Research Fellows Directory
Dr Michael Smith
University of Nottingham
Concentrated suspensions are fluids containing lots of small particles (100nm - 10µm). These kinds of fluids are very common: toothpaste, mayonnaise, cement, blood, printer inks. Under the correct conditions flows of these particulate fluids may change from free flowing to jammed and solid. Understanding this process applies to, for example, inkjet printing or why blood vessels become blocked. Using model systems, where the interactions between particles are well understood we try to understand how the motion of microscopic particles gives rise to these large scale phenomena (jamming or arrest).
As particle fluids jam they try to release energy through various mechanisms such as crack formation. An important additional mechanism is known as ‘shear banding; in which the flow spontaneously separates into two regions which flow at very different speeds. During film formation (e.g paint drying) instabilities can lead to defects in the coating which are highly undesirable. Understanding the microscopic origin of these instabilities has important implications for the design of industrial products.
We are also investigating granular fluids in which small particles move randomly due to vibrations imposed on the system. This enables us to track the motion of every particle in a way that is difficult in large systems of colloidal particles. This complementary approach is being developed to understand dynamics of particles in a concentrated fluid.