Light-Regulated Capillary Force Self-Assembly of Nano-Printed Pillars for Chiroptical Metamaterials

Capillary force self-assembly (CFSA) technology unfolds great potential in the fabrication of functional micro/nanostructures. To date, most self-assembly methods focus on monolithic microstructure manipulation yet it remains a challenge to achieve precise localized control over the CFSA process of micro/nanostructures. Herein, a light-regulated CFSA is proposed to realize the localized precise control of microstructures, leveraging on the synergistic effect of photothermally-responsive hydrogel and self-assembly technique. The micropillars with asymmetric cross-linking densities can readily prepare by applying a rationally designed laser and laser-exposing dosage, thereby realizing the on-demand steering of their bending directions. Significantly, owing to the giant capillary force deriving from the evaporating water, above micropillars can successfully assemble into highly-ordered chiral structures. Simulation coupling with fundamental hydrodynamics enables to shed light on the light steering principle over pillar's actuations. Last, on the basis of vortical dichroism spectra analysis, the chiral characteristics of light-regulated self-assembly including the chiral as well as the achiral self-assembled microstructures are successfully deployed. This strategy provides an avenue for fabricating the localized controllable self-assembly at the microscale and will bloom the field over metamaterials, microsensors, chiral optics, and so on.