Reversible Electron-Beam Patterning of Colloidal Nanoparticles at Fluid Interfaces

TL;DR

This study demonstrates reversible, electron-beam-guided manipulation of colloidal nanoparticles at fluid interfaces, enabling dynamic patterning through controlled beam-particle interactions influenced by solvent flow fields.

Contribution

It introduces a novel method for nanoscale colloidal control using electron beams to create reversible patterns via solvent flow manipulation at fluid interfaces.

Findings

Electron beam voltage controls particle attraction and repulsion.

Solvent radiolysis generates flow fields affecting particle movement.

Reversible patterning achieved on droplet surfaces.

Abstract

The directed self-assembly of colloidal nanoparticles (NPs) using external fields guides the formation of sophisticated hierarchical materials but becomes less effective with decreasing particle size. As an alternative, electron-beam-driven assembly offers a potential avenue for targeted nanoscale manipulation, yet remains poorly controlled due to the variety and complexity of beam interaction mechanisms. Here, we investigate the beam-particle interaction of silica NPs pinned to the fluid-vacuum interface of ionic liquid droplets. In these experiments, scanning electron microscopy of the droplet surface resolves NP trajectories over space and time while simultaneously driving their reorganization. With this platform, we demonstrate the ability to direct particle transport and create transient, reversible colloidal patterns on the droplet surface. By tuning the beam voltage, we achieve precise control over both the strength and sign of the beam-particle interaction, with low voltages repelling particles and high voltages attracting them. This response stems from the formation of well-defined solvent flow fields generated from trace radiolysis of the ionic liquid, as determined through statistical analysis of single-particle trajectories under varying solvent composition. Altogether, electron-beam-guided assembly introduces a versatile strategy for nanoscale colloidal manipulation, offering new possibilities for the design of dynamic, reconfigurable systems with applications in adaptive photonics and catalysis.