Optical Coherence Tomography Picorheology

A large range of materials are classified as 'soft matter'. These materials include biological samples (DNA, proteins, cells, food gels etc), but also many industrial products (soap powders, paints etc). The manner in which soft materials deform and flow when they experience an external force is a fascinating and varied area of scientific research, termed 'rheology'. We plan to build three new instruments to probe the rheology of soft materials. These instruments will allow us to explore the flow properties of minute amounts of biological sample (picolitres) over a huge range of times scales for both runny and more viscous fluids. Crucially the techniques are not harmful to the specimens and can be used on fragile medical samples such as blood clots. When pushed by an external force soft materials can resist the motion (shear thicken) or increasingly travel with the flow (shear thin). However recent studies have shown (in contrast with previous accepted wisdom) that the external forces are not experienced uniformly by specimens of soft materials. The extreme case is where an external force spontaneously gives a fluid that is uniform when stationary a dynamic banded microstructure. The sensitivity of our picorheometer to micron sized quantities of fluids is ideal for us to explore this dynamic banding phenomena in more detail, beyond that available in state of the art equipment (e.g. magnetic resonance imaging).