1. Powering Small Devices

3. Doesn’t that sound nifty?

4. Carbon Nanotubes as Nanoscale Mass Conveyors
Carbon nanotubes: hollow cores, possible conduits for nanoscale amounts of material
Indium nanoparticles on carbon nanotubes, apply current to nanotube:
controllable, reversible atomic scale mass transport along carbon nanotubes,
using indium metal
By applying appropriate current to the carbon nanotube pictured, indium is moved from left (a) to right (b) and back again (c).
B. C. Regan et al. Nature. 2004, 428, 924.

5. Painful Physics Numbers
Points of Interest
Assembly
Range of Motion
Painful Physics Numbers

6. Assembly Nanomotor is constructed and operated in TEM
Indium is evapourated onto the surface of arc-grown carbon nanotubes (ex situ)
Assembled using custom-built nanomanipulation stage: two MWNT are alligned in an overlapping parallel arrangement with an indium nanoparticle present near the overlap

7. Applying the Principle of Transport
External electronics: apply voltage across the MWNT lever arm junction
Electrical current through the lever arms and the junction
Electrically directed indium surface diffusion: indium atoms from the atom
reservoir are transported to the junction region: a single nanocrystal (ram) is grown directly between the lever arms

8. Range of Motion
Apply current: nanocrystal grows in length, pushes MWNT lever arms apart
Reversible: control voltage (upper panel) is switched sequentially between +0.9 and -0.9 V, the ram grows and shrinks
Cycles with a stroke of 45 nm and a speed of 1 nm/s. Increasing the drive voltage increases rate

9. Conclusions
Pressure exerted by the ram is calculated to be 20 bar; with ram cross-sectional area of 36 nm2, force is 2.6 nN
Nanocrystal ram compares favourably with competing motor technologies for power density:
With extension velocities > 1900 nm/sec, power output capability of 5 fW. Available power density is initially 8 GW/m3
The power density of an internal combustion engine is around 50 MW/m3 (calculated for a Toyota Camry 210 hp V6, where the 3L displacement has been taken as the working volume).