USE OF ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS) IN CONTINUOUS GLUCOSE MONITORING

1 . A method for real-time self-calibration of a sensor, said sensor including sensor electronics, a microcontroller, and at least one working electrode, the method comprising:

performing, by said microcontroller, an electrochemical impedance spectroscopy (EIS) procedure for said at least one working electrode to obtain values of at least one impedance-based parameter for the at least one working electrode;

periodically repeating, by said microcontroller, said EIS procedure for said working electrode to obtain additional values of said at least one impedance-based parameter;

calculating, by said microcontroller, values of at least one EIS-based parameter based on said obtained values and additional values of the at least one impedance-based parameter;

monitoring the calculated values of said at least one EIS-based parameter for variations in said calculated values; and

adjusting, by said microcontroller, a calibration factor for said sensor based on said variations in the calculated values.

2 . A method for real-time self-calibration of a sensor, said sensor including sensor electronics, a microcontroller, and at least one working electrode and one counter electrode, the method comprising:

performing, by said microcontroller, a plurality of electrochemical impedance spectroscopy (EIS) procedures for said at least one working electrode;

generating, by said microcontroller, a plurality of Nyquist plots based on respective outputs of said plurality of EIS procedures;

setting a baseline Nyquist plot length;

setting a baseline higher-frequency Nyquist slope;

monitoring, by said microcontroller, the Nyquist plot length and the higher-frequency Nyquist slope across said plurality of Nyquist plots to detect changes in said plot length and said slope; and

adjusting a calibration factor for said sensor based on said changes in the Nyquist plot length and in the Nyquist slope.

3 . A method of performing diagnostics on a subcutaneous or implanted sensor having at least one working electrode, comprising:

defining a vector containing values associated with one or more electrochemical impedance spectroscopy (EIS)-based parameters and values associated with one or more non-EIS-based parameters;

defining a respective threshold value for each of said EIS-based parameters and each of said non-EIS-based parameters;

performing a first EIS procedure to generate a first set of data for said values associated with the one or more EIS-based parameters;

after a calculated time interval, performing a second EIS procedure to generate a second set of data for said values associated with the one or more EIS-based parameters;

updating the vector with said first and second sets of data; and

monitoring said vector values to determine whether the sensor has lost sensitivity.

4 . A method for determining the age of a sensor, the method comprising:

performing an electrochemical impedance spectroscopy (EIS) procedure prior to initialization of said sensor;

generating a Nyquist plot based on the output of said EIS procedure; and

based on a lower-frequency Nyquist slope, determining whether the sensor is new.

5 . A method of differentiating between different glucose sensors, the method comprising:

performing an electrochemical impedance spectroscopy (EIS) procedure for said sensor;

generating a Nyquist plot based on the output of said EIS procedure; and

based on said Nyquist plot, identifying one or more of said different sensors.