Effects of the surface tension gradient and viscosity on coalescence-induced droplet jumping on superamphiphobic surfaces

We present numerical computations of the deformation of an oil-droplet under the influence of a surface tension gradient generated by the surfactant released at the poles (the Greenspan experiment). We find this deformation to be very small under the pure surface tension gradient. To explain the large deformation of oil droplets observed in Greenspan’s experiments, we propose the existence of a phoretic force generated by the concentration gradient of the surfactant. We show that this hypothesis successfully explains the available experimental data and we propose some further tests.

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Tackling the Short-Lived Marangoni Motion Using a Supramolecular Strategy

CCS Chemistry ◽

10.31635/ccschem.019.20180009 ◽

2019 ◽

Vol 1 (2) ◽

pp. 148-155 ◽

Cited By ~ 6

Author(s):

Mengjiao Cheng ◽

Dequn Zhang ◽

Shu Zhang ◽

Zuankai Wang ◽

Feng Shi

Keyword(s):

Surface Tension ◽

Electricity Generation ◽

Adsorption Equilibrium ◽

Molecular Level ◽

Surface Tension Gradient ◽

Aggregation State ◽

Physical Limit ◽

Competitive Kinetics ◽

Air Liquid Interface ◽

Spontaneous Motion

Inspired by the intriguing capability of beetles to quickly slide on water, scientists have long translated this surface-tension-gradient–dominated Marangoni motion into various applications, for example, self-propulsion. However, this classical spontaneous motion is limited by a short lifetime due to the loss of the surface tension gradient. Indeed, the propellant of amphiphilic surfactants can rapidly reach an adsorption equilibrium and an excessive aggregation state at the air/liquid interface. Here, we demonstrate a supramolecular host–guest chemistry strategy that allows the breaking of the physical limit of the adsorption equilibrium and the simultaneous removal of surfactant molecules from the interface. By balancing the competitive kinetics between the two processes, we have prolonged the lifetime of the motion 40-fold. Our work presents an important advance in the query of long-lived self-propulsion transport through flexible interference at the molecular level and holds promise in electricity generation applications .

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Experimental study on the flow instability of a binary mixture driven by rotation and surface-tension gradient in a shallow Czochralski configuration

International Journal of Thermal Sciences ◽

10.1016/j.ijthermalsci.2017.05.001 ◽

2017 ◽

Vol 118 ◽

pp. 236-246 ◽

Cited By ~ 4

Author(s):

Jia-Jia Yu ◽

You-Rong Li ◽

Lu Zhang ◽

Shuang Ye ◽

Chun-Mei Wu

Keyword(s):

Experimental Study ◽

Surface Tension ◽

Binary Mixture ◽

Flow Instability ◽

Surface Tension Gradient

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Effects of a surface-tension gradient on the performance of a micro-grooved heat pipe: an analytical study

Microfluidics and Nanofluidics ◽

10.1007/s10404-008-0282-8 ◽

2008 ◽

Vol 5 (5) ◽

pp. 655-667 ◽

Cited By ~ 14

Author(s):

Balram Suman

Keyword(s):

Surface Tension ◽

Heat Pipe ◽

Analytical Study ◽

Surface Tension Gradient

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On cusped interfaces

Journal of Fluid Mechanics ◽

10.1017/s0022112098008532 ◽

1998 ◽

Vol 359 ◽

pp. 313-328 ◽

Cited By ~ 23

Author(s):

YULII D. SHIKHMURZAEV

Keyword(s):

Surface Tension ◽

Free Surface ◽

Reynolds Numbers ◽

Present Theory ◽

Similar Process ◽

Surface Tension Gradient ◽

Low Reynolds Numbers ◽

Moving Contact Line ◽

Moving Contact ◽

Rate Of Dissipation

An asymptotic analysis of two-dimensional free-surface cusps associated with flows at low Reynolds numbers is presented on the basis of a model which, in agreement with direct experimental observations, considers this phenomenon as a particular case of an interface formation–disappearance process. The model was derived from first principles and earlier applied to another similar process: the moving contact-line problem. As is shown, the capillary force acting on a cusp from the free surface, which in the classical approach can be balanced by viscous stresses only if the associated rate of dissipation of energy is infinite, in the present theory is always balanced by the force from the surface-tension-relaxation ‘tail’, which stretches from the cusp towards the interior of the fluid. The flow field near the cusp is shown to be regular, and the surface-tension gradient in the vicinity of the cusp, caused and maintained by the external flow, induces and is balanced by the shear stress. Existing approaches to the free-surface cusp description and some relevant experimental aspects of the problem are discussed.

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