IN-VIVO ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS)-BASED CALIBRATION

1 - 10 . (canceled)

11 . A method for real-time self-calibration of a glucose sensor, comprising:

performing a plurality of electrochemical impedance spectroscopy (EIS) procedures for at least one working electrode of the glucose sensor;

generating a plurality of Nyquist plots based on respective outputs of the plurality of EIS procedures;

monitoring a Nyquist plot length and a higher-frequency Nyquist slope across the plurality of Nyquist plots to detect changes in the Nyquist plot length and the higher-frequency Nyquist slope;

calibrating the glucose sensor based on the detected changes in the Nyquist plot length and in the higher-frequency Nyquist slope; and

providing a level of glucose using the calibrated glucose sensor.

12 . The method according to claim 11 , further including monitoring a value of a voltage at a counter electrode of the glucose sensor.

13 . The method according to claim 12 , further comprising:

setting a baseline Nyquist plot length; and

setting a baseline higher-frequency Nyquist slope.

14 . The method according to claim 13 , further comprising adjusting or resetting the baseline Nyquist plot length in response to a railing of the voltage value at the counter electrode.

15 . The method according to claim 11 , further comprising discarding one or more glucose values sensed by the glucose sensor in response to the monitored higher-frequency Nyquist slope becoming negative.

16 . The method according to claim 11 , further comprising discarding one or more glucose values sensed by the glucose sensor in response to the monitored Nyquist plot length increasing above a calculated threshold.

17 . The method according to claim 11 , wherein a baseline Nyquist plot length and a baseline higher-frequency Nyquist slope are set at respective values that are reflective of an EIS state at the beginning of the glucose sensor's life.

18 . The method according to claim 11 , further comprising calculating an amount of insulin to be delivered to a user of the glucose sensor based on a calculated level of glucose in the user's body.

19 . The method according to claim 11 , further comprising transmitting the provided level of glucose to an insulin delivery device.

20 . The method according to claim 19 , wherein the insulin delivery device is an insulin pump.

21 . The method according to claim 20 , wherein the glucose sensor and the insulin pump cooperate in a closed-loop system.

22 . A method for self-calibration of a glucose sensor, comprising:

performing a plurality of electrochemical impedance spectroscopy (EIS) procedures for at least one working electrode of the glucose sensor;

generating a plurality of Nyquist plots based on respective outputs of the plurality of EIS procedures;

setting a baseline Nyquist plot length;

setting a baseline higher-frequency Nyquist slope;

monitoring a Nyquist plot length and a higher-frequency Nyquist slope across the plurality of Nyquist plots to detect changes in the Nyquist plot length and the higher-frequency Nyquist slope;

adjusting a calibration factor for the glucose sensor based on the changes in the Nyquist plot length and in the higher-frequency Nyquist slope; and

providing a level of glucose using the adjusted calibration factor.

23 . The method according to claim 22 , further comprising:

monitoring a voltage value at a counter electrode of the glucose sensor; and

adjusting the baseline Nyquist plot length in response to a railing of the voltage value at the counter electrode.

24 . The method according to claim 22 , further comprising discarding one or more glucose values sensed by the glucose sensor in response to the monitored higher-frequency Nyquist slope being negative.

25 . The method according to claim 22 , further comprising discarding one or more glucose values sensed by the glucose sensor in response to the monitored Nyquist plot length increasing above a calculated threshold.

26 . The method according to claim 22 , further comprising discarding one or more glucose values sensed by the glucose sensor in response to a duration and a trend of a reduction in sensitivity of the glucose sensor as determined from the monitored Nyquist slope and the monitored Nyquist plot length.

27 . The method according to claim 22 , wherein the baseline Nyquist plot length and the baseline higher-frequency Nyquist slope are set at repetitive values that are reflective of an EIS state at the beginning of the glucose sensor's life.

28 . The method according to claim 22 , wherein each EIS procedure of the plurality of EIS procedures is performed over a range of frequencies.

29 . The method according to claim 22 , wherein adjusting the calibration factor for the glucose sensor includes obtaining an adjusted real-time calibration factor and the level of glucose is calculated in real time based on the adjusted real-time calibration factor.

30 . A glucose sensor, comprising:

at least one working electrode;

sensor electronics configured to measure an AC current signal for the at least one working electrode; and

a microcontroller configured to:

calibrate the glucose sensor in real-time by:

performing a plurality of electrochemical impedance spectroscopy (EIS) procedures for the at least one working electrode based on the AC current signal;

generating a plurality of Nyquist plots based on respective outputs of the plurality of EIS procedures;

monitoring a Nyquist plot length and a higher-frequency Nyquist slope across the plurality of Nyquist plots to detect changes in the Nyquist plot length and the higher-frequency Nyquist slope; and

calibrating the glucose sensor based on the detected changes in the Nyquist plot length and in the higher-frequency Nyquist slope; and

provide a level of glucose using the calibrated glucose sensor.