Organic semiconductor/water interfaces for photoelectrical viscosity sensing

Most viscosity sensors, which are important in the health, automotive and food production industries, are currently based on mechanical or optical approaches. They are not compatible with emerging flexible and wearable electronics consisting of various lightweight integrated sensors with more compact architecture and lower cost. Here we demonstrate an organic device for sensing the viscosity of nonelectrolyte aqueous solutions which can work at low viscosities (0.9–10 mPa·s). The photoconductivity of devices involving semiconductor/water interfaces was found to obey Walden's rule, suggesting that viscosity could be measured by electrical means. This may be a promising approach for the design of viscosity sensors for portable and wearable applications.