Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Electrophoresis. 2013 Jul;34(14):1991-7. doi: 10.1002/elps.201300040.
Microchannel plate (MCP), a high-porosity glass membrane used as an electron multiplier in analytical/scientific instruments for the detection of energetic photons and charged particles is demonstrated here as a highly effective bipolar electrode (BPE) for electrokinetic focusing of anions. Assembled between a pair of microfluidic channels filled with an electrolyte buffer and subjected to a sufficient bias potential, MCP supports faradaic reactions, owing to its semiconducting characteristics. Thousands of microcapillary tubes fused together define MCP and act in unison such that each microcapillary serves as a tiny BPE surrounding an infinitesimal element of bulk electrolyte with a large surface-area-to-volume ratio and hence performs highly effective as compared to a planar electrode inlaid into a microchannel. This performance has been validated here where concentration enrichment of a fluorescent tracer has been demonstrated at a remarkable rate of up to 175-fold/s exceeding those reported for planar BPEs. We attribute such high performance to the rapid onset of ion-depletion zone and subsequent steep field gradient, signifying the high-porosity structure of MCP as an effective BPE.
微通道板（MCP）是一种高孔隙率的玻璃膜，用作分析/科学仪器中的电子倍增器，用于检测高能光子和带电粒子。在这里，它被证明是一种高效的双极电极（BPE），可用于阴离子的电动聚焦。MCP 组装在一对充满电解质缓冲液的微流道之间，并施加足够的偏置电势，由于其半导体特性，MCP 支持法拉第反应。数千个微毛细管融合在一起定义了 MCP，并协同作用，使得每个微毛细管都作为一个微小的 BPE，围绕着具有大表面积/体积比的微小电解质元素，因此与嵌入微通道的平面电极相比，其性能要高得多。这里已经验证了这种性能，其中荧光示踪剂的浓度富集以高达 175 倍/秒的显著速率得到证明，超过了报道的平面 BPE 的速率。我们将这种高性能归因于离子耗尽区的快速出现和随后的陡峭场梯度，这表明 MCP 的高孔隙率结构是一种有效的 BPE。
