A Reproducible and Self-Repairable Ionic Skin with Robust Performance Retention Enabled by Modulating the Noncovalent Interactions

Ionic hydrogels hold considerable promise in the field of flexible electronic devices, owing to their combination of stretchability and conductivity. In spite of the importance of performance retention of ionic skin after recycling and self-healing, it is struggling to produce a hydrogel-based ionic skin that could robustly preserve their original performance after self-repairing and multiple processing cycles. To address the concern, a mechanically robust, self-healing, and reprocessable poly(acrylic acid-acrylamide)/Fe(III)/lithium chloride (P(AA-co-AM)/Fe(III)/LiCl) hydrogel is fancily built benefiting from the PAA-PAM hydrogen bonding, PAA-Fe(III) coordination, and LiCl-PAA ion-dipolar interactions. The P(AA-co-AM)/Fe(III)/LiCl hydrogel is mechanically strong and highly stretchable with a tensile strength of 0.57 MPa and elongation at break of 1855%. The room-temperature self-healing efficiency of elongation at break and tensile strength can reach 96 and 78%, respectively. Remarkably, this hydrogel ionic skin demonstrates superior recyclability efficiency, maintaining virtually its initial network structure (almost the same internal microstructure as the pristine sample), mechanical performance (90% of the original maximum tensile stress and 97% of elongation at break), and sensing attributes (nearly identical signal to the original gel sensor) following five simple dissolution–drying–swelling regenerating cycles. When being applied as a flexible sensor, this hydrogel exhibits the capability not only to monitor diversified scales of human motion but also to consistently output Morse code information. Consequently, this study sheds light on a viable strategy for manufacturing sustainable sensing devices, which is highly valuable for reducing resource wastage.