Flow-Cell Sensor for Bacteria Detection Using Gate-Modified Organic Electrochemical Transistor

Organic electrochemical transistors (OECTs) have been previously demonstrated in the sensing of cells and metabolic products. In this study, we report a novel approach on the universal detection of bacterial contamination in home liquid goods through the utilization of a microfluidic flow cell that has been integrated with OECT technology. The flow-cell device has been developed for the purpose of detecting minimal concentration (
$\sim 10^{{3}}$
CFU/mL) of several bacterium types [Escherichia coli (E. Coli), Pseudomonas fluorescens (P. flu), and Staphylococcus aureus (S. au)] in various commercial household liquid product blends (see Air Febreze, Tide, and Old SPICE Bodywash). This process can be completed in a testing period of 1 h or less and does not require amplification or a designated binding agent. The flow-cell configuration uses a microporous filter membrane (Au-coated polyethylene terephthalate (PETE), 0.2-
$\mu \text{m}$
pore diameter) designed to concentrate the bacteria within the chamber. The membrane also functions as a gate electrode for the operation of OECT. The presence of bacteria on the gate filter membrane leads to an increase in the total effective gate voltage (
${V}_{\text {eff}}$
), which in turn causes a decrease in the OECT source–drain channel current (
${I}_{\text {DS}}$
). Based on the shift of
${I}_{\text {DS}}$
, the OECT provides good discrimination between bacteria and sterile solutions (0.4-mA difference). The OECT transconductance (
${g}_{\text {m}}$
) exhibits a maximum value at different levels of
${V}_{\text {GS}}$
for sterile and bacteria solutions. This approach exhibits potential for biosensing systems that will enable real-time monitoring at the production line.