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 screens and combines existing theories into one coherent framework and 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.

Particles with ligand-receptor contacts bind and unbind fluctuating ``legs" to surfaces, whose fluctuations cause the particle to diffuse. Quantifying the diffusion of such ``nanoscale caterpillars" is a challenge, since binding...

Particles with ligand-receptor contacts span the nano to micro scales in biology and artificial systems. Such "nanoscale caterpillars" bind and unbind fluctuating "legs" to surfaces, whose fluctuations cause the nanocaterpillar to diffuse over long timescales. Quantifying this diffusion is a challenge, since binding events often occur on very short time and length scales. Here we present a robust analytic framework, validated by simulations, to coarse-grain these fast dynamics and obtain the long time diffusion coefficient of a nanocaterpillar in one dimension. We verify our theory experimentally, by measuring diffusion coefficients of DNA-coated colloids on DNA-coated surfaces. We furthermore compare our model to a range of other models and assumptions found in the literature, and find ours is the most general, encapsulating others as special limits. Finally, we use our model to ask: when does a nanocaterpillar prefer to move by sliding, where one leg is always linked to the surface, or by hopping, which requires all legs to unbind simultaneously? We classify a range of nanocaterpillar systems (viruses, molecular motors, white blood cells, protein cargos in the nuclear pore complex, bacteria such as Escherichia coli, and DNA-coated colloids) according to whether they prefer to hop or slide, and present guidelines for materials design.

Correction for ‘The nanocaterpillar's random walk: diffusion with ligand–receptor contacts’ by Sophie Marbach et al., Soft Matter, 2022, 18, 3130–3146, DOI: https://doi.org/10.1039/D1SM01544C.