Self-assembling
nano boxes open the door to "smart" particles for medicine,
manufacturing
"What is remarkable here is not just that
a structure folds up on its own, but that it folds into a very precise,
three-dimensional shape, and it happens without any tweezers or human
intervention," says David Gracias, a chemical and biomolecular engineer at
Johns Hopkins. "Much like nature assembles everything from sea shells to
gem stones from the bottom up, the idea of self-assembly promises a new way to
manufacture objects from the bottom up."
With support from the National Science
Foundation (NSF), 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.
"We deposit a material in between
the faces and the edges, and then heat them up, which creates surface tension
and pulls the edges together, fusing the structure shut," explains
Gracias. "The angle between adjacent panels in a dodecahedron is 116.6
degrees and in our process, pentagonal panels precisely align at these
remarkably precise angles and seal themselves; all on their own."
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.
"Our process is also compatible
with integrated circuit fabrication, so we envision that we can use it to put
silicon-based logic and memory chips onto the faces of 3-D polyhedra. Our
methodology opens the door to the creation of truly three-dimensional 'smart'
and multi-functional particles on both micro- and nano- length scales,"
says Gracias.
Miles
O'Brien, Science Nation Correspondent
Jon
Baime, Science Nation Producer.
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