2020/06/30 by Stefania Ketzetzi, Joost de Graaf, Daniela J. Kraft · 1 citation
Physics and Astronomy · #cond-mat.soft
paper · pdf · doi:10.1103/physrevlett.125.238001
arxiv created 2020/10/22 · arxiv updated 2020/12/30
Microswimmers typically move near walls, which can strongly influence their motion. However, direct experimental measurements of swimmer-wall separation remain elusive to date. Here, we determine this separation for model catalytic microswimmers from the height dependence of the passive component of their mean-squared displacement. We find that swimmers exhibit "ypsotaxis", a tendency to assume a fixed height above the wall for a range of salt concentrations, swimmer surface charges, and swimmer sizes. Our findings indicate that ypsotaxis is activity-induced, posing restrictions on future modeling of their still debated propulsion mechanism.