| 1. |
- Style, Robert W., et al.
(författare)
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Stiffening solids with liquid inclusions
- 2015
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Ingår i: Nature Physics. - 1745-2473 .- 1745-2481. ; 11:1, s. 82-87
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Tidskriftsartikel (refereegranskat)abstract
- From bone and wood to concrete and carbon fibre, composites are ubiquitous natural and synthetic materials. Eshelby's inclusion theory describes how macroscopic stress fields couple to isolated microscopic inclusions, allowing prediction of a composite's bulk mechanical properties from a knowledge of its microstructure. It has been extended to describe a wide variety of phenomena from solid fracture to cell adhesion. Here, we show experimentally and theoretically that Eshelby's theory breaks down for small liquid inclusions in a soft solid. In this limit, an isolated droplet's deformation is strongly size-dependent, with the smallest droplets mimicking the behaviour of solid inclusions. Furthermore, in opposition to the predictions of conventional composite theory, we find that finite concentrations of small liquid inclusions enhance the stiffness of soft solids. A straightforward extension of Eshelby's theory, accounting for the surface tension of the solid-liquid interface, explains our experimental observations. The counterintuitive stiffening of solids by fluid inclusions is expected whenever inclusion radii are smaller than an elastocapillary length, given by the ratio of the surface tension to Young's modulus of the solid matrix. These results suggest that surface tension can be a simple and effective mechanism to cloak the far-field elastic signature of inclusions.
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| 2. |
- Style, Robert W., et al.
(författare)
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Universal Deformation of Soft Substrates Near a Contact Line and the Direct Measurement of Solid Surface Stresses
- 2013
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 110:6, s. 066103-
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Tidskriftsartikel (refereegranskat)abstract
- Droplets deform soft substrates near their contact lines. Using confocal microscopy, we measure the deformation of silicone gel substrates due to glycerol and fluorinated-oil droplets for a range of droplet radii and substrate thicknesses. For all droplets, the substrate deformation takes a universal shape close to the contact line that depends on liquid composition, but is independent of droplet size and substrate thickness. This shape is determined by a balance of interfacial tensions at the contact line and provides a novel method for direct determination of the surface stresses of soft substrates. Moreover, we measure the change in contact angle with droplet radius and show that Young's law fails for small droplets when their radii approach an elastocapillary length scale. For larger droplets the macroscopic contact angle is constant, consistent with Young's law. DOI: 10.1103/PhysRevLett.110.066103
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