Electrochemical Sensor Chip

• US 20160003760A1
• Filed: 07/07/2014
• Published: 01/07/2016
• Est. Priority Date: 07/07/2014
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Etzkorn, James
• Granted Patent: US 10,004,433 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2560/0468 Built-in electrodes
• CPC Class Codes: A61B 2562/125 characterised by the manufacture of electrodes
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/14507 specially adapted for measuring characteristics of body fluids other than blood devices for taking samples of body liquids A61B10/0045
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1477 non-invasive
• CPC Class Codes: A61B 5/6821 Eye
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: G02C 11/10 Electronic devices other than hearing aids
• CPC Class Codes: G02C 7/04 Contact lenses for the eyes disinfection or sterilisation of contact lenses A61L12/00

Abstract

An electrochemical sensor is disposed on a sensor substrate suitable for flip-chip mounting to another substrate. The electrochemical sensor can be fabricated in bulk by patterning sets of electrodes on a common substrate with vias that electrically couple each electrode to a conductive pad on the opposite side of the substrate. The substrate with electrodes thereon can then be diced and the individual electrochemical sensors can be flip-chip mounted in a body-mountable device in which the sensor can be used to obtain analyte concentrations. As a result, fabrication of the electrochemical sensor electrodes can be isolated from fabrication of the other electronics in the device, which can facilitate efficient fabrication of the sensor and allows for other electronics to be fabricated without restrictions associated with the electrode fabrication.

Claims

1. A device comprising:

a polymeric material formed to include a body-mountable surface;

a first substrate at least partially embedded within the polymeric material;

an antenna disposed on the first substrate;

an electrochemical sensor comprising;

a sensor substrate different from the first substrate, wherein the sensor substrate includes a first side and a second side opposite the first side;

a working electrode disposed on the first side of the sensor substrate;

a reference electrode disposed on the first side of the sensor substrate;

a first conductive connection pad disposed on the second side of the sensor substrate, wherein the first conductive connection pad is electrically coupled to the working electrode; and

a second conductive connection pad disposed on the second side of the sensor substrate, wherein the second conductive connection pad is electrically coupled to the reference electrode; and

a controller electrically connected to the electrochemical sensor via the first and second conductive connection pads, wherein the controller is disposed on the first substrate, and wherein the controller is configured to;

(i) apply a voltage between the working electrode and the reference electrode sufficient to generate an amperometric current related to the concentration of an analyte in a fluid to which the device is exposed;

(ii) measure the amperometric current; and

(iii) use the antenna to indicate the measured amperometric current.

2. The device of claim 1,

wherein an electrical path that couples the working electrode and the first conductive connection pad includes a first via, wherein the first via comprises conductive material that at least partially occupies a first aperture through the sensor substrate, and

wherein an electrical path that couples the reference electrode and the second conductive connection includes a second via, wherein the second via comprises conductive material that at least partially occupies a second aperture through the sensor substrate.

3. The device of claim 1, wherein the sensor substrate includes a semiconductor, and wherein the electrochemical sensor further comprises a passivation layer disposed on the first side of the sensor substrate interposed between at least a portion of the working electrode and at least a portion of the reference electrode.

4. The device of claim 3, wherein the sensor substrate includes silicon, and wherein the passivation layer includes silicon dioxide.

5. The device of claim 1, wherein the reference electrode and the working electrode each include multiple extensions arranged on the sensor substrate so as to be interdigitated with one another.

6. The device of claim 4, wherein each of the multiple extensions of the working electrode include first and second sides that are both adjacent to, and substantially equidistant from, respective ones of the multiple extensions of the reference electrode.

7. The device of claim 1, wherein the first substrate includes at least one of:

parylene, polyamine, or polyethylene terephthalate.

8. The device of claim 1, wherein the controller is electrically coupled to the electrochemical sensor via an electrical path that includes a first terminal and a second terminal each disposed on the first substrate, wherein the first terminal is electrically connected to the first conductive connection pad, and wherein the second terminal is electrically connected to the second conductive connection pad.

9. The device of claim 1, wherein the polymeric material includes a channel situated such that the fluid is conveyed through the channel to the electrodes of the electrochemical sensor.

10. The device of claim 1, wherein the working electrode is partially coated with a passivation layer such that a surface area of the working electrode that is exposed to the fluid is less than a surface area of the working electrode that is adhered to the sensor substrate.

11. The device of claim 1, wherein the polymeric material has a concave surface and a convex surface, wherein the concave surface is configured to be removably mounted over a corneal surface and the convex surface is configured to be compatible with eyelid motion when the concave surface is so mounted.

13. A method comprising:

forming, in a sensor substrate with a first side and a second side opposite the first side, a first depression and a second depression that extend into the first side, and terminate at respective distal ends within the sensor substrate;

filling the first and second depressions with a conductive material that at least partially occupies the first and second depressions between the distal ends thereof and the first side of the sensor substrate;

patterning, on the first side of the sensor substrate, a reference electrode;

patterning, on the first side of the sensor substrate, a working electrode; and

polishing the second side of the sensor substrate so as to expose the first depression and the second depression, and the conductive material occupied therein.

14. The method of claim 13, further comprising, prior to patterning the reference electrode and the working electrode, polishing the first side of the sensor substrate such that the conductive material occupying the first and second depressions is substantially planar with the first side of the sensor substrate.

15. The method of claim 14, wherein the working electrode is patterned so as to overlap a region of the first side of the sensor substrate that includes the substantially planar conductive material occupying the first depression, and wherein the reference electrode is patterned so as to overlap a region of the first side of the sensor substrate that includes the substantially planar conductive material occupying the second depression such that the working electrode and the reference electrode are electrically connected to the conductive material occupying the first depression and the second depression, respectively.

16. The method of claim 12, further comprising patterning, on the polished second side of the sensor substrate, a first conductive pad that overlaps at least a portion of the conductive material exposed in the first depression, and a second conductive pad that overlaps at least a portion of the conductive material exposed in the second depression, such that the first conductive pad and the second conductive pad are electrically connected to the working electrode and the reference electrode, respectively.

17. The method of claim 16, wherein the first conductive pad and the second conductive pad are formed such that each extends beyond a plane of the polished second surface of the sensor substrate.

18. The method of claim 12, further comprising patterning a passivation layer that coats at least a portion of the working electrode such that an exposed, electrochemically active surface area of the working electrode is less than a surface area of the working electrode that is disposed on the first side of the sensor substrate.

19. The method of claim 12, further comprising dicing the sensor substrate to thereby separate an individual flip-chip mountable electrochemical sensor from multiple substantially identical flip-chip mountable electrochemical sensors fabricated on the sensor substrate.

20. A method comprising:

applying, via controller, a voltage between a working electrode and a reference electrode of an electrochemical sensor, wherein the applied voltage is sufficient to generate an amperometric current related to the concentration of an analyte in a fluid to which the electrochemical sensor is exposed, wherein the working electrode and the reference electrode are each disposed on a first side of a sensor substrate, wherein a first conductive pad and a second conductive pad are situated on a second side of the sensor substrate opposite the first side, the first conductive pad and the second conductive pad being electrically coupled to the working electrode and the reference electrode, respectively, wherein the controller is disposed on a first substrate different from the sensor substrate, wherein the controller is electrically coupled to the working electrode and the reference electrode via the first and the second conductive pads, respectively, and wherein the first substrate is at least partially embedded in a body-mountable device;

measuring the amperometric current using the controller; and

using an antenna disposed on the first substrate of the body-mountable device to indicate the measured current.