Photoresponsive surfactants have interfacial properties that can be controlled by light irradiation with specific wavelengths. Active changes in the surface tension facilitate manipulating liquids based on the Marangoni effect. In this paper, we have reported the photoinduced actuation of aqueous solutions containing a light-responsive surfactant (C4AzoTAB) with an azobenzene group. Surface tension measurements of the aqueous C4AzoTAB solutions revealed that the surface tension for cis-C4AzoTAB was higher than that of trans-C4AzoTAB within a specific range of surfactant concentrations. Thus, ultraviolet (UV) light irradiation of the aqueous trans-C4AzoTAB solution increases the surface tension. When UV light is irradiated on only one side of an aqueous trans-C4AzoTAB solution in a quartz glass tube, the surfactant solution moves toward the UV-irradiated side. The aqueous cis-C4AzoTAB solution moves in the opposite direction under visible light irradiation. Notably, for UV-induced actuation, the surface tension during trans-cis photoisomerization changes at only one edge of the fluid. The actuation velocities are related to the magnitude of the UV-induced change in the surface tension of the aqueous C4AzoTAB solution. The photoinduced actuation is caused by changes in the Laplace pressure as the surface tension is varied by light irradiation. Overall, the light energy is converted to the kinetic energy of the actuation through the change in the surface tension of the surfactant solution by trans-cis photoisomerization of the surfactant.

Photoinduced actuation of aqueous solutions containing a photoresponsive surfactant

251st National Meeting (2016)

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