Single-exposure holographic lithography of ultra-high aspect-ratio microstructures

TL;DR

This paper introduces a single-exposure holographic lithography method for fabricating ultra-high aspect-ratio 3D microstructures rapidly and with high precision, enabling complex architectures with minimal exposure time.

Contribution

The authors develop an inverse-designed volumetric phase mask that allows uniform, high-resolution 3D microstructure fabrication in a single exposure, surpassing previous multi-step or slow methods.

Findings

Achieved feature sizes down to 6 μm with aspect ratios over 120:1.

Fabricated complex 3D structures within approximately 20 seconds.

Demonstrated mechanical robustness and controlled fluid transport in printed lattices.

Abstract

Volumetric lithography offers a path to scalable fabrication of complex three-dimensional (3D) micro- and nanoscale architectures, yet existing approaches are limited by quasi-two-dimensional exposure physics or slow serial writing. We present a single-exposure volumetric fabrication strategy that enables creation of ultrahigh-aspect-ratio 3D structures with 6 um minimum features. An inverse-designed volumetric (holographic) phase mask generates an extended-depth-of-field intensity distribution inside a photoresist volume while preserving high transverse resolution, enabling uniform polymerization of the full volume in a single exposure. With exposure times of approximately 20 s, we fabricate lattices, Penrose tilings, and micromechanical elements with feature sizes down to 6 um over volumes up to 800 x 800 x 720 um^3, achieving aspect ratios exceeding 120:1. Quantitative analysis of capillary flow in hollow lattices demonstrates controlled fluid transport with an effective capillary transport coefficient of 176.3 um/(ms)^(1/2). In situ nanoindentation-based micro-compression reveals that the printed 3D hexagonal close-packed lattices exhibit a well-defined linear elastic regime with an effective Young's modulus of 5.7 GPa, followed by progressive buckling and densification characteristic of mechanically robust cellular architectures. Overlapping, tilted and multi-mask exposures further enable quasi-3D complex geometries with potential for reconfigurability. This approach establishes a new regime of high-throughput volumetric fabrication.