Multifunctional crystalline hydrogel with a multistage porous structure inspired by biomineralization and Ostwald ripening process: High elasticity, low hysteresis, and excellent sensing properties

The advent of smart terminals has spurred interest in wearable epidermal electronic components composed of conductive hydrogels, with promising advancements in the real-time health monitoring, clinical diagnostics, medical care, and human–machine interaction sensing. However, despite their high sensitivity, conventional porous hydrogel materials often encounter challenges, such as non-uniform pore structures, inadequate energy dissipation mechanisms, structural instability, and poor fatigue resistance. Drawing inspiration from biomineralization and the Ostwald Ripening (OR) theory, this study rapidly synthesized an electron–ion synergistic P(AM-CO-AA)-PDMM crystalline hydrogel with a multistage pore structure via a one-step method (within 15 min). Additionally, the polydopamine-modified MXene (PDMM) enhanced the adhesion and antioxidant capabilities of the hydrogel. Upon subjecting amorphous calcium carbonate (ACC) to a high-temperature acidic copolymer network, it underwent CO 2 gas release, resulting in a porous structure and transformation into stable calcite crystals uniformly dispersed within the hydrogel. The combination of rigid calcite crystals and a flexible hydrogel network confined network migration under slight strain and dissipated energy under larger strain. The resulting composite hydrogel demonstrated exceptional mechanical compressibility (compression hysteresis < 1.4 % over 7000 cycles), high sensitivity (gauge factor up to 58.64), good conductivity (4 S/m), impressive toughness (28 MJ/m 3 ), a wide detection range (tensile strain: 1 %-400 %, compression: 0–43 kPa), and rapid response recovery time (500 and 400 ms). Furthermore, it effectively detects various human physiological activities, serves as a dependable flexible electrode for capturing and distinguishing the EMG and ECG signals, and can be employed in the single-electrode triboelectric nanogenerator (SE-TENG) for energy harvesting, demonstrating its potential in self-powered flexible sensing devices.