Electron Tractor Beam: Deterministic Manipulation of Liquid Droplets on Solid Surfaces

The motion of liquid droplets is studied across many physics subfields and manipulation of nanoscale droplets on demand holds great promise in, e.g., nanotechnology. In this study, AuGe droplets on a germanium substrate are manipulated by an electron beam in a scanning electron microscope. The electron beam exposure creates a local temperature gradient in a substrate and induces a directional thermomigration of droplets nearby. To quantitatively analyse this phenomenon and to reveal the mechanism behind it, experimental observations under different conditions (beam current, sample temperature, scanning strategy) and simulations are combined. The obtained insights suggest that the droplet motion is limited by the dissolution of the substrate below the droplet. In addition, it is shown that the electron tractor beam is not only able to control the droplet motion but can also be used to split the droplets, thus opening new possibilities for droplet manipulation inside an SEM.

Automated summary

This study investigates the manipulation of AuGe droplets on a germanium substrate using an electron beam in a scanning electron microscope. Experimental observations and simulations are combined to analyze the phenomenon of directional thermomigration induced by the electron beam. It is found that the motion of the droplets is limited by the dissolution of the substrate and the electron tractor beam can both control and split the droplets, offering new possibilities for droplet manipulation inside an SEM.