Reconfigurable Self-Assembly of DNA-Coated Colloids Through Competing Hybridization Reactions

Due to its chemical specificity and combinatorial sequence space, DNA is emerging as an ideal material to guide the self-assembly of colloidal materials. The cooperative interplay of hydrogen bonding, pi-stacking, electrostatic, and hydrophobic interactions between tethered DNA sequences induces attractive pair interactions, which can direct particles to form clusters, ordered crystal lattices, or other interesting structures. In the simplest cases, DNA-mediated binding is a monotonic and near exponential function of temperature, resulting in a single, narrow temperature window for equilibrium assembly, which has frustrated efforts to make multicomponent or reconfigurable structures. Here we show that DNA-coated colloids that interact with competing DNA strands in solution, by a process called toehold exchange hybridization, exhibit temperature dependences that need not be exponential nor monotonic. Using this additional control over the assembly pathways, we design and experimentally demonstrate reconfigurable colloidal systems, ranging from colloidal molecules that undergo reversible, structural isomerization to binary superlattices with temperature-dependent composition. These unique interactions will be useful in the future design of multicomponent, hierarchical, and programmable self-assembling materials.