Programmed Diffusion Induces Anisotropic Superstructures in Hydrogels with High Mechano‐Optical Sensitivity

Abstract

Abstract Most soft biotissues possess intricate anisotropic superstructures, which afford living organism versatile functionalities. However, it remains a big challenge to develop such complex ordered structures in synthetic hydrogels. Here a simple and efficient strategy to fabricate periodically patterned hydrogels with complex anisotropic structures by diffusion‐induced orientation and gelation of a rigid polyanion is reported. Masks with well‐designed holes are used to direct the diffusion of multivalent metallic ions through the holes into the solution of rigid polyanions from one side or from two sides. Various periodically ordered structures are facilely formed under such a programmed diffusion field, which is tunable by pattern design and relative position of the masks. The mechanical properties of the thus formed physical gels can be effectively improved by incorporating a flexible and sparsely cross‐linked network, whereas the intricate superstructures are well maintained. The periodic birefringence pattern of this robust, anisotropic hydrogel is highly sensitive to the mechanical stress and strain, showing promising applications as optical devices and mechano‐optical sensors. The strategy demonstrated here should be applicable to other diffusion‐reaction systems toward designing biomimetic materials with intricate structures and versatile functions.