A light-responsive surface encrypts data by coupling structural color with programmable shape change, enabling secure and reversible information storage without electronics.
(Nanowerk Spotlight) The lines between physical matter and digital information are becoming harder to draw. Across labs and industries, materials are no longer just containers, supports, or coatings. They are becoming tools for communication, concealment, and computation. One area where this shift is especially visible is in the development of materials that change their shape and color in response to light. These are not just visual effects. They are mechanisms for encoding information, controlling visibility, and adapting to complex surroundings.
What makes these materials especially powerful is their capacity to respond in more than one way. A surface that only changes color when exposed to light can be read. A surface that also changes shape at the same time, and only under precise conditions, can hide what it knows. This combination of physical deformation with spectral modulation is not a decorative trick. It is a method for storing and protecting information that does not depend on screens, microchips, or electrical power.
Building such systems has been difficult. Most known materials are designed to respond in only one domain, either optical or mechanical. Getting both to work together with speed, precision, and full reversibility has required more than clever design. It has demanded new ways to structure materials across multiple length scales, from molecules to visible structures.
Now, a team of scientists has created a material that does exactly this. Inspired by animals that blend into their surroundings by changing both their shape and color, they have engineered a soft actuator that encrypts information through tightly synchronized shifts in both form and appearance. When triggered by near-infrared light, this thin film bends, contracts, and changes color across the full visible spectrum within seconds. The response is fast, repeatable, and programmable. It enables a new level of control over what a surface displays and how it interacts with its environment.
None of this requires sensors, processors, or embedded electronics. The response emerges from the structure of the material itself. Through a combination of photothermal nanotechnology and self-organized liquid crystal networks, the film moves and reflects light differently depending on how it is exposed. Because these changes are physical rather than digital, the information it stores cannot be accessed or copied without matching the exact conditions required to unlock it.
A research team at Donghua University describes this system in a recent paper published in Advanced Functional Materials (“Bioinspired Actuators with Morphological–Chromatic Coupling for Information Encryption and Adaptive Camouflage”). Their work centers on a two-layer film engineered to respond to near-infrared light through a coordinated transformation in shape and color. This material functions as an optical encryption device, a camouflage skin, and a model for how physical materials can serve as active carriers of secure information.
Bioinspired synergistic shape-color switchable actuation system. a) Peron’s tree frogs adaptive camouflage through spatiotemporally coordinated chromatophore reorganization and morphing, achieving environmental assimilation. b) Schematic diagram of the Thiol-acrylate click chemistry reaction for LCE network formation. c) Schematic diagram and mechanism of synergistic deformation and discoloration of a bilayer CLCE@MWCNTLCE flexible actuator driven by NIR. d) Photograph of the synergistic shape deformation and discoloration of a CLCE@MWCNT-LCE-based biomimetic flower actuator under 808 nm NIR irradiation. e) Photographs of the color change characteristics and camouflage-driven behavior of biomimetic flowers. (Image: Reprinted with permission by Wiely-VCH verlag) (click on image to enlarge)
The film’s base layer is a liquid crystal elastomer that has been modified by dispersing multi-walled carbon nanotubes throughout its structure. These carbon nanotubes absorb near-infrared light and convert it into heat, which triggers a change in the surrounding polymer. The heat induces a shift from a more ordered state to a less ordered one, causing the film to contract in one direction and expand in another. This motion is rapid, repeatable, and does not require any mechanical input apart from light exposure.
Above this active base lies a cholesteric liquid crystal elastomer, whose molecules naturally self-assemble into a helical structure. The spacing of this helix determines which wavelengths of visible light are reflected. When the lower layer contracts, it compresses the helical pitch of the upper layer. As a result, the film shifts its color across the visible spectrum. The entire system functions through mechanical coupling: the light heats the nanotubes, the nanotubes deform the elastomer, the elastomer compresses the helix, and the helix reflects a different color of light.
The researchers demonstrated that a five percent concentration of carbon nanotubes provided the best balance between light absorption, thermal conversion, and mechanical stability. Higher concentrations led to clumping and loss of uniform behavior. At optimal levels, the film could reach its active temperature in under 15 seconds and return to its original shape on cooling. The color shift was broad, covering a wavelength range of 240 nanometers, and moved continuously through blue, green, yellow, and red.
Fabrication of the composite used a thiol-acrylate click chemistry approach. The lower layer was partially cured with embedded carbon nanotubes, then a precursor mixture containing chiral agents was deposited on top and cured under ultraviolet light. This process allowed the layers to chemically bond into a single integrated film. Stretching and curing locked the liquid crystal molecules into a uniformly aligned state that supported consistent actuation and spectral control.
The team used this structure to build a color-based barcode that encoded information in both geometry and hue. The pattern could only be decrypted under tightly controlled conditions, including the timing and location of near-infrared exposure. Any deviation from the correct sequence or intensity left the information unreadable. The combination of spatial layout, temporal gating, and chromatic change supported over 43 million unique combinations of encoded information.
Unlike conventional barcodes or QR codes, this one could not be read using ordinary light or imaging tools. It required the correct stimulus to activate the correct physical state. Once the light was removed, the barcode reverted to its encrypted condition. Because the transformation is physical rather than digital, it cannot be intercepted or copied by scanning alone. It must be activated in the right way at the right time.
The researchers also tested how the material could be used for adaptive camouflage. Inspired by Peron’s tree frog, which changes both its color and body shape to blend into bark or leaves, the team built films that could shift between red and green tones when placed against different natural backgrounds. A short pulse of near-infrared light caused the film to compress and change color to match red leaves. Without light, it returned to its green stretched state to blend into foliage. Spectral measurements showed that the reflected light from the film closely matched that of its environment in both cases.
These adaptive responses occurred through the same coupled mechanism as the encryption mode. The carbon nanotubes converted light into heat. The heat induced contraction in the elastomer. The contraction compressed the cholesteric layer. The compressed layer shifted its helical pitch and changed the reflected wavelength. Because all of this was controlled through light exposure, no electrical wiring or onboard controls were needed.
The material also proved to be mechanically robust. It withstood repeated cycles of heating and cooling without loss of function. It remained stable at temperatures up to 350 degrees Celsius. Its tensile strength reached almost 4 megapascals, and it stretched to more than 150 percent of its original length without tearing. These properties suggest that the film could be used not only for static displays but also for moving components in soft robotics and other mobile systems.
Synchronous shape change and color shift of the CLCE@MWCNT-LCE camouflage skin under near-infrared photothermal stimulation, demonstrating coordinated mechanical and optical response.
This dual-function material stands out for its integration of two responsive domains. The embedded multi-walled carbon nanotubes provide localized, light-driven heating that drives fast and controlled deformation in the liquid crystal elastomer network. Simultaneously, the cholesteric liquid crystal layer produces vivid, angle-independent color based on structural reflection. The mechanical actuation from the nanotube-doped base layer directly alters the helical pitch of the upper photonic layer, enabling full-spectrum visible color tuning as a function of strain. Without either element, the system could not achieve the spatial, temporal, and spectral control demonstrated in the study.
By engineering a tightly bonded bilayer in which mechanical and optical properties respond to the same input, the researchers created a material that encodes information in both shape and color. The result is a platform that supports multimodal encryption, physical authentication, and responsive camouflage in a single device. It requires no embedded electronics, uses only light as a control signal, and can operate without direct contact.
The study demonstrates how nanoscale thermal conversion, liquid crystal elasticity, and photonic reflection can be coupled within a single structure. The work provides a model for how soft, programmable materials can respond to environmental inputs through precisely coordinated physical changes. Its implications extend beyond data security and concealment, suggesting broader applications in adaptive textiles, intelligent surfaces, and untethered robotic systems where local and reversible responsiveness is essential.
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