A low-cost printed humidity sensor on cellulose substrate by EHD printing

The use of printing technologies is rapidly increasing in area of electronic devices. Electrohydrodynamic (EHD) jet printing has been a target of research because of its aptness to produce high-resolution patterns for wide range functional materials onto flexible substrates. In this paper, a stable humidity sensor was printed utilizing PEDOT: PSS as sensing layer. Meander-type electrodes using silver nanoparticles ink were fabricated using continuous EHD inkjet printing on flexible paper (cellulose) substrate. The sensing material PEDOT: PSS was dissolved in ethylene glycol and then deposited on silver electrodes. The fabricated sensor exhibited decent response toward change in capacitance above 50% relative humidity. The response and recovery time of the printed sensor for increasing and decreasing humidity levels were approximately 0.58 s and 0.7 s, respectively. This low-cost sensor has potential applications in agriculture, food monitoring, medical and industrial environment as a disposable sensor for humidity detection.