David N. Hutchison

Carbon Nanotubes as a Framework for High-Aspect-Ratio MEMS Fabrication

A class of carbon-nanotube (CNT) composite materials was developed to take advantage of the precise high-aspect-ratio shape of patterned vertically grown nanotube forests. These patterned forests were rendered mechanically robust by chemical vapor infiltration and released by etching an underlying sacrificial layer. We fabricated a diverse variety of functional MEMS devices, including cantilevers, bistable mechanisms, and thermomechanical actuators, using this technique. A wide range of chemical-vapor-depositable materials could be used as fillers; here, we specifically explored infiltration by silicon and silicon nitride. The CNT framework technique may enable high-aspect-ratio MEMS fabrication from a variety of materials with desired properties such as high-temperature stability or robustness. The elastic modulus of the silicon-nanotube and silicon nitride-nanotube composites is dominated by the filler material, but they remain electrically conductive, even when the filler (over 99% of the composites mass) is insulating.

High aspect ratio microelectromechanical systems: A versatile approach using carbon nanotubes as a framework

We recently developed a fabrication process for carbon nanotube templated MEMS. The fabrication process involves growing a three dimensional pattern from carbon nanotube forests and filling that forest by chemical vapor infiltration to make a solid structure. This templating process allows us to fabricate extremely high aspect ratio microscale structures from a wide variety of materials. The nanotube structures can be hundreds of microns tall with lateral pattern dimensions down to a few microns. The chemical vapor infiltration has been shown with silicon and silicon nitride but could be extended to many other materials. In this paper, we investigate the microstructure of the filling material and extend the process to the fabrication of comb actuators.