Patent ID: 8221685

Claim:
A sensor for determining the concentration of glucose in a sample fluid, the sensor comprising: a working electrode and a counter electrode, wherein the working electrode and counter electrode are separated by an effective distance in a range of 25 to 1000 μm; a sample chamber for holding the sample fluid, the sample chamber comprising the working electrode and the counter electrode, wherein the sample chamber is sized to contain a volume of no more than about 1 μL of the sample; two indicator electrodes disposed in the sensor, wherein a first indicator electrode indicates when the sample chamber is beginning to fill with sample, and a second indicator electrode indicates when the sample chamber is substantially filled with sample, and wherein the working electrode is disposed between the first and second indicator electrodes; and a glucose-responsive enzyme and a diffusible redox mediator disposed in the sample chamber, the sensor having been configured and arranged so that a background signal generated by the diffusible redox mediator is no more than the signal generated by oxidation or reduction of 80 mg/dL of glucose.