In Situ TEM Imaging of Nanoscale Bubble Collapse and the Resulting Damage

In recent years, it has been suggested that micron and sub-micron scale cavitation can occur in the human brain during explosive pressure wave, blunt trauma, or sports collision type events and that the resulting bubble collapse could be the main cause of damage leading to traumatic brain injuries. However, the behavior of very small bubbles is not yet well understood because of the challenges associated with imaging on the necessary length and time scales. Here, we present the direct imaging of bubble collapse in a liquid cell using the Movie-Mode Dynamic Transmission Electron Microscope (MM-DTEM) at Lawrence Livermore National Laboratory. Bubbles were induced in ~1-3 µm of water using laser heating of 60 nm gold particles and typically found to collapse within 200 ns. Polymer coated on the liquid cell substrates served as witnesses to potential damage. The behavior of the system was further explored with molecular dynamic (MD) simulations.