SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS RESEARCH: CHEMICALLY ACTIVE 3D PRINTS WIN THE 2016 ALTMETRICS AWARD

Intense interest in results demonstrating the chemical reactivity of nanocomposites in 3D printed structures on social media leads to STAM 2016 Altmetrics Award. “People (secretly, sometimes) love having control. They love to be able to design and create and build. 3D printing facilitates this kind of creative control,” suggests Matthew Hartings, a researcher at the American University. “With the technologies that we are developing, we are adding a 4th dimension to 3D printing: chemistry.” Despite the interest 3D printing has attracted, in chemistry so far the technique has been confined to producing structures to help research other materials and structures – such as reactionware – rather than producing structures to be studied themselves. “As a chemist, printed things are kind of boring,” explains Hartings. “I wanted 3D printed objects to be able to do chemistry after they were printed.” Together with researchers at the National Institute of Standards and Technology and the Food and Drug Administration, Hartings has demonstrated that titanium oxide nanoparticles blended into a 3D printed polymer not only enhance the mechanical properties of the structure but also the chemical properties. The Science and Technology of Advanced Materials paper reporting the results attracted so many references in mainstream and social media that it has been awarded the journal’s 2016 Altmetric Award. For Hartings winning the award was a gratifying indication that their research was breaking out of academia and attracting interest from non-specialists. Chemistry with nanoparticles embedded in a 3D-printed polymer composite is possible because polymers are innately permeable. However Hartings points out that the polymer used in the reported results is not optimally suited to the kind of chemistry they are trying to support, leaving lots of room for future work. “I’m really interested in the way that our 3D printed nanocomposites can store and filter gases,” says Hartings. “Developing new ways to trap gases like carbon dioxide and hydrogen and methane will have huge implications for our environment and society.” Background 3D printing 3D printing describes a production process – also referred to generically as additive manufacturing. It was first invented in the 1980s as a process whereby 3D objects were produced by printing a sequence of cross-sectional layers. Subsequent contributions from different inventors around the world developing the technique, including software developments for stereolithography file formats as well as hardware enhancements. Today the term also refers to printed plastic extrusion processes as described by Hartings and colleagues. 3D printing has demonstrated potential in tissue engineering where structures have been seeded with living cells. However until the present work 3D printed structures were generally regarded by chemists as inert objects. TiO2 nanoparticles Titanium dioxide is a semiconductor that occurs with a crystalline structure in several different forms including brookite, rutile and anatase. It is photocatalytic under UV light, particularly in the anatase form. In the form of nanoparticles it has enhanced photocatalytic properties due to the increased surface area. The polymer host Although embedded in a composite when 3D printed in the current work, the polymer host is permeable allowing access between the titanium dioxide nanoparticles and other chemicals in the environment. The two polymers most prevalent in 3D printing are polylactic acid and acrylonitrile butadiene styrene. The researchers used acrylonitrile butadiene styrene because they noticed more decomposition in the polylactic acid during extrusion. However they note that other polymers may make better hosts for future chemical applications of 3D printed structures.