本研究利用微機電技術，且使用陽離子選擇性膜(Nafion)替代奈米管道製作出可用於樣品預濃縮的微流體晶片。當施加電場於微流體晶片時，由於陽離子選擇性膜內孔徑的電雙層重疊現象，使得陽離子選擇性膜內形成離子選擇之特性。此特性造成奈米通道內存在陽離子與陰離子的通量差異，導致在微奈米管道介面形成濃度極化之效應，在離子交換膜附近濃度梯度的發生。陽極端可觀察到離子消散區形成，而在離子消散區與電滲流流場交接處有一電場降幅區，利用電場降幅使離子累積，因此在管道中形成一個高濃度的界面，達到濃度預集中之目的。
本論文主旨，在探討陽離子選擇性膜的改質，在傳統陽離子選擇膜(Nafion)內添加氧化石墨烯應用於樣品預濃縮晶片上，藉由氧化石墨烯內自身的官能基，來提高我們預濃縮現象。探討如何提高富集效果的可行性，進而達到最佳化。因此，我們分別討論氧化石墨烯與Nafion的混合比例和不同氧化石墨烯的含量，找出彼此參雜的最佳比例及濃度，再與單純的Nafion材料，進行比較。由實驗結果可發現，我們利用30 V電壓差進行實驗，在直通管道下，利用0.5 wt %氧化石墨烯與Nafion以體積比三比一進行調配，所製造出的離子選擇膜，可聚集螢光在30分鐘裡達到60倍，優於傳統Nafion的40倍。

In this thesis, we utilized the micro-electromechanical technique using Nafion instead of a nanochannel in microfludic chips for use in sample preconcentration. When an electric field is applied to the micro-nano chip, the cation selective membrane (Nafion) has the characteristic of cation and anion flux difference due to the overlapped double layer effect in the nanochannel, which results in the concentration polarization phenomenon at the micro- and nano-interface. The concentration polarization phenomenon causes a concentration gradient to occur near the membrane. On the anodic side, the ion depletion zone can be induced by applying a voltage. The ion accumulation is the result of the difference in electro-migration at the boundary between the depletion zone and electroosmotic flow. Therefore, it creates a high concentration interface in the channel to achieve ion concentration.

The aim of this study was to explore a modified cation selective membrane by adding graphene oxide (GO) to a traditional Nafion membrane used in preconcentration chips. It was found that the GO functional group, enhanced our preconcentration phenomenon. We also discuss how to enhance the feasibility, after which we optimize the preconcentration effect in this modified membrane. To this end, we respectively mix GO and Nafion with different volume ratios and GO content (%) to find the optimal volume ratio and concentrations. Then, we compare GO/Nafion with Nafion alone. Based on the experimental result, we applied a voltage of 30 V in a straight microchannel. In using 0.5 wt % GO to mix with Nafion, the GO volume was three times more than that of the Nafion. These kinds of GO/Nafion ion selectivity membranes can achieve a 60-fold increase in preconcentration factor within 30 min, which is superior Nafion membranes that offer a 40-fold increase.

Abstract I
中文摘要 III
致謝 IV
Contents V
List of Figures VIII
Abbreviation XIV
Nomenclature XVI
Greeks XVII
Chapter 1 Introduction 1
1.1 Introduction 1
1.2 MEMS Technology ＆ Microfluidic Biochips 1
1.3 Literature review 3
1.4 Motivation 10
Chapter 2 Electrokinetic Effect 12
2.1 Electrical Double Layer, EDL 12
2.1.1 Overlapped Double Layers 14
2.2 Electroosmotic Flow 15
2.3 Electrophoresis 16
2.4 Concentration Polarization Phenomena 17
Chapter 3 Materials and Methods 21
3.1 Materials and Reagents 21
3.2 Mask 21
3.3 Fabrication of the Integrated Microchip 22
3.3.1 Substrate Pretreatment 23
3.3.2 Photoresist Coating 23
3.3.3 Exposure 23
3.3.4 Development 24
3.3.5 PDMS Casting 24
3.3.6 Oxygen Plasma Bonding 26
3.3.7 Nafion Patterned Process 26
3.4 Nafion-mixed GO Patterned Process 27
3.5 Instrument and Software 28
3.6 Raman spectroscopy 31
3.7 Fourier transform infrared spectroscopy (FTIR) 32
3.8 Microchip Design 32
3.9 Experimental Setup 33
Chapter 4 Results and Discussion 35
4.1 Fluorescein Preconcentration Process 35
4.2 Ion Depletion 37
4.3 Effect of Nafion-membrane on Preconcentration 39
4.3.1 5 wt % Nafion Junction 39
4.4 Effect of Nafion/GO Membrane on Preconcentration 40
4.4.1 Nafion Mixed GO in Different Volume Ratios 41
4.4.2 Different GO Content (%) Mixed with Nafion 44
4.5 Comparison of Nafion with Nafion/GO Membrane in terms of Preconcentration Effect 48
4.5.1 Nafion membrane compared with Nafion/GO membrane 48
4.5.2 Utilized Raman spectra and FTIR to confirm GO/Nafion mixing uniformity 49
4.6 GO functional carboxyl group 52
Chapter 5 Conclusion 53
References 54

[1] Manz A, Graber N, Widmer HM, Miniaturized total chemical analysis systems: a novel concept for chemical sensing. Sensors and Actuators B-Chemical 1: 244-248, 1990.
[2] Anderson NL, The human plasma proteome: history, character, and diagnostic prospects. Molecular ＆ Cellular Proteomics 1: 845-867, 2002.
[3] Shoji S, Microfabrication technologies and micro flow devices for chemical and bio-chemical micro flow systems. Microprocesses and Nanotechnology 7B-4-2: 72-73, 1999.
[4] Gravesen P, Branebjerg J, Jensen OS, Microfluidics-a review. Journal of Micromechanics and Microengineering 3: 168-182, 1993.
[5] Richter T, Shultz-Lockyear LL, Oleschuk RD, Bilitewski U, Harrison DJ, Bi-enzymatic and capillary electrophoretic analysis of non-fluorescent compounds in microfluidic devices - Determination of xanthine. Sensors and Actuators B-Chemical 81: 369-376, 2002.
[6] Vinet F, Chaton P, Fouillet Y, Microarrays and microfluidic devices: miniaturized systems for biological analysis. Microelectronic Engineering 61-2: 41-47, 2002.
[7] Beebe D, Wheeler M, Zeringue H, Walters E, Raty S, Microfluidic technology for assisted reproduction. Theriogenology 57: 125-135, 2002.
[8] Reyes DR, Iossifidis D, Auroux PA, Manz A, Micro total analysis systems. 1. Introduction, theory, and technology. Analytical Chemistry 74: 2623-2636, 2002.
[9] Di Carlo D, Wu LY, Lee LP, Dynamic single cell culture array, Lab on a Chip, 6, 1445-1449 ,2006.
[10] Mirzadeh H, Shokrolahi F, Daliri M, Effect of silicon rubber crosslink density on fibroblast cell behavior in vitro, J. Biomedical Materials Research Part B, 67A, 727-732,2003.
[11] Lee JN, Jiang X, Ryan D, Whitesides GM, Compatibility of mammalian cells on surfaces of polydimethylisiloxane, Langmuir 20, 11684-11691, 2004.
[12] Charati SG., Stern SA, Diffusion of gases in silicon polymers: molecular dynamic simulation, Macromolecules 31, 5529-5535, 1998.
[13] Gebauer P, Bocek P, Recent progress in capillary isotachophoresis. Electrophoresis 23: 3858–3864, 2002.
[14] Burgi DS, Chien RL, Optimization in Sample Stacking for High-Performance Capillary Electrophoresis. Analytical Chemistry 63: 2042-2047, 1991.
[15] Khandurina J, Jacobson SC, Waters LC, Foote RS, Ramsey JM, Microfabricated porous membrane structure for sample concentration and electrophoretic analysis. Analytical Chemistry 71: 1815-1819, 1999.
[16] Swerdlow JA-WH, Fluidic Preconcentrator device for capillary electrophoresis of proteins. Analytical Chemistry 75: 5207-5212, 2003.
[17] Oleschuk RD, Shultz-Lockyear LL, Ning YB, Harrison DJ, Trapping of bead-based reagents within microfluidic systems: On-chip solid-phase extraction and electrochromatography. Analytical Chemistry 72: 585-590, 2000.
[18] Song S, Singh AK, Kirby BJ, Electrophoretic concentration of proteins at laser-patterned nanoporous membranes in microchips. Analytical Chemistry 76: 4589-4592, 2004.
[19] Quirino JP, Terabe S, Exceeding 5000-Fold concentration of dilute analytes in micellar electrokinetic chromatography. Science 282: 465-468, 1998.
[20] Yu C, Davey MH, Svec F, Frechet JMJ, Monolithic porous polymer for on-chip solid-phase extraction and preconcentration prepared by photoinitiated in situ polymerization within a microfluidic device. Analytical Chemistry 73: 5088-5096, 2001.
[21] Kim SJ, Song YA, Han J, Nanofluidic concentration devices for biomolecules utilizing ion concentration polarization: theory, fabrication, and applications. Chemical Society Reviews 39: 912-922, 2010.
[22] Foote RS, Khandurina J, Jacobson SC, Ramsey JM, Preconcentration of proteins on microfluidic devices using porous silica membranes. Analytical Chemistry 77: 57-63, 2005.
[23] Cui HC, Horiuchi K, Dutta P, Ivory CF, Multistage isoelectric focusing in a polymeric microfluidic chip. Analytical Chemistry 77: 7878-7886, 2005.
[24] Wang Y-C, Stevens AL, Han J, Million-fold preconcentration of proteins and peptides by nanofluidic filter. Analytical Chemistry 77: 4293-4299, 2005.
[25] Jung B, Bharadwaj R, Santiago JG, On-chip millionfold sample stacking using transient isotachophoresis. Analytical Chemistry 78: 2319-2327, 2006.
[26] Hoeman KW, Lange JJ, Roman GT, Higgins DA, Culbertson CT, Electrokinetic trapping using titania nanoporous membranes fabricated using sol-gel chemistry on microfluidic devices. Electrophoresis 30: 3160-3167, 2009.
[27] Hlushkou D, Dhopeshwarkar R, Crooks RM, Tallarek U, The influence of membrane ion-permselectivity on electrokinetic concentration enrichment in membrane-based preconcentration units. Lab on a Chip 8: 1153-1162, 2008.
[28] Hatch AV, Herr AE, Throckmorton DJ, Brennan JS, Singh AK, Integrated preconcentration SDS-PAGE of proteins in microchips using photopatterned cross-linked polyacrylamide gels. Analytical Chemistry 78: 4976-4984, 2006.
[29] Kim SJ, Li LD, Han J, Multiplexed proteomic sample preconcentration device using surface-patterned ion-selective membrane. Lab on a Chip 8: 596-601, 2008.
[30] Yu H, Lu Y, Zhou YG, Wang FB, He FY, et al., A simple, disposable microfluidic device for rapid protein concentration and purification via direct-printing. Lab on a Chip 8: 1496-1501, 2008.
[31] Kim P, Kim SJ, Han J, Suh KY, Stabilization of ion concentration polarization using a heterogeneous nanoporous junction. Nano Letters 10: 16-23, 2010.
[32] Dhopeshwarkar R, Crooks RM, Hlushkou D, Tallarek U, Transient effects on microchannel electrokinetic filtering with an ion-permselective membrane. Analytical Chemistry 80: 1039-1048, 2008.
[33] Schoch R, Han J, Renaud P, Transport phenomena in nanofluidics. Reviews of Modern Physics 80: 839-883, 2008.
[34] Kim SJ, Li LD, Han J, Amplified electrokinetic response by concentration polarization near nanofluidic channel. Langmuir 25: 7759-7765, 2009.
[35] Kim SJ, Wang Y-C, Lee J, Jang H, Han J, Concentration polarization and nonlinear electrokinetic flow near a nanofluidic channel. Physical Review Letters 99: 044501, 2007.
[36] Wang Y, Pant K, Chen Z, Wang G, Diffey WF, et al., Numerical analysis of electrokinetic transport in micro-nanofluidic interconnect preconcentrator in hydrodynamic flow. Microfluidics and Nanofluidics 7: 683-696, 2009.
[37] Wang YC, Han J, Pre-binding dynamic range and sensitivity enhancement for immuno-sensors using nanofluidic preconcentrator. Lab on a Chip 8: 392-394, 2008.
[38] Rubinstein I, Shtilman L, Voltage against current curves of cation exchange membranes. Journal of the Chemical Soceity-Faraday Transactions II 75: 231-246 1979.
[39] Dukhin SS, Mishchuk NA, Intensification of electrodialysis based on electroosmosis of the second kind. Journal of Membrane Science 79: 199-210, 1993.
[40] Barraga’n VM, Ru?’z-Bauza’ C, Current voltage curves for ion-exchange membranes a method for determining the limiting current density. Journal of Colloid and Interface Science 205: 365–373, 1998.
[41] Zaltzman IRB, Electro-osmotically induced convection at a permselective membrane. Physical Review E 62: 2238-2251, 2000.
[42] Pu QS, Yun JS, Temkin H, Liu SR, Ion-enrichment and ion-depletion effect of nanochannel structures. Nano Letters 4: 1099-1103, 2004.
[43] Chun H, Chung TD, Ramsey JM, High Yield Sample preconcentration using a highly ion-conductive charge-selective polymer. Analytical Chemistry 82: 6287-6292, 2010.
[44] Khandurina J, McKnight TE, Jacobson SC, Waters LC, Foote RS, et al., Integrated system for rapid PCR-based DNA analysis in microfluidic devices. Analytical Chemistry 72: 2995-3000, 2000.
[45] Lee JH, Song, YA, and Han JY, Multiplexed proteomic sample preconcentration device using surface-patterned ion-selective membrane. Lab on a Chip 8: 596-601, 2008.
[46] Kim SJ and Han J, Self-sealed vertical polymeric nanoporous-junctions for high-throughput nanofluidic applications. Analytical Chemistry 80: 7179-7179, 2008.
[47] Chao CC, Chiu PH, Yang RJ, Preconcentration of diluted biochemical samples using microchannel with integrated nanoscale Nafion membrane. Biomedical Microdevices 17(2):25 2015.
[48] Chen CL, Yang RJ, Effects of microchannel geometry on preconcentration intensity in microfluidic chips with straight or convergent-divergent microchannels. Electrophoresis 33: 751-757, 2012.
[49] Ko SH, Song YA, Kim SJ, Kim M, Han J, Kang KH, Nanofluidic preconcentration device in a straight microchannel using ion concentration polarization. Lab on a Chip, 12, 4472-4482, 2012.
[50] Kumar R, Xu C. X, and Scott K, Graphite oxide/Nafion composite membranes for polymer electrolyte fuel cells. Rsc Advances 2: 8777-8782, 2012.
[51] Feng K, Tang B, and Wu P, Sulfonated graphene oxide–silica for highly selective Nafion-based proton exchange membranes. J. Mater. Chem. A 2: 16083-16092, 2014.
[52] Song H, Wang Y, Garson C, Pant K, Concurrent DNA preconcentration and separation in bipolar electrode-based microfluidic device. Analytical Methods 7, 1273-1279, 2015.
[53] Mao P, Han J, Fabrication and characterization of 20 nm planar nanofluidic channels by glass-glass and glass-silicon bonding. Lab on a Chip 5: 837-844, 2005.
[54] Mao P, Han J, Massively-parallel ultra-high-aspect-ratio nanochannels as mesoporous membranes. Lab on a Chip 9: 586-591, 2009.
[55] Kim SJ, Han J, Self-sealed vertical polymeric nanoporous-junctions for high-throughput nanofluidic applications. Analytical Chemistry 80 (9), 3507–3511, 2008.
[56] Huang KD, Yang RJ, Formation of ionic depletion/enrichment zones in a hybrid micro-/nano-channel. Microfluidics and Nanofluidics, 5: 631-638, 2008.
[57] Mishchuk NA, The role of water dissociation in concentration polarisation of disperse particles. Colloids and Surfaces a-Physicochemical and Engineering Aspects 159: 467-475, 1999.
[58] Hunter RJ, Zeta potential in colloid science: principles and applications. Academic Press, New York 8: 386, 1981.
[59] Probstein R F, Physicochemical hydrodynamics: an Introduction (2nd ed.), New York: John Wiley and Sons, 1994.
[60] Yang C, Li DQ, Masliyah JH, Modeling forced liquid convection in rectangular microchannels with electrokinetic effects. International Journal of Heat and Mass Transfer 41: 4229-4249, 1998.
[61] Lyklema J, Electrokinetics after Smoluchowski. Colloids and Surfaces a-Physicochemical and Engineering Aspects 222: 5-14, 2003.
[62] Yang RJ, Fu LM, Hwang CC, Electroosmotic entry flow in a microchannel. Journal of Colloid and Interface Science 244: 173-179, 2001.
[63] Patankar NA, Hu HH, Numerical simulation of electroosmotic flow. Analytical Chemistry 70: 1870-1881, 1998.
[64] Kim SJ, Ko SH, Kang KH, Han J, Direct seawater desalination by ion concentration polarization. Nature Nanotechnology 5: 297-301, 2010.
[65] Strathmann H, Ion-exchange membrane separation processes. Elsevier, 2004.
[66] Ng JMK, Gitlin I, Stroock AD, Whitesides GM, Components for integrated poly (dimethylsiloxane) microfluidic systems. Electrophoresis 23: 3461-3473, 2002.
[67] McDonald JC, Duffy DC, Anderson JR, Chiu DT, Wu HK, et al., Fabrication of microfluidic systems in poly(dimethylsiloxane). Electrophoresis 21: 27-40, 2000.
[68] McDonald JC, Whitesides GM, Poly (dimethylsiloxane) as a material for fabricating microfluidic devices. Accounts of Chemical Research 35: 491-499, 2002.
[69] Bhattacharya S, Datta A, Berg JM, Gangopadhyay S, Studies on surface wettability of poly (dimethyl) siloxane (PDMS) and glass under oxygen-plasma treatment and correlation with bond strength. Journal of Microelectromechanical Systems 14: 590-597, 2005.
[70] Kim SJ, Song Y-A, Han J, Nanofluidic concentration devices for biomolecules utilizing ion concentration polarization: theory, fabrication, and applications. Chemical Society Reviews 39: 912-922, 2010.
[71] Liu V, Song YA, Han J, Capillary-valve-based fabrication of ion-selective membrane junction for electrokinetic sample preconcentration in PDMS chip. Lab on a Chip 10: 1485-1490, 2010.