Flexible piezoresistive pressure sensor with ultra-fast response based on steel wool/PDMS composite and fiber-intertwined contact structure

Piezoresistive flexible sensors exhibit significant potential in wearable health monitoring, electronic skins, and human–machine interaction. However, current flexible sensors are challenged by slow response speeds, the difficulty in synergistically optimizing high sensitivity and wide detection ranges, and high fabrication complexity and costs, which limit their large-scale applications. To address these issues, this study develops a flexible piezoresistive pressure sensor based on a polydimethylsiloxane and steel wool composite. An innovative performance regulation strategy based on the controlled oxidation of the steel wool surface is proposed. By constructing a semiconductive iron oxide layer on the fiber surfaces, the contact resistance between fibers is effectively modulated, significantly enhancing the pressure sensitivity. The results demonstrate that the sensor achieves a high sensitivity (S = 0.9388 kPa−1) and excellent linearity (R2 = 0.992) across a monitoring range of 0–180 kPa. Benefiting from the unique 3D fiber-intertwined structure, the sensor exhibits an ultra-fast microsecond-level response capability, with a rise time of only 12.9 μs, outperforming similar studies by three to four orders of magnitude. Furthermore, the device demonstrates exceptional reliability, with a coefficient of variation of only 0.015% under an 8-h continuous pressure test and a low resolution of 25.46 Pa. In dynamic performance evaluations, the sensor successfully captures characteristic peaks of human pulse waveforms, identifies Morse code tapping signals, and recognizes gait patterns such as walking, jogging, and running. Consequently, this sensor holds great promise for applications in wearable healthcare devices and human–machine interaction.