Programmable thermocapillary shaping of thin liquid films

TL;DR

This paper introduces a method to shape thin liquid films using projected light patterns and thermocapillary effects, enabling rapid fabrication of optical elements with high surface quality.

Contribution

The authors developed a closed-form solution for the inverse problem of thin-film deformation, enabling precise control of surface topography via programmable light patterns.

Findings

Successfully fabricated diffractive optical elements within five minutes.

Achieved sub-nanometric surface quality without post-processing.

Demonstrated versatile applications including phase masks for imaging and microscopy.

Abstract

We present a method that leverages projected light patterns as a mechanism for freeform deformations of a thin liquid film via the thermocapillary effect. We developed a closed-form solution for the inverse problem of the thin-film evolution equation, allowing to obtain the projection pattern required in order to achieve a desired topography. We experimentally implement the method using a computer controlled light projector, which illuminates any desired pattern onto the bottom of a fluidic chamber patterned with heat absorbing metal pads. The resulting heat map induces surface tension gradients in the liquid-air interface, giving rise to thermocapillary flow that deforms the liquid surface. If a polymer is used for the liquid film, it can then be photocured to yield a solid device. Based on the inverse problem solutions and using this system, we demonstrate the fabrication of several diffractive optical elements (DOEs), including phase masks for extended depth of field imaging, and for 3D localization microscopy. The entire process, from projection to solidification, is completed in less than five minutes, and yields a sub-nanometric surface quality without any post-processing.