A breathable and sweat-absorbing pressure sensor based on PDMS gradient foam to achieve high sensitivity and wide detection range

Various designs of porous structures have been introduced to enhance the sensitivity of resistive pressure sensors. However, this method often comes at the cost of narrowing down the measurement range, limiting its use in low-pressure detection. This study proposes a soft pressure sensor with a two-layer gradient foam structure. By finely adjusting the porosity and cross-linking degree of the PDMS, we aim to enhance the sensitivity without compromising the range of the sensor. Testing results demonstrate that the sensitivity of the gradient foam increases with higher porosity, while the measurement range expands with a higher cross-linking degree. The soft sensor with the PDMS gradient stiffness foam (PGSF) achieves a sensitivity of 0.202 KPa-1 in the range of 0-40 kPa, 0.067 KPa-1 in the range of 40-210 kPa, and 0.020 KPa-1 in the range of 210-850 kPa. Furthermore, the sensor exhibits a minimum detection limit of 50 Pa and demonstrates excellent stability (withstanding over 8000 testing cycles), breathability, and sweat absorption ability. Additionally, we conducted motion detection, health monitoring, and pressure mapping tests to showcase the potential applications of our proposed soft sensor in these fields.