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.