Capacitance of IDC depends on the dielectric material used in IDC. I think, capacitance is decreased with increasing frequency because at high frequency dielectric don't hold the charge so charge leakage problem comes. Please suggest me for this.
It's slightly more complicated than this, below are two references which explain the different parameters involved.
1- Optimization of planar interdigitated electrode array for bioimpedance spectroscopy restriction of the number of electrodes ( 2011 Fifth International Conference on Sensing Technology )
2- Physical and Electrical Modeling of Interdigitated Electrode Arrays for Bioimpedance Spectroscopy (January 2011, Lecture Notes in Electrical Engineering 83:169-189)
Usually any capacitor INcreases it C-value with frequency. (Foster theorem).This can be nicely visualized when you display the S11 of such a device in the Smith Chart.(there the capacitor is at 3..4 o clock=open or somewhat below depending on frequency)..at some point the capacitor passes through its first self resonance (9 o clock and becomes inductive).This is another visualisation of the well known Feynman chapter"capacitor at high frequencies" where the parallle plate capacitor becomes a pillbox cavity.Now for the interdigital C the static capacity can be calcuated by numerical or analytical means.When talking about about technical capacitors applied in electronic circuits we can neglect the dielectric material dispersion.However for biological applications things are much more complicated.(electromagntic models of the skin)
You will find that the permittivity and loss-tangent of a so-called microwave dielectric material is independent of frequency, to a good (engineering) approximation, Navneet. In other words, the said capacitance is constant, as long as the frequency is not so high that one must treat your capacitor as a distributed network.
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