Manipulation of single fine particle in liquid by electrical force in combination with optical pressure

Opt-electrostatic micromanipulation, which utilizes electrical force in combination with the optical pressure of a focused laser beam, is proposed in order to manipulate biological cells or molecules. The optical pressure has two components: the optical confinement pressure and the optical drift pressure. Due to the optical confinement pressure, cells can be confined in the focused laser beam. The confined cells are pushed downstream of the laser by the optical drift pressure. The optical drift velocity of yeast cells dispersed in water was measured using an argon-ion laser and was 460 μm/s at a laser power of 500 mW. The combination of light pressure and electrical force was made using an electrode system having an insulating slit. The laser was focused at the center of the slit, where a DC electric field was formed. The yeast cell acquired negative charge in deionized water