Acoustically Manipulating Internal Structure of Disk-in-Sphere Endoskeletal Droplets

TL;DR

This paper demonstrates for the first time the acoustic manipulation of the internal structure of disk-in-sphere endoskeletal droplets, revealing controllable assembly and orientation changes driven by acoustic forces, with potential applications in hierarchical colloidal and biological structures.

Contribution

The study introduces a novel method for acoustic manipulation of internal droplet structures and develops a theoretical model explaining the underlying physical mechanisms.

Findings

Reversible control of disk orientation with acoustic frequency.

Balance of primary and secondary radiation forces drives assembly.

Potential for directed assembly of complex colloidal and biological structures.

Abstract

Manipulation of micro/nano particles has been well studied and demonstrated by optical, electromagnetic, and acoustic approaches, or their combinations. Manipulation of internal structure of droplet/particle is rarely explored and remains challenging due to its complicated nature. Here we demonstrated the manipulation of internal structure of disk-in-sphere endoskeletal droplets using acoustic wave for the first time. We developed a model to investigate the physical mechanisms behind this novel phenomenon. Theoretical analysis of the acoustic interactions indicated that these assembly dynamics arise from a balance of the primary and secondary radiation forces. Additionally, the disk orientation was found to change with acoustic driving frequency, which allowed on-demand, reversible adjusting disk orientations with respect to the substrate. This novel dynamic behavior leads to unique reversible arrangements of the endoskeletal droplets and their internal architecture, which may provide a new avenue for directed assembly of novel hierarchical colloidal architectures and intracellular organelles or intra-organoid structures.