Droplet最新文献

Frontispiece: The cover image is based on the Research Article Water-proofing mechanism of coupling structures observed in ladybird elytra and its bionic application by Zhang et al.

Cover description: Using high-speed imaging, we examine the collision of a waterdrop with the coupling structures of elytra systems. Through a combination of experimental and theoretical approaches, we analyze how the geometry of these coupling structures affects their water-proofing performance. Inspired by this biological mechanism, a water-proofing device is proposed for solar panels to enhance their light energy conversion efficiency. (DOI: 10.1002/dro2.162)

Front Cover: The cover image is based on the Research Article Droplet menisci recognition by deep learning for digital microfluidics applications by Danesh et al.

Cover description: This work showcases the use of a U-Net deep learning model to accurately identify droplet menisci in electrowetting-on-dielectric (EWOD) systems. By achieving high precision, even with complex or low-quality images, the model enhances droplet control and reveals critical insights into fluid properties, reaction kinetics, and dynamic behaviors, advancing the performance and reliability of EWOD microfluidic devices. (DOI: 10.1002/dro2.151)

Back Cover: The cover image is based on the Research Article Design and preparation of a simplified microdroplet generation device for nanoliter volume collection and measurement with liquid microjunction–surface sampling probe–mass spectrometry by Reddy et al.

Cover description: What if creating microdroplets could be as fun and simple as blowing bubbles? Here, we use a laser-micromachining protocol with a surface hydrophobicity treatment to create the ‘NanoWand’ from a glass cover slip, which generates microdroplets within the nanoliter volume range for direct introduction to and volume estimation with ambient ionization mass spectrometry. (DOI: 10.1002/dro2.158)

Inside Front Cover: The cover image is based on the Review Article Advances in precise cell manipulation by Ma et al.

Cover description: Advancing precise clinical care relies on innovative cell manipulation strategies. External fields such as acoustic, optical, electronic, and magnetic fields have significantly improved the feasibility and efficiency of precise cell sorting and assembly. A systematic review of these external-field-assisted techniques provides valuable insights and references for enhancing clinical diagnosis and treatment. (DOI: 10.1002/dro2.149)

Inside Back Cover: The cover image is based on the Research Article Programmable optical window bonding enabled 3D printing of high-resolution transparent microfluidic devices for biomedical applications by Ye et al.

Cover description: We introduce a novel “programmable optical window bonding” 3D printing method that incorporates the bonding of an optical window during the printing process, facilitating the fabrication of transparent microfluidic devices with high printing fidelity. Our approach allows direct and rapid manufacturing of complex microfluidic structure without the use of molds for PDMS casting. (DOI: 10.1002/dro2.153)

Research on cells and organ-like tissues is critical in the fields of molecular biology, genetic analysis, proteomics analysis, tissue engineering, and others. In recent years, advancements in precise cell manipulation technologies have made precise positioning and batch processing of cells feasible. Various methods are used for cell recognition, positioning, manipulation, and assembly, often introducing external fields such as electric, magnetic, acoustic, or optical fields into the liquid environment to interact with cells, applying forces to induce cell movement and rearrangement. Alternatively, three-dimensional (3D) bioprinting technology is employed for precise cell positioning and assembly. This review will comprehensively assess the status, principles, advantages, disadvantages, and prospects of these precise cell manipulation technologies, covering single-cell manipulation, multicellular assembly, and biological 3D printing techniques.

Traditional technologies for manufacturing microfluidic devices often involve the use of molds for polydimethylsiloxane (PDMS) casting generated from photolithography techniques, which are time-consuming, costly, and difficult to use in generating multilayered structure. As an alternative, 3D printing allows rapid and cost-effective prototyping and customization of complex microfluidic structures. However, 3D-printed devices are typically opaque and are challenging to create small channels. Herein, we introduce a novel “programmable optical window bonding” 3D printing method that incorporates the bonding of an optical window during the printing process, facilitating the fabrication of transparent microfluidic devices with high printing fidelity. Our approach allows direct and rapid manufacturing of complex microfluidic structure without the use of molds for PDMS casting. We successfully demonstrated the applications of this method by fabricating a variety of microfluidic devices, including perfusable chips for cell culture, droplet generators for spheroid formation, and high-resolution droplet microfluidic devices involving different channel width and height for rapid antibiotic susceptibility testing. Overall, our 3D printing method demonstrates a rapid and cost-effective approach for manufacturing microfluidic devices, particularly in the biomedical field, where rapid prototyping and high-quality optical analysis are crucial.

The phenomenon of liquid metal “heartbeat” oscillation presents intriguing applications in microfluidic devices, drug delivery, and miniature robotics. However, achieving high vibrational kinetic energy outputs in these systems remains challenging. In this study, we developed a graphite ring electrode with V-shaped inner wall that enables wide-ranging control over the oscillation performance based on droplet size and the height of the V-shape. The mechanism driving the heartbeat is defined as a dynamic process involving the transformation of the oxide layer. Through electrochemical analysis, we confirmed three distinct states of the heartbeat and introduced a novel model to elucidate the role of the V-shaped structure in initiating and halting the oscillations. A comprehensive series of experiments explored how various factors, such as droplet volume, voltage, tilt angle, and V-shape height, affect heartbeat performance, achieving a significant conversion from surface energy to vibrational kinetic energy as high as 4732 J m⁻² s⁻¹. The increase in energy output is attributed to the synergistic effect of the V-shape height and droplet size on the oscillations. These results not only advance our understanding of liquid metal droplet manipulation but also pave the way for designing high-speed microfluidic pumping systems.

We experimentally studied the effect of gas flow rate Q on the bubble formation on a superhydrophobic surface (SHS). We varied Q in the range of 0.001 < Q/Q_cr < 0.35, where Q_cr is the critical value for a transition from the quasi-static regime to the dynamic regime. The bubble geometrical parameters and forces acting on the bubble were calculated. We found that as Q increase, the bubble detached volume (V_d) increased. After proper normalization, the relationship between V_d and Q generally agreed with those observed for bubbles detaching from hydrophilic and hydrophobic surfaces. Furthermore, we found that Q had a minor impact on bubble shape and the duration of bubble necking due to the negligible momentum of injected gas compared to surface tension and hydrostatic pressure. Lastly, we explained the primary reason for the larger V_d at higher flow rates, which was increased bubble volume during the necking process. Our results enhanced the fundamental understanding of bubble formation on complex surfaces and could provide potential solutions for controlling bubble generation and extending the application of SHS for drag reduction, anti-fouling, and heat and mass transfer enhancement.