Vibrations of micron-sized fluid membranes induced via pulsed laser excitation

We study the acoustic vibrations of three different micron-sized square fluid membranes induced by means of a nanosecond pulsed laser. Several vibration modes in the kHz range are excited when the metallic frame, on which the fluid membrane is suspended, undergoes rapid thermal expansion after absorption of the pulsed laser light. The vibration frequencies detected are compared with a model based on bending vibrations of the fluid film similar to those in a solid membrane. Finite element method based simulations are employed to calculate the membrane deformation for different excitation cases of light absorption, as well as the highest excited modes. In addition we explore the effect on the film vibrations due to the inclusion of carbon nanofibers in the fluid membrane. The carbon nanofibers affect the surface tension in a way that couples bending modes to Marangoni waves in the membrane.