Colloidal trains

TL;DR

This paper demonstrates how magnetic fields can be used to create and control colloidal trains, where doublet particles transport single colloids along predefined lanes, revealing new ways to manipulate colloidal assemblies.

Contribution

It introduces a novel method to induce and control colloidal trains using magnetic fields and patterned substrates, highlighting the coordinated motion of particles based on their magnetic interactions.

Findings

Doublets respond to external magnetic field precession and move along lanes.

Single colloids remain static at high modulation frequencies.

Doublets can transport chains of single colloids, forming colloidal trains.

Abstract

Single and double paramagnetic colloidal particles are placed above a magnetic square pattern and are driven with an external magnetic field precessing around a high symmetry direction of the pattern. The external magnetic field and that of the pattern confine the colloids into lanes parallel to a lattice vector of the pattern. The precession of the external field causes traveling minima of the magnetic potential along the direction of the lanes. At sufficiently high frequencies of modulation only the doublets respond to the external field and move in direction of the traveling minima along the lanes, while the single colloids cannot follow and remain static. We show how the doublets can induce a coordinated motion of the single colloids building colloidal trains made of a chain of several single colloids transported by doublets.