3 research outputs found
Electrothermal Actuation of NEMS Resonators: Modeling and Experimental Validation
We study the electrothermal actuation of nanomechanical motion using a
combination of numerical simulations and analytical solutions. The
nanoelectrothermal actuator structure is a u-shaped gold nanoresistor that is
patterned on the anchor of a doubly-clamped nanomechanical beam or a
microcantilever resonator. This design has been used in recent experiments
successfully. In our finite-element analysis (FEA) based model, our input is an
ac current; we first calculate the temperature oscillations due to Joule
heating using Ohm's Law and the heat equation; we then determine the thermally
induced bending moment and the displacement profile of the beam by coupling the
temperature field to Euler-Bernoulli beam theory with tension. Our model
efficiently combines transient and frequency-domain analyses: we compute the
temperature field using a transient approach and then impose this temperature
field as a harmonic perturbation for determining the mechanical response in the
frequency domain. This unique modeling method offers lower computational
complexity and improved accuracy, and is faster than a fully transient FEA
approach. Our dynamical model computes the temperature and displacement fields
in time domain over a broad range of actuation frequencies and amplitudes. We
validate the numerical results by directly comparing them with experimentally
measured displacement amplitudes of NEMS beams around their eigenmodes in
vacuum. Our model predicts a thermal time constant of 1.9 ns in vacuum for our
particular structures, indicating that electrothermal actuation is efficient up
to ~80 MHz. We also investigate the thermal response of the actuator when
immersed in a variety of fluids