Skin-Temperature-Responsive In Situ Hydrogel for Enhanced EMG Recording of Lumbar Muscle

Hydrogel electrodes have been widely applied in surface electromyography (EMG) signal recording due to their excellent flexibility and electrical conductivity. However, most hydrogel electrodes employ a pre-formed method, which often results in low adhesion force and poor conformity to complex skin topographies. To address the challenge, this paper proposed a skin-temperature-responsive in situ hydrogel (GPP) based on the synergistic combination of gelatin, L-Pyrrolidone Carboxylic Acid-Na (PCA-Na), and plant-derived natural polysaccharides. The GPP rapidly gels at skin temperature around 30 °C, forming a highly adhesive hydrogel with strong skin adhesion of 0.38 N/cm and a low elastic modulus of 27 kPa. As a result, a high signal-to-noise ratio (SNR) of 35.2 dB was achieved and it maintains low and stable impedance (28 kΩ) within the range of 0.1-100 Hz. As a promising in situ-forming hydrogel, GPP provides a foundation for the development of next-generation bioelectronic interfaces and offers potential applications in long-term monitoring and analysis of lumbar muscle activity.