Transparent, flexible, and multifunctional starch-based double-network hydrogels as high-performance wearable electronics.

To meet the increasing demands of sustainability and eco-friendliness, biopolymer-based hydrogels combining flexibility and ionic conductivity have drawn great attention for green and wearable sensors. However, the preparation of transparent, flexible, durable, and highly sensitive biopolymer hydrogel-based sensors for strain/pressure and humidity sensing remains a challenge. Herein, a facile one-step strategy is proposed to fabricate transparent, highly flexible, and multifunctional starch/polyacrylamide double-network hydrogels based on natural renewable starch. The resultant hydrogels exhibit fast self-adhesive ability and present high flexibility attributing to the double network consisting of cross-linked starch and polyacrylamide. Then the hydrogels can be assembled as transparent, self-adhesive, flexible, highly sensitive, and multifunctional strain/pressure and humidity sensors for accurate healthcare monitoring. The hydrogel-based sensor shows ultrahigh sensitivity to humidity (35-97% relative humidity). The multifunctionality and biological advantages of starch-based hydrogels offer potential applications in next-generation green and wearable electronics.