Hybrid double-network hydrogel for highly stretchable, excellent sensitive, stabilized, and transparent strain sensors.

Nowadays, great effort has been devoted to fabricate flexible wearable sensor with high stretchability, moderate modulus, favorable durability, excellent transparency, and satisfactory sensitivity. In this work, we report the preparation of a hybrid double-network (DN) hydrogel by a simple one-pot method. First, chitosan was added into an AlCl ₃ solution to form Al ³⁺ -chitosan complex (CS-Al ³⁺ ). Second, the hybrid CS/Al ³⁺ -poly(acrylamide) (PAM) DN hydrogels were constructed via in situ polymerization of acrylamide (AM) in present of Al ³⁺ -chitosan complex. Thanks to the existence of electrically conductive CS-Al ³⁺ networks, the resulting hybrid DN hydrogel exhibits excellent stretchability, fatigue resistance, transparency, and conductivity. Furthermore, the CS/Al ³⁺ -PAM DN hydrogel could be used as strain sensor, and demonstrates many desired virtues, including satisfactory sensitivity (gauge factors of 1.7-12.1), wide detection range (up to 1500%), low limit of discernment (1% strain), high reliability, and excellent durability (1000 cycles). More significantly, the manufactured hydrogel-based strain sensor can be employed as wearable devices to precisely detect various human movements.