Nanocrystal-Powered Nanomotor

Regan et al, "Nanocrystal-Powered Nanomotor"
Nano Lett. 5, 1730 (2005)


Not long ago, Zettl & co. learned that applying electric current to carbon nanotubes leads to heading, which can be used as a mass conveyor belt for indium atoms. Now they extend this effect, using the transport of the indium atoms to create the equivalent of a "frost heave"-based growth of In nanocrystals between two CNTs, in order to create a linear motor, that can be adjust from 0 to 130 nm in extension, at a rate of 1900 nm/s. Applying a reverse bias allows the arm to be retracted again. Based on this frost heave physical analogy, they estimate a force of ~ 1 nN, which is several orders of magnitude greater than known biomolecular linear motors...similarly, the volumetric power density ranges from 8 GW/m^3 to 20 MW/m^3 at full extension; biomolecular linear motors are in the range of 30 MW/m^3, and (as an amusing comparison made by the authors), a V6 car engine (assuming 3 L volume displacement), has a power density of 50 MW/m^3. They also have done similar work with cobalt, and suggest that electrocrystallizing organic materials may also function. Unfortunately there are no movies in the supplementary material, which is a shame, because I first saw this in a seminar several months ago, and was even more astounded when I saw these "in motion".