Laser impact on a drop (Award winning entry 2014) APS-DFD Gallery of Fluid Motion
The energy deposition in a liquid drop on a nanosecond time scale by impact of a laser pulse can induce various reactions, such as vaporization or plasma generation. The response of the drop can be extremely violent: The drop gets strongly deformed and propelled forward at several m/s, and subsequently breaks up or even explodes. These effects are used in a controlled manner during the generation of extreme ultraviolet (EUV) light in nanolithography machines for the fabrication of leading-edge semiconductor microchips. Detailed understanding of the fundamentals of this process is of key importance in order to advance the latest lithography machines. In this video we show the impact of a focused laser pulse onto a millimeter-size drop in a regime comparable to what can be found in lithography machines. The drop’s life was recorded for various impact conditions by high-speed imaging at 20000 frames per second (FPS). The high reproducibility of the dynamics allowed us to use stroboscopic illumination with nanosecond exposure times leading to an effective frame rate of 10 million FPS. We present a scaling law and compare experimental results to numerical simulations, in order to show how the drop is propelled and deformed.
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