Wetting and motion behaviors of water droplet on graphene under thermal-electric coupling field

Zhang, Zhong‐Qiang; Dong, Xin; Ye, Hongfei; Cheng, Guanggui; Ding, Jianning; Ling, Zhijian

doi:10.1063/1.4913207

Cited by 13 publications

(7 citation statements)

References 42 publications

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“…Recent experimental work has shown that the assumed hydrophobicity of graphitic surfaces is the result of hydrocarbon contaminants and that clean graphitic surfaces are actually mildly hydrophilic. − The widespread results for the contact angle of water on the surface obtained from simulations using force field methods − has provoked studies of the water–graphene interaction potential using electronic structure calculations. − These studies can be divided into two classes, namely, those carried out on the “infinite” system using a supercell replicated through periodic boundary conditions and those involving a sequence of H 2 O– cluster models followed by extrapolation to the graphene limit. Due to the challenges of accurately describing the various contributions to the binding energy and in properly extrapolating long-range interactions, these calculations have resulted in a considerable spread in the values of the binding energy.…”

mentioning

confidence: 99%

Comment on “Physisorption of Water on Graphene: Subchemical Accuracy from Many-Body Electronic Structure Methods”

Jordan

Heßelmann

2019

J. Phys. Chem. C

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mentioning

confidence: 99%

Comment on “Physisorption of Water on Graphene: Subchemical Accuracy from Many-Body Electronic Structure Methods”

Jordan

Heßelmann

2019

J. Phys. Chem. C

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“…Sophisticated control of wetting is possible by coupling electrical and thermal effects. MD simulations indicate that increasing the temperature results in a linear reduction in the WCA that can then be reversed by increasing the charge magnitude, enabling a hydrophilic to hydrophobic transition 36 .…”

Section: Extrinsic Tuning Of the Wettability Of 2d Materialsmentioning

confidence: 99%

Interaction of 2D materials with liquids: wettability, electrochemical properties, friction, and emerging directions

et al. 2020

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The emergence of two-dimensional (2D) materials as functional surfaces for sensing, electronics, mechanics, and other myriad applications underscores the importance of understanding 2D material-liquid interactions. The thinness and environmental sensitivity of 2D materials induce novel surface forces that drive liquid interactions. This complexity makes fundamental 2D material-liquid interactions variable. In this review, we discuss the (1) wettability, (2) electrical double layer (EDL) structure, and (3) frictional interactions originating from 2D material-liquid interactions. While many 2D materials are inherently hydrophilic, their wettability is perturbed by their substrate and contaminants, which can shift the contact angle. This modulation of the wetting behavior enables templating, filtration, and actuation. Similarly, the inherent EDL at 2D material-liquid interfaces is easily perturbed. This EDL modulation partially explains the wettability modulation and enables distinctive electrofluidic systems, including supercapacitors, energy harvesters, microfluidic sensors, and nanojunction gating devices. Furthermore, nanoconfinement of liquid molecules at 2D material surfaces arising from a perturbed liquid structure results in distinctive hydrofrictional behavior, influencing the use of 2D materials in microchannels. We expect 2D material-liquid interactions to inform future fields of study, including modulation of the chemical reactivity of 2D materials via tuning 2D material-liquid interactions. Overall, 2D material-liquid interactions are a rich area for research that enables the unique tuning of surface properties, electrical and mechanical interactions, and chemistry. Origin of 2D material interactions with liquids The ideal interaction between a surface and a liquid is dictated by surface forces. Surface forces can be subdivided into three components: van der Waals forces, which exist at any interface between solids and liquids; electrostatic interactions, which exist between charged or polar surfaces and fluids; and structural forces, principally hydrogen bonding 1. These interactions influence the wetting behavior and determine whether the interaction with water is hydrophilic or hydrophobic, control the electronic structure at the liquid-solid interface, influence the frictional interaction, and modulate the chemical activity. However, this ideal picture of the surface interactions is complicated when considering surface heterogeneities, including roughness 2 and contamination 3 , which interfere with the formation of an equilibrium configuration between the liquid and the surface, leading to eccentric behaviors, including superwetting, superslipping, and superhydrophobicity. These surface heterogeneities also allow the surface liquid interactions to be tuned, enabling an array of applications in sensing, chemical transport, and actuation. Two-dimensional (2D) materials, which are extremely thin, have unique electrical properties, and have a tendency to deform and accumulate contamination during proce...

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“…However, the wettability of the monolayer graphene is quite dependent on its substrate, implying that the monolayer graphene is of wetting transparency, and the number of layers is an important parameter for the wettability of graphene . Regarding the fluid–graphene system, the previous efforts were mainly devoted to the static and dynamic wettability, the driving and fast diffusion of water droplets, the liquid–graphene interfacial friction, and the fluid boundary slip confined in the graphene channel, and so forth. − Recently, however, it was demonstrated experimentally that the monolayer graphene, as a coating of the nanochannel, can significantly increase the boundary slip of the confined fluid. It was found that the slip length of the fluid is explicitly sensitive to the substrate of the monolayer graphene.…”

Section: Introductionmentioning

confidence: 99%

Unidirectional Self-Driving Liquid Droplet Transport on a Monolayer Graphene-Covered Textured Substrate

Zhang

Guo

Tang

et al. 2019

ACS Appl. Mater. Interfaces

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Controllable directional transport of liquid droplets on a functionalized surface has been a challenge in the field of microfluidics because it does not require energy supply, and the physical mechanism of such self-driving transport exhibits extraordinary contribution to fundamental understanding of some biological processes and the design of microfluidic apparatus. In this paper, we report a novel design of a surface microstructure that can realize unidirectional self-driving liquid mercury (Hg) droplet transport on a graphene-covered copper (Cu) substrate with a three-dimensional surface microstructure. We have demonstrated that a liquid Hg droplet spontaneously propagates on a grooved Cu substrate covered by a monolayer graphene without any external force fields. Classical molecular dynamics results provide a profound insight on the self-driving process of Hg droplets. It shows that the Hg droplet undergoes acceleration, deceleration, and return stages successively from the narrow to wide ends of the gradient groove. Intriguingly, Hg droplets can move continuously and unidirectionally on the three-dimensional graphene-covered surface microstructure when they accumulate enough kinetic energy from the gradient groove to break the energy barrier at the step junctions between the two neighboring unit cells. The design of the zigzag textured surface covered by a monolayer graphene artfully uses the facts; (1) the monolayer graphene can effectively reduce the droplet pinning on the textured surface, (2) the hydrophobic graphene layer reduces the friction between Hg droplets and the substrate, and (3) the textured surface can permeably interact with the droplets through the monolayer graphene to achieve a continuous self-driving process. The findings reported here open a door to explore the graphene-covered functional surface to directional transport of liquid droplets and provide an in-depth understanding of the self-driving mechanism for liquid droplets on graphene-covered textured substrates.

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Wetting and motion behaviors of water droplet on graphene under thermal-electric coupling field

Cited by 13 publications

References 42 publications

Comment on “Physisorption of Water on Graphene: Subchemical Accuracy from Many-Body Electronic Structure Methods”

Comment on “Physisorption of Water on Graphene: Subchemical Accuracy from Many-Body Electronic Structure Methods”

Interaction of 2D materials with liquids: wettability, electrochemical properties, friction, and emerging directions

Unidirectional Self-Driving Liquid Droplet Transport on a Monolayer Graphene-Covered Textured Substrate

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