A Pseudomembrane‐Inspired Janus Hydrogel Patch With Robust Wet Adhesion and Swelling‐Resistant Capabilities for Accelerated Oral Ulcer Healing

Oral ulcer healing is hindered by the slow formation, weak adhesion, and limited protection of the native pseudomembrane. Here, a light‐curable, swelling‐resistant Janus hydrogel patch is developed as a pseudomembrane‐inspired protective barrier. The tissue‐facing adhesive layer incorporates 2‐phenoxyethyl acrylate (PEA), α‐lipoic acid (LA), and acryloyl NHS esters, achieving a wet tissue shear adhesion strength of 142 kPa. PEA is proposed to facilitate wet tissue contact, LA participates in the polymer network, and NHS esters provide covalent anchoring. The hydrophobic network constrains water uptake, limiting further wet‐state mass gain to approximately 3% and volumetric expansion to approximately 10% after 7 days. Dynamic fluid circulation tests further demonstrate the patch's durability under simulated oral conditions. The outward‐facing zwitterionic layer mimics the mucosal barrier, providing protection against mechanical abrasion and chemical irritation. In a rat model, the patch maintains structural integrity for 3 days, accelerates re‐epithelialization, and modulates the inflammatory microenvironment. This Janus design provides sustained protection for injured mucosal surfaces and facilitates oral ulcer healing.