Plasma Propulsion of a Metallic Micro-droplet and its Deformation upon Laser Impact

TL;DR

This study investigates how nanosecond laser pulses propel and deform tiny liquid metal droplets, developing models that accurately describe the physics and enabling optimization of laser-droplet interactions.

Contribution

We present a scaling law for plasma-driven droplet propulsion and an analytical model for droplet deformation, demonstrating scalability across different droplet sizes and propulsion mechanisms.

Findings

The plasma momentum transfer can be accurately described by a scaling law.

Droplet deformation depends on propulsion velocity and liquid properties.

Hydrodynamic response is scalable and mechanism-independent.

Abstract

The propulsion of a liquid indium-tin micro-droplet by nanosecond-pulse laser impact is experimentally investigated. We capture the physics of the droplet propulsion in a scaling law that accurately describes the plasma-imparted momentum transfer, enabling the optimization of the laser-droplet coupling. The subsequent deformation of the droplet is described by an analytical model that accounts for the droplet's propulsion velocity and the liquid properties. Comparing our findings to those from vaporization-accelerated mm-sized water droplets, we demonstrate that the hydrodynamic response of laser-impacted droplets is scalable and independent of the propulsion mechanism.