Anisotropic hydrogel enabled by infusion of lubricating phase into macroporous robust skeleton with alignment structure

Abstract

Anisotropic hydrogels with direction-dependent properties are of growing interest for applications in bioengineering, soft robotics, and smart actuators, but little attention has been paid to the coupling of mechanics and lubrication behavior. Herein, we report on the design and fabrication of a novel anisotropic hydrogel enabled by the infusion of a lubricating phase into a robust, macroporous skeleton featuring a well-defined alignment structure. The robust macropore skeleton is the first constructed leveraging directional freezing poly (vinyl alcohol)/chitosan (PVA/CS) solution, followed by an ice crystal-assisted salting-out and annealing treatment step to improve structural integrity and mechanical stability. Subsequently, to introduce lubricious behavior, a lubricating phase—typically a superhydrophilic hydrogel component—is infused into the aligned porous matrix. Mechanical characterization demonstrates significant anisotropy in mechanical response, with enhanced stiffness and strength along the alignment direction. Meantime, the lubricating phase facilitates the coefficient of friction of this hydrogel as low as 0.024. Thereupon, this dual-phase configuration endows the hydrogel with anisotropic mechanics and superior lubrication behavior. The synergistic integration of well-organized anisotropic architecture and an internal lubricating phase provides a simple yet powerful approach for engineering innovative slippery hydrogel with superior mechanical and functional properties.