Strain‐Sensitive Performance of a Tough and Ink‐Writable Polyacrylic Acid Ionic Gel Crosslinked by Carboxymethyl Cellulose

Abstract A tough polyacrylic acid ionic gel is obtained using carboxymethyl cellulose as a crosslinker and KCl as a conductive ions donor. The polymerization process is initiated by ceric ammonium nitrate and triggered by visible light, which can be employed as a facile 3D printing process to fabricate arbitrary gel architectures. Curling macromolecular crosslinker and plentiful hydrogen bonds among polymers endow the ionic gel with superior mechanical performance including high tensile strength (≈1.33 MPa), large elongation (>8 times), high toughness (≈5.11 MJ m −3 ), and good self‐recovery property. Importantly, the ionic gel can be assembled into a flexible strain sensor to precisely monitor the diverse human body motions in real time, that is, joints bending and muscle contraction, by recording the capacitance variation. This strain‐sensitive performance, which can recover even after 1000 successive cycles, should enable the detection of body action and provide a potential application in health‐care monitoring or human–computer user interfaces.