Comprehensive view of microscopic interactions between DNA-coated colloids

TL;DR

This study combines experimental measurements and theoretical modeling to quantitatively understand DNA-mediated interactions between colloids, enabling improved control over their self-assembly for advanced material applications.

Contribution

It provides the first in situ measurement of DNA-coated colloid interactions and a first-principles model that accurately predicts these interactions without fitting parameters.

Findings

Interaction range and strength depend on DNA sequence and grafting density.

The model captures the balance between DNA binding and steric repulsion.

Results enable predictive design of colloidal assemblies.

Abstract

The self-assembly of DNA-coated colloids into highly-ordered structures offers great promise for advanced optical materials. However, control of disorder, defects, melting, and crystal growth is hindered by the lack of a microscopic understanding of DNA-mediated colloidal interactions. Here we use total internal reflection microscopy to measure in situ the interaction potential between DNA-coated colloids with nanometer resolution and the macroscopic melting behavior. The range and strength of the interaction are measured and linked to key material design parameters, including DNA sequence, polymer length, grafting density, and complementary fraction. We present a first-principles model that quantitatively reproduces our experimental data without fitting parameters over a wide range of DNA ligand designs. Our theory identifies a subtle competition between DNA binding and steric repulsion and accurately predicts adhesion and melting at a molecular level. Combining experimental and theoretical results, our work provides a quantitative and predictive approach for guiding material design with DNA-nanotechnology and can be further extended to a diversity of colloidal and biological systems.