Jeffrey ChouMarch 5, 2008

EE 235

Carbon Nanotube Based Electrostatic NEMs Devices

MEMS Based Comb Drive ActuatorsAs voltage is

increased, electrostatic forces bring combs together.

Spring is required for restoring force.

Rotational Actuators based on Carbon NanotubesDC or AC voltages

applied to S1, S2, and S3. (~5V)

Control position, speed, and direction of rotation

[Fennimore et al. “Rotational Actuators Basd on Carbon Nanotubes”, Nature 2003]

MWNT Rotor FormationWith high voltages,

sheer off outer layers of a MWNT to expose a rotating inner layer. (~80V)

Utilize the low friction bearing behavior

FabricationE-beam LithographyDeposit Gold/CrLift off processEtch oxide substrate

RotationAsymmetric rotor

plate causes a net torque when there is an applied electric field.

Rotational Velocity is theoretically very high, however direct measurements were limited by the video camera framerate

[Bourlon et al. “Carbon Nanotube Based Bearing for Rotational Motions”, Nano Letters 2004]

Carbon Nanotube Based Switches

• Length: 2microns, • Width: 70nm• After voltages are turned off, 1st and 2nd nanotubes are still stuck together by Van Der Waals forces

•Good for non-volatile memory• Off state can be restored by earth grounding 1st, floating ground 2nd, and 20-25V on 3rd.

[Jang et al. “Nanoelectromechanical Switches with Vertically Aligned Carbon nanotubes”, Applied Physics, 2005]

Shorter Nanotube SwitchesWhen voltages are

off, nanotubes return to off state.

Length: 1.4 micronsWidth: 70nmF = 8E*I*d/L^3As nanotubes

become shorter, their restoring forces become greater than the attractive Van Der Waals forces.

ConclusionMulti Wall Carbon Nanotubes low interlayer

friction provides good rotational motion.High conductivity of carbon nanotubes

work well with electrostatic forces.Carbon Nanotubes are key to effective

NEMS devices.