Scientists from the Institute of Science and Technology Austria (IST Austria) and the King Abdullah University of Science and Technology (KAUST) have presented an alternative method of applying user-defined color to 3D printed objects.
Replacing pigment-based colors, which alter appearance by the selective absorption of electrons in a substance, the scientists have created a computational additive manufacturing design tool to enable structural coloration, tailoring micro or nanostructures of an object to cause various vivid, unfading colors to appear when light it shined through.
There can be many variations of how rays of light bend when passing from one nanoscopic surface into another which causes natural optical effects, such as iridescence.
Advanced 3D printing technologies, in particular, multiphoton lithography – a technique using light to solidify a liquid photopolymer – have allowed for the fabrication of such nanostructures typically found in plants and animals that permit structural coloration. As a result, researchers are more equipped p to replicate such dynamic light patterns.
For example, researchers from the University of California San Diego (UCSD) used nanoscale 3D printing to create complex surfaces which mimic the radiant color patterns distributed by male Peacock Spiders. Similarly, physicists from the University of Surrey and San Francisco State University demonstrated the ability to reproduce the reflective structure of a butterfly wing through 3D printed nanometric gyroids.
Now, with the intention of reducing the use of potentially toxic industrial pigments, which also cannot produce certain color patterns, this design tool automatically creates 3D printable templates for nanostructures that correspond to specific colors.
“The design tool can be used to prototype new colors and other tools, as well as to find interesting structures that could be produced industrially,” said Thomas Auzinger, Postdoctoral Researcher in Computational Fabrication at IST Austria.
A free-form structure
The design tool permits users to enter their desired color, then replicates it through a 3D model nanostructure pattern rather than attempting to reproduce structures found in nature. “No extra effort is required on the part of the user,” added Auzinger. The nanostructure templates are randomly composed which causes directional coloring – where an object appears as a different color depending on the angle it is viewed.
“When looking at the template produced by the computer I cannot tell by the structure alone if I see a pattern for blue or red or green,” explained Auzinger.
“That means the computer is finding solutions that we, as humans, could not. This free-form structure is extremely powerful: it allows for greater flexibility and opens up possibilities for additional coloring effects.”
Nanostructure fabrication and future experimentation
According to the researchers, transparent nanostructures designed to manipulate light “were often impossible to print.” Addressing this concern, the design tool is said to guarantee 3D printability for its users. Researchers have also conducted initial tests of the tool which have yielded “successful results.”
“It’s amazing to see something composed entirely of clear materials appear colored, simply because of structures invisible to the human eye,” said Bernd Bickel, an Assistant Professor, heading the Computer Graphics and Digital Fabrication Group at IST Austria.
“We’re eager to experiment with additional materials, to expand the range of effects we can achieve.”
This project was presented at the computer graphics conference, SIGGRAPH 2018, in Vancouver, British Columbia.
The research paper “Computational Design of Nanostructural Color for Additive Manufacturing” is co-authored by Thomas Auzinger, Wolfgang Heidrich, and Bernd Bickel.
On the lookout for new talent or seeking a career change? Search and post 3D Printing Jobs for opportunities and new talent across engineering, marketing, sales and more.
Featured image shows a fabricated sample of an asymmetric colorization pattern displaying directional coloring. Photo via Thomas Auzinger.