Facile synthesis of highly stretchable, tough and photodegradable hydrogels.

Recently we reported highly stretchable and tough hydrogels that are photodegradable on-demand (Materials Today Bio, 15, 100 325, 2022). Unfortunately, the preparation procedure was complex due to the hydrophobic nature of the photocrosslinkers. Herein, we report a simple method to prepare photodegradable double-network (DN) hydrogels that exhibit high stretchability, toughness and biocompatibility. We synthesized hydrophilic ortho-nitrobenzyl (ONB) crosslinkers with incorporating different poly(ethylene glycol) (PEG) backbones (600, 1000, and 2000 g⋅mol ). These photodegradable DN hydrogels were prepared by the irreversible crosslinking of chains by using such ONB crosslinkers, and the reversible ionic crosslinking between sodium alginate and divalent cations (Ca ). Remarkable mechanical properties are obtained by combining ionic and covalent crosslinking and their synergistic effect, and by reducing the length of the PEG backbone. We also demonstrate the rapid on-demand degradation of these hydrogels by using cytocompatible light wavelength (λ = 365 nm) that degrades the photosensitive ONB units. We have successfully used these hydrogels as skin-worn sensors for monitoring human respiration and physical activities. A combination of excellent mechanical properties, facile fabrication, and on-demand degradation holds promise for their application as the next generation of substrates or active sensors eco-friendly for bioelectronics, biosensors, wearable computing, and stretchable electronics. This article is protected by copyright. All rights reserved.