[Editors] MIT uses nano-origami to build tiny electronic devices

[Elizabeth Thomson]

http://web.mit.edu/newsoffice/2009/nano-origami-0224.html


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MIT uses nano-origami to build tiny electronic devices
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For Immediate Release
THURSDAY, FEB. 26, 2009

Contact: Elizabeth A. Thomson, MIT News Office
E: thomson at mit.edu, T: 617-258-5402

Photo and Video Available

CAMBRIDGE, Mass.--Folding paper into shapes such as a crane or a  
butterfly is challenging enough for most people. Now imagine trying to  
fold something that’s about a hundred times thinner than a human hair  
and then putting it to use as an electronic device.

A team of researchers led by George Barbastathis, associate professor  
of mechanical engineering, is developing the basic principles of nano- 
origami, a new technique that allows engineers to fold nanoscale  
materials into simple 3-D structures. The tiny folded materials could  
be used as motors and capacitors, potentially leading to better  
computer memory storage, faster microprocessors and new nanophotonic  
devices.

Traditional micro- and nano-fabrication techniques such as X-ray  
lithography and nano-imprinting work beautifully for two-dimensional  
structures, and are commonly used to build microprocessors and other  
micro-electrical-mechanical (MEMS) devices. However, they cannot  
create 3-D structures.

“A lot of what’s done now is planar,” says Tony Nichol, a mechanical  
engineering graduate student working on the project. “We want to take  
all of the nice tools that have been developed for 2-D and do 3-D  
things.”

The MIT team uses conventional lithography tools to pattern 2-D  
materials at the nanoscale, then folds them into predetermined 3-D  
shapes, opening a new realm of possible applications.

Smaller, faster

The researchers have already demonstrated a 3-D nanoscale capacitor,  
developed in collaboration with MIT Professor Yang Shao-Horn, which  
was presented at the 2005 meeting of the Electrochemical Society. The  
current model has only one fold but the more folds that are added, the  
more energy it will be able to store. Extra layers also promote faster  
information flow, just as the human brain’s many folds allow for  
quicker communication between brain regions, says Nader Shaar, a  
mechanical engineering graduate student working on the project.

Getting the materials to fold back and forth into an accordion-like  
structure has been one of the researchers’ biggest challenges, along  
with getting the faces and edges to line up accurately.

They have worked out several ways to induce the nanomaterials to fold,  
including:

* Depositing metal (usually chromium) onto the surface where you want  
the fold to be. This causes the material to curl upward, but it does  
not allow for right angles or accordion-type folds.

* Directing a beam of helium ions onto the desired fold location. The  
beams imprint patterns that will cause the material to fold once it’s  
removed from the surface. High-energy beams go to the bottom of the  
material and cause it to fold up; ions from low-energy beams  
accumulate at the top of the material and make it fold down.

* Embedding gold wires in the material. A current running along the  
gold wires interacts with an external magnetic field, creating a  
Lorentz force that lifts the face. This technique is a form of  
directed self-assembly, where the designer provides the template and  
then lets the device assemble itself.

The folded shapes can be fabricated with a few different types of  
material, including silicon, silicon nitride (a type of ceramic) and a  
soft polymer known as SU-8.

Once the material is folded, the tricky part is getting the faces to  
align properly. The researchers have developed a few ways to do this  
successfully: one uses magnets; another involves attaching polymers to  
a certain spot on the faces and melting them with an electric current,  
sealing the two faces together.

They're still working on getting faces and edges of a folded cube to  
line up with nanoscale precision, but Shaar, co-supervised by  
associate professor of mechanical engineering Carol Livermore, has  
devised a promising method that uses three pairs of matching holes and  
protrusions to pull the edge and face into alignment.

The researchers are deep in the development phase of their nano-folded  
devices, but they are starting to think about how the technology could  
be used in the future. "We've got the core components figured out, and  
now we're just having fun with figuring out some applications," says  
Nichol.

--END--

Written by Anne Trafton, MIT News Office
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