Hydrogel Microwells with Light‐Controlled Reversible Closure

ABSTRACT We present a light‐responsive hydrogel nanocomposite engineered into arrays of micrometer‐scale wells that can be selectively and sequentially closed and re‐opened via laser illumination. Polarization‐controlled light exposure induces anisotropic surface deformations, leading to the formation of protrusive flaps sealing the wells. Owing to the intrinsic elasticity and anti‐adhesive properties of the hydrogel matrix, the deformation process is partially reversible, allowing flap retraction and restoration of the original well geometry. This platform facilitates contactless, on‐demand trapping and release of microscale objects using a standard optical microscopy configuration. As a proof of concept, we demonstrate the controlled manipulation of a single polystyrene microbead using optical tweezers, including bead positioning within a well, light‐triggered closure, and subsequent reopening to release the particle into the surrounding aqueous environment.