Fig. 4.

Faceted DNA-coated patchy particles from photo-polymerization of patchy crystalline emulsions. (A) Exposure of patchy crystalline emulsions to UV light triggers droplet polymerization capturing hydrophobic anchors embedded in the droplets to create patchy particles with active DNA. Bright-field image in A, Center shows a large CsCl-like colloidal crystal after photopolymerization. (Scale bar, 10 µm.) Fluorescent image in A, Right shows that DNA fluorescence is preserved when a radical scavenger is used. (A, Right, Inset) Red channel fluorescence image shows distribution of patches on the surface of the droplets. (Scale bar, 5 µm.) (B) Patches on particles reflect the symmetry of the patchy crystalline emulsion. SEM image of typical faceted DNA patchy particles obtained after photo-polymerization of droplets forming large CsCl-like crystals is shown. Patchy particle monodispersity is preserved after rapid droplet photo-polymerization. (Scale bar, 2 µm.) (C) Photo-polymerized 2D CsCl crystalline emulsions produce faceted DNA patchy particles with four selective energy sites. Fluorescence coupled with bright-field image shows 600-nm PS particles coated with cDNA (small green and gray particles) and four-patch faceted patchy particles (large gray particles) holding DNA complementary (red patches) to gray PS colloids. Small gray PS particles bind preferentially to faceted patchy particles due the high concentration of DNA on patches. (C, Insets) Bright-field images show rapid DNA assembly of a chain-like hybrid structure. (Scale bars, 2 µm.) (D) Fluorescence image of faceted patchy particles reveal the cubic distribution of contact points obtained from the original CsCl superlattice (eight patches). Binary mixture of DNA patchy particles can be separated by using DNA-coated magnetic particles (SI Appendix, Fig. S5). Fluorescence image and bright-field (D, Inset) image show 600-nm PS particles coated with cDNA selectively binding to DNA patches on faceted patchy colloid. (Scale bars, 1 µm.)