在微流體裝置中混合液體的困難性，主要是由於在微流體裝置長度限制下，微管道中流體的雷諾數很低（Re < 100），流體僅能以層流（laminar flow）的形式移動。在無擾流（turbulent flow）的作用下，流體間的混合通常只能藉由分子的擴散作用達成，所需時間較長，因此必須藉由一微型混合器，促使流體產生快速的混合效果，以解決混合不易的問題。我們利用 Dukhin 在1991年提出的離子選擇性顆粒的非線性電動流動機制，設計出一非線性電動流動的微型混合器，當施加適當的dc或ac 電場（30∼150 V/cm）於約10 L的混合槽時，由於在1 mm 大小的導電性離子交換顆粒表面不均勻的帶相反電荷離子流進，以及表面不均勻的極化現象，小顆粒周圍產生出高強度的電滲渦流。當此電滲渦流結合與小顆粒的受電泳作用而移動對流體的擾動，或是結合與管道內因電極上電解造成的酸鹼梯度現象而產生之廻流循環，可在微型混合器內製造出劇烈的混沌混合效應。實驗證明，在此系統下試劑的混合效率可大幅提高，原本單純靠擴散作用須半小時才能混合的二個分離染料，在30秒內即可混合完全，其有效混合擴散係數正比於電場的平方。將此系統應用在酵素（trypsin）與其受質（L-BAPA）反應實驗中，可使反應初速度 V0 提高40倍左右。儘管這種電動流動機制在30分鐘內，會因為小顆粒中的電荷飽和而停止，它仍然可以應用在拋棄式的生物晶片或微反應器上。

There have remained many technical difficulties to develop effect mixing devices in microfluidics systems. Due to the constraint of small length scale, typically less than 1 mm, the Reynolds number is low (Re < 100) in these miniaturized systems. Flows in the microchannels are laminar. Therefore mixing in them usually replies on molecular diffusion when turbulent flows are absent. Dukhin’s group has studied a unique nonlinear electrokinetic mechanism to generate micro-vortices around a conductive ion-exchange granule (~ 1 mm) placed in an electric field. In this thesis, we explore using this non-linear electrokinetic phenomenon to develop a simple but effective micro-mixer.
When dc electric fields ( 30 ~ 150 V/cm) are applied across a mixing chamber smaller than 10 L, high-intensity electroosmotic micro-vortices are generated around a small conductive ion-exchange granule. This phenomenon generated by a non-uniform counter-ion flux into the granule and corresponding non-uniform polarization. Coupling between these micro-vortices and another secondary flow, such as fluid-stirring due to granule’s electrophoretic motion or flow circulation induced by pH gradient along the channel generated via electrolysis at electrodes, these vortex flows are able to produce an intense chaotic micromixing action. In the mixing chamber, two segregated dye that require nearly 0.5 h to mix by diffusnion are observed to mix within 30 s. The effective diffusivity scales as E2. In the enzyme reaction experiment, the initial rate V0 can be enhanced to 40 times by this novel micromixer. Although the nonlinear electrokinetic mixing mechanism ceases after 30 min as the granule saturates with the counterion, this micromixer should prove useful for disposable microchip.

第一章 緒論
1-1 研究動機….……………………………………………………..1
1-2 文獻回顧….…………….….…………………………………….3
1-2-1 被動式混合器……….….…………………………………...3
1-2-2 主動式混合器………..….…………………………………..4
1-2-3 混合程度量化方式..….……………………………………..6
1-3 理論基礎.………………...……………………………………….7
1-3-1 濃度偏極化現象…………………………………………….8
1-3-2 非線性電動渦流機制….……………………………………9
1-4 非線性電動渦流混合器之研究架構………………………….13
第二章 實驗器材與方法……………………..………………………15
2-1藥品及裝置………………………………..……………………..15
2-2 溶液之配置………...……………………………………………17
2-3實驗流程…………………………………………………………18
2-3-1非線性電動混合器之架設………………………………….18
2-3-2離子交換顆粒之活化……………………………………….19
2-3-3染色劑之選擇……………………………………………….19
2-3-4直流電場下的混合實驗…………………………………….20
2-3-5酸鹼梯度之實驗…………………………………………….21
2-3-6混合效率的評估…………………………………………….22
2-3-7交流電場下的混合實驗……………………………….……23
2-3-8酵素反應實驗初速度之測定……………………………….23
2-3-9 Lidocaine 固相萃取實驗……………………..…………….24
第三章 結果與討論
3-1 直流電場下的非線性電動混合機制…………………………...26
3-1-1 線性與非線性電動機制下的混合成效之比較…………...26
3-1-2酸鹼梯度現象的探討………………………………………27
3-1-3 混合效率的量化…………………………………………...29
3-2 交流電場下的非線性電動混合機制…………………………...32
3-2-1 交流電場下的混合情形…………………………………...32
3-2-2 電場頻率對混合效率之影響……………………………...33
3-3酵素反應初速度之測定…………………………………………36
3-4 Lidocaine 的固相萃取………………………………………..37
第四章 結論…………………………………………………………..41
第五章 參考文獻………………………………………………………44

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