Droplet最新文献

Inside Front Cover: The cover image is based on the Research Article Containerless emulsification of acoustically levitated composite drop by Cui et al.

Cover description: We report the first realization of containerless emulsification of water and castor oil under ultrasonic levitation. The cover image visually demonstrates how regulating the sound field intensity on the levitated composite drop surface triggers upper-surface atomization, directly facilitating containerless emulsification. This containerless emulsification approach has successfully prepared W/O emulsions with droplet diameters of approximately 2–3 μm, highlighting a novel integration of acoustic levitation and emulsion preparation. (DOI: 10.1002/dro2.70005)

Frontispiece: The cover image is based on the Research Article Micro-size aperture surface acoustic wave generator for cell lysis by Almanza et al.

Cover description: Micro-sized aperture surface acoustic wave generators effectively lyse cells by using focused acoustic energy. The device provides precise, efficient, and scalable cell disruption, potentially benefiting biomedical research and diagnostics by enabling controlled, label-free sample preparation. (DOI: 10.1002/dro2.70015)

Front Cover: The cover image is based on the Research Article Thermo-magnetic soft robot for adaptive locomotion and delivery by Wang et al.

Cover description: This cover illustrates a thermo-magnetic soft robot integrating light-responsive liquid crystal elastomers with embedded magnetic particles. The robot undergoes reversible petal-like shape morphing under near-infrared light and magnetically guided rolling locomotion. Demonstrating adaptive motion and delivery across diverse environments, it paves the way for versatile applications in biomedical transport, environmental sensing, and soft robotic systems. (DOI: 10.1002/dro2.70016)

Chinese distilled liquor, known as Baijiu, typically has a relatively high ethanol content (52 or 53% alcohol by volume, ABV) and is characterized by a powerful, heady scent. When its alcohol content is less than 45% ABV, Baijiu loses its flavor and becomes cloudy and tasteless; thus, it is relatively bland and thin. Since this phenomenon has not been reasonably explained, the aim of this study is to determine its underlying mechanism by examining the droplet evaporation. A 1.0 µL of droplets were applied to the substrate surface for evaporation. The results revealed that a reduction in the alcohol content (<45% ABV) triggered the self-assembly of unique long-chain fatty acid ethyl esters into various nano- or microparticles with sizes ranging from 100 nm to 10 µm within the Baijiu droplets. These particles deposit under the influence of internal flow and exhibit Baijiu-specific coffee-ring effects after drying. Interestingly, these particles encapsulated the water-soluble or insoluble flavor chemicals, resulting in the brightness and aroma/flavor of Baijiu decreased radically; this is the reason that a high alcohol content is needed in Baijiu. These findings offer new insights for the quality control of low-alcohol Baijiu and Baijiu identification.

The breakage of the cellular membrane for releasing intracellular material is the starting point for several diagnostics or treatment processes. Surface acoustic waves can provide a novel and chemical-free approach by inducing acoustic streaming generating high shear stress inside a droplet containing cells. However, the power required to achieve an efficient cell lysis can lead to the displacement of the droplet and even the nebulization of the droplet. This effect is aggravated as the droplet size is reduced. In this work, we demonstrate the possibility overcoming the mentioned issue by a micro-size aperture surface acoustic wave generator operating at high frequency. By reducing the aperture of the surface acoustic wave generator to a fraction of the diameter of the deposited droplet, the localized acoustic streaming can lead to high shear stress while not exceeding the adhesion force of the droplet preventing droplet motion or nebulization. This concept can lyse AC16 human cardiomyocyte cells with efficiencies of 80% comparable to a chemical lysis method in 60 s of exposure time.

Droplet splitting technology presents considerable potential for advancing applications in sample encapsulation, manipulation, chemical reaction control, and precision measurement systems. However, existing methodologies frequently encounter limitations related to complex operation and high cost. To address the need for controllable, high-precision, and cost-efficient droplet splitting, this study combines three-dimensional printing technology with superhydrophobic surface modification to fabricate pyramid microstructures with customized splitting functionalities. The pyramidal sharp edges act as “fluidic blades” to split droplets through the synergistic interaction of edge-induced capillary forces and inertial forces generated at the liquid film periphery during spreading dynamics. Upon penetration by the pyramid apex, the droplet forms an annular liquid ring that subsequently fragments into sub-droplets, enabling programmable splitting. A comprehensive experimental and computational framework was developed to investigate splitting dynamics, force distribution patterns, and geometric dependence of pyramid structures on splitting performance. Results indicate that increased Weber numbers, larger droplet volumes, and reduced pyramid apex angles markedly improve splitting controllability. Additionally, six- and 12-sided pyramid-based splitting/collection devices were engineered to demonstrate practical implementations, including on-demand droplet splitting and liquid marble synthesis. This work establishes a scalable, low-cost platform for precision droplet manipulation with significant implications for microfluidic devices and lab-on-a-chip technologies.

We analytically describe the slip length of the surfactant-covered bubble film under the joint actions of pressure gradient and electric field. Considering the Marangoni effect, the slip length and consequent zeta potential of the liquid‒vapor interface significantly reduced compared to the Marangoni-free interface at low surfactant concentrations, due to the surfactant accumulation at downstream of the bubble liquid film. In addition, we discovered that the friction coefficient of the liquid‒vapor interface becomes field dependent in a regime of strong coupling among volume flow, surfactant transport, and ionic current at the liquid‒vapor interface. We use the Onsager reciprocal relationship to describe the electrokinetic effects within a bubble film, including flow velocity, ionic current, and surfactant transport, which can describe the Marangoni effects while considering multi-physical effects.

Soft robots based on stimuli-responsive materials, such as those responsive to thermal, magnetic, or light stimuli, hold great potential for adaptive locomotion and multifunctionality in complex environments. Among these, liquid crystal elastomers (LCEs) and magnetic microparticles have emerged as particularly promising candidates, leveraging their thermal responsiveness and magnetic controllability, respectively. However, integrating these modes to achieve synergistic multimodal actuation remains a significant challenge. Here, we present the thermo-magnetic petal morphing robot, which combines LCEs with embedded magnetic microparticles to enable reversible shape morphing via remote light-to-thermal actuation and high-speed rolling locomotion under external magnetic fields. The robot can achieve rapid deformation under near-infrared light, transitioning from a closed spherical to an open cross-like configuration with consistent shape recovery across multiple cycles, and demonstrates a maximum locomotion speed of 30 body lengths per second, outperforming many state-of-the-art soft robots. Moreover, the robot's performance remains robust across dry, wet, and underwater conditions, with adjustable magnetic particle concentrations allowing tunable actuation performance. Our work addresses the need for soft robots with enhanced versatility and adaptability in complex environments, paving the way for applications in areas such as targeted drug delivery and industrial material handling.

Frontispiece: The cover image is based on the Review Article Advancements in liquid marbles as an open microfluidic platform: Rapid formation, robust manipulation, and revolutionary applications by Tong et al.

Cover description: Liquid marbles (LMs)—particle-coated non-wetting droplets—reshape microfluidics through their “3R trilogy”: Rapid formation, Robust manipulation, and Revolutionary applications. This review dissects LM generation, structural dynamics under stimuli, and roles in digital microfluidics, biochemical sensing, and soft robotics. Synthesizing advances (2014–2024), it illuminates LM-based platforms' future trajectories, inspiring innovations in open microfluidic systems. (DOI: 10.1002/dro2.160)

Inside Front Cover: The cover image is based on the Review Article Advances in networking droplets by Chong et al.

Cover description: Droplet networks, inspired by compartmentalization in living systems, offer unique and versatile functions for chemical and biological applications. This review summarizes droplet network advancements, including various droplet types, strategies for droplet assembly, and cutting-edge applications of droplet networks. These insights are intended to bridge the gap between fundamental research and practical applications. (DOI: 10.1002/dro2.173)