The design of open surface microfluidics that enable orthogonal control of liquid mobility and chemical compositions is critical for devising the next generation of microfluidic platforms that will find use in applications across chemical, environmental, and biomedical fields. To achieve these desirable functionalities, extensive studies have demonstrated stimuli-responsive liquid mobility on open fluidic platforms based on either micro/nanoscale topographical surfaces or water-immiscible liquid-coated surfaces. However, methods of manipulating droplets’ chemical compositions tend to rely upon chemical adsorption directly from the underlying surface, which has been shown to subsequently pin droplets to the surface and render them immobile.<br/>In this presentation, we report the design of a liquid crystal (LC)-based open surface microfluidic platform that enables the independent manipulation of the mobility and chemical compositions of droplets. Specifically, we use porous LC polymeric networks to stabilize thermotropic LC mesogens to overcome the aforementioned issue of water-induced LC dewetting. We find that the mobility of water droplets on LC-based surfaces depends only on the positional order of the LC: water droplets become highly pinned at LC surfaces in the smectic A phase, whereas droplets can freely slide without pinning at LC surfaces in both the nematic and isotropic phases. Moreover, we experimentally and theoretically demonstrate that the mesogenic orientational order of the LC surface plays a pivotal role in the release of chemicals from the LC surface to droplets. Our work provides novel design principles for fabricating anisotropic liquid-based open surface microfluidics that enable promising applications including liquid droplet-based chemical synthesis and medical diagnostics.

Liquid crystal-infused porous surfaces with molecular order-dependent slipperiness and cargo release

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