Drawn a facile sensor: A fast response humidity sensor based on pencil-trace

Abstract Developing a facile and low cost way for fabricating high performance humidity sensor is one of significant strategies to enhance its practical applications. The pencil-trace is emerging in novel electronic devices due to its excellent properties, low cost and facile fabrication method. Here, the commercial pencil is used to fabricate humidity sensor by drawing the sensing layer on the ceramic substrate with interdigital electrodes. It is found that the drawing times of pencil-trace on ceramic substrate strongly affect the conductivity of the sensing layer which is related to the humidity sensing properties of the sensor. The humidity sensor with good humidity sensing properties can be obtained by adjusting the drawing times. The impedance variation of the humidity sensor with drawing two times is about four orders of magnitude within the whole humidity range from 11% to 95% relative humidity at 100 Hz and the response time is as short as 1 s. The humidity sensor is of good linearity (R2 = 0.9913), small humidity hysteresis (3% RH) and long-term stability. Given the facile fabrication way, low cost and high performance, the humidity sensor based on pencil-trace may be of extensive and practical application values.