Diffusion of DNA-coated colloids on DNA coated surface*

DNA-coated colloids can self-assemble and crystalize into a wide variety of structures. In order

for DNA-coated colloids to anneal and form crystals, they must roll and diffuse while attached to

each other.  Here we report on the diffusion of DNA-coated colloidal spheres on a flat DNA-

coated substrate.  Near the DNA-melting temperature, the mean square displacement is linear in

time as expected for normal diffusion, but the diffusion coefficient is much smaller than for free

diffusion. As the temperature is lowered, the motion becomes sub-diffusive, which suggests the

presence of random free energy barriers in the DNA-mediated interactions. We have found that

DNA induced interactions are highly sensitive to the density and homogeneity of the DNA

distribution. As we reduce the DNA density, the DNA coated colloids diffuse slower. This study

is important for designing and optimizing self-assembly structure of DNA coated colloids.