Making DNA competitive: a new strategy to improve the self-assembly properties of DNA-coated particles

We present a new approach to widen the normally very narrow temperature window for equilibrium self-assembly (e.g. crystallization) of DNA-coated particles. Using Monte Carlo simulations, we first show that not only enthalpic but also entropic effects - due to the multi-bond character of the DNA-mediated interactions - play an important role in the overall binding properties of the particles. We then outline a new strategy that exploits the competition between different types of inter-particle DNA linkages to achieve a temperature-dependent switching of the dominant bond type. Depending on the length ratio of the DNA constructs, the bond switching is either energetically driven or controlled by a combinatorial entropy gain, which arises from the large number of possible binding partners for each DNA strand. Importantly, the resulting particle interaction is less strongly temperature dependent than in ``conventional'' systems with only one bond type, thus enhancing the experimental control over self-assembly. Finally, we will also show that in general stable gas-liquid separation is expected to occur only for particles smaller than a few tens of nanometers, which suggests that nanoparticles and micrometer-sized colloids will follow different routes to crystallization.