Effects of Microorganisms on Drop Formation in Microgravity During a Parabolic Flight with Residual Gravity and Jitter

Wetting and contact-line dynamics, as well as growth (interface creation) and stability of aqueous drops with microorganisms in microgravity is important for understanding and controlling complex fluids in space. The study of biofluid drops in microgravity has applications in biological 3D printing, pharmaceutical production, and bioremediation. Here, liquid cultures of the microorganisms E. coli, S. cerevisiae (baker's yeast), and D. radiodurans were deployed in centimeter-scale drops using a simple tube during a parabolic flight. Residual gravity and g-jitter inherent in parabolic flights allowed for the study of how these forces affect the growth of biofluid drops in microgravity. The growth of drops with microorganisms was compared to sterile growth media. Quasi-static simulations were used to assess whether each solution produced measurable changes in the growing droplet. Images of growing drops were analyzed in terms of drop aspect-ratio, contact angles, and the differences in contact angles due to variations in gravity. Results demonstrate that the presence of microorganisms has minimal influence on the behavior of centimeter-scale drops. The small impact of microorganisms on growing drops bodes well for the adaptation of existing Earth-based drop technologies for working with biofluids in reduced gravity.