January_2021_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y 2 0 2 1 5 6 3D PRINTSHOP 3D-printed milk and multi-food models: (a)-(d) Couch, cloverleaf, fortress, and wheel, respectively; (e) Cone containing liquid chocolate syrup as an internal filling; (f) Cube with four compartments containing various syrups as internal fillings. Courtesy of SUTD. PRINTED PLASTIC WEBS PROTECT PHONE SCREENS A Polytechnique Montréal team recently demonstrated that a fabric de- signed using additive manufacturing absorbs up to 96% of impact energy – all without breaking. The design was in- spired by the properties of spider webs. “A spider web can resist the impact of an insect colliding with it, due to its ca- pacity to deform via sacrificial links at the molecular level, within silk proteins themselves,” professor Frédérick Goss- elin explains. “We were inspired by this property in our approach.” The researchers used polycarbon- ate to achieve their results; when heat- ed, polycarbonate becomes viscous like honey. Gosselin’s team harnessed this property to “weave” a series of fibers less than 2-mm thick, then repeated the process by printing a new series of fibers perpendicularly, moving fast, be- fore the entire web solidified. As it’s extruded by the 3D printer to form a fiber, the molten plastic cre- ates circles that ultimately form a series of loops. “Once hardened, these loops turn into sacrificial links that give the fiber additional strength. When impact occurs, those sacrificial links absorb en- ergy and break to maintain the fiber’s overall integrity,” Gosselin adds. This nature-inspired innovation could lead to the manufacture of a new type of bullet-proof glass or to the pro- duction of more durable plastic protec- tive smartphone screens. “It could also be used in aeronautics as a protective coating for aircraft engines,” Gosselin notes. polymtl.ca. 3D PRINTING MILK-BASED PRODUCTS AT ROOM TEMP Researchers from the Singapore University of Tech- nology and Design (SUTD) de- veloped a method to perform direct ink writing (DIW) 3D printing of milk-based prod- ucts at room temperature, while maintaining its tempera- ture-sensitive nutrients. 3D printing of food has been achieved by different printing methods, including selective laser sintering and hot-melt extrusion. However, these methods are not always compatible with nutrients found in certain types of food. For instance, milk is rich in both calcium and protein, but as these nutrients are temperature sensitive, milk is unsuitable for 3D printing using the aforementioned printing methods which require high temperature. While cold extrusion is a viable alternative, it often requires rheology modifiers or additives to stabilize printed structures. To tackle these limitations, re- searchers from SUTD’s Soft Fluidics Lab changed the rheological properties of the printing ink and demonstrated DIW 3D printing of milk by cold-extrusion with a single milk product – powdered milk. The team found that the concen- tration of milk powder allowed for the simple formulation of 3D-printable milk inks using water to control the rheolo- gy. Extensive characterizations of the formulated milk ink were also conduct- ed to analyze their rheological proper- ties and ensure optimal printability. “Cold-extrusion does not com- promise heat-sensitive nutrients and yet offers vast potential in 3D printing of aesthetically pleasing, nutritionally controlled foods customized for indi- vidual requirements,” says assistant professor Michinao Hashimoto, princi- pal investigator of the study. www.sutd. edu.sg . Polycarbonate webs synthesized using additive manufacturing absorb up to 96% of impact energy. Courtesy of Shibo Zou.