Laser-induced force for bubble-trapping in liquids

The laser-induced thermal force that traps a bubble in an absorbing liquid is studied theoretically and experimentally. The force origins from the thermal gradients of the surface tension induced by a laser beam over the bubble surface. It is shown that this force is proportional to the square of the bubble radius and to the thermal gradient of the surface tension. A simple experimental method based on comparison with the Archimedes' flotation force, is used for the measurement of this force. The experimental results, performed on ethanol solutions of iodine, confirm the theoretical predictions.