A high-sensitivity flexible PDMS@rGO-based pressure sensor with ultra-wide working range based on bioinspired gradient hierarchical structure with coplanar electrodes

Flexible pressure sensors are gaining increasing attention owing to their broad practical application prospects in biomedicine, real-time monitoring, and robotics. Although the microstructure design for improving their performance has been extensively investigated, the fabrication of high-sensitivity flexible pressure sensors (more than 1 kPa⁻¹) with a wide working range (more than 1000 kPa) remains challenging. In this paper, we report a preparation strategy for a high-sensitivity flexible pressure sensor (1.412 kPa⁻¹) with a working range of 1275 kPa. Here, we improved the preparation process by mixing anhydrous ethanol with polydimethylsiloxane (PDMS) and synthesized a small-aperture (50 μm) composite with excellent connectivity. Importantly, the sensing mechanism of these porous composites was theoretically studied, and after excluding the surface-microstructure effect, a mechanical-electrical response model considering the effect of the pore size for uniform porous sensing composite was established. Significantly, we propose a gradient hierarchical structure with coplanar electrodes. This strategy can be combined with the existing surface-microstructure strategy to improve the sensitivity of the composites-based sensor. Finally, the potential of the as-fabricated flexible sensor for application as a wearable device for speech recognition was demonstrated.