Yoshitaka Matsumoto

Trapping and manipulation of a single micro-object in solution with femtosecond laser-induced mechanical force

A nondestructive and noncontact method to trap and manipulate a microparticle in solution is proposed by utilizing femtosecond laser-induced nonlinear phenomena. A 90μm diameter polystyrene bead in solution was trapped and manipulated by scanning femtosecond laser pulses around it, which was ascribed to shockwave, cavitation bubble, and jet flow. The maximum mechanical force exerted by laser irradiation was estimated to be over 1μN. In comparison with conventional optical tweezers, this method provides not only a much larger trapping force but also a noninvasive advantage.

Dual-beam laser micromanipulation for sorting biological cells and its device application

Laser manipulation system combining microfluidic and microimaging devices was developed, in which a cell sorting in a transparent microchip was successfully demonstrated. The microchip containing two microchambers was prepared with laser microfabrication, in which a solution containing yeast cells was injected as a sample. In the microchip, a cell transfer from one chamber to another one was performed by using single, fixed trapping laser beam. Furthermore, to realize an efficient cell sorting, the trapping laser bam was split into two by a polarizing beam splitter and each beam was modulated independently; one trapping beam was used to trap individual cells and to move them, which is freely controlled by a mouse pointer, and another was used to store the selected yeast cells with its liner scanning. In this method, the cells on a locus of the scanned beam were isolated to transfer in the microchip. From these results, it is concluded that shortening of the cell sorting time in microchip by a few time was realized by using dual-beam laser manipulation.

SPATIAL LIGHT MODULATING AND MULTI-TRAPPING WITH A DMD

Although the digital micromirror device (DMD) has been considered to be a spatial light modulator (SLM) for a long time, it is seldom utilized for holographic tweezers practically because of its energy loss. In this work, a multi-trapping system built with a DMD is demonstrated. But a problem of dispersion is found when the DMD is applied to femtosecond laser, and its mechanism is studied.