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

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.