Development of Antifreezing, Printable, Adhesive, Tough, Biocompatible, High-Water Content Hydrogel for Versatile Applications.

Hydrogels with different functionalities such as printability, antifreezing properties, adhesion, biocompatibility, and toughness are being continually developed. However, it has been extremely challenging to design adhesive, antifreezing, tough, and biocompatible multifunctional hydrogels with complex shapes simultaneously and prepare them in a short period. In this paper, novel composite hydrogels, which consist of poly(vinyl alcohol) grafted with styrylpyridinium group (PVA-SbQ) and TEMPO-oxidized cellulose nanofibrils (CNF), were successfully synthesized via UV photo-cross-linking. In addition to UV photo-cross-linking, the PVA-SbQ/CNF hydrogels with different shapes could be rapidly printed by facile visible light-based stereolithography printing and laser direct-writing without any photoinitiators in 3 min and 30 s, respectively. The results show that PVA-SbQ/CNF hydrogels are biocompatible because there are no photoinitiators and cross-linkers required during the printing process under visible light. Moreover, the adhesive, antifreezing, mechanical properties, and water-binding capacity of PVA-SbQ/CNF with high-water contents improved significantly as the CNF contents increased. Such hydrogels, which combine multiple advantages, present great potential for application in wound dressings and portable devices with specific requirements for shapes, adhesion, toughness, and tolerance in extreme environments such as dry environments and low temperatures.