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 (3D) 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.
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.”
support from the National Science Foundation (NSF), Gracias and Govind
Menon, a mathematician at Brown University, are developing
self-assembling 3D micro- and nanostructures that can be used in a
number of applications, including medicine.
team at Brown began designing these tiny 3D 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.
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.
researchers developed an algorithm to sift through all of the possible
choices, narrowing the field to a few compact shapes that easily fold
into 3D structures. Menon’s team sent those designs to Gracias and his
team at Johns Hopkins who built the shapes, and validated the
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.”
era of miniaturization promises to revolutionize our lives. We can make
these polyhedra from a lot of different materials, such as metals,
semiconductors and even biodegradable polymers for a range of optical,
electronic and drug delivery applications,” continues Gracias. “For
example, there is a need in medicine to create smart particles that can
target specific tumors, specific disease, without delivering drugs to
the rest of the body, which limits side effects.”
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.
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.
Source: National Science Foundation