Mechanisms of droplet generation following mechanical impact on liquid-filled container*

Aerosol generation from laboratory accidents has been a subject of periodic interest for decades. While it is known based mostly on deposition-dependent cell culture data that vast numbers of droplets can be generated, these can exhibit notable variability due to the complex dynamics of fluid-structure interaction caused by impact and resultant free surface response. Our experimental study focuses on micro-scale droplets generated from liquid-filled laboratory ware impacting a rigid surface. We developed a Repeatable Accident INitiator (RAIN), a drop tower setup that ensures highly repeatable impact velocities and angles, placed inside a vertical flow chamber with filtered air. Inline holography, high-speed imaging, and optical particle counter are used to examine the droplets' quantity, paths, and forming mechanisms. Preliminary data suggests either vibration-induced Faraday instability or subsequent impulse concentration on the already corrugated free surface to be of significance. We also consider what facilitates the formation of a liquid ligament that eventually undergoes capillary force-triggered instability to create multiple small droplets, rather than a single droplet pinch-off which tends to result in a larger droplet.