All-Natural Milk-Enhanced Polymerizable Deep Eutectic Solvent Elastic Ionogel Fibers toward Flexible Wearable Sensors

Elastic ionogel fibers have scored tremendous achievements with the rapid development of artificial intelligence and electronic techniques. However, conventional elastic ionogel materials usually suffer from poor mechanical strength, high cost, high toxicity, and high pollution, which severely restrict their practical applications. To meet this challenge, we design a biobased elastic ionogel fiber by using eco-friendly polymerizable deep eutectic solvents (PDESs) as the substrate and all-natural milk as the reinforcement. This milk-based PDES ionogel fiber exhibits remarkable mechanical properties (7.52 MPa of tensile stress) due to the intrinsic hydrogen bonding interactions between the PDES molecular network and the milk protein, which is three times as much as that of the pure PDES fiber. Meanwhile, this milk-based PDES ionogel fiber also shows extreme-environment resistance, which can maintain most of the mechanical properties and flexibility after being treated at −60 to 60 °C. More importantly, this milk-based PDES ionogel fiber possesses a self-healing property under high humidity and a strain-sensing behavior, which can be utilized to monitor human motion signals. This work not only developed a high-performance elastic ionogel fiber through a low-cost and green manner but also promoted the fundamental research and industrialization of flexible wearable electronic materials.