The experimental research in our group has two directions: ‘Soft Matter’, a sub-discipline of physics concerned with the study of colloidal suspensions, surfactants and polymers, and Active Matter (see also Physics of Living Matter) the active or life counterparts of soft matter, such as bacterial suspensions and biological polymers
Soft matter displays many fascinating properties. One example is shown above, where suspensions of Perspex spheres that act as hard particles (~1 micron diameter), self assemble into ‘colloidal crystals’ at high densities. The right-hand-side movie, taken with confocal microscopy, shows the crystal growth process, while the iridescence in the main picture is due to individual colloidal crystallites Bragg-scattering incident white light. Soft matter also shows interesting mechanical behaviour. A well known ‘kitchen’ example is ‘shear thickening’ - a concentrated corn starch solution gets harder to stir the harder it is stirred. Significantly, biology is almost entirely made up of ‘living soft matter’ – globular proteins are colloids, DNA is a stiff polymer, and the lipids forming cell membranes are essentially surfactants.
Soft matter has been studied by chemists, chemical engineers and biologists for many years. It is increasingly clear, however, that these systems show generic properties independent of chemical details. For example, all polymers share certain properties simply because they are long strings of balls performing Brownian motion. This is the central reason why physicists are getting interested. Moreover, studying the generic properties of soft matter can give fresh insights into a broad range of fundamental questions that cut across the whole of condensed matter physics, e.g. concerning the nature of disordered solids.
Many experimental projects (mostly done in COSMIC, an interdisciplinary lab for physicists, physical chemists and biologists) are closely related to projects in theory and simulation in our group.