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研究生：	羅浩恩 Luo, Hau-En
論文名稱：	濃度極化現象的微流體海水淡化裝置 Microfluidic Seawater Desalination Device Using Ion Concentration Polarization
指導教授：	楊瑞珍 Yang, Ruey-Jen
學位類別：	碩士 Master
系所名稱：	工學院 - 工程科學系 Department of Engineering Science
論文出版年：	2014
畢業學年度：	102
語文別：	英文
論文頁數：	60
中文關鍵詞：	海水淡化、微流體晶片、電動學、濃度極化現象、電雙層重疊
外文關鍵詞：	Seawater desalination, Microfluidic chip, Electrokinetics, Ion concentration polarization, Overlapped electric double layers
相關次數：	點閱：222 下載：2
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當今淡水資源的短缺已經是一個嚴重的問題。氣候變化導致冰川消失和降雨減少，威脅了全球超過六分之一人口的供水。我們的海水淡化裝置具有以下幾個優點，面積小、便於攜帶、可擴展、功率消耗低，並具有極佳效能。
在這研究中，我們利用微機電系統（MEMS）製造技術和自行密封Nafion的方法製造微流體海水淡化裝置。
當電場被施加穿過一個微米管道和離子選擇性納米管道的交界處，就會在這交界處發生離子濃度極化（ICP）效應。陽離子和陰離子均會被聚集在陰極端的奈、微米交界處，且消散於陽極端的奈、微米交界處。在消散區內的離子濃度相當的低，所以消散區會排斥帶電粒子使得離子無法穿越。這就是ICP海水淡化的基本原理，也是我們的實驗原理。
在海水淡化實驗中，我們施加100V電壓在有著一條Nafion膜的微流體晶片上，並輸入0.5M的NaCl和10-5M 熒光素溶液進入晶片(Q = 5 µl/min)。海水淡化現象被觀察到在施加電壓後的第八分鐘。
我們討論了幾種不同類型的海水淡化裝置及其淡化效果。這些裝置具有不同的Nafion納米管道設計。但最終我們無法產生穩定的海水淡化現象。我們發現實驗裝置的缺陷來自於奈米管道的製作，實驗中使用自行密封Nafion方法，在我們的裝置中製造奈、微米交界，但由於Nafion膜沉積不均勻，導致無法將隙縫完全密封。我們將在第5章詳細討論這些問題。

The shortage of fresh water is a serious problem in the world today. Climate change is leading to vanishing glaciers and reduced precipitation, which threatens the water supply of more than one-sixth of the Earth’s population. Our device is advantageous because it has a small footprint, is portable, scalable, consumes little power, and is highly energy efficient.
In this study, we manufactured a microfluidic seawater desalination device using microelectromechanical systems (MEMS) fabrication techniques and the self-sealed Nafion junction method.
The ion concentration polarization (ICP) effect occurs at the junction of the micrometer and ion-selective nanometer channels when an electric field is applied across the channels. Both cations and anions are enriched at the cathode end and depleted at the anode end of a micro/nanojunction. The ion concentration is very low in the depletion zone; thus, the depletion zone repels charged particles, and no ions can pass through this region. This phenomenon is the principle underlying the ICP seawater desalination method used in this experiment.
In seawater desalination experiments we applied 100 V to the microfluidic chip with One Nafion Junction and introduced a (Q = 5 µl/min) solution of 0.5 M NaCl and 10–5 M fluorescein into the chip. Seawater desalination was observed at the eighth minute after the voltage was applied.
We discuss the desalination effect of several types of seawater desalination devices. These devices exhibit a different design of Nafion nanochannels.
We could not produce a steady seawater desalination phenomenon. The major defect in this experiment lies in the fabrication of the nanochannel. We used the self-sealing method to produce micro/nanojunctions in our device; however, nonuniform Nafion sediment resulted in unsealed gaps. We will discuss these problems in more detail in chapter 5.

Table of contents
中文摘要	I
Abstract	III
致謝	V
Table of contents	VIII
List of Figure	XI
Abbreviation	XIV
Nomenclature	XV
Greek symbols	XVI
Chapter 1 Introduction	1
1-1 Introduction	1
1-2 Microelectromechanical Systems	3
1-3 Reverse Osmosis	4
1-4 Electrodialysis	6
1-5 Microfluidic Chip	7
1-6 Literature Survey	8
1-6.1 Ion Concentration Polarization	8
1-6.2 Self-Sealed Vertical Polymeric Nanoporous Junctions for High-Throughput Nanofluidic Applications	11
1-6.3 Direct Seawater Desalination by Ion Concentration Polarization	12
1-6.4 Out-of-Plane Ion Concentration Polarization for Scalable Water Desalination	14
1-7 Motivation	16
Chapter 2 Electrokinetic Effect	17
2-1 Electrokinetics	17
2-2 Electrical Double Layer (EDL)	17
2-3 Electrical Double-Layer Overlap	20
2-4 Electroosmotic Flow	21
2-5 Electrophoresis	23
2-6 Ion Concentration Polarization Phenomena	24
Chaprer 3 Material and methods	28
3-1 Photomask	28
3-2 Fabrication of Microchip	29
3-2.1 Silicon Wafer Pretreatment	29
3-2.2 Photoresist Coating	30
3-2.3 Exposure	31
3-2.4 Development	31
3-2.5 PDMS Casting	33
3-2.6 Oxygen Plasma Bonding	35
3-2.7 Fabrication of Self-Sealed Polymeric Nanoporous Structures	36
3-3 Fabrication of Microfluidic Conductivity Meter	37
3-3.1 Evaporation Deposition	38
3-3.2 Lift-off Process	39
3-4 Instrument	40
3-4.1 Microscope	41
3-4.2 Image Capture Unit	41
3-4.3 DC Measurements	41
3-5 Microfluidic Seawater Desalination Device Design	42
3-6 Experimental Setup	45
Chapter 4 Result and Discussion	47
4-1 Seawater Desalination Using theIon Concentration Polarization Process	47
4-2 I–V Curves and Ion Depletion	49
4-3 Seawater Desalination Experiments	51
4-3.1 Seawater Desalination Device with One Nafion Junction	51
4-3.2 Using the Seawater Desalination Device with Two Nafion Junctions to Observe the ICP phenomenon	52
Chapter 5 Conclusion	54
5.1 Why was the ICP phenomenon not rapidly induced in the experiment described in section 4-3.1?	54
5.2 Why was the ICP phenomenon rapidly induced in experiment 4-3.2?	56
5.3 Why was the nanochannel (Nafion) damaged in seawater desalination experiments?	57
References	58




List of Figure
Figure 1.1 Reverse osmosis principle schematic diagram	5
Figure 1.2 Electrodialysis principle schematic diagram	6
Figure 1.3 ICP experiment device [11]	9
Figure 1.4 ICP phenomenon [11]	10
Figure 1.5 Effect of buffer concentration on ICP experiment [11]	11
Figure 1.6 Fabrication of Self-Sealed polymeric nanoporous structures [21]	12
Figure 1.7 Seawater desalination by ICP phenomenon [8]	13
Figure 1.8 Out-of-Plane ICP for scalable water desalination device [10]	14
Figure 1.9 Out-of-Plane ICP for water desalination schematic diagram [10]	15
Figure 1.10 Out-of-Plane ICP phenomenon for water desalination [10]	15
Figure 2.1 Schematic of electric double layer and its potential distribution.	19
Figure 2.2 Electrical double layers in nano/microchannels.	20
Figure 2.3 Electroosmotic flow velocity distribution.	22
Figure 2.4 Schematic of electrophoresis phenomenon.	23
Figure 2.5 Schematic illustrating concentration polarization at nano/microchannel interfaces.	25
Figure 3.1 Negative photoresist mold fabrication process.	32
Figure 3.2 Positive photoresist mold fabrication process.	32
Figure 3.3 Microchannel molds on silicon wafer substrate.	33
Figure 3.4 Schematic of PDMS casting process.	34
Figure 3.5 Oxygen plasma machine.	35
Figure 3.6 Schematic of self-sealed polymeric nanoporous structures fabrication process.	37
Figure 3.7 Evaporation and lift-off processes	39
Figure 3.8 Microfluidic conductivity meter	40
Figure 3.9 Microscope, CCD, and source meter	42
Figure 3.10 Seawater desalination device schematic diagram	43
Figure 3.11 Seawater desalination device schematic diagram	43
Figure 3.12 Seawater desalination device schematic diagram	44
Figure 3.13 Seawater desalination device schematic diagram	44
Figure 3.14 Microfluidic seawater desalination device	45
Figure 3.15 Experimental Setup diagram	46
Figure 3.16 Seawater desalination phenomenon using ion concentration polarization	46
Figure 4.1 Schematic of the seawater desalination process based on ion concentration polarization.	47
Figure 4.2 I–V curve showing the ohmic region, limiting current region, and over-limiting current region.	50
Figure 4.3 Photograph of a nanochannel damaged in the seawater desalination experiment	50
Figure 4.4 Photograph of the seawater desalination phenomenon	51
Figure 4.5 Photograph of the ICP phenomenon in a seawater desalination device with two Nafion junctions.	52
Figure 4.6 Photograph showing the expansion of the depletion zone.	53
Figure 5.1 Schematic of nonuniform Nafion sediment resulting in an unsealed gap.	55
Figure 5.2 Fluorescein transport from the cathode side to the anode side under the influence of an electric field.	55
Figure 5.3 Fluorescein transport from the cathode side to the anode side under the influence of an electric field.	56

                                    

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