Pattern formation in the geosciences
Our group studies complex fluids and complex solids – materials that consist of more than one phase of matter, mixed together (i.e. things like paint drying and mud cracking). This work covers a diverse range of topics and questions, but is generally held together by a few simple themes:
(i) connecting the microscopic structure of such materials to their macroscopic properties,
(ii) understanding mechanical instabilities (e.g. fractures, buckling, wrinkling), and
(iii) applying these results in a broad, interdisciplinary way (e.g. geophysical patterns).
Basically, in our research, we are interested in understanding the natural structures that anyone can see around themselves, every day, and using them to explore a range of fundamental problems where complex interactions on one length or timescale give rise to some simple structure, or pattern on another scale. Some past and current research topics include:
- Showing how columnar joints, like those of the Giants Causeway, order and scale, using a combination of analogue experiments in corn starch, field work, and theory.
- Modelling of the vast polygonal permafrost patterns of polar Earth and Mars with the cyclic drying of clay in a Petri dish, to explain how they form and order.
- Shearing polymers to understand the scaling and formation of billion-year old fossil wrinkle structures in microbial mats (i.e. exploring the rheology of ancient life).
- Showing a general route of solidification from disordered liquid, to ordered soft solid, to a final hard solid, as charged colloids (paints, coatings) dry.
- Using this route to understand and control birefringence in photonic materials.
- The elucidation of plastic relaxation mechanisms that can toughen paint when, counter-intuitively, the adhesion between its constituent particles is weakened.
- Characterizing how mutations may cause disease on the level of a protein pathway, rather than the traditional idea of one mutation, one protein, one syndrome.
- Investigating structure (shear-bands; anisotropic solids) in charged colloidal dispersions, and using scattering methods (SAXS) to look at how poly-disperse colloids crystallise.
- Fracture patterns – going from characterising natural crack networks, to explaining how cracks interact and grow, to templating designer structures.
- Development of model materials for studying cohesive granular media (e.g. artificial sandstone): applications include hydraulic fracture, bio-fouling, and biogenic cracks.
- Using microfluidic methods to design model 2D porous media, to critically test pore-network modelling of multiphase flows, e.g. drying; reactive flow; CO2 sequestration.
- Exploring elastic instabilities on curved sheets (e.g. a contact lens). How do you design a curved surface that will spontaneously fold into a desired shape as it wets, or grows?