Discussion Forum

Hi,
I am new to COMSOL (4.2a) and have been stuck with this problem for last couple of days. Any thoughts/ help on this will be greatly appreciated.

The mph file is attached to this post. I have made a model of my device which includes 2 microfluidic capacitors. At the moment, no uFluidic physics is used. Only the dielectric is water like custom electrolyte (should eventually be corrected to PBS solution) . The electodes are made of copper. While I tried to solve this system by giving fixed voltage on the +ve terminal, it worked and comsol could solve this system to give spacial electric field.

Then, I tried to integrate the remaining circuit, by importing spice netlist. It is very simple circuit and it is shown in the diagram attached (Please note that what is shown as capacitors are actually to be taken as FEM elements- They are uFluidic capacitor seen in mph file). I changed the terminals to be driven by circuit, and as you can see in my mph file, added two I Vs U components to my circuit. These are now set to use the es voltages of terminal 1(TE1) & terminal 2(TE2). I tried with stationary study to just see how it solves for electric field between the plates when driven by an voltage source.

However it does not work giving the following error:

======================================================================
Failed to find a solution.
Segregated group 2

Singular matrix.

There are 1 void equations (empty rows in matrix) for the variable mod1.es.Q0_TE1.
at coordinates: (0,0,0), ...
There are 1 void equations (empty rows in matrix) for the variable mod1.es.Q0_TE2.
at coordinates: (0,0,0), ...
Returned solution is not converged.
========================================================================

So any thoughts about solving this problem will be helful. I was wondering if I need to use any explicit ODEs to model the capacitor, which I think should not be the case. I would think that if I have this FEM element and is driven by the voltage source, the voltage & current should be automatically simulated. Eventually I would like to add resistors between the capacitors & ground and measure the differential voltage.


Thanks in Advance,
Regards,
Santosh
PS: I have tried with sine source, but when it didn't work also tried with DC source. However the error remained.