Flexible polymer humidity sensor fabricated by inkjet printing

In this paper a humidity sensor concept is presented which is fully fabricated by inkjet printing. In the first step conductive finger electrodes are inkjet printed on flexible polyimide substrate with a silver neodecanoate based ink. Afterwards a humidity sensitive layer is printed upon using a polymer particle based ink. Two approaches are presented for minimizing the line width of the electrode fingers. The humidity sensitivities of the sensor capacitances are investigated. The results are promising and demonstrate, that inkjet printed sensors are potentially suited for label applications. The achieved sensitivity, repeatability and hysteresis are in acceptable ranges.