Design Framework for the Electrical Characterization of Alcohol Sensors
Engineering
BME 195
The goal of this project was to develop a biosensor capable of detecting toxic alcohol concentrations in the blood. I created an array of organic electrochemical transistors that can sense varying concentrations of ethanol in solution, and plan on extending this functionality to sense other toxic alcohols such as methanol, isopropanol, and ethylene glycol. I quantified the sensitivity and functionality of organic electrochemical transistors by applying bias voltages to the drain of the tranistor, and measuring the respective output currents. After running several characterization tests on small, medium, and large transistor sizes, transconductance was optimized by finding device geometries that would maximize the ratio between the change in current and gate voltage.
Maximizing the ratio between current and gate voltage was essential in using these transistors as toxic alcohol sensors. Ethanol concentrations in solution were quantified by measuring PEDOT:PSS polymer conductivity on electrochemical transistors functionalized with alcohol dehyrogenase and its cofactor NAD+.
Characterization of these organic electrochemical transistors indicates that small voltage fluctuations (mV scale) in gate voltage modulate polymer conductivity.
Using these transistors as sensors for ethanol, I concluded that changes in gate voltage due to the metabolic breakdown of ethanol in the presence alcohol dehydrogenase and NAD+ leads to a noticeable changes in polymer conductivity. Although the sensitivity of the devices was compromised by enzyme functionalization, current responses were quantifiable within the microamp range.
