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【Abstract】

For decades, soft matter experimentalists have strived to create patchy colloids that can be well-regulated. We herein report a new class of user-prescribed building blocks, made from DNA origami, that far surpasses the current generation of patchy colloids, in the ability to design interactions with kBT-scale precision and control the directionality and valence of the interactions with nm-scale accuracy. Guided by computer simulations, the powerful experimental capability then allows us to address fundamental questions in self-assembly.

Typically, the region of parameter space leading to productive assembly is narrow and, even worse, shrinks dramatically as complexity of the target structure increases. Here, we take a step toward uncovering principles to increase the Goldilocks zone by engineering building blocks to preferentially select assembly pathways that avoid kinetically trapped intermediate species in the trajectories. Our experiments and models reveal that designing unequal binding affinities among bonds between building blocks with different symmetries leads to hierarchical assembly pathways, in which particular subassemblies form rapidly and then subsequently associate into the final structure. Importantly, such hierarchical pathways lead to faster assembly with yield that are more robust against affinity variation than egalitarian pathways, in which all binding sites have equal strengths. This finding suggests that hierarchical assembly may be a general engineering principle for optimizing self-assembly of complex target structures.

* This work is supported by National Science Foundation MRSEC-DMR-2011846 and National Institutes of Health R01GM108021.