High sensitivity interdigited capacitive sensors using branched treelike carbon nanotubes on silicon membranes

Branched treelike carbon nanotubes on silicon substrate have been exploited for the realization of high sensitivity interdigital capacitive pressure sensors. The interdigital structure has been realized using a micromachining technique on silicon membranes, whereas the growth of nanotubes has been achieved using a direct-current plasma enhanced chemical vapor deposition method. A sequential growth and hydrogenation has led to the formation of multiple branched structures of nanotubes. The growth in an interdigital manner results in a high overlap between neighboring fingers and consequently a magnified response to mechanical variations in the membrane as a result of applying an external pressure is observed. An oscillatory behavior has been observed which may be attributed to the vibration of nanotubes on thinned membranes.