Hydrogel microwells with light-controlled reversible closure
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.