Nanocomposite Hybrid Biomass Hydrogels as Flexible\nStrain Sensors with Self-Healing Ability in Harsh Environments

Abstract

The current challenges of wearable\nhydrogel sensors need to be\naddressed, especially how they are inevitably frozen at subzero temperature\nand are easily damaged. In this work, we present stretchable, antifreezing,\nand self-healing hydrogels by introducing Ag/TA@CNCs and l-proline into the guar gum (GG)/poly­(acrylic acid) (PAA) hybrid\nnetwork. The existence of Ag/TA@CNCs provided enhanced conductivity,\nmechanical strength, and self-healing properties. The rupture stress\nof the hydrogels improved from 0.45 to 0.69 MPa, and the self-healing\nefficiency increased from 71.4% to 88.3%. Benefiting from zwitterionic l-proline as an emerging cryoprotectant, favorable flexibility\nand self-healing abilities were also achieved in subzero environments\n(the self-healing efficiency could reach 80.8% for 6 h at −15\n°C). Resistive-type hydrogel strain sensors exhibited a high\ngauge factor (GF = 8.65 at strains of 350–550%) and fast response\ntime (190 ms), as well as stable sensitivity even at low temperatures.\nAlso, they could accurately monitor various human movements, including\nsmall (mouth opening and finger bending) and large changes (wrist\nbending, elbow bending, leg lifting, and squatting). The nanocomposite\nhybrid biomass hydrogels were promising for wearable flexible sensors\nwith a long service time in a wide temperature range.