Flexible Biosensor for Non-invasive Continuous Alcohol Monitoring

In this paper, we introduce an inexpensive, lightweight, high-sensitivity, and long-life passive wearable biosensor for wireless non-invasive continuous monitoring of alcohol concentration in biofluids. The sensor consists of a stretchable inductor with a symmetric serpentine structure and a circular interdigitated capacitor to form an resistor-capacitorinductor (RCL) resonant circuit. The alcohol concentration change modifies the environmental dielectric constant of the capacitor and consequently the resonant frequency of the RCL circuit, which can be measured wirelessly with a primary coil. Both high-frequency structure simulator (HFSS) simulations and experiments verify the dependence of the resonant frequency on the alcohol concentration in the alcohol/water mixture. Using pigskin to simulate human skin validate the good sensitivity of the device and its feasibility in continuous monitoring of alcohol concentration in biofluids. Continuous non-invasive monitoring of alcohol concentration may open a new avenue for future flexible wearables and smart medicine.