ABSTRACT
Radiation pressure from a tightly focused laser beam has been widely used as optical tweezers to con„ne, position, and transport microparticles in liquid, after Ashkin’s group demonstrated this technique in 1987 (Ashkin et al. 1987). Optical tweezers provide unique features such as remote manipulation of micro/nano particles in liquid, noninvasive manipulation of biological samples, precise manipulation in sealed environment, and extremely small torque of the order of 10−12 nm. For these reasons, optical tweezers and its related techniques have been widely applied to studies on biological cells and DNA molecules, microchemistry with microdroplets and microbeads, and atom cooling. The history and previous works on optical tweezers were introduced in some review reports (Ashkin 2000, Grier 2003, Molloy and Padgett 2002, Neuman and Block 2004).
