Observation and Analysis of Surface Acoustic Wave Induced Atomization

The ability to excite instabilities in free fluid surfaces via acoustic excitation is well known, even to the point of atomization. Surprisingly, atomization phenomena exist at frequencies up to 1 GHz, because peak piezoelectrically-driven vibration velocities remain remarkably constant at about 1 m/s regardless of the excitation frequency if one makes use of different materials and vibration modes along the way. At 100 MHz, for example, we have maintained surface acoustic waves 1 m/s vibration velocity and measured displacements and accelerations of 10 nanometers and 10 million m/s. At these extreme conditions, fluid microfilaments, multiscale droplet formation, and other curious phenomena appear. Understanding the behaviour is important for applications in rheology and the study of solid-fluid interactions on the micro and nanoscale, and we illustrate methods for observation of the atomization and vibration conduction processes under these conditions.