Method for detecting defective electrodes in a micro-electrode matrix

Abstract

Method for detecting defective electrodes in a micro-electrode matrix The method for detecting defective electrodes in an electrode matrix comprises measurement of an electrochemical impedance spectrum for each of the electrodes. Modeling of the spectrum impedance relative to each electrode by means of an implicit non-integral frequency model is performed in the form of a parameter matrix. Principal components analysis of the matrix is performed to transform said parameter matrix into a final matrix containing decorrelated variables representing the parameter matrix in a new space. The distance between each electrode and a reference point is calculated. These calculated distances are compared with a preset threshold distance and the electrodes having a distance greater than the threshold distance are classified as being defective.

1 . A method for detecting defective electrodes in an electrode matrix comprising impedance measurement of each electrode, method successively comprising:
 measuring an electrochemical impedance spectrum for each of the electrodes,   modeling of the impedance spectrum relative to each electrode by means of an implicit non-integral frequency model, in the form of a parameter matrix,   performing principal components analysis of the matrix, which transforms said parameter matrix into a final matrix containing decorrelated variables representing the parameter matrix in a new space,   calculating the distance between each electrode and a reference point,   comparing the calculated distances with a preset threshold distance, and classifying the electrodes having a distance greater than the threshold distance as being defective.   
   
   
       2 . The method according to  claim 1 , wherein the distance between two electrodes is calculated by means of the Mahalanobis distance. 
   
   
       3 . The method according to  claim 1 , wherein impedance measurement is performed in a solution containing the electrode matrix, a counter-electrode and an electrolyte. 
   
   
       4 . The method according to  claim 3 , wherein the electrolyte is an oxidation-reducing couple. 
   
   
       5 . The method according to  claim 3 , wherein the electrolyte is made of hexamine ruthenium chloride (III). 
   
   
       6 . The method according to  claim 3 , wherein the counter-electrode is of Ag/AgCl type. 
   
   
       7 . The method according to  claim 3 , wherein impedance measurement of an electrode to be characterized is performed by applying a sine-wave voltage between said electrode and the counter-electrode at a plurality of frequencies. 
   
   
       8 . The method according to  claim 1 , wherein principal components analysis comprises:
 transforming the parameter matrix into an intermediate matrix constituted by a plurality of variables, the intermediate matrix being square and diagonalizable,   determining the eigenvalues associated with the intermediate matrix,   calculating the final matrix representative of the parameter matrix of in a new space defined by the eigenvalues associated with the intermediate matrix.   
   
   
       9 . The method according to  claim 8 , wherein a selection is made on some eigenvalues of the intermediate matrix representing the largest eigenvalues, leading to selection of some variables in the final matrix associated with said eigenvalues. 
   
   
       10 . The method according to  claim 8 , wherein the distribution of variables is considered as being gaussian and separable on each component. 
   
   
       11 . The method according to  claim 10 , wherein the reference point is the mass center of the electrode matrix and the distance from the electrode to the reference point corresponds to the distance of normality at the associated gaussian. 
   
   
       12 . The method according to  claim 1 , wherein the distance between the electrode and the reference point and the threshold distance are represented in graphic form to make the comparison.