Towards nanotube linear servomotors

Nanoscale linear servomotors with integrated position sensing are investigated from experimental, theoretical, and design perspectives. Prismatic motion is realized using the interlayer motion of telescoping multiwalled carbon nanotubes (MWNTs). Position sensing can be achieved by monitoring field emission or by measuring resistance change between an MWNT and a gold substrate during sliding movement. Experimental results demonstrate resolution in the nanometer range. Actuation experiments demonstrate the feasibility of a linear nanoservomotor with integrated position sensing based on field emission. A local "kink"-like fluctuation of emission current is observed, which is caused by the change of the protruding length of the nanotube core, thus demonstrating the potential of using emission as a "linear encoder." The complete extension of the inner core is observed and the electrostatic force is calibrated to be tens of nano-Newtons for individual nanotubes - 16.5 nN under a 30-V bias. These results demonstrate the possibility of fabricating linear servomotors at the nanometer scale with integrated position sensing.