May 09 2008
Trapping and moving objects with lasers
Last night’s Café Scientifique was a special outing to the Edinburgh Camera Obscura (which I think is a great place to visit anyway). The talk was given by Will Hossack from the University of Edinburgh.
It was a very good talk (they’re so variable it’s impossible to recommend from one week to the next) — just a shame that the room was too small and too hot for the purposes. It was a windowless room on the fourth floor full of optical illusions and bright lights. Good fun to wander round and play with the exhibits but not great when sitting cheek to jowl on little seats.
But anyway. He explained the general process of laser cooling, by trapping particles with beams of light. Then he went on to describe the work he does with fairly large objects (yeast and fungal spores as well as latex spheres) using the trapping effect to create optical tweezers which can move objects up to a dozen microns in size.
They’ve been wiring up these computer-controlled optical tweezers to some 100x microscopes, and he had some fascinating videos of the things one can do. Apart from getting latex spheres to dance an eightsome reel, he also had a streamer of DNA anchored at one end by the tweezer. The other end was being forced out by the flowing solution it was all bathed in. You could see the long streamer collapse in a flash into a tight little ball when they added some enzyme. Very cool.
It looks like the Edinburgh Café Sci has had a little injection of fresh ideas from teaming up with the post-graduate science communication team (this jolly to the Camera Obscura was their idea) so I hope they follow through with more interesting visits.