Sensor device, a method and a sensor to determine a relative concentration of a first kind of ions with respect to a second kind of ions solute in a drop of liquid

Abstract

A method to determine a relative concentration of a first kind of ions with respect to a second kind of ions solute in a drop of a liquid comprises providing a voltage to a measurement electrode and a counter electrode, the measurement electrode being provided over a semiconductor substrate comprising a plurality of channels, the channels connecting a cavity and the measurement electrode, wherein the counter electrode is arranged to be in contact with the cavity, when the cavity, the measurement electrode and the counter electrode are arranged to accommodate the drop of a liquid and allow a voltage to be applied to the drop of liquid. The method further comprises determining a current or a change of the current flowing through the drop of liquid in response to the applied voltage; and providing an evaluation signal indicative of the relative concentration based on the determined current or the determined change of current.

What is claimed is: 
     
         1 . A method to determine a relative concentration of a first kind of ions with respect to a second kind of ions solute in a drop of a liquid, comprising:
 providing a voltage to a measurement electrode and a counter electrode, the measurement electrode being provided over a semiconductor substrate comprising a plurality of channels, the channels connecting a cavity and the measurement electrode, wherein the counter electrode is arranged to be in contact with the cavity, when the cavity, the measurement electrode and the counter electrode are arranged to accommodate the drop of a liquid and allow a voltage to be applied to the drop of liquid;   determining a current or a change of the current flowing through the drop of liquid in response to the applied voltage; and   providing an evaluation signal indicative of the relative concentration based on the determined current or the determined change of current.   
     
     
         2 . The method according to  claim 1 , wherein providing the voltage comprises providing a plurality of different voltage values, at least one of which is below an electrochemical potential of the first kind of ions, but above an electrochemical potential of the second kind of ions, and at least one of which is above the electrochemical potentials of the first kind of ions and the electrochemical potential of the second kind of ions, wherein determining the current or the change of current comprises determining a plurality of values of the current or the change of current corresponding to the plurality of different voltage values, and wherein providing the evaluation signal comprises providing the evaluation signal based on the plurality of values determined in response to the plurality of different voltage values. 
     
     
         3 . The method according to  claim 1 , further comprising applying a control potential to an electrically conductive region of the semiconductor substrate insulated from the channels, wherein the electrically conductive region is configured to apply a control potential to the drop of liquid. 
     
     
         4 . The method according to  claim 3 , wherein applying the control potential comprises applying a plurality of different control potential values to the electrically conductive region, wherein determining the current or the change of the current comprises determining a plurality of values of the current or the change of current corresponding to the plurality of different control potential values, and wherein providing the evaluation signal comprises providing the evaluation signal based on the plurality of values determined in response to the plurality of different control potential values. 
     
     
         5 . The method according to  claim 1 , wherein the first kind of ions comprises K + -ions, the second kind of ions comprises Na + -ions and the liquid comprises blood.