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Chemists at MIT have found a way to add new polymers to things already printed, which allows them to create more complex objects that have different chemical and mechanical properties. Blue LED light is used to add monomers to an existing polymer chain resulting in growth. (via MIT)


Research funded by the National Science Foundation helped MIT researchers discover a way to add to, and alter 3-D printed objects after they’ve been printed. Until this advancement, objects that were 3-D printed were “dead” upon completion, meaning that polymer chains in the printed object could not be extended upon. As described by Anne Trafton of the MIT News Office, this new technique enables 3-D printing technology to, “...add new polymers that alter the materials’ chemical composition and mechanical properties”, and also, “...fuse two or more printed objects together to form more complex structures.” This technological development appears to have opened a door for further creativity and complexity in 3-D printing.


In 2013, these researchers tried using ultraviolet light to add new features to 3-D printed materials. Trafton describes this process when she writes, “... the researchers used ultraviolet light to break apart the polymers at certain points, creating very reactive molecules called free radicals.” She goes on to explain that these free radicals bind to new monomers from a solution surrounding the object that incorporates the monomers the original material. Ultimately this approach was unsuccessful in that it was damaging to the material and generally uncontrollable due to the reactivity of the free radicals.


Recently though, the researchers have designed polymers that are reactivated by light due to the chemical groups, known as TTCs, within them. Trafton describes these polymers as acting like “a folded up accordion”, and when the blue light from an LED hits the catalyst, new monomers attach to the TTCs, causing them to expand. As the new monomers are distributed into the structure uniformly, they inevitably change the material properties of the printed object.


According to Trafton, the researchers have demonstrated that they can insert monomers that, “...alter a material’s mechanical properties, such as stiffness, and its chemical properties, including hydrophobicity (affinity for water)” and, “...make materials swell and contract in response to temperature…”. Although these innovations are promising, there is a single, but a significant limitation in that this technique’s organic catalyst requires an oxygen-free environment. So, the researchers march onward, and Trafton reports that they are testing other catalysts that work for similar polymerizations in the presence of oxygen.


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