Two of the hottest fields in computer research are nanoelectronics and 3D circuits. A new project from MIT looks to use a novel origami-like construction technique to meld these fields, creating miniature 3D circuit elements.
George Barbastathis, associate professor of mechanical engineering at MIT, has led a team which has devised a folding method which can fold nanoscale polymeric sheets into a multitude of devices. Professor Barbastathis envisions folded 3D structures being used in motors and capacitors, potentially leading to better computer memory storage, faster microprocessors and new nanophotonic devices.
Previously assembly techniques primarily focused on 2D, using X-ray lithography and nano-imprinting to create patterns which are combined to build microprocessors and other micro-electrical-mechanical (MEMS) devices. Tony Nichol, a graduate student on the project, describes, "A lot of what's done now is planar. We want to take all of the nice tools that have been developed for 2-D and do 3-D things."
Folding allows for better electrical storage, such as the storage of charges in the human brain, as well as more complex structures. The team in 2005 created a 3D nanocapacitor with a single fold, but while the capacitor was a significant technical advance, it could store little charge. By devising new folding techniques, the team hopes to remedy this lack.
One folding technique is to deposit chromium or other metal ions onto a fold crease. This technique is good at making materials curl upward, but is poor at making right angles. Another method involves using a beam of helium ions. High energy beams accumulate on the top of the sheet, causing it to fold down, while low energy beams reach the bottom of the surface causing it to fold up. This is one technique to produce almost-right angles.
Another technique which creates angles close to right angles is to run a gold nanowire along the desired crease. Applying a small current to this nanowire causes Lorentz force, which lifts the face. This technique is an example of a method that could allow for dynamic self-assembly.
For the folded material, researchers have tested silicon, silicon nitride (a type of ceramic) and a soft polymer known as SU-8.
Once folded, the remaining challenge is to perfectly seal the faces together, to create designs like cubes or pyramids. Two methods have been previously devised, one using magnets and the other using polymers on the folded faces, which are melted with an electric current at the ideal time to seal the faces together.
A third method was just recently devised by graduate student Nader Shaar, which involves matching a set of protrusions from a face to a series of holes in another face. While the "art" of developing these nanostructures is still in the final stages of being perfected, researchers are already cooking up applications. States Mr. Nichol, "We've got the core components figured out, and now we're just having fun with figuring out some applications."