Laser-thermophoresis and magnetophoresis of a micro-bubble in organic liquids

Yuka Urabe,Hitoshi Watarai,Hideaki Monjushiro

doi:10.1063/5.0027896

Yuka Urabe, Hitoshi Watarai + Show 1 more

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https://doi.org/10.1063/5.0027896

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Abstract

Several hundreds of micrometer migration of a bubble to the laser irradiation point was observed in an organic liquid in a silica capillary. The phenomenon was attributed to the laser-induced thermophoresis, which was due to the surface tension difference between both sides of the bubble induced by the temperature gradient, generated longitudinally in the organic liquid by the laser irradiation of 1064 nm. Alternatively, the application of magnetic field gradient on a bubble in a capillary accelerated remarkably the rising velocity of the bubble due to magnetophoresis. The combination of the laser-thermophoresis and the magnetophoresis could be used to manipulate reversibly the up-and-down vertical migration of a bubble in a liquid. From repeated measurements of magnetophoretic velocity of a bubble, the magnetic susceptibility of the liquid medium was determined.

Highlights

Since Ashkin et al have reported the effect of laser radiation pressure on micrometer and sub-micrometer sized particles in liquids, the methods of laser trapping, optical tweezers, and laser manipulation have been widely investigated in various fields.1 A particle with a higher refractive index than that of the surrounding medium is ready to be trapped by the gradient force of a focused laser beam using an objective lens with a high NA.2–6 the particle with a lower refractive index than the medium is hard to be trapped by an ordinal trapping mode
When a laser beam of 1064 nm was irradiated to the inner wall of the silica capillary where carbon particles are adsorbed, a micro-bubble was quickly generated and trapped by the laser beam at the irradiation position
When the shutter opened and the laser irradiation restarted, the bubble returned to the laser irradiation position moving from the upper position where the bubble was completely out of the beam spot region

Summary

Introduction

Since Ashkin et al have reported the effect of laser radiation pressure on micrometer and sub-micrometer sized particles in liquids, the methods of laser trapping, optical tweezers, and laser manipulation have been widely investigated in various fields.1 A particle with a higher refractive index than that of the surrounding medium is ready to be trapped by the gradient force of a focused laser beam using an objective lens with a high NA.2–6 the particle with a lower refractive index than the medium is hard to be trapped by an ordinal trapping mode. We have observed interesting phenomena that a single bubble rising in an organic liquid in a capillary by buoyancy can be returned to the laser irradiation point, which is about 500 μm lower than the bubble position.

Results

Conclusion