Flexible pressure sensor with bioinspired hierarchical ridge-like microstructures with high sensitivity and wide detection range based on MWCNT composites

Flexible pressure sensors have attracted significant attentions for their promising applications in wearable electronics and healthcare monitoring systems. However, the simultaneous realization of high sensitivity and wide detection range remains highly challenging. To this aim, a flexible piezoresistive pressure sensor with bioinspired hierarchical ridge-like microstructures (BHRM) was proposed to achieve high sensitivity and wide detection range simultaneously. The sensing layer was fabricated by a bionic template method using Arundo donax leaves as the template in a fast and cost-effective way, in which composites of multi-walled carbon nanotubes (MWCNT) and polydimethylsiloxane (PDMS) were synthesized with excellent flexibility and piezoresistive properties. MWCNT/silicone elastomer electrodes were prepared by a direct ink writing (DIW) method. The hierarchical ridge-like microstructures with parallel primary ridges and secondary ridges contributed to enhance contact area and deformation capacity, and maintain continuous contact between the sensing layer and electrodes. The sensor showed a high sensitivity of 3.08 kPa⁻¹ within 0.1–10 kPa and a wide linear measurement range of 0.1–200 kPa. It also presented high stability of over 5000 cycles, short response/relaxation times of 35 ms/40 ms, respectively, and low hysteresis error of 4.7 %. The sensor demonstrated capabilities in real-time movement detection, speech recognition, and pulse and heartbeat monitoring.