Pattern Formation in the Geosciences

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).

Structure formation in multi-phase materials, from our research. From left to right (i) colloidal crystals in drying paints; (ii) shear bands and birefringence in colloidal films; (iii) Kinneyia, a fossil wrinkling instability, and (iv) columnar joints in dried corn starch.

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?
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