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Motion of Optically Heated Spheres at the Water-Air Interface
A Girot1,2, N Danné1,2, A Würger2
1Université de Bordeaux , Centre de recherche Paul-Pascal (CRPP), 33600 Pessac, France.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 27, 2016
Summary
Laser heating causes light-absorbing microparticles to move. At high laser power, particles escape axial trapping and exhibit microswimming behavior, reaching speeds of hundreds of micrometers per second.
Area of Science:
- Physics, Soft Matter
- Microfluidics
- Optical Trapping
Background:
- Micrometer-sized particles at interfaces typically exhibit Brownian motion.
- Light-absorbing particles can be heated by laser irradiation.
- Laser heating can alter particle behavior at interfaces.
Purpose of the Study:
- To investigate the behavior of light-absorbing microparticles at the water-air interface when heated by a laser.
- To characterize the transition from trapped states to active motion.
- To quantify the microswimming velocities achieved.
Main Methods:
- Experimental observation of micrometer-sized spherical particles at the water-air interface.
- Utilizing a vertical laser beam to heat light-absorbing particles.
- Varying laser power to study trapping dynamics and motion.
- Microscopic observation and velocity measurements.
Main Results:
- At low laser power, particles are trapped on the laser axis, similar to optical trapping.
- On-axis trapping becomes unstable at higher laser power.
- Particles escape axial trapping and orbit around the laser axis.
- Laser-heated particles act as microswimmers with velocities up to several hundred micrometers per second.
Conclusions:
- Laser-induced thermal gradients can induce directed motion in microparticles at interfaces.
- The transition from trapping to microswimming is dependent on laser power.
- This phenomenon offers a method for generating controlled microswimmers using light absorption.
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