The key idea of the method is the intricacy of fine-tuning of the specific crossing interaction between origami slats. The attraction needs to be weak between pairwise interacting slats so that spurious nucleation is minimized. Meanwhile when the temperature is raised to the point where multiple (for example, 8 or 16) slats are needed to interact coordinately for stable attachment, seed-dependent growth becomes robust over a wide window of environmental concentrations. Shih calls this strategy “the origami of origamis” as its efficiency rivals that of staple strands forming a single DNA origami. “We argue that this leap in assembly efficiency is due to three advantages over prior strategies, all made possible by the crisscross architecture: (1) strict seed-based control over initiation, (2) startling rapidity of growth and robustness against premature termination, and (3) highly orthogonal combinatorial coding of binding affinities.”
The team explored the vast megastructure space opened up by this method, including various multi-micrometer megastructures as well as periodic ribbons and sheets in one and two dimensions. Using combinatorial coding, they made 1,022-slat sheets that displayed different patterns of handles on their top faces (see illustration). The team navigated around various failure modes, noted Shih. “We had to test a number of different design parameters to obtain the remarkable performance that we reported.” Diffraction-limited optical microscopy can be used to study these megastructures.
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