Dry electrochemical impedance spectroscopy metrology for conductive chemical layers

Patent metadata

Field	Value
Publication number	US-12433515-B2
Application number	US-202117401716-A
Country	US
Kind code	B2
Filing date	Aug 13, 2021
Priority date	Aug 13, 2021
Publication date	Oct 7, 2025
Grant date	Oct 7, 2025

Abstract

A method of testing one or more analyte sensors each comprising a first electrode; a second electrode; and a material layer disposed on or above the first electrode; the method including (a) applying a voltage potential to the first electrode with respect to the second electrode; (b) measuring a test signal comprising an output current from the first electrode that results from the application of the voltage potential; (c) using the test signal from (b) to observe an electrical characteristic of the analyte sensor; and (d) correlating the electrical characteristic a parameter associated with an electrochemical response of the analyte sensor to an analyte, wherein the testing is under dry conditions without exposure of the electrodes to a fluid containing the analyte or an in-vivo environment containing the analyte.

First claim

What is claimed is:

1. A method of testing one or more analyte sensors each comprising a first electrode; a second electrode; and a material layer disposed on or above the first electrode; the method comprising:
(a) applying a voltage potential to the first electrode with respect to the second electrode;
(b) measuring a test signal comprising an output current from the first electrode that results from the application of the voltage potential;
(c) using the test signal from (b) to determine a capacitance of the one or more analyte sensors, wherein the steps (a)-(c) are performed in an environment outside a human body without exposure of the first electrode and the second electrode to a fluid containing glucose;
(d) correlating the capacitance with a measurement of isig, wherein isig is a current associated with an electrochemical response of the one or more analyte sensors to the fluid containing the glucose, wherein the correlating comprises obtaining a plot of the isig versus the capacitance for a plurality of the one or more analyte sensors having different thicknesses of the material layer; and
(e) using the correlating to estimate a thickness of the material layer of the one or more analyte sensors during manufacturing for quality control purposes.

2. The method of claim 1 , further comprising determining the estimate of the thickness from the capacitance and comparing the estimate to one or more predetermined values.

3. The method of claim 1 , further comprising:
automatically testing the one or more analyte sensors in a batch; and
recording the capacitance for each of the one or more analyte sensors in a database so that the capacitance of each of the one or more analyte sensors can be traced and read from the database.

4. The method of claim 1 , wherein the first electrode comprises a working electrode and the second electrode comprises at least one of a reference electrode or a counter electrode.

5. The method of claim 1 , further comprising correlating the capacitance with a property of the material layer, wherein the property comprises:
a dielectric property of the material layer;
an architecture or roughness of the material layer;
a concentration of a component in a composition that forms the material layer; or a homogeneity of a composition that forms the material layer.

6. The method of claim 1 , wherein:
the material layer comprises a high density amine layer, and each of the one or more analyte sensors further comprise:
an analyte sensing layer including an enzyme having a composition that reacts with the glucose to form a byproduct, the byproduct detectably altering an electrical current at the first working electrode; and
an analyte modulating layer disposed over the analyte sensing layer, wherein the analyte modulating layer facilitates a diffusion of the glucose from an external environment to the analyte sensing layer.

7. The method of claim 6 , further comprising correlating the capacitance with a gradient of the isig as a function of a concentration level of the glucose, the gradient used to determine a calibration factor needed to measure the concentration level, and/or
a value of the isig in an absence of the glucose (an intercept).

8. The method of claim 1 , wherein the voltage potential comprises an alternating current (AC) voltage having a frequency, a magnitude between two voltages in a range of 5 volts and −5 volts, and the frequency in a range of 0.1 to 1 megahertz.

9. The method of claim 1 , wherein no ions are transferred between the first electrode and the second electrode in the steps (a)-(c) such that the capacitance is determined solely based on charge transfer within the material layer.

10. The method of claim 1 , further comprising testing the plurality of the one or more analyte sensors in a test chamber comprising the environment having a humidity and a temperature wherein an error in a measurement of the capacitance is less than 10% using the test signal.

11. The method of claim 1 , further comprising testing the plurality of the one or more analyte sensors in a test chamber comprising the environment having a humidity and a temperature such that the capacitance is greater than 25 picofarads.

12. The method of claim 1 , further comprising:
testing the plurality of the one or more analyte sensors in a test chamber comprising the environment having a humidity greater than 40% and using thermal coupling to a temperature chuck having a temperature less than 25° C.;
controlling the humidity so that the humidity varies by less than 1.5% over a period of 10 days or less and the humidity is measured using a humidity probe measuring the humidity with an accuracy of less than +/−0.5%; and
controlling the temperature so that the temperature varies by less than 0.1° C. over the period of 10 days and the temperature is measured using a temperature probe measuring the temperature with an accuracy of less than +/−0.1° C.

13. The method of claim 1 , wherein the first electrode comprises a first set of at least 40 fingers, the second electrode comprises a second set of at least 40 fingers, and the first set of fingers and the second set of fingers are interdigitated such that the capacitance is measured with a signal to noise ratio of at least 1000.

14. The method of claim 1 , further comprising:
normalizing the capacitance to obtain a normalized capacitance, so as to suppress noise contributions to the capacitance induced by any variability in the environment of the plurality of the one or more analyte sensors during the testing.

15. The method of claim 14 , further comprising:
setting a humidity target value for a humidity of the environment;
setting a temperature target value for a temperature of the environment;
obtaining a first peak fluctuation of the temperature with respect the temperature target value;
obtaining a second peak fluctuation of the humidity with respect to the humidity target value;
determining an error in the capacitance using a regression equation and fitting parameters including the first peak fluctuation and the second peak fluctuation; and
wherein the normalizing comprises subtracting the error from the capacitance to obtain the normalized capacitance.

16. The method of claim 15 , further comprising selecting a frequency of the voltage potential for which the error in the capacitance is fit by the regression equation with an R 2 regression coefficient of at least 0.99.

17. The method of claim 1 , wherein the steps (a)-(b) are performed using electrochemical impedance spectroscopy.

18. The method of claim 17 , wherein the step (c) comprises determining the capacitance using:

Capacitance
=

1

2
*
π
*
frequency
*

Z
total

wherein Z total =ΔV/ΔI, ΔV is the voltage potential, and ΔI is output current in response to the voltage potential.

19. The method of claim 1 , further comprising using the correlating to calibrate the one or more analyte sensors for measurement of the glucose.

20. A method of testing one or more analyte sensors each comprising a first electrode; a second electrode; and a material layer disposed on or above the f

Assignees

• Medtronic Minimed Inc

Inventors

• Lin Chi-En
• Srinivasan Akhil
• Probst David L
• Tsang Melissa
• Askarinya Mohsen
• Kimball Riley Clayton
• Mckinlay Robert
• Nguyen Vu
• Dong Wally
• Heng Xin
• Toshner Brennan

Classifications

• G01N27/333

  Ion-selective electrodes or membranes (glass electrodes G01N27/36) · CPC title

• G01N27/26

  by investigating electrochemical variables; by using electrolysis or electrophoresis · CPC title

• G01N27/3272 Primary

  Test elements therefor, i.e. disposable laminated substrates with electrodes, reagent and channels (optical biosensors G01N33/52) · CPC title

• G01N27/026

  Dielectric impedance spectroscopy (electrochemical impedance spectroscopy for measuring corrosion G01N17/02) · CPC title

• G01N27/3274

  Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration (coding of calibration information G01N33/48771) · CPC title