Comb drive - QuickField simulation example
Comb-drive is a MEMS device that utilize electrostatic forces acting between two electrically conductive combs connected to the voltage source.
How to find electrostatic force in MEMS comb drives?
Answer Typical applications Geometry 3D extrusion.
Given
Task
Solution
Results
* Comb drive, from Wikipedia, the free encyclopedia.
Engineering question
Set up a 3D QuickField Electrostatics problem for a MEMS comb drive structure and evaluate electrostatic force from computed field results.
MEMS comb actuators, electrostatic microdrives, micro-positioning structures
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Simulation problem
Problem Type electrostatics.
Comb thickness Lz = 40 um.
Gap between fingers d = 2.5 um.
Relative permittivity of air ε = 1,
Relative permittivity of comb ε = 10,
Potential difference ΔU = 40 V
Find the attraction force per tooth width and compare with 2D analytical solution:*
f = 0.5 · εε0 · n·Lz · U² / d,
where n is number of air gaps.
The simulation model includes only one pair of teeth (two air gaps, n=2). The Dn=0 boundary condition is applied on the plane of symmetry.
Analytical solution (force per one pair of electrodes, n=2):
f = 0.5 · 1 · 8.854e-12 · 2·40e-6 · 40² / 2.5e-6 = 2.27e-7 N.
Force f
Analytical solution
227 nN
2D plane simulation
229 nN
3D extrusion simulation
259 nN
Video
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