Environment-Tolerant Multifunctional Eutectic Gel for Continuous Acquisition of Physiological Electrical Signals

Long-term physiological electrical signal monitoring requires wearable epidermal electrodes to have excellent skin-conforming ability and environmental stability. Herein, a multifunctional eutectic gel with environmental tolerance, surface adhesion, and self-healing performance was successfully synthesized by copolymerizing N-hydroxyethyl acrylamide (HEAA) and acrylic acid (AA) in a eutectic solvent composed of ethylene glycol (EG) and betaine (Bet) and introducing a small amount of Fe3+ simultaneously. Due to the strong hydrogen bonds between the eutectic solvent and the polymer network and the fact that Fe3+ can complex with PAA chains and Bet, a high-density hydrogen-bond and coordination-bond cross-linked network can be formed, endowing the eutectic gel with high mechanical properties (144.48 kPa, 1011%) and excellent self-healing properties. In addition, there is a significant number of carboxyl, hydroxyl, and amide groups on the polymer chain, and a significant number of hydrogen-bond donors and acceptors in the network, which enable the eutectic gel to form noncovalent bonds with various surfaces, thereby effectively improving the adhesion ability (123.41 kPa). Based on good adhesion and stretchability, the eutectic gel electrode can form conformal contact and deform with the skin, showing a low interfacial impedance (≈25 kΩ), and can dynamically monitor various physiological electrical signals, exhibiting high sensitivity and long-term stability. It should be noted that even after continuous operation for 10 h, the eutectic gel electrode still exhibits excellent signal stability, and the signal-to-noise ratio (18.87 dB) of the collected physiological signals shows almost no attenuation.