The non-linear physics of driven colloids and bacteria
Lead Research Organisation:
University of Edinburgh
Department Name: Sch of Physics and Astronomy
Abstract
Statistical mechanics is the branch of physics dealing with how the collective properties of a large number of entities depend ib how they interact with each other. The hardest problems in the subject are those that deal with systems driven off equilibrium by some external force. I propose a programme of experimental research to probe two kinds of driven systems: the deformation and flow of dense colloidal suspensions, and collections of bacteria.The interacting entities in a concentrated colloidal suspension are microscopic particles suspended in a liquid. The flow properties of such suspensions are both a fascination for fundamental science, and important for applications. One of the many everyday examples is the way tooth paste behaves like a liquid when being squeezed out of its tube, but acts like a solid while sitting on the tooth brush. I will use a range of new experimental tools to study the deformation and flow of very well defined, 'model' suspensions. In particular, it is now possible to use advanced optical microscopy to follow the trajectories of individual particles in a suspension in flow. The data obtained will give us an unprecedentedly detailed picture of how the strange flow properties of dense suspensions are related to their constituent particles.There is today emerging a new area of statistical mechanics devoted to the study of 'agents' - complex entities interacting with each other, resulting in novel collective behaviour. The entities can be mobile phones on a network, or stock brokers on a trading floor, or a collection of bacteria. Individual bacteria are about the same size as inert colloidal particles (a thousandth of a millimeter). The main difference is that bacteria are active - they can propel themselves through the surrounding liquid. They also 'signal' to each other by secreting and 'decoding' a range of chemical 'messages'. A large number of bacteria can therefore show novel collective behaviour. Thus, e.g., they can 'swarm' on a surface (much like birds do in air). My research will address a range of bacterial collective behaviour, such as how they clump together to form 'biofilms' - complex two-dimensional bacterial 'cities', and how biofilms deal with 'cheaters', individual mutants who take advantage of their neighbours. I will also draw on the analogy with colloids and compare how suspensions of bacteria differ from suspensions of inert particles. Emerging results from the theory of interacting agents will also be tested experimentally using bacteria as 'models'.
Organisations
People |
ORCID iD |
Wilson Poon (Principal Investigator) |
Publications
Ballesta P
(2012)
Wall slip and flow of concentrated hard-sphere colloidal suspensions
in Journal of Rheology
Besseling R
(2009)
Quantitative imaging of colloidal flows.
in Advances in colloid and interface science
Besseling R
(2010)
Shear banding and flow-concentration coupling in colloidal glasses.
in Physical review letters
Besseling R
(2007)
Three-dimensional imaging of colloidal glasses under steady shear.
in Physical review letters
Croze OA
(2011)
Migration of chemotactic bacteria in soft agar: role of gel concentration.
in Biophysical journal
Dorken G
(2012)
Aggregation by depletion attraction in cultures of bacteria producing exopolysaccharide.
in Journal of the Royal Society, Interface
Isa L
(2009)
Velocity oscillations in microfluidic flows of concentrated colloidal suspensions.
in Physical review letters
Isa L
(2007)
Shear zones and wall slip in the capillary flow of concentrated colloidal suspensions.
in Physical review letters
Koumakis N
(2015)
Tuning colloidal gels by shear.
in Soft matter
Liddle S
(2010)
Polydispersity Effects in Colloid-Polymer Mixtures
Description | We have developed how to image the flow of dense suspensions of particles in a liquid. The technology is now licensed to a company. The findings have revolutionised the understanding of a range of industrial products, from paints to chocolate. A new research area was nucleated - using swimming bacteria to study `active colloids' - suspension of particles that can self propel. The key result here is the discovery of self-assembled self-propelled clusters, which in future applications may function as parts of self-assembled rotors in micro-motors. As part of this work, we have developed a fast and efficient method to measure the average swimming speed of a population of micro-organisms. |
Exploitation Route | Our imaging rheology module has been licensed to a company. Differential dynamic microscopy for characterising swimming bacteria has now been applied to characterise bull sperm motility - a spinout company is in progress of being formed. |
Sectors | Aerospace Defence and Marine Agriculture Food and Drink Chemicals Energy Environment Healthcare Manufacturing including Industrial Biotechology Pharmaceuticals and Medical Biotechnology |
Description | My team invented the technique of differential dynamic microscopy for the high throughput characterisation of bacterial swimming during this project. Since then, we have been in the process of seeking to make the technique work also for mammalian spermatozoa. This effort has now succeeded for bull sperms and we are in the process of commercialising it in partnership with a veterinary service company. |
First Year Of Impact | 2016 |
Sector | Agriculture, Food and Drink,Chemicals,Energy,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology |
Impact Types | Economic |
Description | EPSRC |
Amount | £5,039,693 (GBP) |
Funding ID | EP/J007404/1 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 12/2011 |
End | 06/2017 |
Title | Versatile Imaging Module for Rheology |
Description | Technology is licensed to a rheometer manufacturer. |
IP Reference | |
Protection | Protection not required |
Year Protection Granted | 2011 |
Licensed | Commercial In Confidence |
Impact | Popularising the use of imaging in industrial rheology. Many companies have contacted us for consultancy on this basis. |