jsc2020e030483 (4/20/2020) --- A preflight image sequence from parabolic flight experiments indicating motion of vapor bubble on heated ratchet surface. Asymmetric Sawtooth and Cavity-Enhanced Nucleation-Driven Transport (PFMI-ASCENT) demonstrates a passive cooling system for electronic devices in microgravity using a microstructured surface. When fluids boil over flat heated surfaces in microgravity, vapor bubbles grow larger in size, causing poor heat transfer that can lead to damage of devices. Adding microscopic rachets on the surface may passively enable mobility of vapor bubbles and prevent this damage. (Image courtesy of: Techshot, Inc.)