Colorful 3D Printing Inspired by Chameleons

Innovation: Academia

University of Illinois Urbana-Champaign

2020

Image: Pierre Bamin / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Physically Assemble Structure

Living systems use physical materials to create structures to serve as protection, insulation, and other purposes. These structures can be internal (within or attached to the system itself), such as cell membranes, shells, and fur. They can also be external (detached), such as nests, burrows, cocoons, or webs. Because physical materials are limited and the energy required to gather and create new structures is costly, living systems must use both conservatively. Therefore, they optimize the structures’ size, weight, and density. For example, weaver birds use two types of vegetation to create their nests: strong, a few stiff fibers and numerous thin fibers. Combined, they make a strong, yet flexible, nest. An example of an internal structure is a bird’s bone. The bone is comprised of a mineral matrix assembled to create strong cross-supports and a tubular outer surface filled with air to minimize weight.

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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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Modify Material Characteristics

The materials found in living systems are variable, yet often made from the same basic building blocks. For example, all insect exoskeletons consist of a material called chitin. Because material resources are limited, each material within or used by a given living system must frequently serve multiple purposes. Therefore, living systems have strategies to modify materials’ softness, flexibility, and other characteristics. To ensure survival, the benefits of these modifications must outweigh the living system’s energy and material expenditure to generate them. For example, spiders store the liquid components of spider silk in a gland, converting them into silk thread when needed. Some threads have different characteristics, such as elasticity and UV reflectance, than others.

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3D printing process from University of Illinois, Urbana Champaign uses bottlebrush-shaped polymers to produce multiple colors from the same ink.

Benefits

Cost-effective
Reduced waste

Applications

Banknotes
Security cards
Manufacturing

UN Sustainable Development Goals Addressed

Goal 9: Industry Innovation & Infrastructure

The Challenge

Typical 3D printing materials are made in single colors. When a different color is needed, the machine must take a new cartridge before it can continue on. This process may introduce mistakes and increases time of production, leading to an overall increase in cost.

Innovation Details

The 3D printing process produces photonic crystals that reflect visible light. By adjusting the thickness of the crystals, different wavelengths of light will be reflected, producing different colors. This process allows multiple colors to be created from a single ink. This is similar to the way different organisms such as chameleons are able to produce different colors. The ink itself is made of bottlebrush-shaped s with two bonded, chemically distinct segments. The material is dissolved into a solution that bonds the polymer chains just before printing. After printing and as the solution dries, the components separate at a microscopic scale, forming nanoscale layers. Controlling the speed and temperature of the ink deposition also controls for how thick the nanoscale layers will be, and ultimately what color the ink will be.

Direct-write 3D printing scheme. Photo: Bijal B. Patel/University of Illinois at Urbana-Champaign.

Biological Model

Chameleons are able to change colors through a combination of s and structural colors. Below the layers of chromatophores (color-bearing) cells, there is a layer of cells called iridophores (iridescent chromatophores) that produce structural color. Rather than containing pigment, iridophores contain an organized array of transparent, nano-sized crystals that reflect specific wavelengths of light. The reflected light is perceived as color.

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

Tunable structural color of bottlebrush block copolymers through direct-write 3D printing from solution

Science Advances

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