Magnetically Programmable Hydrogel–Elastomer Composite for Engineering Controlled Equibiaxial Mechanical Microenvironments

Precise and programmable mechanical stimulation is essential for constructing defined cellular microenvironments, yet existing in vitro stretching platforms often suffer from limited control over biaxial strain fields and reliable strain transfer. Here, we present a magnetically driven hydrogel-elastomer composite consisting of an auxetic-like inward-concave chamfered hard-magnetic soft actuator and a central GelMA matrix. Under a parallel magnetic field, the actuator undergoes in-plane expansion, transferring an approximately 10% near-equibiaxial strain to the hydrogel. Benzophenone-mediated interface modification enhances hydrogel-elastomer adhesion and improves interfacial strain-transfer capability. Finite-element-guided geometric optimization identifies a 3 mm inward-concave chamfered design that balances corner constraint reduction and auxetic-like deformation coupling. In a proof-of-concept cell-culture demonstration, RAW264.7 macrophages cultured on the platform exhibited heterogeneous morphological changes and F-actin reorganization during cyclic near-equibiaxial stimulation, supporting the feasibility of the platform for controlled cellular mechanical stimulation. This composite provides a magnetically programmable platform for soft-material deformation and mechanobiological applications.