Droplet最新文献

Front Cover: The cover image is based on the Research Article Programmable droplet manipulation enabled by charged-surface pattern reconfiguration by Fang et al.

The article proposes a novel and unique droplet manipulation method via charged-surface pattern reconfiguration for developing surface-autonomic-controlling fluid handling technologies. This work conceptually opens new avenues for changing external controlling to surface autonomic controlling in droplet manipulation. (DOI:10.10002/dro2.74)

Back Cover: The cover image is based on the Research Article Reproducible reformation of a bilayer lipid membrane using microair bubbles by Hashimoto et al.

A microair bubble facilitates the self-assembly of an amphiphilic lipid monolayer on an aqueous droplet. With this principle, this study demonstrates the reproducible formation of a lipid bilayer by sequentially splitting and contacting of aqueous droplets in a lipid-dispersed solvent using the controlled introduction of a microair bubble. (DOI: 10.1002/dro2.73)

Frontispiece: The cover image is based on the Research Article Target slinging of droplets with a flexible cantilever by Fang et al.

In virtue of the characteristics of softness and superhydrophobicity, the natural leaves can flexibly toss the raindrops in different directions. A bio-inspired strategy to achieve programmed jumping and target shooting of droplets by using a flexible superhydrophobic cantilever is proposed with advantages of high accuracy and resisting droplet fragmentation. (DOI: 10.1002/dro2.72)

Inside Front Cover: The cover image is based on the Review Article Bionic multifunctional fibrous materials for efficient oil/water separation by Guo et al.

When the mixture of water and oil encounters the superwettability fiber materials, which were designed and fabricated based on the interface engineering of surface structure and surface energy inspired by nature, the fiber materials show highly selectivity for liquids, which can achieve high-precision oil-water separation in a short time, and there is almost no presence of another liquid in one separated liquid. (DOI: 10.1002/dro2.75)

Inside Back Cover: The cover image is based on the Research Article Hybrid electrodes effective for both electrowetting- and dielectrowetting-driven digital microfluidics by Geng and Cho.

The cover image illustrates hybrid electrodes for digital (droplet-based) microfluidics that can drive aqueous (conductive) as well as dielectric (non-conductive) liquid droplets on a single platform. The electrodes have capability to generate electrowetting as well as dielectrowetting driving forces. (DOI: 10.1002/dro2.58)

Special wettability fibrous materials have received a lot of attention because of their good connectivity, mechanical flexibility, large specific surface area, and ease of shape manipulation. Their outstanding performance paves the way toward efficient oil/water separation in a variety of environments and for separation requirements. This paper discusses the distinct advantages, challenges, and future research directions of various substrates for fibrous materials, such as nonwoven natural biomass fibers, fabrics, electrospinning fibers, metallic fibers, and inorganic nonmetallic fibers. The special wettability fibrous filter materials and fibrous adsorbents are summarized based on the different separation methods. The principles of preparation of various special wettabilities are introduced, and the unique advantages of fibrous adsorbents are emphasized. The preparation strategy of fibrous filter materials is discussed, as well as some representative work and research progress. The benefits, drawbacks, and research directions in terms of various materials are examined. This article emphasizes the pollution resistance of fibrous filter materials and the elasticity of fibrous adsorbents. Finally, the prospects in terms of the problems, challenges, and future development of special wettability fibrous materials used in oil/water separation are discussed.

The use of double emulsions (DEs), which represent colloidal structures composed of droplets nested within droplets, can provide for unparallel droplet manipulation in droplet-based microfluidic technology due to their unique core–shell structures. The controlled release of cores in DEs is of particular interest. However, this process remains poorly explored. In this work, the thermocapillary flow induced by a temperature gradient is used as a driving force to control the core release and the impacts of different linear temperature gradients, core diameters, shell diameter, and core/shell diameter ratios on the thermocapillary flow and core release characteristics of DE droplets consisting of a water-in-n-hexadecane-in-water system within a cylindrical microchannel are investigated. Most of the core and shell diameter conditions considered result in a double-core release process, where the inner droplet volume is partially ejected before the remaining core is rewrapped by the outer droplet, and the remaining inner droplet volume is ejected later during a second core release event. However, relatively small core diameters of 50 and 75 μm produce conditions where the full inner droplet volume is ejected during a single-core release process. In addition, we provide empirical relationships for accurately determining the time at which core release initially occurs under given DE parameters as well as for precisely determining whether the applied conditions will lead to single- or double-core release processes. Therefore, the results of this study provide insights enabling the development of accurate inner droplet release technologies under thermocapillary migration.

Programmable droplet manipulation based on external stimulation is in high demand in various modern technologies. Despite notable progress, current manipulation strategies still suffer from a common drawback such as single control means of modulating the external stimulation input, which leads to huge challenges in sophisticated and large scale-up droplet handling. Herein, a unique pattern-reconfiguration-driven droplet manipulation method is developed on conductive/nonconductive pattern surfaces under charge deposition. Contactless charge deposition induces the “edge barrier” phenomenon at the boundaries of conductive/nonconductive patterns, analogous to an invisible and tunable wall guiding droplet behaviors. The edge barrier effect can be flexibly tuned by the nonconductive surface pattern. Thus, with charge deposition, surfaces are endowed with protean control functionality. The design of conductive/nonconductive patterns can effectively enable multifunction droplet manipulations, including track-guided sliding, sorting, merging, and mixing. Moreover, dynamical pattern reconfiguration drives programmable fluidics with sophisticated and large scale-up droplet handling capabilities in a low-cost and simple approach.

Control of the directional bounce of droplets impacting solid surfaces is crucial for many agricultural and industrial applications. However, for the universal impact process of raindrops on plant leaves, little is known about how the highly coupled and complicated fluid–structure interaction controls the postimpact motion of droplets and endows the leaves with tenacious vitality. Here, we report a leaf-like superhydrophobic cantilever to flexibly bounce droplets with well-defined directionality and controllability. Through theoretical modeling and three-dimensional fluid–solid coupling simulations, we find that the flexible cantilever significantly relieves the impacting forces of raindrops to reduce droplet fragmentation and enhance water repellency. The results further uncover the scaling relations of the droplet bouncing direction with respect to Weber number and cantilever stiffness. By this technique, the seemed disorganized postimpact movements of droplets are programmable and predictable, achieving the goal of where to point and where to hit automatically. This work advances the understanding of natural droplet impact phenomena, opens a new avenue for delicately controlling liquid motion in space with soft materials, and inspires a plethora of applications like soft robots to transport materials and energies, monitor plant growth as well as predict pathogen transmission in plants.

Planar bilayer lipid membranes (BLMs) are widely used as models for cell membranes in various applications, including drug discovery and biosensors. However, the nanometer-thick bilayer structure, assembled through hydrophobic interactions of amphiphilic lipid molecules, makes such BLM systems mechanically and electrically unstable. In this study, we developed a device to reform BLMs using a microair bubble. The device consists of a double well divided by a separator with a microaperture, where a BLM was formed by infusing a lipid-dispersed solvent and an aqueous droplet into each well in series. When the BLM ruptured, a microair bubble was injected from the bottom of the well to split the merged aqueous droplet at the microaperture, which resulted in the reformation of two lipid monolayers on the split droplets. By bringing the two droplets into contact, a new BLM was formed. An angled step design was introduced in the BLM device to guide the bubble and ensure the splitting of the merged droplet. We also elucidated the optimal bubble inflow rate for the reproducible BLM reformation. Using a 4-channel parallel device, we demonstrated the individual and repeatable reformation of BLMs. Our approach will aid the development of automated and arrayed BLM systems.