Photoacoustic manipulation of particles and cells

The aim of this study is to evaluate the capability of the photoacoustic (PA) effect for manipulation of nonbiological particles or living cells. The principal operation of such "PA tweezers" are based on laser generation pressure gradients in a medium surrounding the particles, that create forces acting on the particles. Depending on the spatial geometry of these forces, particles can be moved in desired directions (asymmetrical forces) or trapped (symmetrical forces). Evaluation of these forces was performed for the laser beam with the conventional circular geometry and a ring geometry. If the laser-induced forces push the particles or cells away from the laser beam, the ring geometry is more preferable for their trapping. The capabilities of such PA tweezers are discussed. (C) 2003 American Institute of Physics.