Capacitive humidity sensors based on oxidized PhotoBCB polymer films: enhanced sensitivity and response time

A fast response capacitive humidity sensor was previously designed with a PhotoBCB film, cured in inert atmosphere with O₂ plasma surface modification. Satisfactory sensitivity (0.15 pF/%RH) and response time (less than 2 s) were due to the oxidized film surface which improved water adsorption. In this paper, full oxidation of the film has been considered to design a new fast response humidity sensor with enhanced sensitivity and response time. The sensitivity of the new sensor is 1.3 times higher, and its response time is less than 350 ms at ambient temperature, thus being more than four times faster than the previous sensor. The enhancement of the sensitivity is particularly noticeable under high humidity levels, and this new sensor could be suitable for medical applications. Future improvements consider decreasing the thickness of the film, with support of predictive simulations