title: Assembly and Speed in Ion-Exchange-Based Modular Phoretic Microswimmers.
abstract: We report an experimental study on ion-exchange-based modular microswimmers in low-salt water. Cationic ion-exchange particles and passive cargo particles assemble into self-propelling complexes, showing self-propulsion at speeds of several micrometers per second over extended distances and times. We quantify the assembly and speed of the complexes for different combinations of ion-exchange particles and cargo particles, substrate types, salt types and concentrations, and cell geometries. Irrespective of the experimental boundary conditions, we observe a regular development of the assembly shape with increasing number of cargo. Moreover, the swimming speed increases stepwise upon increasing the number of cargo and then saturates at a maximum speed, indicating the active role of cargo in modular swimming. We propose a geometric model of self-assembly to describe the experimental observations in a qualitative way. Our study also provides some constraints for future theoretical modeling and simulation.
authors.affiliation: Institut für Physik, Johannes Gutenberg-Universtät Mainz , Staudingerweg 7, 55128 Mainz, Germany.
authors.forename: Ran
authors.identifier: 0000-0001-7791-3914
authors.initials: R
authors.lastname: Niu
authors.affiliation: Institut für Physik, Johannes Gutenberg-Universtät Mainz , Staudingerweg 7, 55128 Mainz, Germany.
authors.forename: Denis
authors.initials: D
authors.lastname: Botin
authors.affiliation: Institut für Physik, Johannes Gutenberg-Universtät Mainz , Staudingerweg 7, 55128 Mainz, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Weber
authors.affiliation: Institut für Physik, Johannes Gutenberg-Universtät Mainz , Staudingerweg 7, 55128 Mainz, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Reinmüller
authors.affiliation: Institut für Physik, Johannes Gutenberg-Universtät Mainz , Staudingerweg 7, 55128 Mainz, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Palberg