DNA self-organization controls valence in programmable colloid design

TL;DR

This paper demonstrates how the nanoscale organization of DNA linkers on microdroplets can program the valence of colloidal assemblies, enabling controlled self-organization into complex structures.

Contribution

It introduces a thermodynamic model linking molecular linker organization to valence control in colloids, validated by experimental results.

Findings

DNA linker organization determines valence in colloids

Thermodynamic model accurately predicts patch formation

Valence transitions depend on linker concentration

Abstract

Just like atoms combine into molecules, colloids can self-organize into predetermined structures according to a set of design principles. Controlling valence -- the number of inter-particle bonds -- is a prerequisite for the assembly of complex architectures. The assembly can be directed via solid `patchy' particles with prescribed geometries to make, for example, a colloidal diamond. We demonstrate here that the nanoscale ordering of individual molecular linkers can combine to program the structure of microscopic assemblies. Specifically, we experimentally show that covering initially isotropic microdroplets with $N$ mobile DNA linkers results in spontaneous and reversible self-organization of the DNA into $Z(N)$ binding patches, selecting a predictable valence. We understand this valence thermodynamically, deriving a free energy functional for droplet-droplet adhesion that accurately predicts the equilibrium size of and molecular organization within patches, as well as the observed valence transitions with $N$. Thus, microscopic self-organization can be programmed by choosing the molecular properties and concentration of binders. These results are widely applicable to the assembly of any particle with mobile linkers, such as functionalized liposomes or protein interactions in cell-cell adhesion.