Liquid crystal–based open surface microfluidics manipulate liquid mobility and chemical composition on demand

Abstract

The ability to control both the mobility and chemical compositions of microliter-scale aqueous droplets is an essential prerequisite for next-generation open surface microfluidics. Independently manipulating the chemical compositions of aqueous droplets without altering their mobility, however, remains challenging. In this work, we address this challenge by designing a class of open surface microfluidic platforms based on thermotropic liquid crystals (LCs). We demonstrate, both experimentally and theoretically, that the unique positional and orient ational order of LC molecules intrinsically decouple cargo release functionality from droplet mobility via selective phase transitions. Furthermore, we build sodium sulfide-loaded LC surfaces that can efficiently precipitate heavy metal ions in sliding water droplets to final concentration less than 1 part per million for more than 500 cycles without causing droplets to become pinned. Overall, our results reveal that LC surfaces offer unique possibilities for the design of novel open surface fluidic systems with orthogonal functionalities.

Stimuli‐Responsive Liquid‐Crystal‐Infused Porous Surfaces for Manipulation of Underwater Gas Bubble Transport and Adhesion

“…We hypothesize that the high surface roughness of smectic A 8CB induces larger CAH and more severe pinning of air bubbles relative to those observed in the nematic phase, which is consistent with our observations of the pinning of water droplets on LC surfaces in different LC mesophases (see Supporting Information for details). [23] We demonstrate that the LC-mesophase-dependent manipulation of gas bubbles on LCIPS provides a platform by which the immobilization and transport of the bubble can be controlled by inducing a smectic A-nematic transition using external stimuli. For instance, a 10 µL bubble remained immobile on a smectic A LCIPS (25 °C) for 6 h but abruptly began to slide upon heating the LC to the nematic phase (33 °C), as shown in Figure 1h, and Figure S6a and Movie S1, Supporting Information.…”

“…We hypothesize that the high surface roughness of smectic A 8CB induces larger CAH and more severe pinning of air bubbles relative to those observed in the nematic phase, which is consistent with our observations of the pinning of water droplets on LC surfaces in different LC mesophases (see Supporting Information for details). [ 23 ]…”

Oil/Water Microreactor with a Core–Shell Wetting State on a SOB/OL-SHB/HL Multilevel Patterned Surface

“…The SOB surface exhibited remarkable superrepellency to water and diverse oils. Droplets, such as water, peanut oil, 1,4-dioxane, and hexadecane, deposited onto the SOB surface were kept in the superlyophobic Cassie state ,− due to droplet–solid point contact caused by the isolation of the gas layer in the microstructures. Here 10 μL of water, peanut oil, 1,4-dioxane, and hexadecane presented CAs of 152°, 146°, 144°, and 147°, as shown in Figure a–c, and the interface morphologies of diverse droplets are shown in Figure S2a,b.…”

“…Droplet-based open microfluidics give a surface platform on which mini-discrete droplets are used to accomplish various chromogenic/fluorescence reaction-based detections. − Compared to the generation of droplets in microfluidic channels, , droplet-based open microfluidics abandon the fabrication of intricate chips with sealed microfluidic channels, simplifying the platform and auxiliary devices. As one of the primary forms of laboratories on a chip, droplet-based open microfluidics are important for the microminiaturization of synthesis/analysis systems in the fields of medicine, pharmacy, environics, fine chemicals, and material science due to distinct advantages, which include flexible processing of reagents, controllable microenvironment, low cost, simple auxiliary devices, mini volume of reagents, quick response, high throughput, and high integration.…”

Modularizable Liquid‐Crystal‐Based Open Surfaces Enable Programmable Chemical Transport and Feeding using Liquid Droplets

“…Very recently, we reported the design of a porous LC polymeric network to stabilize LC films against water‐droplet‐induced dewetting, enabling chemical feeding to droplets on an LC surface platform. [ 11 ] However, the integration of these LC surfaces to achieve the programmable and automatic release of multiple chemicals to manipulate (bio)chemical reactions in droplets without droplet pinning, a prerequisite for the design of advanced open surface droplet reactors, has not yet been achieved.…”