Spinnable adhesive functional-hydrogel fibers for sensing and perception applications

Abstract

Spider silk has received increasing attention because of its high strength, good flexibility and adhesiveness. Herein, we demonstrate a simple method for the fabrication of one type of flexible, multi-functional hydrogel fiber that exhibits the reversible adhesiveness of spider silk on a variety of substrates. This fiber is conductive and freeze-tolerant (freezing temperature < −40 °C). Additionally, it also exhibits good weight retention (weight loss ratio ∼ 10% for 17 days at 25 °C and 25–28% relative humidity), strain sensing and light guiding capability, demonstrating great potential in fabricating functional devices. This fiber was facilely prepared by post-stretching a pre-cured, polyacrylamide-polyethyleneimine-glycerol-salt composite hydrogel. The diameter of the fibers can be easily tuned from 98 ± 5 μm to 314 ± 4 μm by adjusting the stretching ratio of the original hydrogel. Interestingly, a single hydrogel fiber of ∼2 mg could adhere and lift a flat polypropylene plate of ∼185 mg, which is more than 90 times the weight of the fiber itself. In addition, the elastic deformation of the fiber quickly recovered in less than 1 s after being detached from the plate. Further strain-resistance tests showed that the hydrogel fibers could detect a series of strains ranging from 0.5% to 34.5% with negligible drifting within 200 stretch–release cycles. Importantly, we successfully emulated the capture and perception capability of a spider web in the designed hydrogel fiber web. The fiber provides new opportunities for designing flexible electronic devices for various engineering applications.