Discussion Forum

Hello,

I'm modeling electric fields in a cell membrane undergoing electroporation (creation of
nano-defects, or pores under the influence of electric fields). I am using the ac/dc module in 4.3.

Basically, when electric field is applied, after the initial transients (charging of the cell's membrane
which can be modeled as a spherical capacitor), the conductivity of the cell's membrane dramatically increases
and currents start flowing into the internals of the cell.

I would like to model this phenomena using comsol.
For this I model the pore density evolution which is a property of the membrane surface of the cell.
For this purpose i use the "Boundary ODEs and DAEs (bode)" physics model, which works fantastic.

Now my question is : how can i correlate between the conductivity of the cell's membrane (which has a finite thickness,
and is modeled as two concentric circles, 2d for simplicity) , and the pore density, which is a property of the membrane's surface, i.e. the external circle only ?

Basically, I would like to be able to associate a conductivity value for each (x,y) which has to do with the point closest to the solution of pore density at (R,theta) when R corresponds to the cell's radius, and theta is the radial angle matching x and y.

I tried to solve the pore density for the membrane as a whole (as opposed to surface only), but it doesn't make physical sense, nor does the solution look reasonable, and this seems contrived. I feel there must be a more elegant way.

The way i chose to deal with it now is that i solve for the pore density on the surface, plot the data and then manually
go and update the conductivity in a few selected regions of my membrane. But this is tedious and non-systematic.


Would appreciate any advice.
Kind regards,
Lenny

p.s. I've tried spreading the pore density on the surface of the membrane radially by defining
Nradial = Ns(cell_radius*x/sqrt(x^2+y^2), cell_radius*y/sqrt(x^2+y^2))
where Ns is the surface pore density and Nradial is the "virtual" density which would later dictate the conductivity.

But Comsol complains about Ns which is unknown function or operator, which makes me wonder if it is possible at all to relate two variables in different spatial locations...

Thanks.