Electric response of a cell of hydrogel: Role of the electrodes

We investigate the dielectric properties of hydrogel by means of the impedance spectroscopy technique. Our experimental data relevant to the frequency dependence of the real and imaginary parts of the electrical impedance of the cell indicate that, in the low frequency region ( f < 20 Hz ) , the electric response of the cell is dominated by surface effects, weakly dependent on the thickness of the sample. On the contrary, in the high frequency region ( f > 100 Hz ) , the electric response of the sample is mainly due to the bulk properties. The observed frequency dependence of the electrical impedance of the cell can be well interpreted by means of the Poisson-Nernst-Planck model taking into account the Ohmic character of the interface electrodes-hydrogel.