Bioinspired Gradient Poly(ionic liquid) Ionogels for Ionic Skins with an Ultrawide Pressure Detection Range

Recently, with the increasing demand for artificial skins and human bodily motion/physical signals monitoring, flexible pressure sensors with a wide detection range are urgently needed. Transparent and stretchable gels with ionic conductivities are considered to be ideal candidates for flexible pressure sensors. However, the gel-based pressure sensors usually show a relatively narrow detection range, which significantly limits their practical applications. Herein, we report an unprecedented bioinspired highly flexible modulus/conductivity-dual-gradient poly(ionic liquid) (PIL) ionogel, which is achieved by constructing three layers of PIL ionogels with different monomer concentrations via a layer-by-layer gelation method. The flexible pressure sensor based on the gradient PIL ionogel exhibits an ultrabroad detection range of 10 Pa–1 MPa. This wearable pressure sensor is highly stable in environments and able to monitor both the tiny pressures as low as 10–100 Pa and the high pressures up to 0.1–1 MPa during human body movements. This work provides a powerful strategy for the preparation of flexible gradient materials that are promising for wearable electronics with a wide pressure detection range.