Reconfiguring Colors of Single Relief Structures by Directional Stretching

Abstract

Color changes can be achieved by straining photonic crystals or gratings embedded in stretchable materials. However, the multiple repeat units and the need for a volumetric assembly of nanostructures limit the density of information content. Inspired by surface reliefs on oracle bones and music records as a means of information archival, here, surface‐relief elastomers are endowed with multiple sets of information that are accessible by mechanical straining along in‐plane axes. Distinct from Bragg diffraction effects from periodic structures, trenches that generate color due to variations in trench depth, enabling individual trench segments to support a single color, are reported. Using 3D printed cuboids, trenches of varying geometric parameters are replicated in elastomers. These parameters determine the initial color (or lack thereof), the response to capillary forces, and the appearance when strained along or across the trenches. Strain induces modulation in trench depth or the opening and closure of a trench, resulting in surface reliefs with up to six distinct states, and an initially featureless surface that reveals two distinct images when stretched along different axes. The highly reversible structural colors are promising in optical data archival, anti‐counterfeiting, and strain‐sensing applications.

Reversible Mechanochromisms via Manipulating Surface Wrinkling

“…Inspired by the coloring strategy in nature, scientists and engineers have devoted much effort to artificially designing and manufacturing the structural color materials responsive to various stimuli, such as solvent, light, humidity, temperature, magnetic or electric fields, − and especially mechanical stress. − Mechanochromic effects can be directly achieved by deformation-induced changes in ordered nanostructures of the structural color materials. Two techniques are typically developed to fabricate structural color materials, namely, the lithography-derived techniques for producing nanostructures − and the self-assembly methodologies for creating nanoparticles arrays. − However, these methods either require multiple steps and specialized equipment, causing high cost and great difficulty to large-scale fabrication, or involve weak interactions between adjacent particles or between hard particles and soft elastomers, , leading to a lack of mechanical stability during deformation.…”

Full Geometric Control of Hidden Color Information in Diffraction Gratings under Angled White Light Illumination

“…If necessary, these errors can be mitigated by using adaptive stitching algorithms 50 and printing an additional base layer beneath the gratings. 30 The gratings with different heights that comprised the "snake swallow elephant" image is shown in the magnified scanning electron microscope (SEM) image of Figure 3a(iii).…”

“…However, the combined use of these parameters to hide color information in gratings has not been achieved efficiently. Though previous works have used polarization selectivity , and directional stretching to encode color information in gratings, they are limited to only 2 independent polarization states or stretching directions that reveal the encoded information with no crosstalk. Hence, a solution to increase the information storage capacity of gratings is necessary.…”

Metasurface‐Assisted Optical Encryption Carrying Camouflaged Information

“…Among them, optical encryption, which scrambles and encodes the information of plaintext through optical transformations such as interference, diffraction, and imaging, opens a new path for information security. Owing to the abundant degrees of freedom (DOF) of light (e.g., amplitude, phase, polarization, and frequency), optical encryption technology has significant advantages of multi-dimensionality, large capacity, high design freedom, and high security.Metasurface is an artificially planarstructure material that has the superior capability of controlling DOF of light at subwavelength scale, [1][2][3][4][5][6][7][8] leading to a series of novel optical encryption technologies. [9][10][11][12][13][14][15][16][17][18][19][20] For nanoprinting, [21][22][23][24] these DOFs offer the possibility of encoding multiple meta-images into different optical dimensions, thus improving the security and capacity of optical encryption.…”

“…Metasurface is an artificially planarstructure material that has the superior capability of controlling DOF of light at subwavelength scale, [1][2][3][4][5][6][7][8] leading to a series of novel optical encryption technologies. [9][10][11][12][13][14][15][16][17][18][19][20] For nanoprinting, [21][22][23][24] these DOFs offer the possibility of encoding multiple meta-images into different optical dimensions, thus improving the security and capacity of optical encryption.…”