US Patent 7402531 - Fabrication of multiple length nanowire array

http://www.freepatentsonline.com/7402531.html

This patent from Hewlett Packard teaches a method of forming an array of nanotubes differentiated by length useful for applications such as optical sensing. Claim 1 reads:

1. A method for selectively controlling lengths of nanowires in a substantially non-uniform array of nanowires, the method comprising:

establishing at least two different catalyzing nanoparticles on a substrate; and

substantially simultaneously growing a nanowire from each of the at least two different catalyzing nanoparticles, wherein at least one of the nanowires has a length different from that of at least an other of the nanowires.

Similar technology for bending nanotubes was also developed by Hon Hai Precision (see US 7,291,319).