Electrokinetically Enhanced Sampling of Bacteria in Planar Quadrupolar Microelectrodes
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The detection of biologically infectious agents, such as bacteria, in water is often a cumbersome process that can only be performed by trained personnel in a well-equipped laboratory and may require sufficient time (sometimes days) until detectable concentration levels of the pathogen are reached. Surface-based biosensors, on the other hand, have shown great promise as miniaturized devises that can provide efficient and de-centralized detection of bacteria. Their operation involves the selective capture of the target pathogen from a liquid sample to a surface (“sampling”) and their subsequent detection via signal transduction. Sampling currently presents a major bottleneck in the successful operation of these sensors as it relies on the extremely slow diffusive transport of the target particle from the bulk of the sample to the capture surface. The present work investigates how alternating current (AC) electric field effects produced by planar microelectrode arrays embedded into a solid surface can improve capture of bacteria. Specifically, numerical and experimental work is combined toward the analysis of a host of electric field generated phenomena (electrophoresis, electroosmosis, and electrothermal fluid flow) that can potentially guide and enhance the transport of K12 E. coli bacteria to the capture surface inside an electric field to find the effective frequency/voltage combination for an efficient capture. Bacteria capture at concentrations as low as 104 particles/mL was experimentally achieved. Proof of principle demonstrations on how antibody-functionalized microelectrode arrays can accelerate and selectively capture K12 E. coli bacteria (target pathogens) from samples containing debris or mixed bacteria populations are also demonstrated.