DIFFUSERTYPE PERISTALTIC MICROPUMP OPTIMIZATION: THEORY AND REALIZATION

DIFFUSERTYPE PERISTALTIC MICROPUMP OPTIMIZATION: THEORY AND REALIZATION Southern Taiwan University Institute of Mechatronic Science and Technology Ph.D. Thesis DIFFUSERTYPE PERISTALTIC MICROPUMP OPTIMIZATION: THEORY AND REALIZATION 擴散閥門蠕動式微型幫浦之最佳化:理論與實驗 Graduate Student: NgocBich Le Advisor：YiChu Hsu May, 2010 Institute of Mechatronic Science and Technology So u t h e rn Ta i w an U n i v e r s i t y Student no.: D96Z0201 Ph.D. Thesis DiffuserType Peristaltic Micropump Optimization: Theory and Realization Graduate Student: NgocBich Le i SOUTHERN TAIWAN UNIVERSITY INSTITUTE OF MECHATRONIC SCIENCE AND TECHNOLOGY STU DIFFUSERTYPE PERISTALTIC MICROPUMP OPTIMIZATION: THEORY AND REALIZATION 擴散閥門蠕動式微型幫浦之最佳化:理論與實驗 NgocBich Le LifeChip Laboratory Institute Of Mechatronic Science And Technology Southern Taiwan University Submitted to the Institute Of Mechatronic Science And Technology, Southern Taiwan University in partial fulfillment of the requirements for the degree of Doctor of Philosophy. Tainan, Taiwan, May 2010 ii The research described in this thesis was carried out at the life chip Laboratory, Mechanical Engineering Department, Southern Taiwan University, Tainan, Taiwan. Many persons have been involved in this work and I am very grateful for their help. Subject headings: μTAS microsystem technology micropump microvalves modeling iii 擴散閥門蠕動式微型幫浦之最佳化:理論與實驗 黎成心 南台科技大學機電科技研究所 中文摘要 摘要 蠕動型的擴散式塑膠微型幫浦相較於普通微型幫浦有著較佳的性能（例如：流 量、背壓等）。在製作及應用上也較便利（例如：便宜、輕巧以及用完即可丟棄 等）。因此本論文針對蠕動型的擴散式塑膠微型幫浦做出整體參數改善的研究討 論，包括致動薄膜厚度、致動器形狀、擴散閥之尺寸及腔體親水性等條件。首先 應用軟體分析計算出理論值（如：Mathematica, Matlab, OriginPro 等)，再以實驗的 數據加以佐證。本研究採用三種不同參數所設計出之蠕動型的擴散式塑膠微型幫 浦做出討論。其中兩個為相似的進口面積（約16000μm 2），但流道尺寸不同。一 為經過改善設計之參數，另一為對照組的尺寸。第三個也是採用改善設計但較小 的流道尺寸，進口面積為（80×80 μm2）。理論數值及實驗結果皆證明本論文之參 數調整可成功的運用於微型幫浦，可得到更佳設計之效能。 iv Thesis for the degree of Doctor of Philosophy at Southern Taiwan University, 2010 Abstract Diffuser type peristaltic micropump was reported primarily by the current group with the significant improvement of pump performance (i.e. flow rate, backpressure, and disposable…) owing to integrated diffuser elements and PMMA material. Continue to that achievement, this thesis presents an overall optimization process for diffuser type peristaltic micropump. Specifically, optimum process is performed for the key components such as actuatormembrane thickness, actuator shape, diffuser valve, chamber’s wettability. Specifically, theoretical calculation process was proposed with a simply application using some well known commercial packages (i.e. Mathematica, Matlab, OriginPro,…). Furthermore, experiment was conducted to validate the theoretical calculation process. Optimum actuator shape selection and membrane thickness was discussed using experiment combined with FEM analysis and theoretical calculation. Optimization process for diffuser element which is the most significant component for improving pump performance was introduced. In addition, the frequency dependent characteristic of the current designed diffuser element was investigated by utilizing two different methods, theoretical equivalent network calculation and SPICE (Simulation Program with Integrated Circuit Emphasis) analysis. Chamber’s wetting optimization for bubble free operation was performed by introducing and experimentally optimizing the hydrophilic material (TiO2) layer pattern. Three pump designs were then investigated to verify the overall optimization process. That is, two designs with the same channel characteristic (i.e. similar inlet area of 16000μm2) in which one is optimized and one is arbitrarily design were observed to validate the optimization process. In addition, another optimized design with different channel characteristic (i.e. inlet area is 80×80μm2) was investigated to first verify the optimization process and second investigate the effect of channel geometry on pump’s performance. v Acknowledgments First of all, I would like to dedicate my happiness and success to my deceased father who would be very proud and happy if reads this thesis. I would like to express my thanks to my mother, my fiancé and my family for everything they have been done to me. I want to thank my supervisor Prof. YiChu Hsu for support, encouragement and professional guidance. It has been a great pleasure to work with her. I also want to give special thanks to Mr. JiaHao Li, MauSheng Lin for all their help with different mechanical and electrical setups and all my other current and former colleagues at the Life Chip Laboratory for valuable help and discussion during the work. Thanks Ming Can, NanCan, JiaHao, MauSheng, YanTing, WeiChun, and YongXiong. I would like to express my gratitude to the many faculty professors especially Prof. ChinTu Lu, Zhu Chi Liang, Tai Zi Yao, who support me in software and experiment equipments as well as graduate students who helped this work come together. I am particularly indebted to Prof. ShangHe Lin, Director of Center for Development of Teaching and Learning, Southern Taiwan University of Technology, for all of his kindly help. I am thankful to my colleagues at Nong Lam University, Ho Chi Minh City, Vietnam, particularly to Prof. Hay Nguyen and Prof. Le Van Ban for their constant support and fruitful collaboration. I would like to thank Prof. LingSheng Jang, LifeChip Laboratory, instrumentation Chip Group, Department of Electrical Engineering, National Cheng Kung University for his valuable suggestions as well as his critical comments. I also would like to express my gratitude to Nanotechnology Center, National Cheng Kung University for experimental equipments supporting. My last thanks goes to my all the different friends that have been a part of my life during the last two and a half years. Thanks Tainan, May 2010, NgocBich Le vi Contents 中文摘要……………………………………………………………………………iii Abstract……………………………………………………………………….…………iv Acknowledgement…………………………………………………………………….....v List of figures…………………………………………………………………………….x List of tables……..…………………………………………………………….…….….xi Chapter 1: Introduction and motivation…………………………………….…...…..1 Chapter 2: Recent advance and application in micropump devices and theoretical concept…………………………………………………………………………..……....5 2.1. Recent applications ……………………………………………………..…………5 2.2 Summary on recent advanced and related works……………………...….……..6 2.3 Electrichydraulic analogy and SPICE modeling background……………..….14 2.3.1 Channel resistance ……………………………………………….…..….....14 2.3.2 Capacitance ………………………………………………………..……….14 2.3.3 Inductance of equivalent components in an electrical circuit…….…..….15 2.3.4 Diffuser valve efficiency…………………………………………………....15 2.3.5 SPICE modeling for diffuser micropump……………………………..….16 2.3.6 SPICE modeling for peristaltic micropump………………………...…….20 2.3.7 PZT actuation simulation…………………………………………..………25 Chapter 3: Investigation on the effect of actuatormembrane shape for pump’s performance improvement …………………………………..…………………..…..28 3.1. Introduction…………………………………………………………………..…..28 3.2. Design, Fabrication and Actuation Scheme……………………………………29 3.2.1 Design and fabrication……………………………………………………..29 3.2.2 Actuation scheme…………………………………………...….……..……..30 3.3. Experiments and Results……………………………………………………..….31 vii 3.3.1 Experimental setup…………………………………………………..……..31 3.3.2 Pump performance…………………………………………………..……...31 3.4. ANSYS simulations of actuatormembrane displacement………………..…....35 3.5. Results and discussion……………………………………………………..……..36 Chapter 4: Investigation on the effect of actuatormembrane thickness for pump’s performance improvement ………………………………………………….……….39 4.1 Introduction……………………………………………………………….………39 4.2 Theory……………………………………………………………………..……….39 4.3 Experiment for membrane thickness validation……………………..………….45 Chapter 5: Diffuser valve effects and its geometry design to improve the pump performance ……………………….………………………………………………….48 5.1 Introduction…………………………………………………………..…...………48 5.2. Diffuser valve effects and its geometries optimization…………………..……..48 5.3 Operation frequency dependent properties of diffuser valve…………..………51 5.4 Experiment…………………………………………………………..…………….54 Chapter 6: Bubble solving for microfluidic system and pump stability, robustness, and accuracy enhancement………………………………………………….……….62 6.1 Introduction…………………………………………………………….…………62 6.2. Basic concept on wetting and spreading dynamics………………….…………63 6.3. Experiment…………………………………………………………..……………66 6.3.1 TiO2 film stability evaluation……………………………………..………..66 6.3.1.1 Fabrication process of microwave plasma surface modification method..………………………………………………………………………………...66 6.3.1.2 Fabrication process of deposition method……………………..…………67 6.3.1.3 Time dependent evaluation……………………………………………..…68 6.3.1.4 Microwave plasma surface modification time dependent evaluation…....68 6.3.1.5 Wear resistance evaluation…………………………………………..……69 viii 6.3.2 Bubble observation experiment………………………………..…………..72 6.4. Results and Discussion………………………………………………..………….75 Chapter 7: Conclusions and future works……………………………..……………80 7.1 Conclusions……………………………………………………………..…………80 7.2 Future works………………………………………………………..…………….81 Reference………………………………………………………………..…………….83 Biography……………………………………………………………………………...90 Publication…………………………………………………………………………….92 List of symbols……………………………………………………………………..….93 ix List of figures Figure 1.1: Explosive view of diffusertype peristaltic micropump with PZT actuation . 3 Figure 2.1: Valve integration for calculating hydraulic resistance and inductance of diffuser .................................................................................................................... 14 Figure 2.2: Flow induced by compression of fluid......................................................... 14 Figure 2.3: Diffuser micropump equivalent circuit ........................................................ 19 Figure 2.4: Diffuser micropump output flow behavior in time domain at 200Hz operating frequency ................................................................................................ 19 Figure 2.5: Equivalent electrical circuits of a) actuatormembrane, b) chamber with resistance difference switch, and c) microchannelstubing. ................................... 22 Figure 2.6: Fourphase actuation sequence of peristaltic micropump. ........................... 23 Figure 2.7: Change in resistance during two halfcycles of pumping operation: a) membrane deflects in upward direction; and b) membrane deflects in downward direction. ................................................................................................................. 24 Figure 2.8: Block diagram of equivalent electrical circuit for peristaltic micropump. .. 25 Figure 3.1: Schematic overview of fabrication process.................................................. 30 Figure 3.2: Photograph showing fullyassembled peristaltic micropumps..................... 30 Figure 3.3: Schematic illustration of experimental setup ............................................... 31 Figure 3.4: Variation of peaktopeak actuatormembrane displacement with driving frequency at constant driving voltage of 100 Vpp.................................................. 32 Figure 3.5: Variation of flow rate with driving frequency at constant driving voltage of 100 Vpp................................................................................................................... 33 Figure 3.6: Variation of flow rate with driving voltage at constant driving frequency of 400 Hz..................................................................................................................... 34 Figure 3.7: Correlation between flow rate and back pressure at constant driving voltage of 120 Vpp .............................................................................................................. 34 Figure 3.8: Displacement contours of (a) square and (b) circular actuatormembrane structures in first resonance mode .......................................................................... 36 Figure 4.1: Internal stress behavior and moment balance of actuatormembrane under actuation.................................................................................................................. 39 Figure 4.2: Theoretical calculation of actuatormembrane displacement....................... 44 Figure 4.3: Theoretical calculation of the effect of glass plate thickness on actuatormembrane displacement ......................................................................................... 44 Figure 4.4: Theoritical calculation of the effect of bonding layer thickness on actuatormembrane displacement ......................................................................................... 45 Figure 4.5: Actuatormembrane sample ......................................................................... 45 Figure 4.6: Experimental and theoretical results of the effect of passive plate thickness on actuatormembrane displacement ...................................................................... 46 Figure 5.1: Diffuser element designed geometry............................................................ 49 Figure 5.2: Typical performance maps for flatwall diffusers 61. ............................... 50 Figure 5.3: Diffuser element best designs, a) 80 μm inlet width, and b) 127 μm inlet width. ...................................................................................................................... 51 Figure 5.4: Diffuser element equivalent network. .......................................................... 52 Figure 5.5: Diffuser element equivalent network for SPICE modeling. ........................ 53 Figure 5.6: Diffuser element rectification efficiency vs. operation frequency............... 54 Figure 5.7: Schematic overview of PMMA peristaltic micropump fabrication process.55 Figure 5.8: Geometry of diffuser valves and micropump chambers. ............................. 55 Figure 5.9: Completed peristaltic micropump. ............................................................... 56 Figure 5.10: Schematic illustration of experimental setup. ............................................ 57 x Figure 5.11: Variation of actuatormembrane displacement with driving frequency at constant driving voltage of 100 Vpp........................................................................ 58 Figure 5.12: Variation of flow rate with driving frequency at constant driving voltage of 100 Vpp.................................................................................................................... 58 Figure 5.13: Variation of maximum flow rate with back pressure for driving voltage of 100 Vpp and excitation frequency of 150 Hz. ......................................................... 60 Figure 6.1: Macroscopic picture of droplet spreading on a flat surface 73.................. 64 Figure 6.2: Experimental setup of microwave plasma surface modification. ................ 66 Figure 6.3: Deposition results for various TiO2 solution concentrations. ...................... 68 Figure 6.4: Contact angle of D.I. water resting on a PMMA wafer treated with microwave plasma a) within 12h of fabrication and b) after 1 week. .................... 69 Figure 6.5: Contact angle of D.I. water resting on a PMMA wafer treated with TiO2 deposition................................................................................................................ 69 Figure 6.6: Experimental results for samples with solution concentration ratios of a) 1:120 and b) 1:700. ................................................................................................. 70 Figure 6.7: Experiment setup for bubbles observation. .................................................. 73 Figure 6.8: a) Explosive view and b) geometry detail of micropump system. ............... 74 Figure 6.9: Experiment setup of micropump performance test and bubble observation.75 Figure 6.10: Fluid spreading dynamics of a) untreated, b) uniformly covered, c) ellipse, d) horizontal, and e) vertical strips. ........................................................................ 76 Figure 6.11: Spreading behavior and bubble formation mechanism of a) half, b) threesection, and c) foursection vertical strips. ............................................................. 76 Figure 6.12: Performance of micropumps. a) Flow rate and b) backpressure. ............. 77 Figure 6.13: Hydrophilic thin film observation using PLM …………………………...79 xi List of tables Table 2.1 Parameters and corresponding unit of diffuser micropump ........................... 18 Table 2.2 Corresponding unit for equivalent circuit components .................................. 18 Table 3.1 Experimental performance of two micropumps ............................................. 35 Table 3.2 Simulation parameters .................................................................................... 35 Table 3.3 Experimental and numerical results obtained for actuator displacement given various actuator geometries and dimensions .......................................................... 37 Table 4.1 Experimental results of samples displacement at 37.5 Hz ............................. 46 Table 5.1 Designed optimum parameters ....................................................................... 50 Table 5.2 Characteristics comparison of three designs................................................... 60 Table 6.1 Various contact angles and their corresponding solidliquid and liquidliquid interactions.............................................................................................................. 64 Table 6.2.1 TiO2 film properties for various concentration ratios (Opaque TiO2 thin film) ................................................................................................................................ 71 Table 6.3 Comparison between plasma and deposition methods………………...…….72 xii This presented thesis is based on the following papers: 1. Inertial effects on flow rate spectrum of diffuser micropumps YiChu Hsu, NgocBich Le J. Biomedical Microdevices, Volume 10, Number 5 October, 2008. 2. Equivalent electrical network for performance characterization of piezoelectric peristaltic micropump YiChu Hsu, and NgocBich Le J. Microfluidics and nanofluidics, Volume 7, Number 2 August, 2009. 3. An experimental and numerical investigation into the effects of the PZT actuator shape in polymethylmethacrylate (PMMA) peristaltic micropumps YiChu Hsu, JiaLong Hsu, and NgocBich Le J. Microsystem Technologies, v 15, n 4, April, 2009, p 565–571. 4. An experimental and numerical investigation into the effects of diffuser valves in polymethylmethacrylate (PMMA) peristaltic micropumps YiChu Hsu, JiaHao Li, and NgocBich Le J. Sensors and Actuators A: Physical, Volume 148, Issue 1, 4 November 2008, Pages 149157. 5. Investigation on hydrophilic modification for bubblefree operation in microfluidic systems and micropump applications NgocBich Le and YiChu Hsu J. Advances in Natural Sciences: Nanoscience and Nanotechnology 1 (2010) 015006 6. Investigation on The Frequency Discrepancy between ActuatorMembrane Displacement and Flow Rate Spectrum of Diaphragm Micropumps, YiChu Hsu and NgocBich Le Submited to JJAP for journal publication 7. Diffuser type PZT actuation peristaltic micropump optimization: theory and realization YiChu Hsu, NgocBich Le Processing for journal publication 8. Optimum Design and Investigation on Diffuser Polymethylmethacrylate (PMMA) Peristaltic Micropumps YiChu Hsu, NgocBich Le, MauSheng Lin, LingSheng Jang, 2009 IEEE international conference on robotics and automation, Kobe, Japan, May 1217, 2009. xiii The work has also been presented at the following international conferences: 1. YiChu Hsu, NgocBich Le, MauSheng Lin, LingSheng Jang, “Optimum Design and Investigation on Diffuser Polymethylmethacrylate (PMMA) Peristaltic Micropumps”, 2009 IEEE international conference on robotics and automation, Kobe, Japan, May 1217, 2009. 2. YiChu Hsu, and NgocBich Le, “Effects of the PZT Actuator Shape in Polymethylmethacrylate (PMMA) Peristaltic Micropumps: Experimental and Numerical Investigation”, 2008 International Symposium On Nano Science And Technology, Tainan, Taiwan, November 7, 2008. 3. YiChu Hsu, and NgocBich Le, “Diffuser polymethylmethacrylate (PMMA) peristaltic micropumps: Optimum design and investigation”, 2008 International Symposium On Nano Science And Technology, Tainan, Taiwan, November 7, 2008. 4. YiChu Hsu, and NgocBich Le, “Piezoelectric peristaltic micropump characterization using spice modeling with lumpedelement” , 2008 International Symposium On Nano Science And Technology, Tainan, Taiwan, November 7, 2008. 5. YiChu Hsu, NgocBich Le, “Investigation on The Frequency Shift Between ActuatorMembrane Displacement And Flow Rate Spectrum Of Diaphragm Micropumps”, AsiaPacific Conference on Transducers and MicroNano Technology 2008, Tainan, Taiwan from 2225 June, 2008, (2008). 6. YiChu Hsu, JiaLong Hsu, NgocBich Le, “An Experimental and Numerical Investigation into the Effects of the PZT Actuator Shape in Polymethylmethacrylate (PMMA) Peristaltic Micropumps”, AsiaPacific Conference on Transducers and MicroNano Technology 2008, Tainan, Taiwan from 2225 June, 2008, (2008). 7. NgocBich Le, YiChu Hsu, LingSheng Jang, Mausheng Lin, “Inertance Effects To Diffuser Micropumps Flow Rate Spectrum”, Proceedings of MNHT2008, MicroNanoscale Heat Transfer International Conference (ASME), January 69, (2008) 8. YiChu Hsu , NgocBich Le, “Investigation On The Frequency Shift Of Micropump ActuatorMembrane Displacement And Flow Rate”, 2007 International Symposium On Nano Science And Technology Tainan TAIWAN, 910 November 2007 9. YiChu Hsu, NgocBich Le, “Inertance Effects To Diffuser Micropumps Flow Rate Spectrum”, 2007 International Symposium On Nano Science And Technology Tainan TAIWAN, 910 November 2007 10. Yi – Chu Hsu, Jia – Hao Li, Ngoc – Bich Le, “Research on Actuator Geometry Optimum Design for Diffuser Based Plastic Peristaltic Micropumps”, SNDT 2007 symposium on nano device technology, 9 15, May 2007 1 Chapter 1 Introduction and Motivation Set the scene and problem statement. Introduce structure of thesis, state contributions icropumps 1 are a desired component of MEMS, bioMEMS and microfluidic devices because of their wide application in analytical chemistry 2, biological applications 3, pharmaceutical development 4, chemical synthesis systems 5,drug delivery and controlled insulin system 6, and fuel cell 7. Micropumps may be coupled with other microfluidic devices such as microfilters for particle 8 or molecular filtration 9, microflow sensors for flow measurements 10, micromixers 11 for analyte and reactant dosing and reaction engineering, microneedles 12 and microdispensers 13 for precise fluid delivery, and microseparators 14 for biological component separations. Moreover, as in any field, systematic and efficient design techniques are required to shorten the development lead time and to improve the reliability of new micropump designs. In any design process, the engineer is typically faced with a vast number of possible design solutions and parameterizations. Although many of these design directions can be immediately dismissed based on the available knowledge and or experience gained from previous designs, the number of solutions which remain is frequently so large that their systematic evaluation using formal techniques is difficult, if not impossible, to achieve. Consequently, the choice of design direction is invariably based upon a trialanderror approach, and depends more than anything on the skill of the engineer and downright luck. Therefore, optimization for individual components or the whole designing process for a specific micropump prototype is excessively significant. Many researches on micropump optimization for different types of micropump were reported. Morris et. Al. 15 presented an optimization work of a circular piezoelectric bimorph for a micropump driver. In his work, the actuator dimension was optimized with a given passive plate geometry. Specifically, this paper utilized the finiteelement method to optimize the deflection of a circular bimorph M 2 consisting of a single piezoelectric actuator, bonding material and elastic plate of finite dimensions. Optimum actuator dimensions were determined for given plate dimensions, actuatortoplate stiffness ratio and bonding layer thickness. Morganti at al. 16 conducted a research work for optimization of single chamber membrane valves and diffuser valves micropump for medical application purposes. However, because equivalent network was utilized for optimization purpose, the author just focused themselves on membrane valves and diffuser valves effects on micropump performances. In another work, Ahmadian at al. 17 also performed an optimization work on valveless diffuser micropump. By using finite element method, the authors conducted an extended numerical study on fluid flow through micropump chamber and diffuser valves to define the optimum parameters of diffuser element corresponding to different operation conditions. And again, the dominant attempt is on the diffuser elements. More recently, valveless micropump excited by a piezoelectric actuator for medical applications was investigated and optimized by Liu at al. 18. Specifically, PZT actuator thickness and diffuser geometries were investigated to obtain the optimum values. Gong at al. 19 designed and optimized a fourlayer electromagnetic micropump. His optimum goal was to obtain the strongest driving force under limited conditions by changing the structure parameters of the actuator. Consequently, this research also limited in the electromagnetic actuator structure optimization. Flexural plate wave micropump (FPWpump) was designed and optimized by Nguyen at al. 20. The optimum design problem was conducted by investigating the dependence of velocity profile and flow rate on the wave amplitudeapplied voltage, the channel height, and the backpressure. The most recent optimization work on peristaltic micropump is performed by Zhu et. Al. 21. In his work, a low cost multimaterial peristaltic micropump optimization was presented. A detailed optimization design of geometric parameters of the piezoelectrically actuated diaphragm is undertaken by use of 3D finite element method (FEM). Peristaltic pumps 22 have many advantages for biomedical applications and for integration with general micrototalanalysis systems (mTAS). For example, their lack of moving parts reduces the risk of damaging the particles and living cells as they are transported through the microchip and avoids the problem of channel clogging and mechanical wear inherent in micropumps with moving valve systems. Furthermore, peristaltic pumps offer the potential to accomplish bidirectional flows via a simple 3 adjustment of the actuation sequence. Finally, peristaltic micropumps are easily fabricated, have a planar structure (and are therefore readily integrated with other microfluidic devices), generate a high pumping force, and are compatible with a wide variety of working fluids (Hsu et al. 2008 23). However, in some specific applications such as fuel cell, biomedical, biochip, wallclimbing microrobot… high backpressure is required. Conventional PZT actuation peristaltic micropump is incapable of fulfill those applications. Consequently, in an attempt to improve the back pressure performance of the conventional design, integration of diffuser elements was considered. The diffuser element has a flow directing capability in the diffuser direction. Furthermore, diffuser element has the ability to reduce the velocity and increase the static pressure of fluid passing through a system 24. The directing capability of diffuser element is expected to increase the valving efficiency, thus, raising the flow rate. In addition, the ability to increase the static pressure in the reverse direction of diffuser element is predicted to increase the pressure difference (back pressure) significantly. Diffuser type peristaltic micropump was presented primarily by Hsu at al. 25 (our research group) with the pump performance improvement owing to integrated diffuser elements. Continue to that work 25, this paper present an overall optimization process for diffuser type peristaltic micropump (see Figure 1.1). Specifically, optimum process is performed for the key components such as actuator shape, actuatormembrane thickness, diffuser element, chamber treatment for bubble free purpose. Figure 1.1: Explosive view of diffusertype peristaltic micropump with PZT actuation 4 The structure of this thesis is divided into 7 chapters. Chapter 1 sets the scene and states the problem. Chapter 2 reviews the recent advance in micropump technology and presents the theoretical, analytical concepts used in the subsequent Chapters. The stated problem is solved from Chapter 3. Specifically, Chapter 3 and Chapter 4 present an experimental and analytical procedure for actuatormembrane shape and thickness optimization, respectively. Chapter 5 discusses the valving effects of the diffuser elements by theoretical and lumpelement analysis and performs an optimization work for these elements. Chapter 6 discusses and suggests a bubble solving method for stabilizing, and enhancing microfluidic system and peristaltic micropump performance and accuracy. Chapter 7 concludes the main achievements and state some future works. 5 Chapter 2 Recent advance and application in micropump devices and theoretical concept The material in this chapter was mainly referred from reference 26 and has been published as journal papers 27, 28 2.1. Recent applications There has been a recent surge in studies exploring micropump technologies, motivated in part by the need to develop pumping mechanisms for biological fluid handling such as for polymerase chain reaction (PCR) and LabonaChip and micro Total Analysis Systems (μTAS) 29. Additionally, micropumps are being considered for application in the cooling of microelectronics as the use of liquid cooling has become increasingly necessary to alleviate the extremely challenging cooling constraints in these compact systems 30. Thermal management of electronic components is of increasing concern in the development of portable and reliable electronic devices. Of the strategies available for thermal management in electronic systems, liquid cooling in microchannels has the ability to increase power dissipation while also maintaining a small form factor. Contact and spreading resistances can be reduced by integrating the channels directly on the back side of common flipchip designs. Further, by using liquid cooling, the heat generation and heat rejection components can be separated, releasing the convective surface area for ultimate heat rejection to the ambient from being constrained by the microprocessor area 31. Thus, the heat exchanger in the cooling loop can be placed at any convenient location in the device. However, the requirement of large pumps to drive the liquid flow and the associated large pumping power have limited the application of microchannel heat sinks in spaceconstrained electronics 30. Innovative micropumping solutions are thus critical for facilitating wider use of liquid cooling approaches in electronic systems. Strategies for the development of cell and biological analysis tools have also exploited microfluidic devices since they can be used to sample, trap, separate, sort, 6 treat, detect and analyze biological materials 32. Microfluidic devices offer many attractive benefits for biological handling and analysis. For example, reducing device size also reduces sample requirements and reagent volumes which can reduce overall cost. Test chips are often disposable which is important for sterility. Using microfluidic chips also allows for a closed system, thus protecting the operator from chemical exposure. The small size accommodates parallel operations and thereby reduces cell sorting, analysis and treatment times. Combining different functions on a single microchip is another step toward maintaining a completely closed system that can be fully automated, reduce contamination, and eliminate human intervention and error 33. However, for microfluidic devices to capitalize on all of the above benefits, integration of the fluid pumping mechanism is imperative. Micropumps are also a crucial component of analytical chemistry 34, biological applications 35, pharmaceutical development 36, chemical synthesis systems 37, drug delivery and controlled insulin system 38, and fuel cell 39. Micropumps may be coupled with other microfluidic devices such as microfilters for particle 40 or molecular filtration 41, microflow sensors for flow measurements 42, micromixers 43 for analyte and reactant dosing and reaction engineering, microneedles 44 and microdispensers 45 for precise fluid delivery, and microseparators 46 for biological component separations. 2.2 Summary on recent advanced and related works 26 Piezoelectric: Applied voltage signal generates induced stress which in turn produces actuated moment by utilizing additional membrane. Electrostatic: Electrostatic actuation employs the use of electrostatic forces generated between electrodes to drive diaphragm motion Electromagnetic and magnetic: The electromagnetic actuation mechanism generally consists of a permanent magnet attached to a diaphragm and surrounded by a coil. Advantages: small voltage (~5 V), simple design of driver electronics. Mechanical displacement micropumping techniques Diaphragm displacement Thermal: Thermal actuation involves the volume expansion or induced stress 7 of a material in response to applied heat like SMA. Thermopneumatic actuation occurs when a secondary fluid (separate from the driven fluid) is heated (usually by a thin film resistive heater) causing it to expand and deflect the pump diaphragm. Pneumatic: Pneumatic pumps exploit fluctuations in gas pressure on a diaphragm to effect vibration. Composite materials: An ionic polymermetal composite (IPMC) material was electromechanically actuated, similar to piezoelectric materials, to create a larger bending deformation (over 1% bending strain) under a low input voltage by (Lee and Kim 2006, Lee et al. 2005). The manufacturing costs of this composite are stated to be competitive with other actuator technologies. Peristaltic: By applying an appropriate voltage control scheme, the membranes can be actuated sequentially in such a way that fluid is drawn into the pump and driven peristaltically along its length to the outlet pipe. Dynamic geometry: Dynamicgeometry valves are defined as structures that provide flow direction by deformation, motion or deflection. It can be active (i.e. required energy) or passive (i.e. require no energy). Valve Static geometry 8 Staticgeometry valves employ no moving parts or boundaries for flow rectification. It can be active (i.e. required energy) or passive (i.e. require no energy). simple design and low risk of failure. Ferrofluid: Actuation of the ferrofluid is performed by the linear periodic motion of an external permanent magnet, thereby giving rise to a ferrofluidic piston. Fluid displacement pumps Phase change: Utilize volume changes from phase transition to displace fluid for pumping. Liquidtovapor phase change is the most interest because of the significant increase in volume. Bubble pumps and electrochemical pumps are common to this category of pumps. 9 Rotating gear: Typically rotatinggear micropumps drive the finned or toothed gear with an electric motor for rotation. Rotary pumps Viscous force: Fluid displacement using viscous forces generated by a rotating component has been investigated by several researchers, each with different configurations, 10 Inductiontype EHD: Inductiontype EHD pumps require either a gradient in the electrical conductivity or permittivity of the working fluid. Movement of induced charges due to electric field carries with them the bulk fluid due to viscous effects. Electro and Magneto Kinetic micropumping techniques Electrohydrodynamic pumps Injectiontype EHD: In injectiontype EHD micropumps, electrochemical reactions at the electrodes cause the injection of free ions into the bulk liquid. These ions experience Coulomb forces due to the presence of the electric field. This causes the movement of ions, which in turn carry the bulk fluid with them. 11 Polarizationtype EHD: Dipoles in the section of channel bounded by the electrodes will have lower energies than those outside the electrode region and fluid external to the electrode section will move into the channel causing a pumping action DC electroosmotic: With an applied DC electric field, the force experienced by the fluid near the capillary wall is much higher due to the high charge density in its vicinity. These charges move in response to the electric field and the fluid motion is propagated to the channel interior due to viscous forces. Electroosmotic pumps AC electroosmotic: 12 AC electroosmotic flow has emerged as a viable microscale pumping mechanism for conductive or electrolytic solutions. Small voltages of less than 10 V, bidirectional Iondrag pumps: Most electrokinetic pumping mechanisms (such as induction EHD, injection EHD, electroosmosis, etc.) use ion drag as the force to drive the fluid. Magnetohydrodynamic pumps: The fluid experiences a Lorentz force acting along the length of the channel which leads to induced flow. Electrowetting pumps: When an electric voltage is applied along the interface of a liquid metal droplet in an electrolyte, charge redistribution occurs resulting in a gradient in surface tension at the interface which causes movement of the droplet to regions of lower surface tension. Switching the direction of the applied voltage also changes the direction of motion. Optoelectrostatic microvortex: Fluid flows have been generated with an optoelectrostatic microvortex (OEMV) mechanism in which a vortexlike fluid flow is generated around the focal point of a laser beam in the presence of an intense AC electric field Other Flexural plate wave pumps: The acoustic field leads to fluid motion near the membrane surface in the direction of the wave. 13 2.3 Electrichydraulic analogy and SPICE modeling background Many software packages have been proposed for the modeling of both macro and microfluidic systems, including ANSYS, ABAQUS, COSMOSM, FLUENT, FIDAP, FLOW3D, NASTRAN, CFDRC, and so on. However, the application of these packages to the modeling of peristaltic micropump systems such as those considered in the current study is challenging due to the complex nature of the coupling between the fluidic and mechanical fields during the actuation process. As a result, in this study, the micropump system is converted into equivalent electrical circuits and is then analyzed using the SPICE (Simulation Program with Integrated Circuit Emphasis) analog circuit simulation package (CircuitMake 6.2 Pro). The following part of this section present some concepts of electronichydraulic analogy. 2.3.1 Channel resistance Hydraulic resistance (Rhyd), which represents energy dissipation due to fluid’s viscous friction against component’s walls, is calculated by integrating the velocity profile over the crosssectional area of channel such that flowrate as function of pressure drop is known 47. Different geometries require different equations. Equations 21 and 22 were used to calculate Rhyd for square and circular channels, respectively. In Eqs. 21 and 22, l is channel length, α is 50% of channel width, b is 50% of channel height and μ is fluid viscosity. Rhyd= 1 4 4 3 )} 12 3.36 (1 3 4 {16 − − − a b a b ab μl (Square channel) (21) Rhyd= 4 8 a l π μ (Circular channel) (22) When calculating Rhyd of a diffuser valve that is asymmetrical, Eqs. 21 and 22 can not be used directly because they are only for symmetric geometries. Therefore, diffuser valve was divided into very small differential volume elements. Figure 2.1 shows the details for differential parameters used in calculations. After differentiating the valve into a very small part, each small part was considered a rectangular, symmetric channel. The value of α, which is illustrated in Figure 2.1, is substituted into Eq. 21 and the equation is integrated respected to x from zero to valve length yields 14 dx a b a b ab lv 1 4 4 0 3 )} 12 3.36 (1 3 ∫ 4μ 1 {16 − − − where 40 10 6 1041 107 40 + × − − a = x . This concept is also applied to the inductance calculation. Figure 2.1: Valve integration for calculating hydraulic resistance and inductance of diffuser 2.3.2 Capacitance Hydraulic capacitance (Chyd) represents the elastic behavior of the microfluidics component, and links volume V variation to pressure P difference 48: C dV hyd dP = (23) This variation is due both to structural deformation and the elastic property of the fluid. Consider a flow induced by compression of fluid (Figure 2.2) Figure 2.2: Flow induced by compression of fluid In Figure 2.2, p is pressure, t is time, V0 is initial volume, IV is flow induced by compression of volume V, and ĸ is finite compressibility. Thus, I dV dt dV dp dp dt V dp V dt = = =κ 0 (24) Compare to electric current yields: I C dU el el dt = (25) Where, Iel is electrical current, Cel is electrical capacitance, U is voltage and t is time. 15 Thus: C = ĸV0 = V0Kc (26) Where Kc is compresspermissibility. The second form V0Kc was used in this calculation process. For membrane capacitance, C S membrane k = (γ m)2 (27) Where, k Eh r m m = − 64 12 1 2 3 ( υ ) 2 υπ Sm =πrm2 (Membrane area) Where, rm is membrane radius, E is membrane Young’s modulus, hm is membrane thickness, υ is membrane Poison’s ratio. 2.3.3 Inductance of equivalent components in an electrical circuit The hydraulic inertia (Ihyd) represents the effect of a certain mass accelerated in the device, and can be both due to the fluid moving in the component or to a part of the device that moves, such as a membrane or a cantilever 48. ΔP I d hyd dt = φ (28) Where, ΔP is pressure drop, Ihyd is hydraulic inductance and dφdt is hydraulic flow variation with respected to time. Hydraulic inertia is proportional to length l, density ρ of the fluid and inversely proportional to the crosssectional area A. I l hyd A = ρ (29) 2.3.4 Diffuser valve efficiency Efficiency of the diffuser valve is important to the behavior of microfluidics. Consequently, this study calculated the efficiency carefully by using ANSYS® 8.1. The diffuser valve efficiency is defined originally as 48: 16 ε = − + R R R R pos neg pos neg (2 10) Where, Rpos and Rneg are resistances of the diffuser valve when liquid moves in positive and negative directions, respectively. Resistance is defined as R P Q = (211) Where, P is pressure drop and Q is flow rate Substituting Eq. 211 into Eq. 210 yields, ε = − + = − − + P Q P Q P Q P Q Q Q Q Q pos neg pos neg pos neg pos neg ( ) (2 12) Where Qpos is flow rate corresponding to the conduction condition or the positive direction, and Qneg is valve flow rate corresponding to the leakage condition or negative direction. Because the diffuser valve is too small to determine flow rates experimentally, an alternative is to calculate flow rates and valve efficiency using ANSYS® 8.1 and computational fluid dynamics (CFDRC)PlotTran. The parameters of diffuser valve were tabulated in Table 2.1. The analytical flow rates are as follows, Qin = 53.529 μls and Qout = 46.905 μls. The valve efficiency is computed as: ε = − − + = − − + = − ( ) (53. . ) . . . Q Q Q Q pos neg pos neg 529 46 905 53529 46 905 0066 The relationship between negative and positive resistances and inductance is as follows, RNeg = RPos − + 1 1 ε ε (213) I Neg = I Pos − + 1 1 ε ε (214) 2.3.5 SPICE modeling for diffuser micropump 17 The equivalent circuit of the whole system consists of an actuator, membrane, chamber, valves, inletoutlet channels, and inletoutlet tubing (Figure 2.3). i) The PZT actuator is represented by a voltage source because the actuator applies a pressure to the system; this is equivalent to applying a voltage to a network node. ii) The membrane has both inductive and capacitive effects. The inductive effects are related to inertia of the membrane when moving and the capacitor effects represent the deformation of the membrane with the consequent volume variation. The equivalent circuit is the serial connection of an inductor and a capacitor. iii) For the chamber, frictional effects are not considered in its equivalent network because the pump chamber is relatively wide compared to the inletoutlet channels and valves. The equivalent circuit only has an inductor and capacitor representing the inertia and compressibility of fluid in the chamber, respectively. iv) Valves have different behaviors in ‘forward’ and ‘reverse’ conditions. Their equivalent network is divided into two branches; the ideal diodes select which one works. Each branch is obtained by analyzing valve behavior under each condition the negative and positive direction. As no parts move, no capacitive effect is considered. Instead, a considerable mass of fluid moves through the diffuser valve and its inertial effect is represented by an inductor. v) Inletoutlet channels are represented by a simple equivalent network in which the resistor is associated with the frictional effect of flowing fluid, the inductor with its dynamic inertia and the capacitor with its elasticity. The inlet and outlet tubes in this equivalent circuit were not considered in some studies 48. However, we assumed that the inlet and outlet tubes affect flow rate behavior considerably, hence, the tubes were considered in the equivalent circuit. Table 2.1 lists diffuser micropump parameters and its corresponding symbols and units. Using Eqs. 21, 22, 26, 27, 29, 213 and 214 with the respective parameters in Table 2.1, all the equivalent parameters can be obtained with corresponding symbols and units tabulated in Table 2.2. 18 Table 2.1 Parameters and corresponding unit of diffuser micropump Elements Symbol Value Membrane radius rm mm Membrane thickness hm mm Cosinusoidal flexion γ Nonunit Young’s modulus of Pyrex glass E GPa Pyrex glass Poisson’s ratio υm Nonunit Pyrex glass density ρm Kgm3 Actuator density ρa Kgm3 Actuator radius ra m Actuator thickness ha m Pump chamber depth hc m Pump chamber radius rc m Valves efficiency ε Nonunit Valves length lv m Valves minimum width α min m Valves max width α max m Valve width at x location 2 α 40 1041 107 40 + − a = x (μm) Valve height b m Channel length lt m Channel width and height 2 α t, 2bt m Tube length lp m Tube inner radius rp m Water compresspermissibility Kc GPa Water density ρ Kgm3 Water viscosity μ m2s1 Table 2.2 Corresponding unit for equivalent circuit components Component name Symbol Calculation result Membrane inductance Imembrane Ns2m5 Membrane capacitance Cmembrane m5N1 Chamber inductance Ichamber Ns2m5 Chamber capacitance Cchamber m5N1 Diff. valve positive inductance IPos Ns2m5 Diff. valve negative inductance INeg Ns2m5 Diff. valve positive resistance RPos Nsm5 Diff. valve negative resistance RNeg Nsm5 Channel inductance Ich Ns2m5 Channel capacitance Cch m5N1 Channel resistance Rch Nsm5 Tube inductance Itube Ns2m5 Tube capacitance Ctube m5N1 Tube resistance Rtube Nsm5 19 Figure 2.3: Diffuser micropump equivalent circuit Figure 2.4: Diffuser micropump output flow behavior in time domain at 200Hz operating frequency Figure 2.5 presents the accumulated volume at the pump outlet during one cycle (200 Hz). The net flow rate is determined by the flow difference between the pump mode (when the flow direction is going out of the outlet) and supply mode (when the flow direction is going into the outlet). 20 2.3.6 SPICE modeling for peristaltic micropump This section describes the equivalent electrical network used in the SPICE simulations to model the peristaltic micropump. Note that the electrical formulae used in the simulations to model the hydraulic resistance (Rhyd), inertance (Ihyd) and capacitance (Chyd) of the various elements within the micropump are presented in Section 2.3.1 with two considerations that, first, the epoxy layer was considered in the present simulation. Its mass contributes to the membrane inductance as follow 49, 28, 2 2 . ( . ) ( ) ( . ) chamber actuator epoxy membrane chamber Eff membrane S m m m S m I γ γ γ + + = = (215) Where, Imembrane is membrane inductance mactuator is PZT actuator’s mass mepoxy is epoxy layer’s mass mmembrane is glass membrane’s mass Schamber is the area of chamber γ is cosinusoidal flexion The second consideration is the error due to the combination of Nickel layers to PZT chip when calculating actuatormembrane inductance. Specifically, the error comes from the discrepancy between weigh density of PZT and Nickel which in turn causes the mass discrepancy of Nickel layers when considering Nickel layers as PZT and themselves. The error contributed by mass discrepancy is, PZT Chip Ni PZT Ni t t m err m × − × × = Δ = ρ (ρ ρ ) 2 (216) Where, err is error contributed by mass discrepancy. Δm is mass discrepancy of Nickel layers when considering Nickel layers as PZT and themselves. 21 m is PZT chip mass when considering Nickel layers as PZT material. tNi is Nickel’s thickness. tChip is chip’s thickness when considering Nickel layers as PZT material (i.e. 191 μm). Ni ρ is Nickel weigh density. PZT ρ is PZT weigh density. Substitute the corresponding parameters into Eq. 216 we will get the error contributed by mass discrepancy. In constructing the equivalent electrical circuit, the pressure applied by the PZT actuator membrane to the fluid system is modeled as a simple voltage source (see Figure 2.5(a)). The membranes are assumed to have both an inductive and a capacitive effect. The inductive effect reflects the physical inertia induced in the fluid system as the membrane deflects in the upward or downward direction, while the capacitive effect represents the change in chamber volume as the membrane deflects. As shown in Figure 2.5 (a), the inductance and capacitance are modeled in series in the equivalent circuit of the actuatormembrane. In modeling the three chambers of the micropump, it is assumed that the frictional effects acting on the fluid are negligible since the crosssectional area of the chamber is significantly greater than that of the inletoutlet channels or the interconnection channels between the chambers. As a result, the chambers are simply modeled using an inductor and a capacitor to represent the inertia and fluid compressibility effects, respectively (see Figure 2.5(b)). The inletoutlet channels and the chamber interconnection channels are modeled using a series arrangement of a resistor and an inductor connected in parallel with a capacitor to represent the frictional effects, the dynamic inertia effects and the channel elasticity, respectively (see Figure 2.5(c)). It has been reported that the external tubing system 22 connected to the input output ports of a micropump has a significant effect upon the system performance 28, 50. Thus, in the present electrical circuit, the tubes are modeled in a similar manner to that used for the inletoutlet channels, with the only difference being that they are considered to have a circular rather than rectangular crosssection when performing the calculations. Figure 2.5: Equivalent electrical circuits of a) actuatormembrane, b) chamber with resistance difference switch, and c) microchannelstubing. The key factors when modeling the peristaltic micropump are the sequencing operation of the actuatormembranes and its valving effect. In the considered peristaltic micropump, a pumping effect is induced by carefully controlling the actuation sequence of the three PZT actuatormembranes in such a way that a sequential pressure drop is induced among the three chambers, causing the fluid to be driven peristaltically from the inlet to the outlet. As described above, in the equivalent electrical network developed in this study, the driving force acting on the fluid is modeled using a simple voltage source. The actuation sequence of the three membranes within the micropump is 23 modeled by controlling these simple voltage sources using the fourphase actuation scheme shown in Figure 2.6, in which +Vp causes the membrane to deflect in the upward direction and –Vp causes the membrane to deflect in the downward direction. As shown, this fourphase sequence (i.e. 100–110–011–001, where “1” indicates “membrane is up” and “0” indicates “membrane is down”) induces a peristaltic pumping effect in which fluid is drawn into the micropump in phases 1 and 2, and is pumped out of the micropump in phases 3 and 4. Figure 2.6: Fourphase actuation sequence of peristaltic micropump. As shown in Figure 2.6, the individual PZT actuators are driven by a stepfunction waveform. In practice, however, the effects of mechanical and fluidic response delays cause the dynamic pressure variation within the individual channels to deviate from this ideal pulselike characteristic. Furthermore, as discussed by the current group in a previous study 51, limitations of the driving signal control circuit inevitably prevent the electrical actuation signals from having a perfect pulselike form 51. Thus, in performing the SPICE simulations, the actuation voltage was modeled as a sine wave rather than a step function. 24 Figure 2.7(a) shows that as the actuatormembrane within the chamber moves in the upward direction, the chamber volume increases, and thus the flow resistance decreases. Conversely, as the membrane deflects in the downward direction, the chamber volume reduces, and thus the flow resistance increases (see Figure 2.7(b)). In the equivalent electrical circuit, this change in flow resistance is achieved using a voltagecontrolled switch (see Figure 2.5(b)) which selects a noresistance branch when the membrane moves in the upward direction and a resistance branch when the membrane deflects in the downward direction. Note that when choosing a suitable electrical device with which to model the switching operation in the micropump, a BJT Transistor, a MESFET, a TRIAC, an optoisolator, and a voltagecontrolled switch were all considered. However, the first four devices are frequency dependent, and thus their output signals are unstable at certain frequencies. Consequently, their use was rejected in favor of the voltagecontrolled switch since the response of this switch is independent of the frequency and therefore enables the micropump performance to be modeled over a wider range of experimental conditions. Figure 2.8 presents an overall block diagram of the piezoelectric peristaltic micropump. Note that the individual blocks in this figure correspond to the electrical circuit blocks shown in Figure 2.5. Figure 2.7: Change in resistance during two halfcycles of pumping operation: a) membrane deflects in upward direction; and b) membrane deflects in downward direction. 25 Figure 2.8: Block diagram of equivalent electrical circuit for peristaltic micropump. Calculation process for parameters and corresponding unit are similar to diffuser micropump. 2.3.7 PZT actuation simulation Piezoelectrics is the coupling of structural and electric fields, which is a natural property of materials such as quartz and piezoceramics. Applying a voltage to a piezoelectric material creates a displacement, and vibrating a piezoelectric material generates a voltage. PZT actuation simulation can be carried out with many available commercial packages such as ANSYS, CFDRC, ABACUS… This study used ANSYS as analysis software and the following discussion is applied for ANSYS simulation. To do a piezoelectric analysis using ANSYS, we need to use one of these element types: • PLANE13, KEYOPT(1) = 7 coupledfield quadrilateral solid • SOLID5, KEYOPT(1) = 0 or 3 coupledfield brick • SOLID98, KEYOPT(1) = 0 or 3 coupledfield tetrahedron • PLANE223, KEYOPT(1) = 1001, coupledfield 8node quadrilateral • SOLID226, KEYOPT(1) = 1001, coupledfield 20node brick • SOLID227, KEYOPT(1) = 1001, coupledfield 10node tetrahedron • Simulation type: structure + electric Meterial properties: Density: 26 7800 Kgm3 Dielectric matrix: The permittivity values represent the diagonal components ε11, ε22, and ε33 respectively of the permittivity matrix εS. For our application, the corresponding matrix is, ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ 0 0 3400 0 3130 0 3130 0 0 Piezoelectric matrix e (Cm2): We can define the piezoelectric matrix in e form (piezoelectric stress matrix) or in d form (piezoelectric strain matrix). The e matrix is typically associated with the input of the anisotropic elasticity in the form of the stiffness matrix c, while the d matrix is associated with the compliance matrix s. This 6 x 3 matrix (4 x 2 for 2D models) relates the electric field to stress (e matrix) or to strain (d matrix). Both the e and the d matrices use the data table input described below: 27 For our application, the corresponding matrix is, ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ − − 17 0 0 0 17 0 0 0 0 0 0 23.3 0 0 6.55 0 0 6.55 Stiffness matrix: This 6 x 6 symmetric matrix (4 x 4 for 2D models) specifies the stiffness (c matrix) or compliance (s matrix) coefficients. The elastic coefficient matrix uses the following data table input: For our application, the corresponding matrix is, 10 ( ) 2.35 2.35 0 2.3 0 0 11.7 0 0 0 12.6 8.41 0 0 0 12.6 7.95 8.41 0 0 0 × 10 Kg ms2 ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ 28 Chapter 3 Investigation on the effect of actuatormembrane shape for pump’s performance improvement The material in this chapter was published as journal paper 52. 3.1. Introduction Lead Zirconate Titanate (PZT) compounds have the unique ability to transform an electrical signal into a corresponding mechanical deformation and are therefore widely applied throughout the sensor and actuator fields. Previous studies have demonstrated the feasibility of using PZTbased actuators as the driving mechanism for MEMS devices such as peristaltic micropumps 28 and micromixers 53. To enhance the performance of such devices, it is necessary to design an appropriate actuation control scheme and to optimize the geometry of the actuators. However, a review of the literature suggests that the problem of optimizing the actuator geometry has received little attention. Furthermore, as reported by other researches 28, 54, the actuatormembrane’s natural frequency (i.e. resonant frequency) is approximately three order higher than the pump’s maximum flow rate frequency; therefore, the impedance curves were not included in the present study. This chapter performs a series of experimental and numerical investigations to examine the effect of the PZT actuator geometry on the pumping performance of peristaltic micropumps. With the present pump design (see Figure 1.1), the actuatormembranes are integrated to the square opening windows, consequently, there are four options for actuator shape, that is, square, circular, ellipse, rectangle. However, from the mechanical point of view, square and circular shape should give better performance. Furthermore, square and circular shapes are the best match to the square opening window and these shapes are also easier to be simulated and calculated. Therefore, using the solventassisted bonding method presented in 55, two diffuservalve peristaltic micropumps are fabricated, one with circular actuators and the other with square actuators. Experimental trials are performed to determine the back pressure and flow rate characteristics of the two devices under driving voltages of 80~150 Vpp and actuation frequencies ranging from 10 Hz to 1 kHz. The difference in the experimental response of the two devices is quantified by performing ANSYS finite 29 element simulations to clarify the effects of the actuator size and geometry on the magnitude of the membrane deflection under representative actuation conditions. 3.2. Design, Fabrication and Actuation Scheme 3.2.1 Design and fabrication Figure 3.1 presents a schematic overview of the fabrication process used in the current study. For each micropump, the fabrication process commenced by using a sputtering system to deposit a thin (2000 Å) aluminum adhesive layer on the upper surface of a silicon wafer with a thickness of 500 μm. Utilizing a traditional photolithography method and a deep reactive ion etching (DRIE) technique with an Al etchant, microchannels with a depth of 200 μm and a width tapering from 80 μm at their inlet end to 500 μm at their outlet end were patterned on the substrate surface. The photolithography etching process was then repeated to create a linear array of three actuating chambers with a depth of 15 μm and a diameter of 7 mm diameter (see Figure 3.1(a)). A thin gold layer was then evaporated onto each patterned silicon wafer (see Figure 3.1(b)). Using the patterned silicon wafer as a mold, a complementary nickel wafer was fabricated using an electroforming system (see Figure 3.1(c)). The patterned nickel wafer was then used to transfer the microchannel and microchamber configuration to a PMMA substrate by performing a hot embossing process at a temperature of 130 0C (see Figure 3.1(e)). Meanwhile, two blank PMMA wafers were machined using a CO2 laser beam to create an array of square or circular openings, respectively, to accommodate the actuatormembrane structures. The upper and lower PMMA chips were carefully aligned (see Figure 3.1(f)) and were then bonded using the solventassisted technique described in 55 (see Figure 3.1(g)). Finally, PZT patches with a thickness of 235 μm and a side length or diameter of 7 mm were cut from a commercially available bulk PZT chip (Piezo Systems, Inc. PSI5H4E) and attached to glass membranes with a thickness of 150 μm using epoxy glue. Figure 2 presents a photograph of the two completed micropumps. 30 Figure 3.1: Schematic overview of fabrication process Figure 3.2: Photograph sh

Southern Taiwan University Institute of Mechatronic Science and Technology Ph.D Thesis DIFFUSER-TYPE PERISTALTIC MICROPUMP OPTIMIZATION: THEORY AND REALIZATION 擴散閥門蠕動式微型幫浦之最佳化:理論與實驗 Graduate Student: Ngoc-Bich Le Advisor：Yi-Chu Hsu May, 2010 S o u t h e r n Ta i w a n U n i v e r s i t y Institute of Mechatronic Science and Technology Ph.D Thesis Student no.: D96Z0201 Diffuser-Type Peristaltic Micropump Optimization: Theory and Realization Graduate Student: Ngoc-Bich Le SOUTHERN TAIWAN UNIVERSITY INSTITUTE OF MECHATRONIC SCIENCE AND TECHNOLOGY STU DIFFUSER-TYPE PERISTALTIC MICROPUMP OPTIMIZATION: THEORY AND REALIZATION 擴散閥門蠕動式微型幫浦之最佳化:理論與實驗 Ngoc-Bich Le Life-Chip Laboratory Institute Of Mechatronic Science And Technology Southern Taiwan University Submitted to the Institute Of Mechatronic Science And Technology, Southern Taiwan University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Tainan, Taiwan, May 2010 i The research described in this thesis was carried out at the life chip Laboratory, Mechanical Engineering Department, Southern Taiwan University, Tainan, Taiwan Many persons have been involved in this work and I am very grateful for their help Subject headings: μTAS / microsystem technology / micropump / microvalves / modeling ii 擴散閥門蠕動式微型幫浦之最佳化:理論與實驗 黎成心 南台科技大學機電科技研究所 中文摘要 摘要 蠕動型的擴散式塑膠微型幫浦相較於普通微型幫浦有著較佳的性能（例如：流 量、背壓等）。在製作及應用上也較便利（例如：便宜、輕巧以及用完即可丟棄 等）。因此本論文針對蠕動型的擴散式塑膠微型幫浦做出整體參數改善的研究討 論，包括致動薄膜厚度、致動器形狀、擴散閥之尺寸及腔體親水性等條件。首先 應用軟體分析計算出理論值（如：Mathematica, Matlab, OriginPro 等)，再以實驗的 數據加以佐證。本研究採用三種不同參數所設計出之蠕動型的擴散式塑膠微型幫 浦做出討論。其中兩個為相似的進口面積（約 16000µm 80ì80 àm iii Thesis for the degree of Doctor of Philosophy at Southern Taiwan University, 2010 Abstract Diffuser type peristaltic micropump was reported primarily by the current group with the significant improvement of pump performance (i.e flow rate, back-pressure, and disposable…) owing to integrated diffuser elements and PMMA material Continue to that achievement, this thesis presents an overall optimization process for diffuser type peristaltic micropump Specifically, optimum process is performed for the key components such as actuator-membrane thickness, actuator shape, diffuser valve, chamber’s wettability Specifically, theoretical calculation process was proposed with a simply application using some well known commercial packages (i.e Mathematica, Matlab, OriginPro,…) Furthermore, experiment was conducted to validate the theoretical calculation process Optimum actuator shape selection and membrane thickness was discussed using experiment combined with FEM analysis and theoretical calculation Optimization process for diffuser element which is the most significant component for improving pump performance was introduced In addition, the frequency dependent characteristic of the current designed diffuser element was investigated by utilizing two different methods, theoretical equivalent network calculation and SPICE (Simulation Program with Integrated Circuit Emphasis) analysis Chamber’s wetting optimization for bubble free operation was performed by introducing and experimentally optimizing the hydrophilic material (TiO2) layer pattern Three pump designs were then investigated to verify the overall optimization process That is, two designs with the same channel characteristic (i.e similar inlet area of 16000µm2) in which one is optimized and one is arbitrarily design were observed to validate the optimization process In addition, another optimized design with different channel characteristic (i.e inlet area is 80ì80àm2) was investigated to first verify the optimization process and second investigate the effect of channel geometry on pump’s performance iv Acknowledgments First of all, I would like to dedicate my happiness and success to my deceased father who would be very proud and happy if reads this thesis I would like to express my thanks to my mother, my fiancé and my family for everything they have been done to me I want to thank my supervisor Prof Yi-Chu Hsu for support, encouragement and professional guidance It has been a great pleasure to work with her I also want to give special thanks to Mr Jia-Hao Li, Mau-Sheng Lin for all their help with different mechanical and electrical set-ups and all my other current and former colleagues at the Life Chip Laboratory for valuable help and discussion during the work Thanks MingCan, Nan-Can, Jia-Hao, Mau-Sheng, Yan-Ting, Wei-Chun, and Yong-Xiong I would like to express my gratitude to the many faculty professors especially Prof Chin-Tu Lu, Zhu Chi Liang, Tai Zi Yao, who support me in software and experiment equipments as well as graduate students who helped this work come together I am particularly indebted to Prof Shang-He Lin, Director of Center for Development of Teaching and Learning, Southern Taiwan University of Technology, for all of his kindly help I am thankful to my colleagues at Nong Lam University, Ho Chi Minh City, Vietnam, particularly to Prof Hay Nguyen and Prof Le Van Ban for their constant support and fruitful collaboration I would like to thank Prof Ling-Sheng Jang, Life-Chip Laboratory, instrumentation Chip Group, Department of Electrical Engineering, National Cheng Kung University for his valuable suggestions as well as his critical comments I also would like to express my gratitude to Nanotechnology Center, National Cheng Kung University for experimental equipments supporting My last thanks goes to my all the different friends that have been a part of my life during the last two and a half years Thanks! Tainan, May 2010, Ngoc-Bich Le v Contents 中文摘要……………………………………………………………………………iii Abstract……………………………………………………………………….…………iv Acknowledgement…………………………………………………………………… v List of figures…………………………………………………………………………….x List of tables…… …………………………………………………………….…….….xi Chapter 1: Introduction and motivation…………………………………….… … Chapter 2: Recent advance and application in micropump devices and theoretical concept………………………………………………………………………… …… 2.1 Recent applications …………………………………………………… …………5 2.2 Summary on recent advanced and related works…………………… ….…… 2.3 Electric-hydraulic analogy and SPICE modeling background…………… ….14 2.3.1 Channel resistance ……………………………………………….… … 14 2.3.2 Capacitance ……………………………………………………… ……….14 2.3.3 Inductance of equivalent components in an electrical circuit…….… ….15 2.3.4 Diffuser valve efficiency………………………………………………… 15 2.3.5 SPICE modeling for diffuser micropump…………………………… ….16 2.3.6 SPICE modeling for peristaltic micropump……………………… …….20 2.3.7 PZT actuation simulation………………………………………… ………25 Chapter 3: Investigation on the effect of actuator-membrane shape for pump’s performance improvement ………………………………… ………………… … 28 3.1 Introduction………………………………………………………………… … 28 3.2 Design, Fabrication and Actuation Scheme……………………………………29 3.2.1 Design and fabrication…………………………………………………… 29 3.2.2 Actuation scheme………………………………………… ….…… …… 30 3.3 Experiments and Results…………………………………………………… ….31 vi 3.3.1 Experimental setup………………………………………………… …… 31 3.3.2 Pump performance………………………………………………… …… 31 3.4 ANSYS simulations of actuator/membrane displacement……………… … 35 3.5 Results and discussion…………………………………………………… …… 36 Chapter 4: Investigation on the effect of actuator-membrane thickness for pump’s performance improvement ………………………………………………….……….39 4.1 Introduction……………………………………………………………….………39 4.2 Theory…………………………………………………………………… ……….39 4.3 Experiment for membrane thickness validation…………………… ………….45 Chapter 5: Diffuser valve effects and its geometry design to improve the pump performance ……………………….………………………………………………….48 5.1 Introduction………………………………………………………… … ………48 5.2 Diffuser valve effects and its geometries optimization………………… …… 48 5.3 Operation frequency dependent properties of diffuser valve………… ………51 5.4 Experiment………………………………………………………… …………….54 Chapter 6: Bubble solving for microfluidic system and pump stability, robustness, and accuracy enhancement………………………………………………….……….62 6.1 Introduction…………………………………………………………….…………62 6.2 Basic concept on wetting and spreading dynamics………………….…………63 6.3 Experiment………………………………………………………… ……………66 6.3.1 TiO2 film stability evaluation…………………………………… ……… 66 6.3.1.1 Fabrication process of microwave plasma surface modification method ……………………………………………………………………………… 66 6.3.1.2 Fabrication process of deposition method…………………… …………67 6.3.1.3 Time dependent evaluation…………………………………………… …68 6.3.1.4 Microwave plasma surface modification time dependent evaluation… 68 6.3.1.5 Wear resistance evaluation………………………………………… ……69 vii 6.3.2 Bubble observation experiment……………………………… ………… 72 6.4 Results and Discussion……………………………………………… ………….75 Chapter 7: Conclusions and future works…………………………… ……………80 7.1 Conclusions…………………………………………………………… …………80 7.2 Future works……………………………………………………… …………….81 Reference……………………………………………………………… …………….83 Biography…………………………………………………………………………… 90 Publication…………………………………………………………………………….92 List of symbols…………………………………………………………………… ….93 viii Chapter Conclusions and Future Works 7.1 Conclusions An overall optimization procedure for diffuser type peristaltic micropump was proposed and validated First, theoretical calculation process for actuator-membrane thickness optimization was conducted successfully with experimental validation Both experimental and theoretical displacement maximizes at the membrane thickness of around 0.21mm Second, actuator shape selection for enhancing pump performance was discussed Specifically, utilizing the solvent-assisted PMMA-PMMA bonding technique presented by the current group in a previous article [3], this study has fabricated two PMMA peristaltic micropumps with square and circular PZT-based actuation structures, respectively The effects of the actuator shape on the performance of the two micropumps has been examined by performing experimental trials using driving voltages of 80~150 Vpp and actuation frequencies ranging from 10 Hz to kHz The experimental results have shown that the micropump with square actuators yields a maximum flow rate of 217 μL/min and maximum back pressure of 9.2 kPa, while the pump with circular actuators yields a maximum flow rate and back pressure of 131 μL/min and 2.7 kPa, respectively The ANSYS finite element simulations performed in this study shows that the circular actuators have greater deflection efficiency than square actuators of an equivalent surface area Consequently, it has been argued that the relatively poorer performance of the micropump with circular actuators is the result of smaller actuation area and at least in part of thermal damage to the PZT patches during their removal from the bulk PZT die during the fabrication process Nonetheless, a realistic shape for actuators would be rectangular And a rectangular actuator with the side of mm could have higher deflection than a circular actuator with the diameter of mm In practicality, a rectangular actuator is a suitable design for higher performance of peristaltic micropumps 80 Third, optimization process was introduced for the diffuser elements In addition, the frequency dependent characteristic of the current designed diffuser element was investigated by utilizing two different methods, theoretical equivalent network calculation and SPICE (Simulation Program with Integrated Circuit Emphasis) analysis The results support the following conclusions: For the optimized designs, the design with larger diffuser inlet area provides a higher flow rate; however, the flow rate reduces more rapidly with an increasing backpressure at higher values of diffuser inlet area, which yields a lower maximum back pressure Optimization for the diffuser elements is significant and the results demonstrated that the optimized design significantly improves both flow rate and maximum back-pressure Finally, a bubble-free method for microfluidic systems and micropump applications was developed Two methods of hydrophilic film formation were investigated; TiO2 thin film deposition exhibited better stability and was therefore selected for improving surface wettability Various hydrophilic strip shapes and numbers of strips were investigated The results indicate that the vertical design with a three-section strip most effectively discharges the bubbles in microfluidic devices The optimum design was applied to a peristaltic micropump The results indicate that the micropump stability and robustness were significantly increased The number of bubbles was significantly reduced at the pump’s operation frequency (i.e., 75 ± 10 Hz) The results show that frequencies of below 100 Hz are considered a stable operation frequency range for the pump Although the proposed method produces lower pumping rates and backpressure, the results are considered important for microfluidic systems and micropumps 7.2 Future works In the present thesis, the optimization projects for components were performed separately Components’ optimization and corresponding results were presented individually Therefore, whole device optimization can be performed in the future work in which Taguchi Method can be used as a powerful tool For many applications, an ideal micropump would supply sufficient flow rate and pressure while having a low voltage requirement, low power consumption, a simple control system, and low cost Therefore, high operation voltage (i.e 100 Vpp) and high 81 power consumption are some drawbacks of the current design and need to be improved For the first issue, an alternative actuating method can be considered to reduce the operation voltage The second issue is though to be the result of square wave applied signal Specifically, the suddenly rising of applied signal causes a high rising of current which increases the power consumption However, due to the mechanical inertia and damping, the actuator-membrane structure does not catch up with such a high rising speed Consequently, optimization on applied signal to increase pump power consumption efficiency should be performed The current actuator-membrane bonding method utilizing silver epoxy has some drawbacks such as: hard to control the thickness, the bonding layer hardness is uncontrollable, expensive… Therefore, looking for a new bonding method that is low cost, batch-product compatible, stable properties, productivity is essential An alternative fabrication process with fewer steps, simpler, low cost, batchproduct compatible, productivity is also significant and urgent Some suggested methods can be considered such 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District, Tien Giang Province – Viet Nam - E-mail address: lngbichmt@yahoo.com - Phone number: (+86) 930.524726, (+84) 903096857 Education: 2007-2010: Ph.D program of Mechatronics - Southern Taiwain University, Taiwan 2005-2007: Master program of Mechatronics - Southern Taiwain University, Taiwan 1999-2004: Undergraduate program of Mechatronics - Bach Khoa University (former name: Polytechnics University), Ho Chi Minh City, Vietnam 1997-1999: Long Binh Secondary School 1994-1999: Long Binh Junior Secondary 1989-1994: Long Binh Elementary School 90 Publications Journal paper: Yi-Chu Hsu, Ngoc-Bich Le, “Inertial effects on flow rate spectrum of diffuser micropumps”, J Biomedical Microdevices, Volume 10, Number / October, 2008, p 681–692 Yi-Chu Hsu, and Ngoc-Bich Le, "Equivalent electrical network for performance characterization of piezoelectric peristaltic micropump", Microfluidics and nanofluidics, Volume 7, Number / August, 2009, p 237–248 Yi-Chu Hsu, Jia-Long Hsu, and Ngoc-Bich Le, "An experimental and numerical investigation into the effects of the PZT actuator shape in polymethylmethacrylate (PMMA) peristaltic micropumps", Microsystem Technologies, v 15, n 4, April, 2009, p 565–571 Yi-Chu Hsu, Jia-Hao Li, and Ngoc-Bich Le, “An experimental and numerical investigation into the effects of diffuser valves in polymethylmethacrylate (PMMA) peristaltic micropumps”, Sensors and Actuators A: Physical, Volume 148, Issue 1, November 2008, Pages 149–157 Yi-Chu Hsu, Ngoc-Bich Le, “Coupling Coefficient Determination Based On Simulation And Experiment For St-Cut Quartz Saw Delay-Line Response”, Journal for Microsystem Technologies, Vol 14, n 4-5, April 2008, p 615–622, (2008) Ngoc-Bich Le, Yi-Chu Hsu, “Investigation on hydrophilic modification for bubble-free operation in microfluidic systems and micropump applications”, J Advances in Natural Sciences: Nanoscience and Nanotechnology (2010) 015006 Yi-Chu Hsu, Ngoc-Bich Le, Mau-Sheng Lin, and Wei-Chun Tseng, “Development of bubble-free method for micro-fluidic system and micropump application”, Submitted to J of Applied Biomechanics for Journal publication Yi-Chu Hsu and Ngoc-Bich Le, “Investigation on The Frequency Discrepancy between Actuator-Membrane Displacement and Flow Rate Spectrum of Diaphragm Micropumps”, Submitted to JJAP for journal publication International conference paper: Yi-Chu Hsu, and Ngoc-Bich Le, Mau-Sheng Lin, L S Jang, “Optimum design and investigation on diffuser polymethylmethacrylate (PMMA) peristaltic micropumps", IEEE ICRA2009, May 12-17, Kobe, Japan Yi-Chu Hsu, and Ngoc-Bich Le, “Effects of the PZT Actuator Shape in Polymethylmethacrylate (PMMA) Peristaltic Micropumps: Experimental and Numerical Investigation”, 2008 International Symposium On Nano Science And Technology, Tainan, Taiwan, November 7, 2008 Yi-Chu Hsu, and Ngoc-Bich Le, “Diffuser polymethylmethacrylate (PMMA) peristaltic micropumps: Optimum design and investigation”, 2008 International Symposium On Nano Science And Technology, Tainan, Taiwan, November 7, 2008 Yi-Chu Hsu, and Ngoc-Bich Le, “Piezoelectric peristaltic micropump characterization using spice modeling with lumped-element” , 2008 International Symposium On Nano Science And Technology, Tainan, Taiwan, November 7, 2008 91 Yi-Chu Hsu, Ngoc-Bich Le, “Investigation on The Frequency Shift Between ActuatorMembrane Displacement And Flow Rate Spectrum Of Diaphragm Micropumps”, AsiaPacific Conference on Transducers and Micro-Nano Technology 2008, Tainan, Taiwan from 22-25 June, 2008, (2008) Yi-Chu Hsu, Jia-Long Hsu, Ngoc-Bich Le, “An Experimental and Numerical Investigation into the Effects of the PZT Actuator Shape in Polymethylmethacrylate (PMMA) Peristaltic Micropumps”, Asia-Pacific Conference on Transducers and MicroNano Technology 2008, Tainan, Taiwan from 22-25 June, 2008, (2008) Yi-Chu Hsu, Ngoc-Bich Le, “Coupling Coefficient Determination Based On Simulation And Experiment For St-Cut Quartz Saw Delay-Line Response”, Proceedings of SPIE The International Society for Optical Engineering, v 6589, Smart Sensors, Actuators, and MEMS III, 2007, p 65891Q, (2007) Ngoc-Bich Le, Yi-Chu Hsu, Ling-Sheng Jang, Mau-sheng Lin, “Inertance Effects To Diffuser Micropumps Flow Rate Spectrum”, Proceedings of MNHT2008, Micro/Nanoscale Heat Transfer International Conference (ASME), January 6-9, (2008) Yi-Chu Hsu , Ngoc-Bich Le, “Investigation On The Frequency Shift Of Micropump Actuator-Membrane Displacement And Flow Rate”, 2007 International Symposium On Nano Science And Technology Tainan TAIWAN, 9-10 November 2007 Yi-Chu Hsu, Ngoc-Bich Le, “Inertance Effects To Diffuser Micropumps Flow Rate Spectrum”, 2007 International Symposium On Nano Science And Technology Tainan TAIWAN, 9-10 November 2007 Yi-Chu Hsu, Ngoc-Bich Le, Ling-Sheng Jang, “Simulation and experiment on St-cut quartz saw delayline response”, Conference on Smart sensors, Actuators and MEMs, SPIE European Symposium on Microtechnologies for the New Millennium, paper number 6589-61, May-2007 Ngoc-Bich Le, Sung-Po Hsun, Yi-Chu Hsu, Ling-Sheng Jang, “St-Cut Quartz Saw Delay-Line Response Simulation”, 2006 International Symposium On Nano Science And Technology Tainan TAIWAN, 9-10 November 2006 Yi - Chu Hsu, Jia - Hao Li, Ngoc - Bich Le, “Research on Actuator Geometry Optimum Design for Diffuser Based Plastic Peristaltic Micropumps”, SNDT 2007 symposium on nano device technology, 9- 15, May 2007 92 List of symbols Symbol rm hm γ E υm ρm ρa hc rc ε lv α α max 2α b lt α t, 2bt lp rp Kc ρ μ Imembrane Cmembrane Ichamber Cchamber IPos INeg RPos RNeg Ich Cch Rch Itube Ctube Rtube Rhyd Chyd Ihyd ΔP dφ/dt ρ A Imembrane mactuator Meaning Membrane radius Membrane thickness Cosinusoidal flexion Young’s modulus of Pyrex glass Pyrex glass Poisson’s ratio Pyrex glass density Actuator density Actuator radius Actuator thickness Pump chamber depth Pump chamber radius Valves efficiency Valves length Valves minimum width Valves max width Valve width at x location Valve height Channel length Channel width and height Tube length Tube inner radius Water compress-permissibility Water density Water viscosity Membrane inductance Membrane capacitance Chamber inductance Chamber capacitance Diff valve positive inductance Diff valve negative inductance Diff valve positive resistance Diff valve negative resistance Channel inductance Channel capacitance Channel resistance Tube inductance Tube capacitance Tube resistance Hydraulic resistance Hydraulic capacitance Hydraulic inertia Pressure drop hydraulic flow variation with respected to time Fluid density Cross-sectional area Membrane inductance PZT actuator’s mass 93 mepoxy mmembrane Schamber γ Δm tNi ρ Ni ρ PZT [e] [s] [c] d/A W2 Dc Dp M eb d31 Cp 2θ W1 W2 εdyn Ω θ h(t) R(t) Fd(t) γab Epoxy layer’s mass Glass membrane’s mass Area of chamber Co-sinusoidal flexion Mass discrepancy Nickel’s thickness Nickel weigh density PZT weigh density Piezoelectric matrix Compliance matrix Stiffness matrix Coefficient of displacement over actuation area Deformation of the multiple-layer structure Modulus of multi-layer structure Modulus of passive plate (glass membrane) Moment Strain of the bonding material Mechanical coupling coefficient in the z-direction Pressure-recovery coefficient Divergence angle of diffuser element Throat/inlet width Exit/outlet width Dynamic rectification efficiency Droplet volume Contact angle Drop thickness Radius of the thin droplet Dynamic driving force for the spreading Interfacial tension between phases a and b 94 ... SCIENCE AND TECHNOLOGY STU DIFFUSER-TYPE PERISTALTIC MICROPUMP OPTIMIZATION: THEORY AND REALIZATION 擴散閥門蠕動式微型幫浦之最佳化:理論與實驗 Ngoc-Bich Le Life-Chip Laboratory Institute Of Mechatronic Science And Technology... Displacement and Flow Rate Spectrum of Diaphragm Micropumps, Yi-Chu Hsu and Ngoc-Bich Le Submited to JJAP for journal publication Diffuser type PZT actuation peristaltic micropump optimization: theory and. .. s i t y Institute of Mechatronic Science and Technology Ph.D Thesis Student no.: D96Z0201 Diffuser-Type Peristaltic Micropump Optimization: Theory and Realization Graduate Student: Ngoc-Bich Le