Optical trapping of colloids at a liquid-liquid interface

TL;DR

This paper demonstrates optical trapping of colloids at a liquid-liquid interface using DNA tethers, enabling the study of quasi-2D colloidal assembly and interactions with potential applications in controlled material design.

Contribution

It introduces a method to confine colloids at a liquid-liquid interface with optical trapping and DNA tethers, allowing measurement of weak interactions in a quasi-2D system.

Findings

Colloids are optically bounded on a liquid-liquid interface.

Weak interactions like depletion can be measured in the system.

The system serves as a template for studying optically controlled colloidal assembly.

Abstract

We demonstrate the realization of (laterally) optically bounded colloidal structures on a liquid-liquid interface of an emulsion droplet. We use DNA tethers to graft the particles to the droplet surface, effectively confining them to a quasi-2D plane with minimum constraints on the lateral movement even when optically trapped in a common single-beam configuration. We show that relatively weak interactions such as depletion can be measured in the optically bounded crystals by video-microscopy imaging and analysis. This illustrates the possible use of our system as template to study optically controlled quasi two-dimensional colloidal assembly on liquid-liquid interfaces.