Specific yet transient bonds between anisotropic colloids

TL;DR

This paper demonstrates controlled, transient bonding between 3D-printed anisotropic colloids via depletion interactions, enabling tunable bond lifetimes and potential for directional self-assembly.

Contribution

It introduces a method to control bond duration between anisotropic colloids using depletion interactions, with experimental validation and a simple physical model.

Findings

Longest-lasting bonds occur at flat face interactions.

Bond lifetime is tunable by depletant concentration.

Experimental results agree with the physical model.

Abstract

Self-assembly of colloidal particles is a promising avenue to control the shape and dynamics of larger aggregates. However, achieving the necessary fine control over the dynamics and specificity of the bonds between such particles remains a challenge. Here we demonstrate such control in bonds mediated by depletion interactions between anisotropic colloids that we 3D-print in the shape of half disks with sub-micron resolution. When brought together by diffusion, the particles interact in different configurations but the interaction through the flat faces is by far the longest-lasting. All bonds are flexible and transient, and we demonstrate control over their life time through the depletant concentration in quantitative agreement with a simple physical model. This basic design could be extended to manufacture particles with multiple binding sites to engineer directional assembly with multiple particles.