Anisotropic Nanofluidic Ionic Skin for Pressure-Independent Thermosensing

Ionic skin can mimic human skin to sense both temperature and pressure simultaneously. However, a significant challenge remains in creating precise ionic skins resistant to external stimuli interference when subjected to pressure. In this study, we present an innovative approach to address this challenge by introducing a highly anisotropic nanofluidic ionic skin (ANIS) composed of carboxylated cellulose nanofibril (CNF)-reinforced poly(vinyl alcohol) (PVA) nanofibrillar network achieved through a straightforward one-step hot drawing method. The inherent anisotropic nanostructures endowed the ANIS with a modulus (20.9 ± 4.9 MPa) comparable to that of human cartilage and skin, alongside higher fracture energy (41.4 ± 0.3 kJ/m²) and fatigue threshold (1360 J/m²). Incorporating carboxylated CNF not only improves the negative potential but also increases the ionic conductivity of ANIS up to 0.001 S/cm, even at very low ionic concentration (1.0 × 10^-6 M). Furthermore, the ANIS exhibits pressure-independent temperature sensitivity due to its high deformation-resistant performance. Thus, this work introduces a facile strategy for fabricating ANIS with pressure-independent thermosensing properties, promising prospects for practical healthcare applications.