title: Microchannel plate as a novel bipolar electrode for high-performance enrichment of anions.
abstract: 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.
authors.affiliation: Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Cao
authors.forename: Levent
authors.initials: L
authors.lastname: Yobas
mesh_terms: D000838:Anions / Q000302:isolation & purification*; D004566:Electrodes; D053841:Electroosmosis; D004867:Equipment Design; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*
chemical_list: D000838:Anions