Process Development and Performance Analysis of Additively Printed Humidity Sensor using Aerosol Jet Printing

Flexible and stretchable devices have attracted great interest in the printed electronics industry for health monitoring of critical infrastructure applications. Additive printing technology is gaining much popularity for fabrication of flexible circuits due to its ease of setup, cost-efficient and its ability of miniaturization. Aerosol Jet Printing is one of the methods of additive printing, which is a popular technology due to non-contact printing, precision and good quality print on flexible substrates, low setup time and reduction of fabrication cost. All these versatilities can be easily applied sensors for health monitoring. Ability to print sensors allows for a tighter integration into the underlying structures providing new opportunities for placement of sensor ever closer to the point of measurement than possible with discrete sensors. In this paper, the humidity sensor is designed and fabricated with the help of aerosol-jet printing on paper substrate. Two kinds of papers with different surface quality used in this study with varied number of passes of the printed conductive line. The printed sensors were tested under the controlled environment of 30°C and relative humidity varying in the range of 20% to 90%. The sensor was also tested for its performance in up sweep and down sweep of relative humidity to quantify the hysteresis. Long-term stability and repeatability have also been quantified.