A thermodynamic approach to adhesion and deformation of DNA-bound droplets

TL;DR

This paper develops a thermodynamic model for DNA-coated droplet adhesion, accurately predicting binding behaviors and morphologies, and experimentally confirms the model's predictions, providing insights for designing colloidal structures.

Contribution

The study introduces a comprehensive free energy functional that integrates microscopic DNA mechanics and droplet elasticity, advancing understanding of DNA-mediated droplet adhesion.

Findings

Quantitative agreement between theory and experiments on droplet binding.

Identification of a weak effective binding strength of approximately 3.7 kBT.

Prediction of adhesion size and morphology transitions based on DNA coverage.

Abstract

Here we derive and experimentally test a free energy functional that captures the adhesion of DNA-coated emulsion droplets. Generalizing previous approaches, the theory combines important energetic and entropic effects of microscopic DNA mechanics and droplet elasticity. It simultaneously predicts adhesion size, morphology, and binder concentration as a function of experimental control parameters. Notably, droplets transition from undeformed binding to flat droplet interfaces at a characteristic DNA coverage. These equilibrium predictions agree quantitatively with experiments on droplet-substrate and droplet-droplet binding, revealing a weak effective binding strength of $3.7\pm0.3\text{k}_{\text{B}}\text{T}$ owing to entropic costs. Our results open the path to rich design strategies for making colloidal architectures.