Construction of Transparent, Adhesive, and Conductive Ionogels and Use for Strain Sensors

Hydrogels with adhesion and conductivity properties have certain applications in the field of strain sensing equipment. With the semi-interpenetrating structure formed by branched polyethylenimine (PEI) and the dynamic cross-linking of hydrophobic microspheres, a hydrogel with universal adhesion, conductivity, stretchability, and transparency was successfully prepared. The hydrophobic microspheres formed by the hydrophobic monomer octadecyl acrylate (C18) can enhance the mechanical properties of the hydrogel. The introduction of branched PEI gives the hydrogel excellent stretchability; the optimal tensile strain is 903%. The hydrogel is endowed with a broad spectrum of adhesion, making it have good adhesion to organic, inorganic, and biological skin. The presence of mobile ions in the hydrogel network makes it have a certain degree of conductivity. At the same time, the hydrogel can show a response to different strains (10%, 50%, 100%) and weights (20 g, 50 g, 100 g, 200 g) through changes in resistivity. Subsequently, the hydrogel is attached to the wrist and finger joints to detect the impact on the human body. Experimental results prove that this hydrogel has the potential to be applied to strain sensors and can sense and detect changes in human joints through ionic conduction and resistance changes caused by shape deformation.