Worth Reading CHEM *7530/750 Olivier Nguon February, 28th 2006

1. Worth Reading CHEM *7530/750 Olivier Nguon February, 28th 2006

2. Nanoscale Motor Composition • Ram: Metal nanocrystal (Indium) • Storage matter reservoir: Metal nanocrystal (Indium) • Lever arms: Multiwalled carbon nanotubes (MWNTs)

3. Nanoscale motor: principle • “Atom reservoir”: sources metal atoms for ram extension and sinks metal atoms for ram contraction • Atom transfer controlled by an electrical current

4. Atom transfert • Recent discovery1 • Electrical currents driven through nanotubes • Transport metal atoms on the nanotube surface • Reversing the current direction reverses the direction of atom transport. 1. Regan, B. C.; Aloni, S.; Ritchie, R. O.; Dahmen, U.; Zettl, A. Nature 2004, 428, 924-927.

5. Construction of the nanomotor Raw materials prepared: • Arc-grown MWNTs • Decorated with indium nanoparticles via thermal evaporation In high-resolution transmission electron microscope (TEM): • Nanomanipulation stage to mount the motor • External electronics to apply voltage

6. Reversible process • Ram growth rate and final length controlled by the voltage applied • The ram extension process is reversible • Allows cyclical motor operation

7. TEM images

8. Features • Voltage: switched between +0.9 / -0.9 V • Length: depends on reservoir (150 nm) • Rate: 1900 nm/s • Pmax: 20 bar • Power: 5 fW • Power density: 8 to 20 GW/m3

9. Limiting Conditions • At low drive voltages: Thermally activated atom transport dramatically slows as the Joule heating is reduced • The drive voltage upper limit and hence maximum speed: Fixed, as nanocrystal has to remain below its melting point

10. Applications • Radiation-resistant, vacuum-compatible actuation • Wide class of materials known to electrocrystallize, as cobalt, calcium, carbonate23 and organic conductors

11. Thank you !