Static and dynamic wetting of soft substrates

Drop impact on solid surfaces is encountered in numerous natural and technological processes. Although the impact of single-phase drops has been widely explored, the impact of compound drops has received little attention. Here, we demonstrate a self-lubrication mechanism for water-in-oil compound drops impacting on a solid surface. Unexpectedly, the core water drop rebounds from the surface below a threshold impact velocity, irrespective of the substrate wettability. This is interpreted as the result of lubrication from the oil shell that prevents contact between the water core and the solid surface. We combine side and bottom view high-speed imaging to demonstrate the correlation between the water core rebound and the oil layer stability. A theoretical model is developed to explain the observed effect of compound drop geometry. This work sets the ground for precise complex drop deposition, with a strong impact on two- and three-dimensional printing technologies and liquid separation.

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“…Production of a compound drop by the injection method (pinch-off). References (61)(62)(63)(64)(65)(66)(67)(68)(69)(70)(71)(72)(73)(74)(75)(76)…”

Section: Supplementary Materialsmentioning

confidence: 99%

Rebound of self-lubricating compound drops

et al. 2020

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“…The material was applied in stomatology. Chen et al [18] summarized the study of dynamic wetting characteristics of soft substrates. Liu et al [19] got a wetting model to describe the wetting of the straw surface.…”

Section: Introductionmentioning

confidence: 99%

Numerical study on dynamic wettability of micro-structure surface

Han

Yang

Yang³

et al. 2019

THERM SCI

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Wettability plays a vital role in many fields. In this paper, the shortcomings of current experimental measurement of dynamic wetting characteristics are described. The dynamic wettability of droplets on the simplified triangular wave micro-structure surface is studied by volume of fluid method. The results are compared with the dynamic wettability of droplets on the smooth surface and the rectangular wave micro-structure surface. The results show the similarities and differences of the motion characteristics of droplets on smooth surface and different micro-structure surface. Under the action of volume force, the droplets are first deformed and then moved. The droplets move as a whole on the smooth surface. But the droplets partially slip on the micro-structure surface, and the threephase contact point on the left side does not move.

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“…Substrate deformation should balance this extra force in the case of deformable substrate. However, even after modification, Young's equation still cannot be applied directly, as it gives rise to deformation singularity (surface deformation goes to infinity) near the three-phase contact line [5][6][7][8][9][10][11][12][13]. To avoid this singularity, several researchers have tried different approaches.…”

Section: Introductionmentioning

confidence: 99%

“…Using the same concept, Style and Dufresne generalized a three-dimensional configuration, which allowed applying Neumann's consideration for small droplets on soft solids [11]. However, it is important to mention that Neumann's triangle of forces applied near the three-phase contact line could only be regarded as valid in the case of an equilibrium configuration [5] and as long as the necessary equilibrium conditions are satisfied [13].…”

Section: Introductionmentioning

confidence: 99%

Sessile Droplets on Deformable Substrates

Ahmed

Koursari

Trybała

et al. 2018

Colloids and Interfaces

Self Cite

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Wetting of deformable substrates has gained significant interest over the past decade due to a multiplicity of industrial and biological applications. Technological advances in the area of interfacial science have given rise to the ability to capture interfacial behavior between a liquid droplet and an elastic substrate. Researchers have developed several theories to explain the interaction between the two phases and describe the process of wetting of deformable/soft substrates. A summary of the most recent advances on static wetting of deformable substrates is given in this review. It is demonstrated that action of surface forces (disjoining/conjoining pressure) near the apparent three-phase contact line should be considered. Any consideration of equilibrium droplets on deformable (as well as on non-deformable) substrates should be based on consideration of the excess free energy of the system. The equilibrium shapes of both droplet and deformable substrate should correspond to the minimum of the excess free energy of the system. It has never been considered in the literature that the obtained equilibrium profiles must satisfy sufficient Jacobi’s condition. If Jacobi’s condition is not satisfied, it is impossible to claim that the obtained solution really corresponds to equilibrium. In recently published studies, equilibrium of droplets on deformable substrates: (1) provided a solution that corresponds to the minimum of the excess free energy; and (2) the obtained solution satisfies the Jacobi’s condition. Based on consideration of disjoining/conjoining pressure acting in the vicinity of the apparent three-phase contact line, the hysteresis of contact angle of sessile droplets on deformable substrates is considered. It is shown that both advancing and receding contact angles decrease as the elasticity of the substrate is increased and the effect of disjoining/conjoining pressure is discussed. Fluid inside the droplet partially wets the deformable substrate. It is shown that just these forces coupled with the surface elasticity determine the deformation of the deformable substrates.

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Static and dynamic wetting of soft substrates

Cited by 79 publications

References 126 publications

Rebound of self-lubricating compound drops

Rebound of self-lubricating compound drops

Numerical study on dynamic wettability of micro-structure surface

Sessile Droplets on Deformable Substrates

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