Tuesday, April 24, 2012

#3D: "Nano Self-Assembly Enables Precision Manufacturing"

In the near future, complete 3D product manufacturing will be performed by smart self-assembling nanoscale building blocks, according to these National Science Foundation (NSF) researchers. R. Colin Johnson

3D micro-printing and of two-dimensional sheets of polymers can fold into three-dimensional shapes when water is added. Technique uses a photomask and ultraviolet (UV) light to "print" a pattern. In the absence of UV exposure, the polymer will swell and expand uniformly when exposed to water; however, when polymer molecules within the sheet were exposed to UV light, they became crosslinked--more rigidly linked together at a number of points. Credit: Zina Deretsky, National Science Foundation

Here is what NSF says about their 3D self-assembling manufacturing research: While it is relatively straightforward to build a box on the macroscale, it is much more challenging at smaller micro- and nanometer length scales. At those sizes, three-dimensional (3-D) structures are too small to be assembled by any machine and they must be guided to assemble on their own. And now, interdisciplinary research by engineers at Johns Hopkins University in Baltimore, Md., and mathematicians at Brown University in Providence, R.I., has led to a breakthrough showing that higher order polyhedra can indeed fold up and assemble themselves.

New York University (NYU) researchers have demonstrated an ability to make new materials with empty space on the inside, an advancement that could potentially control desired and unwanted chemical reactions. Mike Ward, of NYU's department of chemistry, and a team of researchers created molecular "flasks," which are essentially self-assembling cage-like containers capable of housing other compounds inside them. These flasks may eventually allow researchers to isolate certain chemical reactions within or outside the flask. The molecular flasks described by Ward and his collaborators take the shape of a truncated octahedron, one of 13 shapes described as an Archimedean solid--discovered by the Greek mathematician Archimedes. Archimedean solids are characterized by a specific number of sides that meet at corners which are all identical. The regularity of these shapes often means they are of particular interest to chemists and materials researchers looking to create complex materials that assemble themselves. Credit: Michael D. Ward, New York University

With support from the National Science Foundation (NSF), David Gracias and Govind Menon, a mathematician at Brown University, are developing self-assembling 3-D micro- and nanostructures that can be used in a number of applications, including medicine.

Menon's team at Brown began designing these tiny 3-D structures by first flattening them out. They worked with a number of shapes, such as 12-sided interconnected panels, which can potentially fold into a dodecahedron shaped container. "Imagine cutting it up and flattening out the faces as you go along," says Menon. "It's a two-dimensional unfolding of the polyhedron."

And not all flat shapes are created equal; some fold better than others. "The best ones are the ones which are most compact. There are 43,380 ways to fold a dodecahedron," notes Menon.

The researchers developed an algorithm to sift through all of the possible choices, narrowing the field to a few compact shapes that easily fold into 3-D structures. Menon's team sent those designs to Gracias and his team at Johns Hopkins who built the shapes, and validated the hypothesis.

Imagine thousands of precisely structured, tiny, biodegradable, boxes rushing through the bloodstream en route to a sick organ. Once they arrive at their destination, they can release medicine with pinpoint accuracy. That's the vision for the future. For now, the more immediate concern is getting the design of the structures just right so that they can be manufactured with high yields.
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