- 學位論文
於電控微流體平台上操控鐵磁流體液滴
Ferrofluid Droplet Manipulations on an Electromicrofluidic Device
摘要
鐵磁流體因其同時具有磁性且可流動之雙重特性，在電子設備、機械工程、國防航空、生物醫學等領域得到應用，也因其奈米級粒子尺寸，可充分使用於微奈米流體機械系統中。儘管鐵磁流體被廣泛用於微流體系統中，充當栓塞、閥門、活塞等驅動其他不互溶之流體，但對於鐵磁流體本身之操控卻很少有研究報導。本研究主要於微流體平台上，運用介電濕潤、介電泳及電磁力操控鐵磁流體液滴，比較不同的力在不同條件下對鐵磁流體的操控表現，以尋求鐵磁流體在微流體平台上操控的最佳條件。我們選用了水性鐵磁流體（EMG 700, Ferrotec Corporation）和油性鐵磁流體（EFH 1, Ferrotec Corporation）兩種基載液不同的鐵磁流體。首先，探討了在ITO玻璃為基板之平行板裝置上，於不同環境（空氣、2 cSt矽油）中和不同兩板間距（50 μm、100 μm）下，產生液滴並操控其來回移動所需的最佳操作頻率，以及不同電壓下液滴的移動速度。然後，在晶片上以介電潤濕原理驅動由水性鐵磁流體、油性鐵磁流體、純水、2 cSt矽油組成的三種核殼結構液滴移動情況。接著，在晶片上運用介電泳原理，探討在不同環境（空氣、矽油）中，施加電壓與液體形成的最小寬度之間的關係，以此驗證鐵磁流體被高精度圖案化的可能性。此外，我們採用了含有螺旋線圈圖案的PCB板，通過接通直流電產生局部磁場，企圖以電磁力驅動板上的鐵磁流體液滴，並比較PCB板和ITO玻璃上以介電潤濕力驅動液滴之情況。
並列摘要
Ferrofluids, synthesized as a stable colloidal suspension of permanently magnetized particles such as magnetite of 10 nm diameter, are an excellent choice for micro/nanoelectromechanical system (MEMS/NEMS). Although magnetically actuated plugs of ferrofluids have been used to design microfluidic valves, pistons, and pumps, manipulations of ferrofluids with electromicrofluidic have not been systematically investigated. In this thesis, we demonstrated fundamental studies of ferrofluid droplet manipulations by electrowetting-on-dielectric (EWOD), liquid dielectrophoresis (LDEP), and electromagnetic forces. We examined water-based (EMG 700) and oil-based (EFH 1) ferrofluids from Ferrotec Corporation. EWOD occurred in a parallel-plate ITO-glass device when voltage greater than the threshold voltage was applied to move the water-based ferrofluid droplets at a voltage-dependent velocity. The optimal frequency and required minimum voltage to drive a droplet following the signal applied back and forth on the five driving electrodes for at least one cycle between two plates with varied space (height 50 and 100 μm) and in different surroundings (air and 2 cSt silicone oil) were recorded and plotted. In addition, we prepared three kinds of core-shell encapsulated droplets: water-core and oil-shell, water-based-ferrofluid-core and oil-shell, and water-core and oil-based-ferrofluid-shell, to evaluate the relationship between the velocity and applied signal. Moreover, we patterned ferrofluids by designed electrodes on ITO-glass chips by pumping ferrofluids with LDEP in air or silicone oil on a tapered electrode with a decreasing width from 200 to 10 μm and measured linewidth against the applied voltages across the two plates 50 μm apart. We adopted spiral coils arrays on PCB to generate local electromagnetic fields and to manipulate ferrofluid droplets by electromagnetic forces.