Our Research
"Smart fluids" : Electro-rheological fluids and magneto-rheological suspensions (focussing on microstructural mechanisms governing the field-induced increase in viscosity)
The viscosities of ER and MR fluids can increase several orders of magnitude by applying large electric and magnetic fields, respectively. The “tunable” flow properties of these particulate suspensions offer many potential applications, including active shock absorbers, fluid clutches and actuator systems. The widespread commercialisation of this technology has been hindered by a lack of understanding of the underlying mechanisms. The goals of our research are to understand the microscopic mechanisms that control the flow behaviour of these materials, and to determine the relationships between constituent properties and macroscopic behaviour. Our approaches include an experimental program, as well as theoretical modelling employing particle-level mechanics.
Rheology and microstructure in colloidal suspensions
Novel techniques for viscoelastic measurement
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Figure : The viscosity change with voltage in an electro-rheological fluid. Left : An electro-rheological fluid (black) is retained between the two vertical electrodes when a voltage is applied. Right : When the voltage is switched off, the viscosity is greatly reduced and the fluid flows readily. |
Our group's research interests lie in rheology, fluid mechanics and transport processes. We have a special interest in fundamental studies of complex fluids – these are materials which are composed of microstructural elements that interact via interparticle and hydrodynamic forces. Familiar examples of such fluids are suspensions of solid particles (slurries), liquid crystals, ferrofluids, electrorheological fluids, magnetorheological fluids, paper pulp suspensions and polymer solutions and melts. In all of these systems the basic question is one of understanding the relationship between the material's microstructure and the macroscopic rheological properties.
There are Masters and PhD research projects available in most of these research areas. Please contact the School for more details .
Laboratory instruments available include
(a) Anton Paar Physica MCR 300 and MCR301 rheometers
These state of the art instruments can be operated in the following modes
- electrorheological
- magnetorheological
- standard rheometrical
(b) Goettfert Capillary Rheometer (Rheo Tester 2000)
This is a capillary rheometer with a dynamic speed range of 1:400000, with digital measuring and online calibration. It can achieve a maximum extrusion force of 20kN and a speed of 20mm/s.
(c) Linkam CSS450 optical shearing system
This system allows microstructural dynamics of complex fluids to be directly observed via a standard optical microscope while undergoing shear deformation.
Example :
Photograph below shows poly(styrene-co-divinylbenzene) particles in silicone oil under steady shearing (shearing direction is towards the bottom of the photograph).
Scale : the bottom edge of the photograph is approx 75µm.
