Electrochemical Characterization of Nickel Electrodes in Phosphate and Carbonate Electrolytes in View of Assessing a Medical Diagnostic Device for the Detection of Early Diabetes

In view of optimizing a multi-electrode device using proprietary technology for noninvasive assessment of eccrine sweat gland activity and thus the early detection of diabetes, we thoroughly explored the electrochemical behavior of a nickel electrode in a three-electrode set up combining a nickel counter electrode and a nickel pseudo-reference electrode in synthetic buffered phosphate and carbonate solutions in presence of chloride, lactate and urea that mimic the composition of physiological sweat. This approach provides insight into the origin of the onset of responses measured upon the application of low voltage potential with variable amplitudes to Ni electrodes on the skin. For low voltage amplitude of ca. Delta E = 0.6 V, the electrochemical reactions measured at the electrodes are those related to the oxidation of Ni leading to the formation of a passive layer, as well as the reduction of this passive layer. For voltage amplitude higher than 1 V, or current densities higher than 1 mA/cm(2), the breakdown of the passive layer becomes the main electrochemical anodic reaction, while its reduction and the electrolytic solution govern the cathode reactions. This brings explanation of the nonlinear current-voltage features measured during the clinic tests. Finally, the obtained results make possible the definition of the experimental electrochemical conditions where the Ni electrodes can be renewed.