that can provide in-plane bidirectional operation. This design is based on two lateral thermal bimorph actuators7 with total length of microtweezer is 250 µm and initial tip opening of 30 µm. A gold layer of 1 µm thick is considered on inner side of narrow arm and outer side of wide arm that acts as heaters. The properties of PMMA and gold are listed in Table 1.
  • 2. Design And Simulation Of Electrothermally... www.theijes.com The IJES Page 56 Table 1 Properties of PMMA and Gold It has four anchors out of which anchor A1 and A4 are connected to outer layer of gold while anchor A2 and A3 are connected to inner layer. Any one from anchors A1 and A2 is supplied with potential of 1 volt depending upon the direction of operation either inward or outward and A4 and A3 are connected to ground. Structure of microtweezer is shown in Figure 1. The design is simulated in MEMS module of COMSOL Multiphysics 4.2a. Figure 1 Geometrical representation electrothermal microtweezer III. RESULTS AND DISCUSSIONS This microrweezer provides bidirectional operation as single device depending upon the potential applied to either anchor A1 or anchor A2. When potential is applied to anchor A1, microtweezer gives converging displacement of 11.38 µm as shown in Figure.2. Figures 3 and 4 show the stress and temperature distribution for inward displacement of microtweezer, respectively. Figure 2 Total inward displacement in microtweezer Figure 3 Stress distributions for inward deflection of microtweezer Properties PMMA Gold Co-efficient of thermal expansion 70x10-6 per K 14.2x10-6 per K Thermal conductivity 0.19W/mK 317 W/mK Heat capacity 1420 J/Kg K 129 J/Kg K Density 1190 Kg/ m3 19300 Kg/m3 Young’s modulus 3x109 Pa 70x109 Pa Electrical conductivity 1x10-19 s/m 4.6x106 s/m Poisson ratio 0.4 0.44 Relative permittivity 3 ---
  • 3. Design And Simulation Of Electrothermally... www.theijes.com The IJES Page 57 When the potential of 1 volt is applied at anchor A2 then, the microtweezer provides diverging displacement of 8.0613 µm as shown in Figure 5. The stress and temperature distributions for outward deflection of microtweezer are shown in Figures 6 and 7, respectively. Figure 4 Temperature distributions for inward deflection of microtweezer Figure 5 Total outward displacement in microtweezer Figure 6 Stress distribution for diverging displacement Figure 7 Temperature distributions for diverging displacement
  • 4. Design And Simulation Of Electrothermally... www.theijes.com The IJES Page 58 The variations in inward and outward displacement of microtweezer with applied potential are graphically shown in igure 8. Figure 8 Inward and outward displacement with applied potential IV. CONCLUSIONS Most of microtweezers provide either converging displacement or diverging displacement but the device designed in this paper provides both i.e converging as well as diverging displacement which increases range of its deflection up to 46 µm. It can be used as a microtweezer for handling biological samples as PMMA being a biocompatible material. V. ACKNOWLEDGEMENT The authors are thankful to NPMASS for funding this activity and setting up a Design Center for research in MEMS/NEMS at Electronic Science Department, Kurukshetra University. VI. REFERENCES [1] R. Voicu, R. Muller, L. Eftime, “Design Optimization for an Electro-Thermally Actuated Polymeric Microgripper”, DTIP of MEMS and MEOMS, 9-11 April 2008. [2] TimothyMoulton, G.K. Ananthasuresh, “Micromechanical devices with embedded electro-thermal-compliant actuation”, Sensors and Actuators A 90, 38-48 (2001). [3] Roberto Venditti, Jacky S H Lee, Yu Sun and Dongqing Li, “An in-plane, bi-directional electrothermal MEMS actuator”, Journal of Micromechanics and Microengineering, vol. 16, 2067–2070 (2007). [4] V. Vidyaa , G. Arumaikkannu, “Hybrid Design of a Polymeric Electrothermal Actuator for Microgripper”, International Journal of Mechanical and Industrial Engineering (IJMIE), Volume-1, Issue-2, 31-35 (2011). [5] Susumu Sugiyama, Satoshi Amaya and Dzung Viet Dao, “Development of polymer MEMS process technology as an approach to a sustainable production system”, Advances in Natural Sciences: Nanoscience and Nanotechnology, vol. 3, 1-7 (2012). [6] Dan Sameoto, See-Ho Tsang, M. Parameswaran, “Polymer MEMS processing for multi-user applications” Sensors and Actuators A 134, 457-464 (2007). [7] J K Luo, A J Flewitt, S M Spearing, N A Fleck and W I Milne, “Comparison of microtweezers based on three lateral thermal actuator configurations”, Journal of Micromechnics and Microengineering, vol.- 15, 1294–1302 (2005).