Using the art of origami a group of scientists [MIT tech talk (2009) 53, 4] and [Arora, et al., J. Microelec. Syst. (2009) 18, 98] have successfully fabricated a functional microscale super capacitor, which is essentially a nanostructured 3D device. It consists of one electrode placed on a fixed substrate and the other on a folding membrane. Folding over the single membrane flap brings the two electrodes together to form one super capacitor cell. The microscale super capacitor could potentially be used as an effective, integrated power source for stand alone microsystems.
“Origami” is the japanese art of paper folding; nanostructured origami is the manufacturing process that folds nanopatterned thin films into a desired 3D shape. In the first step of the process, standard planar fabrication tools and techniques are used to create a micro and nanopatterned 2D membrane. The membrane can be thought of as the analog of “paper” used in conventional origami and, in addition to being patterned directly, can provide a base on which to grow or deposit nanostructured materials.
The nanostructured origami process provides several advantages over current fabrication methods. First, a multilayer device can be made by patterning and repeatedly folding a single layer, thus avoiding fabrication difficulties associated with multilayer devices. Improved alignment and spacing among the folded layers can be achieved through the use of pyramid-shaped alignment features. In addition, whereas current nanofabrication methods are largely limited to building nanostructures on the top surface of a horizontally oriented substrate, the origami method allows the patterned surfaces to be oriented arbitrarily within the final 3D system.
Because the origami method of fabrication is based on standard 2D fabrication tools and techniques, a wide range of origami devices, including the origami super capacitor, can be integrated with pre-existing micro and nanosystems.
In addition, the origami super capacitor benefits greatly from the use of nanostructured surfaces and 3D geometry, two main features of origami fabrication. The use of high surface area carbon electrode with nanoscale pores and particles resulted in a 50 × increase in capacitance, whereas the ability to vertically stack the layers resulted in devices with a real footprint of less than 1 mm. Future devices will incorporate more complex nano architecture to further increase performance