Colloidal interactions and self-assembly using DNA hybridization

The specific binding of complementary DNA strands has been suggested as an ideal method for directing the controlled self-assembly of microscopic objects. Using an optical tweezer method, we have directly measured the attractive interaction and dynamics between DNA-grafted colloidal microspheres. The interactions measured can be modeled in detail with no free parameters, using well-known statistical physics and chemistry, boding well for their application to directed self-assembly. The microspheres' binding dynamics, however, show a surprising power-law scaling that can significantly slow annealing and crystallization. These slow dynamics are due to the lubrication forces in the nanoscale, polymer-filled gap between the spheres. Reducing the density of grafted DNA strands can speeds the dynamics sufficiently to grow small colloidal crystals.