#northwestern university
Dynamic 3-D printing process features a light-driven twist
The speed of light has come to 3-D printing. Northwestern University engineers have developed a new method that uses light to improve 3-D printing speed and precision while also, in combination with a high-precision robot arm, providing the freedom to move, rotate or dilate each layer as the structure is being built.
Most conventional 3-D printing processes rely on replicating a digital design model that is sliced into layers with the layers printed and assembled upwards like a cake. The Northwestern method introduces the ability to manipulate the original design layer by layer and pivot the printing direction without recreating the model. This “on-the-fly” feature enables the printing of more complicated structures and significantly improves manufacturing flexibility.
“The 3-D printing process is no longer a way to merely make a replica of the designed model,” said Cheng Sun, associate professor of mechanical engineering at Northwestern’s McCormick School of Engineering. “Now we have a dynamic process that uses light to assemble all the layers but with a high degree of freedom to move each layer along the way.”
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When mixing granular matter, order among disorder
Mixing liquids is easy, or at least scientifically understood: a drop of food coloring will eventually mix into a cup of water through diffusion, and a dollop of cream can be mixed into coffee with a spoon through what is called turbulent mixing.
But what if the material has the properties of both liquids and solids, which is the case for materials like concrete, paint, and sand? Called yield stress materials, these mixtures can both flow like liquids and remain still like solids.
Understanding how these materials mix has implications in industries such as pharmaceuticals and concrete manufacturing, but little is still known about how to best mix them.
In a new paper in Nature Communications, Northwestern Engineering professors find that mixing yield stress materials creates both mixed and non-mixed regions, providing a fundamental beginning to understanding how to best design mixing protocols. Julio M. Ottino, Paul Umbanhowar, and Richard Lueptow served as the paper’s co-authors.
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“Body By Wisconsin” - a “dummy” in a footballer’s uniform laid out in a wicker casket with a banner below reading, “Body By Wisconsin”. Just a bit of antagonistic pre-game rivalry between Northwestern Univeristy, Illinois and Wisconsin University. Photo, c. 1920s.
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