Out-of-Contact Elastohydrodynamic Deformation due to Lubrication Forces

Wang, Yumo; Dhong, Charles; Fréchette, Joëlle

doi:10.1103/physrevlett.115.248302

Cited by 59 publications

(67 citation statements)

References 55 publications

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“…7,8,12,39 For each experimental configuration ( R ,  , V , k ) the shaded areas show how changing the modulus of the coating, from 0.5 MPa to 10 MPa (elastomers), would change K and  . Lowering the elasticity further would bring most experimental conditions into the K   regime, which is solved here.…”

Section: Results and Discussion Choice And Relevance Of Parameters Invmentioning

confidence: 99%

“…The three dashed lines indicate the range of spring parameter and elasticity investigated here. The shaded areas represent experimental configuration of prior experimental studies for reduced modulus of the soft coating between 0.5-10 MPa, where purple: Charrault et al 8 , blue: Kaveh et al 7 red: Wang et al 12 , and grey: Honig et al 39 A slope of 0.8 in log-log scale is illustrated in the bottom right corner. The green regime above the green dashed line indicates…”

Section: Results and Discussion Choice And Relevance Of Parameters Invmentioning

confidence: 99%

“…Throughout, the strain in the elastic coating always remains within the bounds of linear elasticity theory, the maximum normal strain we predict is ~6% and for the great majority of the reported results the strain is less than 2% , which falls safely in the linear regime, although the deformation of the coating can be of order of the fluid film thickness. 12 During the measurement of dynamic surface forces, one surface is typically mounted on a cantilever spring. In this case, the surface separation is different from the displacement of the driving motor due to the deflection of the spring.…”

Section: Problem Formulationmentioning

confidence: 99%

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Elastic deformation of soft coatings due to lubrication forces

2017

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Elastic deformation of rigid materials with soft coatings (stratified materials) due to lubrication forces can also alter the interpretation of dynamic surface forces measurements and prevent contact formation between approaching surfaces. Understanding the role of elastic deformation on the process of fluid drainage is necessary, and the case where one (or both) of the interacting materials consists of a rigid substrate with a soft coating is still limited. We combine lubrication theory and solid linear elasticity to describe the dynamic of fluid drainage past a compliant stratified boundary. The analysis presented covers the full range of coating thicknesses, from an elastic foundation to a half-space for an incomressible coating. We decouple the individual contributions of the coating thickness and material properties on the elastic deformation, hydrodynamic forces, and fluid film thickness. We obtain a simple expression for the shift in contact position during force measurements that is valid for many experimental conditions. We compare directly the effect of stratification on the out-of-contact deformation to the well-known effect of stratification on indentation. We show that corrections developed for stratification in contact mechanics are not applicable to elastohydrodynamic deformation. Finally, we provide generalized contour maps that can be employed directly to estimate the elastic deformation present in most dynamic surface force measurements. IntroductionRigid materials with soft coatings are ubiquitous in tribology, 1 microfluidic devices, 2 biomaterials, 3 or colloidal and particulate systems. 4 Under many practical settings they are employed in fluid environments where they are in close proximity to another surface. Under these conditions viscous forces due to the relative movement of the two surfaces can exert fluid pressures and cause elastic deformation (see Figure 1). More specifically, lubrication forces can lead to elastic deformation, also known as elastohydrodynamic deformation or EHD, which can prevent contact formation as fluid drains from a gap separating compliant materials. [5][6][7] If unaccounted for, EHD can lead to the misinterpretation of dynamic surface forces measurements. The surface forces apparatus (SFA) 6 or the atomic force microscope (AFM) 8 are commonly employed under dynamic conditions and can be used with soft materials. In particular, an exact description of lubrication forces is necessary to rely on dynamic surface forces measurements for the characterization of, for example, conservative surface forces, 9 fluid structure, 10 or surface slip 11 on compliant materials. In addition, recent reports show that ignoring the effect of elastic deformation can lead to a misinterpretation of the force data, contact position, and slip at the solid-liquid surfaces. 8,12 Most previous efforts to describe unsteady normal fluid drainage past an elastic boundary studied the case where the soft materials could be considered a half-space. For instance, Davis et al. studied normal e...

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Section: Results and Discussion Choice And Relevance Of Parameters Invmentioning

confidence: 99%

Section: Results and Discussion Choice And Relevance Of Parameters Invmentioning

confidence: 99%

Section: Problem Formulationmentioning

confidence: 99%

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Elastic deformation of soft coatings due to lubrication forces

2017

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“…A second equation results from the relation between pressure p(x) inside the lubrication film and the shape of the interface h(x). For capillary interfaces this is given by the Laplace pressure 2 , which in terms of the scaling law gives…”

Section: A Bretherton Bubbles: α = 2/3mentioning

confidence: 99%

“…1, comparing an image of liquid drop impact (left panel [1]) and the approach of a rigid sphere above a soft elastic layer (right panel [2]). In both cases, a squeeze flow appears in the thin gap between the impactor and the substrate; this leads to a buildup of a lubrication pressure that is able to deform the droplet and the elastic layer [1][2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Analogies between elastic and capillary interfaces

Snoeijer

2016

Phys. Rev. Fluids

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In this paper we exploit some analogies between flows near capillary interfaces and near elastic interfaces. We first consider the elastohydrodynamics of a ball bearing and the motion of a gas bubble inside a thin channel. It is shown that there is a strong analogy between these two lubrication problems, and the respective scaling laws are derived side by side. Subsequently, the paper focuses on the limit where the involved elastic interfaces become extremely soft. It is shown that soft gels and elastomers, like liquids, can be shaped by their surface tension. We highlight some recent advances on this class of elastocapillary phenomena.

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Underwater Adhesives Produced by Chemically Induced Protein Aggregation

Wilson,

Lu,

Nachtrieb

et al. 2023

Adv Funct Materials

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Barnacles convert hydrophilic proteins into an insoluble, yet aqueous, material that functions as a permanent underwater adhesive. Here, it is demonstrated that a common hydrophilic protein, bovine serum albumin, can be chemically triggered underwater to aggregate into a similar aqueous adhesive that mimics the formation of the natural adhesive. The combined action of multiple chemical denaturants initiates rapid gelation followed by further curing over time in artificial seawater. The adhesive strengths of this waterborne adhesive measured by lap shear are comparable to many bioinspired adhesives that use organic solvents and a high fraction of hydrophobic components. This approach establishes a bioinspired adhesive that can be deployed at practical scales in marine environments, produced sustainably, and sourced from low‐cost materials.

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Out-of-Contact Elastohydrodynamic Deformation due to Lubrication Forces

Cited by 59 publications

References 55 publications

Elastic deformation of soft coatings due to lubrication forces

Elastic deformation of soft coatings due to lubrication forces

Analogies between elastic and capillary interfaces

Underwater Adhesives Produced by Chemically Induced Protein Aggregation

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