Screen-printed capacitive pressure sensors with high sensitivity and accuracy on flexible substrates

Printable elastic conductors promise large-area stretchable sensor/actuator networks for healthcare, wearables and robotics, among other areas. Force pressure sensors are one of their most attractive applications, although their large-area integration has been limited by difficulties in their processability or bendability and their use by their insufficient sensitivity or stability. In this work, we present a flexible screen-printed capacitive pressure sensor, able to be modularly integrated in large-area systems thanks to the substrate flexibility, bending within itself capability and not only at its intersections, and cuttability, allowing a range of modifications in size and shape for complex structures. We built the sensors with a microstructured dielectric, whose hill radii were tuned (between 125 and 375 µm) until obtaining a measurement range of five orders of magnitude, with a logarithm sensitivity above 20% dB⁻¹ at the maximum pressure peak of 750 kPa and of 80% kPa⁻¹ at the lowest test value of 0.5 kPa. These results went along completely with the theoretical model that we also developed. Besides, while smaller pillars showed a significant hysteresis for decreasing pressures, we observed how large hills performed with a small hysteresis of down to 3%, way ahead of the published sensors to the best of our knowledge.