Vapor-based fabrication of PEDOT coating for wearable strain sensors with excellent sensitivity and self-cleaning capability

Poly(3,4-ethylenedioxythiophene) (PEDOT) coating is advantageous in constructing flexible sensors, due to its good flexibility, high conductivity, and excellent physical and chemical stability. Traditional solution-based coating methods, however, are difficult to retain the micro- and nanostructures of the substrates, thus decreasing the sensitivity of the resulted sensors. In this work, we prepared superhydrophobic (SHB) strain sensors using a piezoresistive composite made from consecutive vapor deposition of conformal polymer coatings, i.e. PEDOT and poly(perfluorodecyl acrylate-co-ethylene glycol diacrylate) on fabrics using oxidative and initiated chemical vapor deposition methods. Compared with the pristine fabric sample, the composite materials displayed significantly improved initial currents, which are attributed to more conductive paths created by PEDOT coating. The resulted strain sensor displayed great flexibility, large sensitivity, wide sensing range, and excellent reliability. Furthermore, the sensor has been successfully employed to monitor various human motions in real time. The hydrophobic outer layer endows the sensor self-cleaning and durability capacities, indicating possible applications under harsh environment.