Diffusion-Based Height Analysis Reveals Robust Microswimmer-Wall Separation

Stefania Ketzetzi, Joost De Graaf, Daniela J. Kraft

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

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.

Original languageEnglish
Article number238001
Number of pages7
JournalPhysical Review Letters
Volume125
Issue number23
DOIs
Publication statusPublished - 2 Dec 2020

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