High-sensitivity humidity sensor utilizing PEDOT/PSS printed quartz crystal microbalance

In this work, quartz crystal microbalance humidity sensor was fabricated by inkjet printing technique. Poly (3, 4 ethylenedioxythiophene)/poly-styrene-sulfonic acid (PEDOT7 PSS), one of the most widely used polymer composites, was printed on QCM electrode as sensing layer using Dimatrix material inkjet printer. The main advantage of this coating method is its high precision of solution coating with accurately controlled volume and area. The printed layer was varied from 1 to 20 layers. With 20 PEDOT/PSS printed layers, the humidity sensitivity is found increased by more than three orders of magnitude compared to uncoated QCM. In addition, the PEDOT/PSS coated QCM exhibits fast humidity detection with short response and recovery times. Thus, the PEDOT/PSS printed on the QCM electrode is an effective way to improve humidity-sensing characteristic of QCM.