Switching of radiation pressure acting on microparticles by using T-type photochromic reactions

Abstract

Manipulation of small particles can be achieved by using the radiation pressure of a laser beam. The strength and direction of the radiation pressure depends on the dielectric constant of target materials. It can therefore be expected to induce mechanical motions of small materials in optical trap by changing their optical property by chemical reactions. Along this line, we recently demonstrated switching of radiation pressure acting on single optically trapped microparticles by using photochromic molecules (Refs. 3, 4). To explore more flexible mesoscopic motions synchronizing photochemical reactions, we have investigated in the present study the micromechanical motion of optically trapped particles containing a T-type photochromic molecule, naphthopyran (NP), with multiple thermal back-reaction rates. The single microparticle with NP was optically trapped with CW 532-nm laser and the photochromic reaction was induced by UV irradiation, resulting in the modification of the optomechanical responses of the particle under laser trapping.