Non-contact self-powered electronics are proposed based on a thermoelectric hydrogel, which can be applied in remote-controlled small electronics, wireless information interaction and monitoring solar intensity via photo-thermal-electric conversion.

Facial expression is vital for assessing psychological health, especially in adolescents. Current facial expression recognition systems face challenges such as poor breathability, limited electromechanical performance, and insufficient environmental stability. Here, an air-permeable self-powered hydrogel array designed for continuous mental monitoring based on facial expression recognition is proposed. The remarkable breathability of the patch composed of thermogalvanic hydrogel and gelatin films is achieved by the through-holes structure design. Additionally, the hydrogel leverages a double network structure and phytic acid with rich hydrogen ions, achieving a trade-off between mechanical (1.07 MPa) and electrical (34.4 mS cm⁻¹) properties. Due to the multiple hydrogen bonds among phytic acid, glycerol, and water, the hydrogel maintains over 80% of its original electrical performance after 10 days, demonstrating its excellent environmental stability. Integrated with a deep learning algorithm, the hydrogel array can recognize six facial expressions with a high accuracy of 100% and provide long-term monitoring of mental states based on the positive-to-negative emotion ratio. This work paves the way for a new generation of wearable mental monitoring platform for healthcare and human–machine interfaces.

The corrosion behavior of soluble Mg–Gd-based alloys was systematically investigated by analyzing two key aspects: environmental factors and microstructural characteristics. Environmental influences were evaluated using immersion weight loss tests under varying Cl⁻ concentrations and temperature conditions. From a microstructural perspective, the study examined the impact of different initial microstructural morphologies on corrosion performance. The second-phase compound Mg₅Gd, formed in alloys prepared via melting, was subjected to both immersion weight loss and electrochemical testing. The results demonstrated that corrosion rates increased with higher Cl⁻ concentrations and elevated temperatures, albeit in a nonlinear manner. Notably, significant effects on corrosion rates were observed in the Cl⁻concentration range of 1% to 3% and at temperatures between 75 °C and 100 °C. Additionally, the dissolution rate of the alloy increased markedly from 8.37 mg/cm²/h in the as-cast state to 43.85 mg/cm²/h following extrusion combined with perforation deformation. Microstructural analysis revealed that the extrusion process disrupted the coarse, reticulated second-phase structure observed in the as-cast state, thereby diminishing its corrosion-inhibiting properties. Electrochemical testing further confirmed that the Mg₅Gd second phase, formed through the incorporation of the rare-earth element Gd, exhibited high electrochemical activity.