OMITEC: Public dissemination

Public dissemination

Optical sorting 

Co-operating groups of Prof. P. Zemanek from ISI and Prof. K. Dholakia from University of St. Andrews presented a unique method that uses only light to separate objects of different sizes immersed in water medium. This method does not need fluid flow but the mixture of objects smaller than micrometer is illuminated by an optical conveyor belt created from two counter-propagating evanescent fields. Self-sorting of the objects is based on different sensitivity of objects of various sizes to moving optical pattern. Objects of some sizes are dragged by the travelling field, however objects of other sizes would stay uninfluenced. Therefore the beam coming opposite to the conveyor belt motion is more intensive and so the insensitive objects are pushed away. This mechanism of "optical Cinderella" separates both object sizes to opposite sides and the smallest achieved difference between both separated objects was 60 nm.

Optical conveyor belt 

Optical conveyor belt used for manipulation with microobjects in liquid media was demonstrated by cooperating teams of Prof. Zemanek (Institute of Scientific Instruments, Brno, Czech Republic) and Prof. Kishan Dholakia (University of St. Andrews, Scotland). Two non-diffracting beams are used. Each of them creates light thread 2 micrometers in diameter and hundreds of micrometers long. These counter-propageting beams create standing wave (similar to nodes on the light thread), in which the particles are held. Precise movement of trapped particles is possible with changing the phase of one of the beams (moving the nodes on the thread).

Send comments to webmaster
Last modification: 30 Mar 2007