US Patent 7791433 - Nanotube array RF filter

http://ip.com/patent/US7791433

It has been demonstrated that carbon nanotube arrays may be used to construct tunable RF filters. However, the geometry of the nanotube array can result in a non-uniform charge distribution resulting in the creation of a DC path of current that can destroy the device. This patent from Nokia teaches a circular nanotube array that can avoid this problem. Claim 1 reads:

1. An apparatus comprising:

a first electrode having a first edge;

an array of nanotubes distributed in a closed path, where the closed path surrounds the first electrode and adjacent to the first edge, the closed path is locally straight, and where each of the nanotubes comprises an end that is free to oscillate; and

a second electrode having a second edge surrounding both the first electrode and the array of nanotubes.