Design and characterization of PDMS-CB-ZnO-ternary composite based flexible capacitance pressure sensors for wearable applications

Abstract Flexible pressure sensors are emerging as a pivotal technology for applications such as robotics, prosthetic devices, electronic skin (e-skin), and human-machine interactions. Among various transduction mechanisms for flexible pressure sensors, the capacitance pressure sensors (CPS) have garnered significant attention due to their simplicity in architecture, high sensitivity, and potential for flexible and wearable designs. A typical CPS in parallel-plate geometry consists of a dielectric layer sandwiched between two conductive electrodes. However, achieving high sensitivity and a wide linear operating range remains a challenge in the development of wearable CPS in terms of the material section and fabrication procedures. In this study, a highly sensitive CPS was developed using a polymer nanocomposite as the dielectric layer. The nanocomposite incorporates high-dielectric zinc oxide (ZnO) nanoparticles and conductive carbon black (CB) fillers, which are uniformly dispersed within the polymer matrix to enhance its dielectric properties. This dielectric layer is integrated between silver conductive electrodes that are screen-printed onto flexible polyimide substrates. Among the PDMS-x wt% CB-y wt% ZnO (x-0&3,y-0, 1&, 2) composite sandwiched layers studied, the PDMS-CB (3 wt%)-ZnO (2 wt%) composite sandwiched layer based fCPS shows high sensitivity of 6.6083 pF kPa −1 (0.109 kPa −1 ) in 0–240 kPa pressure range with fast response and recovery times of 0.6 s and 0.48 s respectively, a low hysteresis value of 5.7% and long durability. These exceptional attributes demonstrate the sensor’s suitability for applications in e-skin and wearable devices, where precise pressure detection and reliable performance are critical.