(A) Fluorescent image of two dragons of CdSe QDs without shrinking; the inset shows a resolution of ~200 nm. (B-F) SEM (top) and EDX (bottom) images of a monkey of Ag; pig of Au-Ag alloy; snake of TiO2; dog of Fe3O4; and rabbit of NaYREF4, respectively. (G) Designed dragon patterns in (A). (H) Optical microscopy image of an ox of diamond. (I-M) Fluorescent images of a tiger of graphene QDs; goat of fluorescent Au; horse of polystyrene; rooster of fluorescein; and mouse of fluorescent protein, respectively. (N-R) 3D models and fluorescent images (maximum-intensity projection) of the fabricated structures in shapes of a C60 molecule, regular dodecahedron, regular octahedron, cube, and regular tetrahedron of different materials, respectively. (S) Top view of a five-layer split ring resonator (SRR) structure; inset: SRR unit; and (T) trimetric view of the SRR structure; inset: slice view of an SRR unit. (U) SEM image of the top layer of an SRR structure after shrinking and dehydration. (V) 3D model of a woodpile structure containing 16 vertical rods along the z-axis. (W, X) SEM cross-sectional images of the fabricated woodpile at the two cut planes in (V), respectively. (Substrate tilt angle: 52°). Scale bars are 1 µm for (B-F, U, W, X, and the insets of S and T); and 10 µm for (A, H-M, N-T). Credit: Carnegie Mellon University

(A) SEM image and a zoom-in view of a fabricated DOE. (B) Simulated intensity distribution at the Fourier plane of the DOE; inset: the encoded smiley. (C) Image recorded from the fabricated DOE in (A). The 0th order is spatially blocked to avoid camera damage. (D) Schematic of the optical setup to record the encoded image. (E-G) Demonstration of optical storage and encryption: (E) an expanded hydrogel patterned with designed information; (F) the gel in (E) after fully shrinking and dehydration to realize physical encryption; (G) the re-expanded gel is deposited with CdSe and developed to decrypt the stored patterns. (H) Optical image showing two encrypted 7-layer hologram patterns in (F). (I) Fluorescent images of the decrypted holograms, where “Science” is decoded; and (J, K) 3D views of the decrypted holograms. Credit: Carnegie Mellon University

Nanostructures demonstrating minimum feature sizes. (A) 3D model of a nonconnected “NANO” structure comprised of arrays of parallel nanowires. (B) SEM cross-sectional images of the “NANO” structure cut by focused ion beam (FIB); (C) zoom-in view of the letter “A” in (B); and (D) zoom-in view (C). (E) Four cross-sectional patterns of the “NANO” structure (in the x-z plane of (A)). (F) SEM images showing the trenches of the gel sample opened by the FIB-cut, where the positions of each letter are labeled. All cross-sectional images were taken at a substrate tilt angle of 52°. Credit: CUHK and CMU teams