Photocurable, Highly Stretchable, and Stable Hydrogel Enabled by Acrylic Acid and Oxidized Sodium Carboxymethyl Cellulose

A type of polymer material with a three-dimensional network structure shows great potential for motion detection and health monitoring applications due to the favorable biosafety profile of its raw materials and tunable physicochemical properties. Traditional single-network hydrogels suffer from critical mechanical limitations─fracture toughness <10 J m –2 and tensile strength <0.1 MPa─due to sparse, inhomogeneous cross-linked networks. We addressed this issue by designing a dual-network MIg hydrogel (MIg) via UV-initiated copolymerization, where sodium carboxymethyl cellulose (CMC) was first oxidized by sodium periodate to introduce aldehyde groups for dynamic covalent cross-linking. The oxidized CMC was then mixed with acrylic acid (AC), choline chloride (ChCl), acrylamide (AM), N, N ′-methylenebis(acrylamide) (MBAA), glycerol (Gly), and the photoinitiator phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide (TPO), and the homogeneous precursor solution was rapidly cured under UV light (<60 s, 405 nm) to yield an interpenetrating dual-network architecture comprising a rigid poly(acrylamide- co -acrylic acid) covalent network and a reversible CMC-based dynamic network that enables efficient stress distribution and energy dissipation, endowing the MIg with a tensile strength of 0.90 MPa (9-fold higher than conventional hydrogels), fracture strain of 550%, fatigue resistance over 1000 cycles (λ = 1.25), 88% self-healing efficiency within 12 h at 25 °C (recovery progressing from 20% at 0.5 h to 70% at 9 h), high ionic conductivity (105 mS cm –1 ), low swelling ratio (≈20%), and robust thermal stability (75 h at 80 °C). As a resistive sensor, the MIg demonstrates rapid response/recovery times (90/45 ms), broad detection range (0–350% strain), and segmented sensitivity with gauge factors (GF) of 0.94, 2.06, and 4.21 at strain intervals of 1–2.5, 2.5–4.4, and 4.4–10, respectively, for precise signal discrimination across diverse deformation regimes. We applied this in 3 × 3 pixel array circuits for spatial pressure mapping and wearable devices for motion tracking and ECG monitoring, with stable signal output over 450 s of continuous operation, demonstrating a scalable material platform for flexible electronics, motion monitoring, and human-machine interfaces.