3D Printable Polyelectrolyte Complex‐Integrated Interpenetrating Network Hydrogels with Customizable Mechanical Strength and pH‐Responsiveness.

Herein, a novel 3D printable ink designed for the fabrication of interpenetrating polymer network (IPN) hydrogels is introduced, ingeniously integrating a polyelectrolyte complex (PEC) of hyaluronic acid (HA) and chitosan (CS) with a photo‐crosslinkable P(OEGMA‐co‐EGDEMA) polymer. Initially, the carboxyl group of HA is modified with a photo‐labile ortho‐nitrobenzyl group, preventing premature PEC formation during 3D ink formulation. Subsequent UV illumination via digital light processing (DLP) simultaneously triggers the photo‐deprotection of the carboxyl group of HA and the photopolymerization of OEGMA crosslinked hydrogel, together creating a PEC‐integrated IPN hydrogel. Comprehensive characterizations, including NMR, IR, UV/Vis, TGA, DSC, SEM, and mechanical tests are conducted to evaluate the structural, morphological, and rheological properties of these hydrogels. Furthermore, adjustments to the composition of the 3D ink enable the production of hydrogels with a spectrum of mechanical strength and elastic modulus ranging from 1 to 10 kPa. The resultant PEC‐IPN hydrogels display excellent flexibility, compressive strength, high strain tolerance, pH responsiveness, and thermal stability. In essence, the approach seamlessly merges natural polyelectrolytes with technological innovation to refine 3D ink production. This method could mark a pivotal advancement in the realm of 3D materials, unlocking numerous prospective applications. [ABSTRACT FROM AUTHOR]