All-optical Lithography for Spatiotemporal Patterning of High-Modulation Azopolymer Microreliefs

TL;DR

This paper introduces an all-optical holographic method to create and reconfigure high-modulation azopolymer microreliefs with complex shapes and hierarchical structures, enabling dynamic surface patterning without masks or molds.

Contribution

It demonstrates a novel spatiotemporal holographic approach for fabricating and reconfiguring high-contrast azopolymer microstructures directly from flat films.

Findings

Single exposures create isolated protrusions and arrays.

Sequential exposures reshape microrelief morphology.

Write-erase-rewrite cycles are achievable on the same surface.

Abstract

Microstructured surfaces are central to photonics, biointerfaces, and coating technologies, but they are typically fabricated through multistep workflows involving masks, molds, and postprocessing. Azopolymers offer a direct light-driven route to surface structuring, yet holographic photopatterning of flat films has mainly remain limited to smooth, shallow, and engraving-like reliefs with limited vertical modulation. Here we show that computer-generated holograms with co-designed bright and dark regions can spatially confine inward mass transport and directly generate isolated protruding microstructures with several micrometer surface modulation from pristine flat azopolymer films. Single exposures produce individual protrusions and protrusion arrays, whereas sequential tailored exposures further reshape microrelief morphology over time. Using this spatiotemporal scheme, we fabricate flattenedtop micropillars, programmable arrays, freeform continuous microreliefs, and hierarchical structures from a pristine flat film, and we demonstrate write-erase-rewrite cycles in the same surface region. These results establish an all-optical strategy for generating and reconfiguring high modulation azopolymer microreliefs through combined control of spatial and temporal degrees of freedom of holographic illumination.