Multi-height micropyramids based pressure sensor with tunable sensing properties for robotics and step tracking applications

Precise sensing of pressure is essential for various mechanical and electrical systems. The recent emergence of flexible pressure sensors has enabled novel applications, such as human–machine interfaces, soft robotics, and wearable devices. Specifically, the piezoresistive sensing scheme is widely adapted for flexible pressure sensors as it is simple and exhibits outstanding measurement sensitivity and stability. The sensing properties of piezoresistive pressure sensors mainly depends on the materials and contact morphologies at the interface. This paper proposes a flexible pressure sensor based on multi-height microstructures in which the measurement sensitivity and detection range are tunable. Such tunability is due to the sequential contact of micropyramids with different heights. The multi-height micropyramid structured PDMS layer with stamp-coated multi-walled carbon nanotubes (MWCNTs) acts as a conductive active layer and a gold interdigitated electrode (IDE) patterned polyimide (PI) layer works as the bottom electrode. The fabricated sensor exhibits a sensitivity of 0.19 kPa⁻¹, a fast response speed of 20 ms, and a detection range of up to 100 kPa. The sensor is applied to a robotic gripper for object recognition and integrated into a shoe to track walking motions.