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Spontaneous formation of aligned DNA nanowires by capillarity-induced skin folding

Significance Developing a method that is capable of manipulating the size, geometry, and alignment of DNA nanowires would expand their uses in fabricating functional materials and performing genetic analysis. Here, we present an approach that yields arrays of size-controllable straight or undulated DNA nanowires. This approach uses a template composed of a thin skin that dynamically changes its surface morphology in response to water. In particular, we exploit capillary forces of water containing DNA molecules to induce a wrinkle-to-fold transition of the template surface in an unconventional way, which in turn stretches and confines the molecules in the folded regions without any external forces and consequently forms the nanowires. This approach could make possible new fabrication opportunities for functional materials. Although DNA nanowires have proven useful as a template for fabricating functional nanomaterials and a platform for genetic analysis, their widespread use is still hindered because of limited control over the size, geometry, and alignment of the nanowires. Here, we document the capillarity-induced folding of an initially wrinkled surface and present an approach to the spontaneous formation of aligned DNA nanowires using a template whose surface morphology dynamically changes in response to liquid. In particular, we exploit the familiar wrinkling phenomenon that results from compression of a thin skin on a soft substrate. Once a droplet of liquid solution containing DNA molecules is placed on the wrinkled surface, the liquid from the droplet enters certain wrinkled channels. The capillary forces deform wrinkles containing liquid into sharp folds, whereas the neighboring empty wrinkles are stretched out. In this way, we obtain a periodic array of folded channels that contain liquid solution with DNA molecules. Such an approach serves as a template for the fabrication of arrays of straight or wrinkled DNA nanowires, where their characteristic scales are robustly tunable with the physical properties of liquid and the mechanical and geometrical properties of the elastic system.