Daniels Nonlinear Lab

Surfactant-Driven Gel Fracture

The image at left was taken of a droplet of food coloring spreading within self-generated fractures at the surface of gel agar in a Petri dish. This is quite different from the circular way which surfactant-laden droplets spread on either solid or liquid surfaces, and is related to the fact that the gel substrate is a viscoelastic material which can fracture. We are studying how this instability arises from competition between the surface tension of the droplet and the elastic properties of the substrate. Such instabilities are important to understand in order to reliably work with non-Newtonian fluids in industrial and biomedical settings.

Publications

K. E. Daniels, S. Mukhopadhyay, P. J. Houseworth, and R. P. Behringer. Instabilities in droplets spreading on gels. Physical Review Letters 99 124501 (2007) [ Link ]

Gel Heterogeneity

We study the heterogeneity of gels near the sol-gel transition through the spatial variations in gel strength. The correlated motion of fluorescent polystyrene microspheres suspended in gels (see image at right) is measured via two-point microrheology. Analysis of this correlated motion provides a local measure of gel heterogeneity.

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