Discussion Forum

I am building a digital microfluidics model in which a water droplet is sandwiched between the two copper coplanar electrodes.
1) I have built the model by taking size of electrodes as 37.1x 37.1um^2. A layer of sio2 (1.45um thickness) is there on the top of lower electrode. Then again a layer of teflon ( 0.055um thickness) is there on the top of Sio2 layer and at the bottom of the upper electrode. Basically the droplet sandwiched between the electrodes is such that there is a teflon layer on top and bottom of it. The gap between electrodes is 20um.
I have subtracted the circle from the top and bottom electrode. Is is correct method? How do i sandwiched a droplet between the electrodes?
2) By using my method (in which i have subtracted the circle from rectangle) and then putting the material properties. I have set terminal voltage (1V) to bottom electrode and ground to the top electrode. Now theoretically, the capacitance should be the parallel combination of all the capacitance (Cdroplet, Csio2, Cteflon). When i am simulating my model in COMSOL, i am getting very different values from theoretical. Can anyone explain me how i can get the correct values of capacitance?
3) I have put my model in large circle so as to get the right value, however it is not showing it?
4) I have learned about the 'energy method' to calculate the capacitance. Can anybody explain me how i can do the simulation using this method?
I hope to get reply soon.
Thank you.