Cell manipulation by use of diamond microparticles as handles of optical tweezers

We report the experimental results of our using irregularly shaped diamond microparticles as handles for laser tweezers. Because of their irregular optical shape, control of the rotation of diamond microparticles can easily be achieved in a gradient force optical trap by use of a fixed linearly polarized beam with a fundamental Gaussian mode. By changing the laser focal plane upon a diamond particle near the liquid surface or interfaces, one can fully manipulate both the direction and speed of the rotation. The ability to manipulate a diamond-particle-tagged biological specimen by optical tweezers is discussed. The application of these particles as handles for optical tweezers is demonstrated by optical manipulation of biological cells. Independent movement of linear translation and rotation, with controllable rotation directions and speeds, is successfully achieved.