Electrochemical biosensor analysis system

A biosensor for an analysis system, said biosensor comprising:

• a carrier layer;
• an electrode structure located on the carrier layer, the electrode structure comprising at least two electrodes;
• a test field located on the carrier layer and generally covering the electrode structure, the test field being capable of absorbing a sample liquid applied to the biosensor and containing a reagent system configured to react with the sample liquid and to produce a change of an electrical measurement variable, said measurement variable being characteristic for a desired analysis result and measurable by means of an analysis measurement employing at least two of the electrodes, the test field further comprising a sample application surface on an upper side of the test field and facing generally away from the carrier layer;
• wherein
• two electrodes of the electrode structure are provided in an interdigitated array, each electrode comprising a primary conductor and a plurality of secondary conductors branching from the primary conductor and running transversely to the direction of the primary conductor, the secondary conductors of each electrode alternately interleaving with the secondary conductors of the other electrode.

A method for analyzing a sample liquid using a biosensor analysis system, comprising:

• providing a biosensor comprising a carrier layer, an electrode structure located on the carrier layer and comprising at least two electrodes, and a test field located on the carrier layer and generally covering the electrode structure, the test field being capable of absorbing the sample liquid and containing a reagent system configured to react with the sample liquid and to produce a change of an electrical measurement variable, said measurement variable being characteristic for a desired analysis result and measurable by means of an analysis measurement employing at least two of the electrodes, the test field further comprising a sample application surface on an upper side of the test field and facing generally away from the carrier layer, the electrode structure being distributed on an effective electrode structure area which area is wettable by the sample liquid, the distribution of the electrode structure on the electrode structure area being generally homogeneous with respect to an AC resistance measurement performed on a liquid layer having a defined conductivity and layer thickness;
• providing an analysis instrument comprising an analytical measuring device configured for measuring the measurement variable while the biosensor is positioned in a measurement position and electrically connected to the measuring device, the analysis instrument further comprising an evaluation unit configured for determining the desired analysis data from the measured values of the measurement variable;
• contacting the sample application surface from above with a droplet of the sample in such a manner that it diffuses over at least a partial area of the sample application surface and causes a corresponding partial area of the effective electrode structure area to be wetted;
• performing, within a time period during which the size:
• of the wetted area does not significantly change, an analysis measurement in which the measurement variable is measured using the electrodes;
• performing, within a time period during which the size of the wetted area does not significantly change, an area compensation measurement in which an AC resistance value is measured between two electrodes of the electrode structure;
• and
• using the measured AC resistance value, when determining the analysis data, as a measure of the partial area of the effective electrode structure area wetted by the sample liquid.