Chemical Control Over Optical Trapping Force at an Interface

摘要

So far, the optical trapping potential is controlled by tuning the physicalconditions of the system. Herein, for the first time, an approach, in which theinduced optical force or optical potential is controlled, by an external chemicalstimulus, is reported. The key to realize this is to design an optical trappingcondition in conjunction with resonant excitation, the so-called opticalresonance effect (ORE). For this purpose, phenalenone, a well-known tripletphotosensitizer, is embedded inside polystyrene particles. The optical resonanceeffect is achieved through a two-laser system: a 405 nm widefield laserto excite the phenalenone molecules to T_1 state and a 488 nm trapping laser toinduce the T_1–T_n–T_1 resonance cycle. Thus, the triplet state is mainly responsiblefor the optical force enhancement. Since oxygen is an excellent tripletquencher, the triplet populations, and hence, the optical force is controlled bychanging the dissolved oxygen concentration. The results presented here pavethe way to chemically control the optical force through ORE with promisingapplications in several research fields ranging from physics to biology.