Color-Changing Material Inspired by Chameleon Skin

Innovation: Academia

University of Chinese Academy of Sciences

2021

Image: Arnold Straub / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Modify Light/Color

Color in living systems comes from pigments and the interaction of light with surfaces. Color serves many purposes for living systems, such as attracting prey or mates, providing warnings, or protecting through camouflage. To create the effects needed for each purpose, living systems must control the expression or visibility of pigments and the interactions (such as reflectance and refraction) of light. To do so, they have strategies that modify color or light to increase or decrease the color’s position, intensity, opacity, and more. Male hummingbirds, for example, have brightly colored feather patches on their throats; the coloring comes from pigments, structures that refract light, or a combination of the two. When a male hummingbird hovers near a potential mate, it modifies the angle of these feathers to create a bright, colorful display. However, when it needs to mute the colors to reduce conspicuousness, such as to avoid a predator, it modifies the angle again.

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Sense Atmospheric Conditions

For some living systems, the ability to detect changes in atmospheric conditions can be very valuable. By predicting changes in regional weather or in very localized conditions, living systems can avoid or take advantage of those changes. Since such adjustments can be very subtle, living systems must be able to detect miniscule variations in moisture, barometric pressure, ions in the air, and other environmental cues. Many insects and birds, for example, can predict oncoming storms and take cover before their lives are put at risk.

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Sense Temperature Cues From the Environment

Some living systems use their ability to perceive temperature to find prey or avoid predators, or as a way to gain information about their environment, such as whether they are near a warm or cold place. Temperature gradients can be subtle and modulate as they travel through water, air, or solids. Living organisms must therefore have a variety of thermal sensors appropriate to a given medium (liquid, gas, solid). Some even have a way to “visualize” a signal’s source. For example, the rattlesnake has heat sensors with thousands of nerve endings located in pit-shaped holes on each side of its face. The sensitivity of the pits overlaps, giving the snake a bifocal image of the heat’s source.

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Material from University of Chinese Academy of Sciences has core-shell structured layers which enable the display of a seamless range of vivid colors.

Benefits

Robust
Vibrant
Dynamic

Applications

Food packaging
Electronics
Robotics
Anti-counterfeiting technology

UN Sustainable Development Goals Addressed

Goal 12: Responsible Production & Consumption

The Challenge

Many materials are able to change colors to display images and patterns. Unfortunately, these synthetic materials often have only discreet color options, inhibiting the material from smoothly transitioning between a wider range of colors.

Innovation Details

The material is made of hydrogel layers that contain luminogens, molecules that emit light. The layers together make up a “core-shell” matrix. The core is a red fluorescent hydrogel that serves as the template for the other layers. This core is surrounded by blue fluorescent hydrogel laye, surrounded by a separate green fluorescent hydrogel. The unique layer configuration allows the material to show a spectrum of colors. Furthermore, the material functions as a chemosensor, altering color in response to changes in temperature or pH.

Biomimicry Story

Chameleons are able to alter their colors through a combination of s and structures. Beneath the layers of color-bearing cells called chromatophores, a layer of cells called iridophores (iridescent chromatophores). Rather than using pigment, iridophores contain an organized array of transparent, nano-sized crystals that reflect specific wavelengths of light corresponding to different colors.

See Related Strategy

green, red, blue and brown chameleon on brown tree branch

Biological Strategy

Shifting Crystals Change Chameleons’ Color

Short-horned chameleon

Pigments and nanoscale structures collaborate to help chameleon change its look.

References

Journal article

A panther chameleon skin-inspired core@shell supramolecular hydrogel with spatially organized multi-luminogens enables programmable color change

CellPress

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