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3D Printing Technique Allows You to Change a 3D Printed Object’s Color

Wired UK reports on a startling new 3D printing-related development from a team of chemists at MIT.

The MIT team has developed a 3D printing technique allowing you to change an object’s color using light.  These malleable 3D printed objects can change colors by altering their polymers.  The team did this by utilizing Stereolithography – one of the most cutting edge forms of 3D printing.

For those who don’t know, Stereolithography works by “shining light onto a liquid solution of monomers – the building blocks of plastic and other materials – to form layer upon layer of solid polymers in a specific design or pattern, until the final shape is complete.”

Before now, “once an object had been printed these polymers were considered ‘dead’ – they couldn’t be extended to form new polymer chains, which would alter the printed object.”  However, with this process just developed by the team at MIT, polymer can be added to “alter the material’s chemical composition and mechanical properties.”

As Jeremiah Johnson, the Firmenich career development associate professor of Chemistry at MIT explains, “the idea is that you could print a material and subsequently take that material and, using light, morph the material into something else, or grow the material further.”

Back in 2013, Johnson and his team “demonstrated…they could use UV light to stimulate the polymers and add new features to 3D printed materials.  They experimented by using the light to break apart the polymers at certain points in a printed object, which created free radicals (extremely reactive molecules).”

These “free radicals would then bind to new monomers to form a solution surrounding the object and become incorporated in the original material.  Unfortunately, the radicals were found to be too reactive: they were difficult to control and could be damaging to the material.”

In order to work around this issue, “the MIT team designed new polymers that would react to light.  The polymers contained chemical groups known as TTCs, that are activated when turned on by light.  For instance, when blue light from an LED shines on the polymers, it attaches new monomers to the TTCs, which makes them stretch out.”  The 3D printed object is made from these monomers, which give the object’s material new properties.

Along with changing the color of a 3D printed object, the team also discovered “they could make materials become bigger or smaller using different temperatures by adding a specific monomer.”  This technique is still in its infancy, however.  It is “limited by the fact it requires an oxygen-free environment.”

The good news is that the team is “now working on finding different catalysts that can be used in the presence of oxygen.”

Image and Quotes Courtesy of Wired UK

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