Biomedical subjects

Dominic Vella

Publications and source records attributed to Dominic Vella.

4 recordsLinked to original sources

PubMed2006

The load supported by small floating objects.

We consider the equilibrium flotation of a two-dimensional cylinder and a sphere at an interface between two fluids. We give conditions on the density and radius of these objects for them to be able to float at the interface and discuss the role played by the contact angle in determining these conditions. For cylinders with a small radius, we find that the maximum density is independent of contact angle but that, for spheres, the contact angle enters at leading order in the particle radius. Our theoretical predictions are in agreement with experimental results.

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PubMed2006

Dynamics of surfactant-driven fracture of particle rafts.

We investigate the dynamic fracture of a close-packed monolayer of particles, or particle raft, floating at a liquid-gas interface induced by the localized addition of surfactant. Unusually for a two-dimensional solid, our experiments show that the speed of crack propagation here is not affected by the elastic properties of the raft. Instead it is controlled by the rate at which surfactant is advected to the crack tip by means of the induced Marangoni flows. Further, the velocity of propagation is not constant in time and the length of the crack scales as t(3/4). More broadly, this surfactant-induced rupture of interfacial rafts suggests ways to manipulate them for applications.

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PubMed2006

Sinking of a horizontal cylinder.

We study the sinking of a dense cylinder initially supported horizontally at an air-water interface and then released. The sinking motion is studied experimentally and agrees quantitatively with a simple hydrodynamic model of the process. In particular, our model predicts that the time taken for the cylinder to become immersed in the liquid should be tsink approximately theta((lc/g)1/2), where lc is the capillary length and g the acceleration due to gravity, in good agreement with what is observed experimentally.

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PubMed2006

A simple microscopic model for the dynamics of adhesive failure.

We consider a microscopic model for the failure of soft adhesives in tension based on ideas of bond rupture under dynamic loading. By focusing on adhesive failure under loading at constant velocity, we demonstrate that bimodal curves of stress against strain may occur due to effects of finite polymer chain or bond length and characterize the loading conditions under which such bimodal behavior is observed. The results of this analysis are in qualitative agreement with experiments performed on unconfined adhesives in which failure does not occur by cavitation.

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