Digital light 3D printed fast- and controlled degradation of covalent hydrogel networks

Digital light processing (DLP)-based 3D printing of hydrogels with sophisticated structures has been widely used in myriads of fields. However, the inherent covalently crosslinked network of hydrogels limits their further applications, such as working as sacrificial molds. In this work, a photocurable hydrogel system with labile covalent bonds suitable for DLP based printing to fabricate 3D complex hydrogel structures with fast- and controlled degradation ability is reported. The hydrogel precursor is composed of polyethylene glycol 400 (PEG400), a water soluble photoinitiator, and PEGDA575-Do, a degradable photocurable diacrylate monomer that can be degraded in aqueous condition via reversable aza-Michael addition reaction. The mechanical properties of formed hydrogels can be regulated by changing the PEG content and water content, and the degradation rate can be regulated by changing parameters such as PEG400 content, water content and the treating temperature. Moreover, the DLP printed degradable hydrogels networks can be used as sacrificial molds to fabricate structures from materials that cannot be directly used for DLP 3D printing (e.g. thermoplastic polycaprolactone (PCL), epoxy-based resin, and chocolate). As proofs-of-concept, a microfluidic chip is fabricated by using the biocompatible 3D printed hydrogel as a sacrificial template. Similarly, a flexible RFID tag and a flexible self-powered device are also prepared, demonstrating the potential applications in the field of flexible electronics.