Self-Healing, Freeze-Resistant, and Sustainable Aloe Polysaccharide-Based Hydrogels for Multifunctional Sensing

Although designing wearable sensors by using sustainable hydrogels has been gaining widespread attention, the fabrication of inexpensive biobased hydrogel sensors with fast self-healing and antibacterial abilities remains challenging. In this study, biobased green hydrogels were prepared from aloe vera polysaccharides (AP), poly(vinyl alcohol), and sodium alginate (SA). Their mechanical, electrical, biodegradable, and self-healing characteristics were investigated. The hydrogel with an AP/SA ratio of 9:2 demonstrated excellent tensile properties with an elongation at break, tensile toughness, and electrical conductivity of 1477.3%, 1.19 MJ/m3, and 12.67 × 10–2 S/m, respectively. The hydrogel remained electrically conductive at −20 °C. During strain sensing, it exhibited excellent stability and sensitivity (gauge factor: 9.2), a wide strain range (up to 1400%), and a high self-healing efficiency of 96.1% over 4 min. It was also able to detect low strains (1%). These properties enabled the hydrogel assembly into wearable sensors to monitor physiological signals generated by large movements of body joints, small facial expression changes, talking, and drinking. An assembled humidity sensor detected relative humidity levels of 45–98% and monitored human body respiration patterns in different exercise states. Consequently, the prepared hydrogel is a potential functional material for sustainable, flexible, wearable electronics.