• Physics 16, s35
If a helical micro organism’s tail propulsion is robust sufficient to deform the yield-stress fluid forward of the swimmer, locomotion proceeds.
We all feel like we’re forcing our way through mud sometimes, but for some creatures, that’s reality. Many microorganisms move in fluids that behave like solids until forced to flow by stresses imposed by the microorganism’s swimming motion. Now in an experiment that mimics a helical bacteria swimming in mucus, Hadi Mohammadigoushki of Florida State University and his colleagues pinpoint two critical thresholds that a swimmer must overcome to propel itself in these yield-stress fluids .
The crew made a 3D-printed corkscrew-shaped mannequin of a micro organism, positioned it in a high-viscosity polymer gel, and brought on it to rotate utilizing a magnetic area. Then, with particle monitoring and imaging strategies, the researchers measured the swimmer’s velocity and visualized the circulate area round it. Their experiments revealed that first the swimmer should overcome the fluid’s yield pressure to have the ability to rotate. Then the fluid’s yield stress should be sufficiently low that a big quantity of fluid will get set into movement across the swimmer. Both circumstances solely lead to motion if the tail propulsion is robust sufficient to deform the fluid across the swimmer; if the tail propulsion is simply too weak, the swimmer stays caught within the fluid. Finally, as soon as locomotion is underway, the pitch of the swimmer’s corkscrew-shaped tail determines how briskly motion proceeds.
The understanding might assist to foretell how Helicobacter pylori corkscrewing via gastric mucus causes ulcers, how earthworms burrowing within the floor improve soil aeration, and the way parasites consuming via fruit infect crops. The experimental strategy might additionally enable additional investigation of issues of organism motility and materials design in biology, well being, and agriculture which have till now solely been accessible via concept.
Rachel Berkowitz is a Corresponding Editor for Physics Magazine primarily based in Vancouver, Canada.
- F. Nazari et al., “Helical locomotion in yield stress fluids,” Phys. Rev. Lett. 130, 114002 (2023).