Effect of Dielectric and Stiffness of Soft Material between the Electrodes of a Capacitive Pressure Sensor on its Performance

The soft dielectric material between the electrodes of a parallel plate type capacitive pressure sensor plays a key role in their overall response. Yet its influence has not been studied. Herein, capacitive pressure sensors fabricated with different elastomeric dielectric layers have been used to evaluate the performance. Ecoflex™ and Polydimethysiloxane (PDMS) with three different stiffnesses are utilized to fabricate four capacitive pressor sensors and their sensing performance compared. The Ecoflex-based pressure sensor reveals higher sensitivity, of 4.11kPa$^{-1}$ than the PDMS-based sensors (1.11kPa $^{-1}$) at a low-pressure regime $(\lt 1$ kPa), which is suitable for light touch. With the sensitivities of 2.32kPa $^{-1}$ and 0.08kPa $^{-1}$ in the region 1 (1 to 10kPa) and region 2 (10 to 160kPa) respectively, the PDMS with 7.5:1 ratio reveals highest sensitivity among the three PDMS-based devices. The results indicate that careful selection of soft dielectric layer is important for obtaining pressure or touch sensor with desired sensitivity.