Damping Modulation of Dampened Kapton Surfaces

Vibrating droplets exhibit complex sloshing motion, an understudied behavior in drop physics. In general, sloshing involves a combination of droplet motion, deformation, and mass redistribution in all three dimensions. For microflyers in damp or wet environments, the dynamics of these drops on flight surfaces can significantly alter performance. As part of a larger project studying droplet adhesion and ejection on flexible, millimeter-scale wings, the current effort addresses the influence of a sloshing droplet on a highly flexible structural element inspired by insect wings. The ability of drops to deform and even relocate complicates the task of determining the dynamics of a microflyer wing. Our current understanding of sloshing stems from previous work on droplets of various viscosities placed at the end on the top surface of a cantilever beam. These experiments were repeated across a range of various beam thicknesses and demonstrated an influence that depended on the beam’s excitation frequency. This paper investigates how the droplet viscosity and volume influence its fundamental sloshing natural frequency. Experiments revealed an inverse relationship between drop volume and natural frequency. Moreover, comparing drops with the same volume but different viscosity showed an additional inverse relationship between drop viscosity and natural frequency. In addition, increasing drop viscosity significantly increased the drop damping; i.e., drop free vibrations damped out much more quickly than in drops with lower viscosity.