Generation and stability of nanobubbles under microgravity conditions: unlocking a new horizon

Nanobubbles (NBs) have attracted considerable interest for applications in gas-limited systems and environmental processes. However, their existence and functionality under microgravity conditions remain unverified, limiting their potential for space exploration-related applications. Here, we evaluate the stability, generation, and gas-transfer properties of air, oxygen, and carbon dioxide NBs under microgravity conditions achieved during parabolic flights. By exposing NBs generated under terrestrial atmospheric conditions to microgravity, we observe negligible changes in NBs concentration and size distribution, even when varying the headspace of NBs storage systems. When NBs are generated directly under microgravity, nanoparticle tracking analysis reveals a statistically significant increase in NBs concentration relative to the background signal, demonstrating their formation and stabilization in the absence of gravity. This behavior is further confirmed under dynamic gravity conditions (~0–1.8 g), where a continuous increase in NBs concentration is observed. Consistent with NBs generation trends, gas-transfer performance is assessed through dissolved oxygen and pH variations for oxygen and carbon dioxide NBs, respectively. These results enabled elucidating fundamental mechanisms of NBs formation, establishing the viability of NBs under microgravity, and highlighting their potential to enable new strategies for overcoming gas/liquid mass transfer limitations in space environments.