Antisolvent Crystallization of L -histidine in Micro-Channel Reactor under Microgravity

The influence of gravity (including 0 G, 0.16 G, 0.38 G, 1 G and 1.8 G) on the antisolvent crystallization of L -histidine was investigated in a self-designed micro-channel crystallizer on a zero-G flight, which was successfully launched on June 13th, 2018. The stable form of L -histidine was obtained under microgravity, while only the metastable form can be observed in the ground experiments with the same inlet conditions. The possible reason is the extremely ordered flow field of the system in microgravity environment. A large amount of small particles aggregated at 1.8 G due to the enhanced micromixing, which favors nucleation. Bigger particles crystalized at Moon gravity (0.16 G) without the excessive consumption of the supersaturation by explosive nucleation and with moderate convection of the system. It is concluded that both nucleation and crystal growth were influenced by the micromixing status in the system due to the altered gravity extent.