Flexible Capacitive Pressure Sensors with Ultrasonically Engineered Cu-Filled PDMS Dielectric Layers

Flexible capacitive pressure sensors have garnered significant attention in wearable electronics and robotic tactile sensing due to their high flexibility and simple structure. However, non-uniform distribution of conductive fillers in composite dielectric layers often compromises dielectric stability and sensing performance. In this work, a Cu/PDMS composite dielectric layer was fabricated using ultrasonic-assisted homogenization to enhance Cu particle dispersion and suppress sedimentation. A theoretical model and finite element simulations were employed to investigate the effects of particle distribution on permittivity, capacitance, electric field, and current density. The results indicate that uniform Cu dispersion improves dielectric stability and mitigates local electric-field concentration. Compared with conventionally prepared sensors, the ultrasonically treated sensor demonstrated higher sensitivity, enhanced dielectric stability, and a broader working range. Specifically, the sensor achieved a sensitivity of 0.157 kPa^-1 within 0-1 kPa and maintained stable performance over 1000 loading cycles. These findings confirm that ultrasonic-assisted homogenization is an effective approach for improving the dielectric and sensing performance of flexible capacitive pressure sensors.