LAUSR

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-1 ). 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 (Ca2+ ). 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.