Transparent conductive eutectogels with tunable mechanical properties, environmental stability, self-adhesion and self-healing ability for multifunctional sensing and triboelectric nanogenerator

Deep eutectic solvent (DES)-based eutectogels have been extensively studied. However, existing eutectogel sensors still have several problems, such as poor adhesiveness and self-healing ability, limited ionic conductivity, and instability in low-temperature environments. Herein, a "glycerol-water in DESs" solvent system is developed to address these limitations. A series of fully physically crosslinked P(DES-HEAA)x eutectogels were fabricated via one-step photoinitiated copolymerization of N-(2-hydroxyethyl) acrylamide (HEAA) and the polymerizable "glycerol-water in DESs" solvent (x represents the mass ratio of glycerol-water). All of the P(DES-HEAA)x eutectogels have good light transmittance, excellent adhesion, and antifreezing and antidrying abilities. In particular, the P(DES-HEAA)50 eutectogel not only can resist low temperatures of -80 degrees C but also has ultrahigh tensile properties (5000 %) and high conductivity (0.42 S/m). Moreover, the P(DES-HEAA)50 eutectogel multifunctional sensors allow high sensitivity, which enables not only accurate real-time and stable monitoring of human activities and physiological signals but also probing the movement of a robot at -80 degrees C. Furthermore, the P(DES-HEAA)50 eutectogel can also be used as a temperature sensor, exhibiting impressive temperature sensitivity in the range of 20-70 degrees C. Moreover, the prepared triboelectric nanogenerator (TENG) based on the gel has excellent output voltage/power density and can be used for energy harvesting and motion monitoring. Most importantly, the electromechanical properties of P(DES-HEAA)x eutectogels can be easily tuned by adjusting the glycerol-water ratio in the solvent system. Consequently, P(DES-HEAA)x eutectogels have great potential applications in the fields of flexible wearable devices, personal healthcare, self-powered sensors and human-machine interfaces.