Novel Cell Migration Assay Based on Microtissue Technology and Tissue-Specific Matrices

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Publication . Teixeira, Miguel; Arscott, Steve; Cox, Simon; Teixeira, Paulo

• In confined foams there exist wall Plateau borders (PBs), or menisci, where the films meet the confining substrates. • What is the shape of a PB of a given size on a surface of a given wettability (i.e., contact angle θc)? Can that surface support a foam? • This is important for firefighting foams, containers for foamy foodstuffs, etc • We solve the Young-Laplace equation with gravity for a planar film spanning a gap between two horizontal, flat substrates, to predict the shape of the PBs. • Validate results by comparing with Surface Evolver and experimental data

2017-07Conference object

Open access

When is a surface foam-phobic or foam-philic?

Publication . Teixeira, Miguel; Arscott, Steve; Cox, Simon; Teixeira, Paulo

It is commonly assumed that the liquid making up a sessile bubble completely wets the surface upon which the bubble lies. However, this need not be so, and the degree of wetting will determine how well a collection of bubbles - a foam - sticks to a surface. As a preliminary to this difficult problem, we study the shape of a single vertical soap film spanning the gap between two flat, horizontal solid substrates of given wettabilities. For this simple geometry, the Young-Laplace equation can be solved (quasi-) analytically to yield the equilibrium shapes, under gravity, of the two-dimensional Plateau borders along which the film contacts the substrates. We thus show that these Plateau borders, where most of a foam's liquid resides, can only exist if the values of the Bond number Bo and of the liquid contact angle yc lie within certain domains in (yc, Bo) space: under these conditions the substrate is foam-philic. For values outside these domains, the substrate cannot support a soap film and it is foam-phobic. In other words, on a substrate of a given wettability, only Plateau borders of a certain range of sizes can form. For given (yc, Bo), the top Plateau border can never have greater width or cross-sectional area than the bottom one. Moreover, the top Plateau border cannot exist in a steady state for contact angles above 901. Our conclusions are validated by comparison with both experimental and numerical (Surface Evolver) data. We conjecture that these results will hold, with slight modifications, for non-planar soap films and bubbles. Our results are also relevant to the motion of bubbles and foams in channels, where the friction force of the substrate on the Plateau borders plays an important role.

2018-07-14Journal article

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