Electrokinetically Enhanced Sampling of Bacteria in Planar Quadrupolar Microelectrodes
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Abstract 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” enable efficient detection of bacteria. Their operation relies on the selective capture of the target pathogen from a liquid sample onto the detection surface (a process called “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 at concentrations as low as 104 particles/mL. 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. 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 demonstrated.