Jumping velocity of an electrowetting-actuated droplet: A theoretical and numerical study

Du, Jia Lei; Chamakos, Nikolaos T.; Papathanasiou, Athanasios G.; Li, Yanzhi; Min, Qi

doi:10.1103/physrevfluids.6.123603

Cited by 17 publications

(4 citation statements)

References 58 publications

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“…The highly distorted interface induces the generation of capillary waves. , According to the red dashed circle in Figure a, the spreading factor begins to oscillate during late spreading, which may result from the capillary waves that repeatedly propagate upward and downward. To confirm our speculation, numerical simulation based on an effective, sharp-interface, continuum-level modeling method is implemented, which has been validated and widely used to investigate the impact dynamics in our previous work. − This modeling approach is originally developed by Chamakos et al , , who also presented the details of the modeling setup. Up to now, it is still challenging to incorporate the influence of the oxide layer into a continuum-level modeling method.…”

Section: Resultsmentioning

confidence: 87%

How an Oxide Layer Influences the Impact Dynamics of Galinstan Droplets on a Superhydrophobic Surface

Wang

et al. 2022

Langmuir

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When exposed to air, gallium-based alloys rapidly form a thin oxide layer with viscoelasticity and high adhesion. Although previous work demonstrated that an oxide layer inhibits liquid metal droplet rebound, there is still a lack of a quantitative study to elaborate how an oxide layer affects the impact dynamics. To address this issue, we experimentally investigate Galinstan droplet impingement on a superhydrophobic CuO nanoblade surface and physically explain the difference in the dynamic characteristics of oxidized and unoxidized droplets. Experimental results show that the effect of an oxide layer becomes prominent during the retraction phase. The high adhesion significantly suppresses retraction and rebound, while the elastic response prevents a droplet from sufficiently stretching and maintains the stability of the morphology. More importantly, we systematically and quantitatively explore the influence of an oxide layer on several critical impact parameters, which contributes to a comprehensive understanding of the impact dynamics of liquid metal droplets. It is indicated that an oxide layer has little effect on the maximum spreading factor and spreading time, whereas it causes a 45% reduction of the restitution coefficient and a 36% increase in contact time. Notably, the scaling laws that describe the critical impact parameters of unoxidized droplets show good agreement with the ones known from ordinary Newtonian fluids.

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Section: Resultsmentioning

confidence: 87%

How an Oxide Layer Influences the Impact Dynamics of Galinstan Droplets on a Superhydrophobic Surface

Wang

et al. 2022

Langmuir

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“…Since the microstructures of organisms such as lotus leaf and water strider were discovered [73,74], bio-inspired textured surfaces have been rapidly developed. Various methods have been developed to modulate surface wettability, which greatly promote the development of water-driven electricity generators [20,35,[74][75][76][77][78][79][80][81][82][83][84]. Therefore, an understanding of the effect of texture on the hydrophobicity of materials is necessary.…”

Section: Bio-inspired Waving or Flowing Water-driven Electricity Gene...mentioning

confidence: 99%

Bio-inspired water-driven electricity generators: From fundamental mechanisms to practical applications

Wang¹,

Xu²,

Zhang³

et al. 2023

Nano Research Energy

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Harvesting water energy in various forms of water motion, such as evaporation, raindrops, river flows, ocean waves, and other, is promising to relieve the global energy crisis and reach the aim of carbon neutrality. However, this highly decentralized and distributed water energy poses a challenge on conventional electromagnetic hydropower technologies that feature centralization and scalization.Recently, this problem has been gradually addressed by the emergence of a myriad of electricity generators that take inspiration from natural living organisms, which have the capability to efficiently process and manage water and energy for survival in the natural competition. Imitating the liquid-solid behaviors manifested in ubiquitous biological processes, these generators allow for the efficient energy conversion from water-solid interaction into the charge transfer or electrical output under natural driving, such as gravity and solar power. However, in spite of the rapid development of the field, a fundamental understanding of these generators and their ability to bridge the gap between the fundamentals and the practical applications remains elusive. In this review, we first introduce the latest progress in the fundamental understanding in bio-inspired electricity generators that allow for efficient harvesting water energy in various forms, ranging from water evaporation, droplet to wave or flow, and then summarize the development of the engineering design of the various bio-inspired electricity generator in the practical applications, including self-powered sensor and wearable electronics. Finally, the prospects and urgent problems, such as how to achieve large-scale electricity generation, are presented.

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“…Based on the conversion of surface energy to gravitational potential energy, several schemes have been proposed to force droplets to jump and be detached from their supporting substrate. Electrowetting schemes can be used to induce an increase in the surface area of droplets, which may subsequently result in an increase in their gravitational potential energy and the jumping of droplets. , Hong and Lee investigated the electrowetting-induced detachment of sessile droplets immersed in immiscible fluids from a hydrophobic surface . Cavalli et al investigated the influence of wettability on the electrowetting-driven detachment process .…”

Section: Introductionmentioning

confidence: 99%

Vibration and Jumping of Ferrofluid Marbles under an Initial Magnetic Perturbation

et al. 2023

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Liquid marbles are being promoted as a replacement for conventional droplets in digital microfluidics. Liquid marbles can be remotely controlled by an external magnetic field if ferrofluid is utilized as their liquid cores. In this study, the vibration and jumping of a ferrofluid marble is experimentally and theoretically investigated. An external magnetic field is utilized to induce deformation in a liquid marble and an increase in its surface energy. As the magnetic field is switched off, the stored surface energy converts to gravitational potential and kinetic energies until it is dissipated. An equivalent linear mass-spring-damper system is used to study the vibration of the liquid marble, and the effect of its volume and initial magnetic stimulus on the vibrational characteristics, such as natural frequency, damping ratio, and deformation of the liquid marble, is experimentally examined. By analyzing these oscillations, the effective surface tension of the liquid marble is evaluated. Also, a novel theoretical model is proposed to obtain the damping ratio of the liquid marble, suggesting a new tool for the measurement of liquid viscosity. Interestingly, it is observed that the liquid marble jumps from the surface in the case of high initial deformation. Based on conservation law of energy, a theoretical model for predicting the liquid marbles jumping height and the boundary between jumping and non-jumping zones in terms of nondimensional numbers, namely, magnetic and gravitational Bond numbers and Ohnesorge number, is proposed with an acceptable error compared to experimental data.

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Jumping velocity of an electrowetting-actuated droplet: A theoretical and numerical study

Cited by 17 publications

References 58 publications

How an Oxide Layer Influences the Impact Dynamics of Galinstan Droplets on a Superhydrophobic Surface

How an Oxide Layer Influences the Impact Dynamics of Galinstan Droplets on a Superhydrophobic Surface

Bio-inspired water-driven electricity generators: From fundamental mechanisms to practical applications

Vibration and Jumping of Ferrofluid Marbles under an Initial Magnetic Perturbation

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