Transcript No Slide Title

Powering Small Devices
Doesn’t that sound nifty?
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.
Points of Interest
•Assembly
•Range of Motion
•Painful Physics
Numbers
c-grown carbon nanotubes
Assembly
sing
custom-built
•Nanomotor
is constructed and operated in TEM
tion
stage: two MWNT are
•Indium is evapourated onto the surface of arc-grown carbon
overlapping
nanotubes (exparallel
situ)
with
an indium
•Assembled using custom-built nanomanipulation stage: two MWNT
are alligned in an overlapping parallel arrangement with an indium
nanoparticle
the
overlappresent near the overlap
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
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
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).