Authors:	Möller, Nadir Liebchen, Benno Palberg, Thomas
Title:	Shaping the gradients driving phoretic micro-swimmers : influence of swimming speed, budget of carbonic acid and environment
Online publication date:	4-Jul-2022
Year of first publication:	2021
Language:	english
Abstract:	pH gradient-driven modular micro-swimmers are investigated as a model for a large variety of quasi-two-dimensional chemi-phoretic self-propelled entities. Using three-channel micro-photometry, we obtain a precise large field mapping of pH at a spatial resolution of a few microns and a pH resolution of ∼0.02 pH units for swimmers of different velocities propelling on two differently charged substrates. We model our results in terms of solutions of the three-dimensional advection–diffusion equation for a 1:1 electrolyte, i.e. carbonic acid, which is produced by ion exchange and consumed by equilibration with dissolved CO2. We demonstrate the dependence of gradient shape and steepness on swimmer speed, diffusivity of chemicals, as well as the fuel budget. Moreover, we experimentally observe a subtle, but significant feedback of the swimmer’s immediate environment in terms of a substrate charge-mediated solvent convection. We discuss our findings in view of different recent results from other micro-fluidic or active matter investigations. We anticipate that they are relevant for quantitative modelling and targeted applications of diffusio-phoretic flows in general and artificial micro-swimmers in particular.
DDC:	530 Physik 530 Physics
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 08 Physik, Mathematik u. Informatik MaxPlanck GraduateCenter
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-7285
Version:	Published version
Publication type:	Zeitschriftenaufsatz
License:	CC BY
Information on rights of use:	https://creativecommons.org/licenses/by/4.0/
Journal:	The European physical journal : E, Soft matter 44
Pages or article number:	41
Publisher:	Springer
Publisher place:	Berlin u.a.
Issue date:	2021
ISSN:	1292-895X
Publisher DOI:	10.1140/epje/s10189-021-00026-9
Appears in collections:	JGU-Publikationen