Gandhi, Tanvi; Mac Huang, Jinzi; Aubret, Antoine; Li, Yaocheng; Ramananarivo, Sophie; Vergassola, Massimo; Palacci, Jérémie AIST Austria
Active navigation relies on effectively extracting information from the surrounding environment, and often features the tracking of gradients of a relevant signal—such as the concentration of molecules. Microfluidic networks of closed pathways pose the challenge of determining the shortest exit pathway, which involves the proper local decision-making at each bifurcating junction. Here, we focus on the basic decision faced at a T-junction by a microscopic particle, which orients among possible paths via its sensing of a diffusible substance's concentration. We study experimentally the navigation of colloidal particles following concentration gradients by diffusiophoresis. We treat the situation as a mean first passage time (MFPT) problem that unveils the important role of a separatrix in the concentration field to determine the statistics of path taking. Further, we use numerical experiments to study different strategies, including biomimetic ones such as run and tumble or Markovian chemotactic migration. The discontinuity in the MFPT at the junction makes it remarkably difficult for microscopic agents to follow the shortest path, irrespective of adopted navigation strategy. In contrast, increasing the size of the sensing agents improves the efficiency of short-path taking by harvesting information on a larger scale. It inspires the development of a run-and-whirl dynamics that takes advantage of the mathematical properties of harmonic functions to emulate particles beyond their own size.
Physical Review Fluids
Gandhi T, Mac Huang J, Aubret A, et al. Decision-making at a T-junction by gradient-sensing microscopic agents. Physical Review Fluids. 2020;5(10). doi:10.1103/physrevfluids.5.104202
Gandhi, T., Mac Huang, J., Aubret, A., Li, Y., Ramananarivo, S., Vergassola, M., & Palacci, J. A. (2020). Decision-making at a T-junction by gradient-sensing microscopic agents. Physical Review Fluids. American Physical Society. https://doi.org/10.1103/physrevfluids.5.104202
Gandhi, Tanvi, Jinzi Mac Huang, Antoine Aubret, Yaocheng Li, Sophie Ramananarivo, Massimo Vergassola, and Jérémie A Palacci. “Decision-Making at a T-Junction by Gradient-Sensing Microscopic Agents.” Physical Review Fluids. American Physical Society, 2020. https://doi.org/10.1103/physrevfluids.5.104202.
T. Gandhi et al., “Decision-making at a T-junction by gradient-sensing microscopic agents,” Physical Review Fluids, vol. 5, no. 10. American Physical Society, 2020.
Gandhi T, Mac Huang J, Aubret A, Li Y, Ramananarivo S, Vergassola M, Palacci JA. 2020. Decision-making at a T-junction by gradient-sensing microscopic agents. Physical Review Fluids. 5(10), 104202.
Gandhi, Tanvi, et al. “Decision-Making at a T-Junction by Gradient-Sensing Microscopic Agents.” Physical Review Fluids, vol. 5, no. 10, 104202, American Physical Society, 2020, doi:10.1103/physrevfluids.5.104202.
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