Laser-Induced Marangoni Convection in the Presence of Surfactant Monolayers

Marangoni convection was induced by laser heating in shallow layers of solutions of crystal violet in ethylene glycol and water. Single- and double-beam instrumentations were developed for monitoring the deformation generated on the solution surfaces and to detect the influence of surfactants. In the single-beam configuration, the depression of the liquid surface acted as a converging lens, focusing the reflected beam, and the magnitude of the lens effect was measured as in a classical thermal lens experiment. In the double-beam configuration, the depression of the surface was induced by a pump beam, and the deflection of a probe beam reflected on the surface near the deformed region was monitored by a position sensor detector. The influence of surfactants as hexadecanol, DPPC, and cardiolipin was studied by forming monolayers on the surface of the solutions. The results showed that the lens effect, as well as the deflection of the probe beam, can be suppressed by a small amount of surfactant deposited on...