Pressure Sensors with Microstructured Polydimethylsiloxane Dielectrics Fabricated Via the Breath Figures Method

Flexible pressure sensors with high sensitivity show promise in applications such as touch screens, biomedical diagnostic technologies such as wearable heart rate monitors, and artificial “electronic skin” for robotics or prosthetic devices.  For “electronic skin” applications, there exists a need for low-cost and scalable methods for producing pixels to sense both medium (10-100 kPa) and low pressures (<10 kPa).  In this work, pressure sensors have been fabricated by incorporating compressible, microstructured polydimethylsiloxane (PDMS) and poly(styrene-butadiene-styrene) (SBS) dielectric layers into capacitors.  The "breath figures" (BFs) technique, a simple, self-assembly based method for producing honeycomb-structured polymer films, was used to structure the PDMS and SBS films.  Capacitive sensors incorporating microstructured PDMS dielectrics varied widely in structure and quality, but consistently showed high reproducibility, little hysteresis, and high sensitivity at lower pressures with decreased sensitivity at higher pressures.  SBS dielectrics, on the other hand, resulted in more desirable linear responses to pressure, but exhibited lower sensitivity and some hysteresis.  Future work to increase reliability of PDMS and SBS film formation will lead to the incorporation of these dielectrics into transistor-based pressure sensing devices and, eventually, biomedical applications.