Microfluidic Actuation Using Electrochemically Generated Bubbles

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• 作者：Susan Z. Hua ; Frederick Sachs ; David X. Yang ; and Harsh Deep Chopra
• 刊名：Analytical Chemistry
• 出版年：2002
• 出版时间：December 15, 2002
• 年：2002
• 卷：74
• 期：24
• 页码：6392 - 6396
• 全文大小：322K
• 年卷期：v.74,no.24(December 15, 2002)
• ISSN：1520-6882

文摘

Bubble-based actuation in microfluidic applications isattractive owing to elementary microfabrication requirements. In the present study, the mechanical and chemicalcharacteristics of electrochemically generated bubblevalves were studied. By generating electrochemical bubblesas valves directly inside the channel, valves could beclosed and opened in milliseconds. Whereas bubbleinflation (or valve closing) rate increases with appliedvoltage, small microfluidic dimensions accelerate bubbledeflation rates. It is found that bubbles need not collapsefully to restore full flow, and the channel opens when itshydraulic resistance equals that between the bubble andthe wall-a process requiring only milliseconds. Since onlypicomoles of salt are needed to generate bubbles, pHgradients that are invariably associated with electrochemical reactions were readily suppressed by using a smallamount of buffer, as visualized by a pH-sensitive fluorescent dye. A range of common laboratory reagents andelectrolytes in varying concentrations, including weak tostrong acids and bases, as well as nonaqueous/aqueousmixtures were successfully tested. Using such bubblevalves, an eight-way multiplexer was fabricated and tested.