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## electrostatic force cause displacement in parallel plate capacitor in COMSOL

Posted Jan 23, 2013, 10:50 AM EST MEMS & Nanotechnology, MEMS & Nanotechnology, Structural Mechanics & Thermal Stresses Version 4.0 20 Replies

I have been designed a parallel-plate capacitor in COMSOL. Where one plate is connect to voltage of 10V and other one is connected to GND. and a air box is around the parallel plate capacitor.

As I know, if I applied a voltage in plate 1 then there will displace in plate one. I want to know how can I measure and plot this displacement of the plate. I have been stooped here for couple of week.

Would any one please help me in this regard.

Thank in Advance.

-Suzan

You can model the deflection by coupling Electrostatics, Solid Mechanics, and Moving Mesh interfaces. Use the Maxwell surface stress tensor for the boundary load on an electrically conducting material. I've attached an example model showing the implementation. If the deflection is very small compared to the gap, the Moving Mesh interface would not be required, as the electrostatic force would not vary significantly with the displacement.

Luke Gritter

AltaSim Technologies

Attachments:

Hope it will help me

I used Electromechanic physic..but there is some error . they need young's modulus and poission ratio of air.

As we know that air has no Young's modulus and poission ratio.

How can I overcome from this problem. Would anyone tell me.

Thanks in advance

Thanks

EMI is ES (static) and Solid together, you must add Domain nodes to distinguis "Linear Elastic Material" (without voltage solving) and "Linear Elastic Dielectric" (for solving with V i.e,.) by defining correctly the domains of solid as Linear Elastic material, you will not be asked for the Young modulus of air = linear electric material.

Note this physics module does not solve for conduction, so you need to define your GND and Terminal at the interface between solid (Linear Elastic Material), Linear Electric and/or Linear Ealstic Dielectric materials. Check carefully your doc

by the way this applies in my 4.3a version might be less rich in the previous ones

--

Good luck

Ivar

Suzan,

You can model the deflection by coupling Electrostatics, Solid Mechanics, and Moving Mesh interfaces. Use the Maxwell surface stress tensor for the boundary load on an electrically conducting material. I've attached an example model showing the implementation. If the deflection is very small compared to the gap, the Moving Mesh interface would not be required, as the electrostatic force would not vary significantly with the displacement.

Luke Gritter

AltaSim Technologies

Hello,

I'm working on COMSOL 4.0a and I'm trying to compute a piece of PDMS which is compressed between two gold plates electrostatically actuated. I add two phisics Electrostatic and Solid. The electric field is correct but I don't get any displacement. Can someone help me please. I tryed to chek on Luke's code but I can not open it. I add mine to this message.

Thanks for the help!

Dolu

EDIT:

I add the moving mesh

Attachments:

me too i have the same probleme

Attachments:

order is important, also for the physics nodes !

ALE and solid interact: you should put the ALE BEFORE=ABOVE Solid physics node in the node list, as "solid" has it's own frame representation that is equivalent to ALE and disables the ALE physics for the "solid" domain.

If you put ALE after solid you double lock the solid mesh, no good ;)

Then you calculate the forces in the ES but you have no boundary load force input in your solid. You must couple manually i.e. define the output of one and the input nodes to the other physics, and ensure the variables point to each other

--

Good luck

Ivar

I reordered the nodes but now the program tells me that there is duplicate variable names. I thought it was because I deleted physics and add other so I made a new file but it still doesn't work.

Also is the order right now? -> electrostatics with the calculus of the force -> Moving mesh with free deformation and then -> the solid node with a boundary load with the ES force computed before to applie on the solid.

Thanks for the help.

Dolu

Attachments:

thank you for your help

Thanks

the eigenfrequency analysis is not influenced by forces, at best by some initial stress in your material. In your case you have a non-linear force applying on the plates so the eigenfrequency will be influenced in a non linear way, but this is not caught by a linear eigenfrequency analysis, and I believe the frequency you look for depends on the amplitude.

That is far trickier, one way is to run a time series with enough resolution (long time to wait, and let the system damp down from an oscillatory starting point, and do an running FFT on that result)

--

Good luck

Ivar

the samples is attached just delete the step2 of analysis eigenfrquency then doying the study, then you get the deformation rapidshare.com/#!download|982p2|1449448277|3DCantileverBeam_mod.mph|6079|0|0

Unfortunately I couldn't upload the file in the forum because of the size limitation.

thank you for your help so i changed my study to : step1:stationary, step2: time dependant modal and next the study???

thank you for ur help

Thanks

You can upload larger file. see the following link:

www.comsol.com/support/knowledgebase/1098/

i'm designing a resonator with a parallel Terminal, the Gnd is elastic metal part in the middle. The idea is to move the grd up n down b/n the two electrodes/terminals (top and bottom electrode), a voltage will be applied simultaneously to the top and bottom electrode so that the Gnd in the middle deforms towards the terminal with applied voltage.

How ? Which model would you recommend me? i m working with the comsol 43b version. How can i realize the switching b/n the two terminals?

See the attachment file!

i would be very thankful for any help

Tatek

Attachments:

This link isn't working can you please send another link.

Thanks

The discussion in this thread is a bit dated and slightly incorrect. If you are interested in modeling electrostatic actuation, then we would recommend that you use the Electomechanics interface available within the MEMS Module.

If you're interested in learning about this interface, we suggest that you start with these examples:

www.comsol.com/model/biased-resonator-models-3d-11748

www.comsol.com/model/pull-in-of-an-rf-mems-switch-16379

www.comsol.com/model/electrostatically-actuated-cantilever-444

as well as the other examples within the MEMS Module:

www.comsol.com/models/mems-module

Best,

Walter

While modelling elctrostatic actuation in Electromechanics module when i choose a Hyperelastic material instead of Linear elastic dielectric, the solver shows error which reads as follows

'Failed to evaluate variable.

- Variable: mod1.emi.nTsx'.

could you please help me overcome this problem.

Thank you.

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