Knowing when to fold: Engineers use 'nano-origami' to build tiny electronic devices (Video)

Feb 25, 2009 By Anne Trafton
MIT researchers have developed a way to fold nano- and microscale polymer sheets into simple 3D structures. Photo / Nader Shaar

(PhysOrg.com) -- 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.

This video is not supported by your browser at this time.

"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.

A team of MIT researchers folded this polymer sheet into one corner of a cube. The edge of each face is about 800 microns. Photo / Nader Shaar

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 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.

Provided by MIT

Explore further: Team finds electricity can be generated by dragging saltwater over graphene

add to favorites email to friend print save as pdf

Related Stories

JILA's short, flexible, reusable AFM probe

Apr 09, 2014

(Phys.org) —JILA researchers have engineered a short, flexible, reusable probe for the atomic force microscope (AFM) that enables state-of-the-art precision and stability in picoscale force measurements. ...

Real-time simulation of textiles

Mar 20, 2014

Fashion designers, pattern makers and tailors produce new collections using computer programs. The Fraunhofer Institute for Computer Graphics Research IGD in Darmstadt is working with partners on connecting ...

The amazing anatomy of James Webb Space Telescope mirrors

Mar 20, 2014

When you think of a mirror, there really isn't that much needed to describe it, but when you look at a mirror that will fly aboard NASA's next-generation James Webb Space Telescope, there's a lot to the anatomy ...

Recommended for you

First direct observations of excitons in motion achieved

Apr 16, 2014

A quasiparticle called an exciton—responsible for the transfer of energy within devices such as solar cells, LEDs, and semiconductor circuits—has been understood theoretically for decades. But exciton ...

User comments : 0

More news stories

Thinnest feasible nano-membrane produced

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...