Laser-assisted three-dimensional rotation of microscopic objects

We describe an approach for laser-assisted three-dimensional rotation of microscopic objects that is rather simple to implement. In our approach a tangential force is applied on the object to cause its rotation by focusing a pulsed near infrared laser beam at a point on the periphery of the object. Rotation of a leaf tissue section in three dimensions about various axes including those orthogonal to the beam propagation axis could be demonstrated using this approach. Further, with this approach an optically trapped dividing chloroplast could be oriented to permit imaging from different angles of view. (C) 2004 American Institute of Physics.