Science and Engineering at The University of Edinburgh

Soft Condensed Matter, Biological Physics Experiment & Statistical Physics Seminars

Explanatory note

This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend.

Speakers should read this note

Week beginning 7 February 2016

Monday 8 Feb 16 - 1:00pm

Spatially controlled activity of light-driven E. coli suspensions

Jochen Arlt (University of Edinburgh)

Suspensions of swimming bacteria, such as Escherichia coli, are widely used as model active colloids. But the swimming speed of bacteria normally cannot be easily tuned. However, E. coli can be genetically modified to swim only when illuminated with green light, potentially giving biological active colloids with an externally tuneable speed v. We studied several mutants of E. coli for which their swimming speed can be controlled by the intensity of incident green light and we specially engineered mutants which adjust their speed rapidly in response to changes in intensity. By projecting intensity patterns of light onto a suspension of such bacteria we are then able to spatially control the activity of these suspensions over large length-scales (~1 mm). In order to characterise our active suspensions we introduce a spatially resolved version of Differential Dynamic Microscopy. This allows us to extract key parameters, e.g. swimming speed v, relative changes in local cell density ?/?0 and the fraction of non-motile cells ?. We compare our quantitative findings with theoretical predictions that the local density is inversely proportional to the swimming speed.

Upcoming meetings

Monday 15 Feb 16 - 1:00pm - Room 2511 JCMB

To be confirmed

Monday 22 Feb 16 - 1:00pm - Room 2511 JCMB

To be confirmed

Benno Liebchen (University of Edinburgh)

Monday 29 Feb 16 - 1:00pm - Room 2511 JCMB

To be confirmed

Andrew Matheson (University of Edinburgh)

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Note for speakers

  • We try to encourage an informal atmosphere.
  • To encourage discussion, talks are limited to 30/40 mins plus up to 20/10 mins for questions.
  • Almost any style of talk is allowed and resident speakers are encouraged to give a variety of different types of talk during their stay at Edinburgh. Examples include talks about the speaker's research, a particular paper or publication (`Journal Club' talks), pedagogical talks, question-and-answer sessions, etc.
  • Speakers are encouraged to pitch their seminars to the whole group.
  • I would be grateful if the next speaker on the list could inform me of the title and short abstract (it should fit onto the usual advertising poster) of his/her talk by Wednesday of the week before, to allow me to do the advertising.
  • Anyone unable to give their talk on the scheduled date should in the first instance try to rearrange with someone else on the list, and only then inform me of the final outcome so that I can change the rota.
  • Talks of soft condensed matter students can only be cancelled with permission from Prof. Cates, and should be done as far in advance as possible to give some chance of finding a replacement.
  • If anyone would like to volunteer a seminar themselves, knows of a visitor or new arrival who might be willing to give a talk, or for any other queries, please contact the seminar organiser (see below for email address).