Hi,
I need to use COMSOL to simulate a comb drive as a resonator. I used poly-Si for the comb drive and covered it by air. I assume that I need to choose Electromechanics Physics for my model. It means that I have to apply a voltage for the comb drive and investigate the eigenfrequency, which is also the resonant frequency.
However, I got 2 problems:
1. After applying bias voltage for the comb drive, I cannot choose the boundaries to fix. It says that the boundaries I chose are not applicable.
2. When I try to compute, there has been an error saying that the mass matrix is zero. I think this may be because of the boundary problem above.
How can I fix my problem? I attach my model here for the convenience.
I am a newbie in COMSOL and I appreciate any help.
Thank you in advance.