近接場領域におけるナノ微粒子の動的特性に関する研究

抄録

Many industrial processes for manufacturing fine particles face the problem of how to maintain the uniformity of product’s physical properties. Particle-particle separation technology has important potential for improving product quality and uniformity. Separation between micronorder and smaller particles is of particular importance, since no conventional method is able to separate particles of this small size effectively. In our previous study, long-range movement of a particle in a weakly focused Gaussian beam was confirmed to be strongly affected by the particle’s refractive index; any optical separation method is likely to actualized base on differences in particle transport distance under laser radiation pressure. To this end, however, the most important and difficult problem to overcome is how to improve particle throughput.

In this study, the repetitive scanning of a focused laser beam was applied to increase the throughput of particle separation using laser radiation pressure. The relationship between the scanning conditions, specifically laser output power, scanning distance, scanning frequency, and the characteristics of particle transportation, was investigated using micron-sized polystyrene-latex particles. The improvement of particle throughput by laser scanning was confirmed through a separation experiment using a mixture of micron-sized synthetic diamond and graphite particles. The results showed that the optimized laser beam scan-system enables particle separation throughput to be increased by approximately 70 % compared to the non-scanning state.