Introducing controlled fluid motion inside a droplet turns out to be of outstanding scientific importance. In this work, we suggest a new method of flow manipulation inside a sessile droplet by simply deploying a static charge produced by triboelectric effect. This is physically actuated by charge transfer between the two lateral electrodes within which the droplet is entrained, triggering a strong ionized air current. The flow inside the droplet is generated due to the shear exerted at the liquid-air interface by the charged induced ionized air flow around the droplet, a paradigm that has hitherto remained unexplored. The strength of the fluid flow can be controlled by adjusting the supplied charge. Such unique controllability without sacrificing the physical simplicity opens up new possibilities of flow manipulation in a multitude of applications in droplet based microfluidics.
Ambient-pressure effects on shock emission and liquid-shell expansion following optical breakdown inside water droplets
Advanced Research Center for Nanolithography (ARCNL)（纳米光刻先进研究中心）；LaserLab, Department of Physics and Astronomy, Vrije Universiteit Amsterdam（阿姆斯特丹自由大学物理与天文学系激光实验室）
Respiratory droplets exhaled during speaking, coughing or sneezing have been responsible for the spread of the ongoing Covid-19 pandemic. The droplet dynamics depend on the surrounding air velocity, temperature and relative humidity. Droplets evaporate to form aerosols which contain the disease spreading virus. In a confined space like an elevator, the risk of transmission becomes higher when there is an infected person inside the elevator with other individuals. In this work, a numerical study is carried out in a 3D domain resembling an elevator using OpenFoam. Different modes of air circulat…
Self-assembled filament layers in drying sessile droplets: from morphology to electrical conductivity
Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IET-2), Forschungszentrum Jülich（于利希研究中心埃尔朗根-纽伦堡亥姆霍兹可再生能源研究所）；Friedrich-Alexander-Universität Erlangen-Nürnberg（埃尔朗根-纽伦堡弗里德里希·阿列克桑德大学）
Cavitation by phase shift of focused shock waves inside a droplet
ETH Zürich（苏黎世联邦理工学院）；Imperial College London（帝国理工学院）；Tokyo University of Agriculture and Technology（东京农工大学）；Otto-von-Guericke-University Magdeburg（马格德堡奥托·冯·格里克大学）；ESRF – The European Synchrotron（欧洲同步辐射装置）；Institut Max von Laue - Paul Langevin (ILL)（马克斯·冯·劳厄-保罗·朗之万研究所）
A comprehensive analysis of the effect of ventilation and climatic conditions on covid-19 transmission through respiratory droplet transport via both airborne and fomite mode inside an elevator
An electrohydrodynamic numerical model is used to explore the electrospray emission behavior of both moderate and high electrical conductivity liquids under electrospray conditions. The Volume-of-Fluid method, incorporating a leaky-dielectric model with a charge relaxation consideration, is used to conserve charge to accurately model cone-jet formation and droplet breakup. The model is validated against experiments and agrees well with both droplet diameters and charge-to-mass ratio of emitted progeny droplets. The model examines operating conditions such as flow rate and voltage, with fluid p…
Spontaneous epicuticular charging affects droplet dynamics on living leaves
Fondazione Istituto Italiano di Technologia (IIT)（意大利技术研究院）；Bioinspired Soft Robotics Laboratory, Fondazione Istituto Italiano di Tecnologia（意大利技术研究院仿生软体机器人实验室）；The BioRobotics Institute, Sant’Anna School of Advanced Studies（圣安娜高等学院生物机器人研究所）；Harvard University（哈佛大学）
We develop a minimal hydrodynamic model, without an orientational order parameter, for assemblies of contractile swimmers encapsulated in a droplet of a binary-fluid emulsion. Our model uses two coupled scalar order parameters, $ϕ$ and $ψ$, which capture, respectively, the droplet interface and the activity of the contractile swimmers inside this droplet. These order parameters are also coupled to the velocity field $\bm u$. At low activity, our model yields a self-propelling droplet whose center of mass $(CM)$ displays rectilinear motion, powered by the spatiotemporal evolution of the field $…
The dispersion of respiratory saliva droplets by indoor wake structures may enhance the transmission of various infectious diseases, as the wake spreads virus-laden droplets across the room. Thus, this study analyses the interaction between vortical wake structures and exhaled multi-component saliva droplets. A self-propelling analytically-described dipolar vortex is chosen as a model wake flow, passing through a cloud of micron-sized evaporating saliva droplets. The droplets' spatial location, velocity, diameter, and temperature are traced and coupled to their local flow field. For the first …
The flow of deformable particles, such as droplets, dragged by a fluid, through a network of narrow pores inside rocks or other porous media is key in a range of applications, from enhanced oil recovery and water filtration to lab on a chip sorting of cells. The collective dynamics and its impact on the flow are poorly understood. Here, using droplets as a prototype, we show that collective transport can occur for conditions under which a single particle would get trapped at a pore channel. When a series of droplets gets trapped, the fluids flow is affected significantly, leading to an increas…
