the coatingincreases the stiffnessof the electrode, which is useful for penetratingtissueusingneedle electrodes.Another reason is biocompatibility.Anyway, the electrode impedance will be different fromzerobecause it is a simple way to increase thetrue surface area of the electrodes and to reduce the electrode polarizationcompared to shiny platinum.

This chapter discusses the role of two different electrodes, namely, Ag-AgCl wick and chlorided metal, in measuring the electrical properties of dry bone samples. These data have been analyzed using electrode area variation technique, frequency variation technique, and variation of capacitance with inverse of the sample thickness. The chapter presents variation of mean capacitance of six samples for bovine-compact bone with its surface area and also a similar variation of the capacitance with inverse of the specimen thickness. These data were obtained using two different electrodes, namely, chloride metal and Ag-AgCl wick electrodes. The capacitance values were measured at different frequencies, and the corresponding theoretical values were calculated. The results showed that chlorided-metal electrode coupled to the sample with the help of a conducting gel, produced less electrode polarization than Ag-AgCl wick electrode. The capacitance increases linearly with the electrode area.

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