ceramics in biomedicine twice refused to provide an interview opportunity to discuss why Bioglass is not included in the US formulation of the product. Instead. the company’s media contact for North America consumer products, Deborah Bolding, replied via email. “Sensodyne Repair & Protect is a new product here in the US and does not contain NovaMin,” she wrote. “The FDA approved the formulation. We work with regulatory authorities in each market on formulations for the product to be marketed and sold in that specific market. There are variances by market depending on the local regulatory body and other factors.” Another request, this one for contact information for a dentist featured in a testimonial video for the product, elicited the following reply: “I am pleased that I could address a number of your questions regarding Sensodyne Repair & Protect here in the US. Unfortunately, further comment will not be available on our strategy, rationale and future plans.” Bottom line: If you have sensitive teeth and want “real” Repair & Protect, you are still going to have to go outside the US to buy it! n Simulation, 3D printing combine to duplicate (or improve!) natural materials In a synthesis of computational materials science, 3D printing, and bioinspired materials engineering, researchers at Massachusetts Institute of Technology are quickly designing and testing materials that duplicate or exceed the strength and toughness of natural materials. Bone is an example of a natural structural material that is a composite of hydroxyapatite and collagen. The challenge in duplicating its properties lies in the way the two materials are arranged: The complex structure changes “at every scale of the composite, from the micro up to the macro,” according to an MIT news release. Associate professor Markus Buehler and coworkers used a 3D printer capable of working with two or more materials at once to create “computeroptimized designs of soft and stiff polymers placed in geometric patterns that replicate nature’s own patterns,” the release says. “The geometric patterns we used in the synthetic materials are based on those seen in natural materials like bone or nacre, but also include new designs that do not exist in nature,” Buehler says in the release. “We can design our own, which may perform even better than the ones that already exist.” The materials do not appear at all like their natural counterparts. The scientists’ 3D printed bonelike material, for example, features a microscopic pattern similar to a brick wall, with stiff blue polymer bricks and a soft black polymer “mortar.” Turning to 3D printing, the authors used the two polymers to fabricate composites with three configurations based on their computational model: A bonelike structure with stiff platelets “mortared” with the soft polymer, a calcite-type structure where the stiff and soft polymers alternate in columns, and a rotated bonelike structure where the stiff constituent is shaped like a diamond instead of a rectangular brick (for increased flexibility of the composite). They subjected each of three composite samples to tensile and other mechanical testing, which validated their computational models and simulation process. “Most importantly, the experiments confirmed the computational prediction of the bonelike specimen exhibiting the largest fracture resistance,” says graduate student Leon Dimas. “And we managed to manufacture a composite with a fracture resistance more than 20 times larger than its strongest constituent.” According to the release, the process “could be scaled up to provide a cost-effective means of manufacturing materials that consist of two or more constituents, arranged in patterns of any variation imaginable and tailored for specific functions in different parts of a structure.” “The possibilities seem endless, as we are just beginning to push the limits of the kind of geometric features and material combinations we can print,” Buehler concludes. Results of the work are reported in the Advanced Functional Materials paper “Tough composites inspired by mineralized natural materials: Computation, 3D printing, and testing.” n 16 www.ceramics.org | American Ceramic Society Bulletin, Vol. 92, No. 6 (Credit: M. Buehler/MIT; photo by Graham Bratzel.) The brick-and-mortar pattern of MIT’s simulated bone and nacre material does not look much like the real thing, but it behaves a lot like it.
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