Community Research and Development Information Service - CORDIS


PHYSAPS Report Summary

Project ID: 340877
Funded under: FP7-IDEAS-ERC
Country: United Kingdom

Mid-Term Report Summary - PHYSAPS (The Physics of Active Particle Suspensions)

The study of ‘active matter’ is one of the newest and most exciting fields of contemporary physics. One form of active matter consists of suspensions of microscopic particles that are able to propel themselves, or swim, by absorbing energy from their environment. Physicists currently have no general theory for predicting the behaviour of such a collection of ‘active particles’. To make progress, carefully designed experiments using ‘model systems’ are required. A model system of active particles is one for which the mechanism of individual self propulsion as well as the way pairs of active particle interact with each other are known. This ERC project is first or all focussed on establishing a number of model systems of active particles, and then using them to discover new physics. To date, we have learnt how to coax a suspension of motile Escherichia coli bacteria to behave as a model system of active particles. In particular, we now know how to using suitable nutrients to keep them swimming at constant speed without any oxygen for extended periods of time. We have now studied how they navigate an obstacle course, respond to confinement, and swim in goo. Apart from generating data to challenge theoretical physicists to come up a new framework to describe the behaviour of collections of micro-swimmers, our results have important practical implications. Thus, for example, encapsulating suitable motile bacteria in droplets of water (a form of confinement) dispersed in oil may be the basis of a probiotic treatment for acnes. To take another example, how bugs may swim in mucus – the goo that covers our guts – is important because this mucus acts as a defensive barrier against many infections. We have also learnt how to control the swimming of certain harmless bacteria using light. This may lead to new ways of using these organisms to assemble complex structures on the microscopic scale. Finally, a fast and efficient method for measuring bacterial swimming speeds is now being adapted to provide on-farm measurement of bull sperm motility, an important parameter in helping vets optimise the productivity of herds.

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United Kingdom
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