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Question about electrostatic pressure on the conductor surface

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Dear all,

I am using MEMS --> Electrostatics (emes) application mode to find the electrostatic pressure on a conductor surface. I tried two methods to find the pressure. I expected to have the same answers but it was not. I don't know why.

Method 1:
After the emes simulation, I go to "Postprocessing"-->"Domain Plot Parameters"-->"Line/Extrusion"-->Draw the "Exterior electric Maxwell stresses tensor (Fes_nTEy_emes)". I think this is the electrostatic pressure based on the "2d comb drive" tutorial in COMSOL model library (under MEMS module).

Method 2:
I think the formula for the electrostatic pressure is: P_es = (1/2) * conductor relative permittivity * (Electric field)^2. So I manually type in the formula as (0.5) * (4.5 * 8.85 * 1e-12[F/m]) * Vy * Vy, and ask COMSOL to find the result along the same boundary. (4.5 is the relative permittivity of poly-Si, and Vy is the electric field in y-direction) This formula is based on two references. The first one is the same as the above -- the model tutorial document. The other one is the electrodynamics text book.

However, the pressure I found by using these two methods are different. Can anyone help me on this issue? Did I correctly understand the electrostatic pressure in COMSOL? Thanks.

CMS

0 Replies Last Post 16 mar 2010, 21:08 GMT-4
COMSOL Moderator

Hello CMS GP

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