The culmination of 3.5 years of research has led to controllable monocopter that can autorotate like a maple seed (Acer diabolicum Blume) and fly like a helicopter (hover and forward flight). The vehicle, invented at the University of Maryland, Aerospace Engineering Autonomous Vehicle Laboratory and Alfred Gessow Rotorcraft Center, is the smallest and most capable to date as it meets most of the challenges set forth by DARPA's nano-air-vehicle program.
University of Maryland web page about Proj9 Robotic Samara
Courtesy S. Cho and M. S. Fuhrer, University of Maryland Graphene could replace silicon as the material of choice for many applications like high-speed computer chips and biochemical sensors.
Michael Fuhrer in a paper published online in Nature Nanotechnology explains that in graphene, the intrinsic limit to the mobility, a measure of how well a material conducts electricity, is higher than any other known material at room temperature.
If other extrinsic factors that limit mobility in graphene, such as impurities and lattice vibrations in the substrate on which graphene sits, could be eliminated, the intrinsic mobility in graphene would be more than 100 times higher than silicon.
The low resistivity and extremely thin nature of graphene makes it ideal for applications like touch screens, photovoltaic cells, and chemical and biochemical sensors. The research group was led by principal investigator Michael Fuhrer of the University of Maryland's Center for Nanophysics and Advanced Materials and the Maryland NanoCenter.
Fuhrer said the electrical current in graphene is carried by only a few electrons moving much faster than the electrons in a metal like silver.
"Our current samples of graphene are fairly 'dirty' due to some extraneous sources of resistivity,"
"Once we remove that dirt, graphene, at room temperature, should have about 35 percent less resistivity than silver, the lowest resistivity material known at room temperature."
Because graphene is only one atom thick, current samples must sit on a substrate, in this case silicon dioxide. The electron mobility within the graphene is effected by the substrate. Trapped electrical charges in the silicon dioxide (a sort of atomic-scale dirt) and vibrations of the silicon dioxide atoms can also have an effect on the graphene which are stronger than the effect of graphene's own atomic vibrations.
"We believe that this work points out the importance of these extrinsic effects, and creates a roadmap for finding better substrates for future graphene devices in order to reduce the effects of charged impurity scattering and remote interfacial phonon scattering." Fuhrer said.