Direct Measurements and Models of DNA-Induced Colloidal Interactions and Binding Dynamics

DNA hybridization can be used to induce specific attractive interactions between colloidal particles, which in turn have been used to direct the assembly of particle-based materials having a variety of crystalline structures. A robust and experimentally validated model for such pair-interactions will be essential to design and produce unique materials having more complex microstructures or the ability to replicate or reconfigure. Unlike previous studies of DNA interactions, which have been mostly limited to model-dependent bulk measurements, we use scanning-line optical tweezers to make spatially resolved measurements of equilibrium, DNA-induced interactions and adhesive dynamics between pairs of polystyrene microspheres, ranging up to binding strengths of 6 k_BT. Our results are well described by a conceptually simple and numerically tractable model that captures both the spatial and temperature dependence of the DNA-induced interaction quantitatively without free parameters or empirical corrections. This interaction model is also validated for the more complex and experimentally relevant case of brushes containing multiple DNA species having competitive interactions. In all experiments, the microspheres’ binding dynamics have a surprising power-law scaling that can be tuned by altering the DNA brush concentration.  This work motivates a design approach where new functional structures can be found in simulation and then reliably realized in experiment.