Programmable thermocapillary shaping of thin liquid films

Abstract

We present a method that leverages projected light patterns as a mechanism for freeform deformation 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 us 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, including phase masks for extended depth of field imaging, and for three-dimensional 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.

Liquid-shaped microlens for scalable production of ultrahigh-resolution optical coherence tomography microendoscope

“…1d, e ) on a substrate. Furthermore, the liquid-shaped microlens provides a reflective surface with sub-nanometer surface roughness 29 , 30 (Fig. 1a(i) ), eliminating the additional angle-polishing process required in conventional methods based on GRIN fiber and fiber ball lens.…”

“…4e ). This sub-nanometer roughness is due to the smoothness of the liquid-air interface in the liquid shaping technique 29 , 30 . Meanwhile, we noted a surface roughness of 0.53 ± 0.11 nm on the flat reflective surface of the microlens, owing to the use of an ultra-flat glass substrate (see Fig.…”