Development of a sensor device with polymer-coated piezoelectric micro-cantilevers for detection of volatile organic compounds

Exhaled breath contains thousands of volatile organic compounds (VOCs), some of which have been associated with respiratory disease. We describe a sensor device with an array of eight polymer-coated piezoelectric micro-cantilevers (two of each polyacrylic acid, polyethylenimine and polyethylene glycol and two uncoated cantilevers) and an electronic resonant frequency readout, designed for analysis of VOCs. We have measured the system's response to temperature (24 °C to 40 °C), pressure (200 mmHg to 760 mmHg), and humidity (10% to 50% RH), evaluated the reproducibility of measurements between micro-cantilevers (n = 3), and tested the stability of the system over six months. By measuring the frequency shift of the resonating micro-cantilevers, and using the inflection point of a fitted sigmoid model, we show that acetone, ethanol, octane are distinguishable from one another, with a measurement limited of detection of 1568, 383, and 87 ppmv, respectively. From interpolation of the electronic readout, we found the lowest estimated measurement to be 5 ppmv (acetone on polyacrylic acid). We have also shown that polar mixture (acetone, ethanol, and water) and non-polar mixture (increasing octane concentration and decreasing polar mixture constituents) can be differentiated.