Electrochemical FET sensor

Abstract

A sensor includes a working electrode in contact with an analyte solution; an amplifier includes: a source terminal; a drain terminal; a back gate terminal; and nanowires, each of which electrically connects the source terminal to the drain terminal; and an insulator having a first side and a second side. The working electrode is located on the first side of the insulator. The source terminal, the drain terminal, and the nanowire are located on a second side of the insulator. The insulator prevents direct electrical contact between the working electrode, the analyte solution, and the source terminal, the drain terminal, or the nanowire. The working electrode is configured such that when the chemical substance is present in the analyte solution, a change in the electric field is induced at the location of the nanowire, thereby inducing a corresponding current change between the source terminal and the drain terminal.

Description

[0001] Case information

[0002] This application is a divisional application of the invention patent application with application number 202080062414.0 filed on July 10, 2020 and invention name “Electrochemical FET Sensor”.

[0003] Priority declaration

[0004] This patent application claims priority to U.S. Provisional Application No. 62 / 873,440, filed on July 12, 2019, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0005] The disclosure relates to sensing and, more particularly, to systems and methods for detecting biological analytes in biological fluids. Background Art

[0006] Detection of a wide variety of chemical and biological analytes in aqueous or other solutions can be achieved using different established electrochemical methods including amperometry, potentiometry or impedance-based techniques.

[0007] Many commercially available three-electrode amperometric sensors include a working electrode, a counter electrode, and a reference electrode. In a typical setup, the three electrodes are in contact with or immersed in an analyte solution. The major dimension of commercially available amperometric sensors is typically about 10 mm long. In the case of amperometric techniques, a fixed voltage is applied to the reference and working electrodes, driving the redox reaction of a specific analyte and generating a detectable current between the working and counter electrodes.

[0008] Conventionally, potentiometric techniques, on the other hand, can be configured to passively measure the potential between two such electrodes without an electrochemical reaction via electrons. Thus, in potentiometric measurements, the analyte to be measured is not affected by the measurement process. Conventionally, potentiometric sensors minimally use a two-electrode arrangement comprising a working electrode and a reference electrode to measure changes in the potential of the working electrode caused by the presence of redox species in solution. Summary of the invention

[0009] This summary is a high-level overview of various aspects of the invention and introduces some of the concepts that are described in further detail in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used alone to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification, any or all of the drawings, and each claim.

[0010] Embodiments of the disclosed text relate to a sensor, comprising: a working electrode, the working electrode being configured to be positioned to contact an analyte solution; an amplifier, comprising: a source terminal; a drain terminal; and a plurality of nanowires, wherein each of the plurality of nanowires electrically connects the source terminal to the drain terminal; and an insulator, the insulator having a first side and a second side opposite the first side, wherein the working electrode is located on the first side of the insulator, wherein (a) the source terminal, (b) the drain terminal, and (c) the plurality of nanowires are located on the second side of the insulator, whereby the insulator The insulator is configured to prevent direct electrical contact between the working electrode and (a) the source terminal, (b) the drain terminal or (c) the multiple nanowires, and thereby, the insulator is configured to prevent direct contact between the analyte solution and (a) the source terminal, (b) the drain terminal or (c) the multiple nanowires, wherein the working electrode is configured so that when an electron transport medium is present in the analyte solution, an electric field change at the position of the multiple nanowires is induced, and wherein the multiple nanowires are configured so that when the electric field changes, a corresponding current change between the source terminal and the drain terminal is induced.

[0011] In one embodiment, the distance between the source terminal and the drain terminal is in the range of 10 microns to 100 microns.

[0012] In one embodiment, the thickness of the insulator ranges from 10 microns to 1 mm.

[0013] In one embodiment, each of the plurality of nanowires has a length in a range of 10 microns to 100 microns.

[0014] In one embodiment, the working electrode, field effect transistor, and insulator are in a stacked configuration.

[0015] In one embodiment, the working electrode material comprises at least one of gold, titanium, or platinum.

[0016] In one embodiment, the sensor has a 0.00005 mm 2 To 0.005mm 2 The footprint of the

[0017] In one embodiment, the working electrode has a major dimension of 1 micron to 10,000 microns.

[0018] In one embodiment, the nanowires have one of a square, rectangular, triangular, or trapezoidal cross-section.

[0019] In one embodiment, the sensor comprises 1 to 100 nanowires.

[0020] In one embodiment, the sensor further includes a hydrogel disposed on the working electrode, the hydrogel including at least one enzyme configured to interact with an analyte in the analyte solution.

[0021] In one embodiment, the enzyme comprises one of glucose oxidase, lactate oxidase, 3-hydroxybutyrate dehydrogenase, cholesterol oxidase, pyruvate oxidase, glycerol oxidase, alcohol oxidase, glutaminase oxidase, L-glutamate oxidase, xanthine oxidase, L-glutamate oxidase, choline oxidase, sarcosine oxidase and ascorbate oxidase or creatininase, creatinase, peroxidase, laccase, tyrosinase, glucose dehydrogenase, lactate dehydrogenase, alcohol dehydrogenase or glutamate dehydrogenase.

[0022] In one embodiment, the hydrogel is configured to interact with at least one of β-d-glucose, L-lactate, glutamine, cholesterol, glycerol, pyruvate, ethanol L-glutamate, choline acetylcholine, L-ascorbic acid, cortisol, creatine, creatinine, 2-hydroxybutyrate, 3-hydroxybutyrate, or acetoacetate.

[0023] In one embodiment, the electron transfer mediator is one of hydrogen peroxide, nicotinamide adenine dinucleotide (NADH), ascorbic acid, caffeine, acetaminophen, flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), or a quinone cofactor.

[0024] In one embodiment, the sensor further comprises an adhesive layer deposited on the working electrode, the adhesive layer being configured to adhere the hydrogel to the working electrode.

[0025] In one embodiment, the diameter of each nanowire is in the range of 1 to 500 nanometers.

[0026] Embodiments of the disclosure also relate to a microprobe sensing device, comprising: a plurality of microprobes, each microprobe comprising a tip configured to be inserted into an analyte solution and a sensor located at the tip, each sensor comprising: a working electrode, the working electrode configured to be positioned to contact the analyte solution; an amplifier, comprising: a source terminal; a drain terminal; and a plurality of nanowires, wherein each of the plurality of nanowires electrically connects the source terminal to the drain terminal; wherein each of the plurality of nanowires has a diameter in the range of 1 to 500 nanometers; and an insulator, the insulator having a first side and a second side opposite the first side, wherein the working electrode is located on the first side of the insulator, wherein (a) A source terminal, (b) a drain terminal, and (c) a plurality of nanowires are located on a second side of an insulator, whereby the insulator is configured to prevent direct electrical contact between the working electrode and (a) the source terminal, (b) the drain terminal, or (c) the plurality of nanowires, and whereby the insulator is configured to prevent direct contact between the analyte solution and (a) the source terminal, (b) the drain terminal, or (c) the plurality of nanowires, wherein the working electrode is configured so that when an electron transport medium is present in the analyte solution, an electric field change at the location of the plurality of nanowires is induced, and wherein the plurality of nanowires are configured so that when the electric field changes, a corresponding current change between the source terminal and the drain terminal is induced.

[0027] In one embodiment, each sensor on a plurality of microprobes shares a working electrode.

[0028] In one embodiment, the plurality of microprobes are configured to detect at least two electron transport mediators.

[0029] In one embodiment, a plurality of microprobes are positioned in parallel.

[0030] Embodiments of the disclosure also relate to a method for determining the presence of glucose in an analyte solution, the method comprising: inserting a tip of a first microprobe and a tip of a second microprobe of a sensing device into the analyte solution, each of the first and second microprobes comprising a sensor at the tip, each sensor comprising: a working electrode configured to be positioned in contact with the analyte solution; an amplifier comprising: a source terminal; a drain terminal; and a plurality of nanowires, wherein each nanowire electrically connects the source terminal to the drain terminal; and an insulator having a first side and a second side opposite the first side. , wherein the working electrode is located on a first side of an insulator, wherein (a) a source terminal, (b) a drain terminal, and (c) a plurality of nanowires are located on a second side of the insulator, whereby the insulator is configured to prevent direct electrical contact between the working electrode and (a) the source terminal, (b) the drain terminal, or (c) the plurality of nanowires, and whereby the insulator is configured to prevent direct contact between an analyte solution and (a) the source terminal, (b) the drain terminal, or (c) the plurality of nanowires, wherein the working electrode of the sensor of the first microprobe comprises a hydrogel embedded therein, wherein the hydrogel comprises Glucose oxidase; inducing a first change in a first electric field at the locations of the plurality of nanowires of the sensor of the first microprobe by: (a) the glucose oxidase reacting with glucose in the analyte solution to form hydrogen peroxide; and (b) a redox reaction of the working electrode of the sensor of the first microprobe with: (1) a redox substance present in the analyte solution, and (2) hydrogen peroxide formed by the reaction of the glucose oxidase with glucose; inducing a second change in a second electric field at the locations of the plurality of nanowires of the sensor of the second microprobe by a redox reaction of the working electrode of the sensor of the second microprobe with the redox substance present in the analyte solution; inducing a first change in a first current between a source terminal of the sensor of the first microprobe and a drain terminal of the sensor of the first microprobe, the first change in the first current corresponding to the first change in the first electric field; inducing a second change in a second current between a source terminal of the sensor of the second microprobe and a drain terminal of the sensor of the second microprobe, the second change in the second current corresponding to the second change in the second electric field; and determining the amount of glucose present in the analyte solution based on a difference between the first change in the first current and the second change in the second current.

[0031] Embodiments of the disclosed text also relate to a method for undesired detection of interfering chemicals present in an electrochemically filtered analyte solution, the method comprising: inserting a sensor located at a tip of a sensing device into the analyte solution, the sensor comprising: a working electrode, the working electrode being configured to be positioned in contact with the analyte solution; an amplifier comprising: a source terminal; a drain terminal; and a plurality of nanowires, wherein each of the plurality of nanowires electrically connects the source terminal to the drain terminal; and an insulator having a first side and a second side opposite the first side, wherein the working electrode is located on the first side of the insulator, wherein (a) the source terminal, (b) the drain terminal, and (c) the plurality of nanowires are located on the second side of the insulator, whereby the insulator The body is configured to prevent direct electrical contact between the working electrode and (a) the source terminal, (b) the drain terminal or (c) multiple nanowires, and thereby, the insulator is configured to prevent direct contact between the analyte solution and (a) the source terminal, (b) the drain terminal or (c) multiple nanowires, wherein the working electrode is configured so that when chemical substances are present in the analyte solution, an electric field change at the position of the multiple nanowires is induced, wherein the multiple nanowires are configured so that when the electric field changes, a corresponding current change between the source terminal and the drain terminal is induced, and (a) the back gate voltage; (b) the working electrode voltage; and (c) the source voltage are adjusted to minimize the change in current between the source terminal and the drain terminal caused by the presence of undesirable chemical substances.

[0032] Embodiments of the disclosed text also relate to a method for calibrating sensitivity and drift correction, the method comprising: inserting a sensor at a tip of a sensing device into an analyte solution, the sensor comprising: a working electrode, the working electrode being configured to be positioned to contact the analyte solution; an amplifier comprising: a source terminal; a drain terminal; and a plurality of nanowires, wherein each of the plurality of nanowires electrically connects the source terminal to the drain terminal; and an insulator having a first side and a second side opposite to the first side, wherein the working electrode is located on the first side of the insulator, wherein (a) the source terminal, (b) the drain terminal, and (c) the plurality of nanowires are located on the second side of the insulator, whereby the insulator is configured to prevent the working electrode from contacting (a) the source terminal, The invention relates to a sensor for a given analyte, wherein the insulator is configured to prevent direct electrical contact between the analyte solution and (a) the source terminal, (b) the drain terminal or (c) the multiple nanowires, wherein the working electrode is configured so that when a chemical substance is present in the analyte solution, an electric field change at the position of the multiple nanowires is induced, wherein the multiple nanowires are configured so that when the electric field changes, a corresponding current change between the source terminal and the drain terminal is induced, and a single point in the performance diagram of the sensor for a given analyte is identified by adjusting (a) the back gate voltage; (b) the working electrode voltage; and (c) the source voltage so that the maximum change in current between the source terminal and the drain terminal is induced by the presence of the analyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Some embodiments of the disclosure are described herein by way of example only with reference to the accompanying drawings. Now with specific reference to the accompanying drawings, details are shown by way of example, and for the purpose of illustrative discussion of embodiments of the present invention. In this regard, the description in conjunction with the accompanying drawings makes it clear to those skilled in the art how to implement embodiments of the present invention.

[0034] Figure 1 is a schematic diagram of an exemplary silicon nanowire (SiNW) field effect transistor (FET) sensor according to some embodiments of the disclosure;

[0035] Figure 2 According to some embodiments of the disclosure Figure 1 Schematic diagram of an exemplary cross-sectional shape of a nanowire of a SiNW FET sensor;

[0036] Figure 3 is a schematic diagram of a working electrode having an enzyme-containing sensing hydrogel according to some embodiments of the disclosure;

[0037] Figure 4 is a schematic diagram of a SiNW FET system used in experiments performed according to some embodiments of the disclosure;

[0038] Figure 5 is a graph of changes in current through a nanowire of a SiNW FET system in response to a redox reaction according to some embodiments of the disclosure;

[0039] Figure 6 is another schematic diagram of a SiNW FET system used in experiments performed according to some embodiments of the disclosure;

[0040] Figure 7 is a graph of changes in current through a nanowire of a SiNW FET system in response to a redox reaction according to some embodiments of the disclosure;

[0041] Figure 8 is a schematic diagram of an exemplary SiNW FET sensor according to some embodiments of the disclosure;

[0042] Fig. 9 is a schematic diagram of an exemplary SiNW FET sensor according to some embodiments of the disclosure;

[0043] Fig.10 is a graph of Isd current when an exemplary FET sensor according to some embodiments of the disclosure is introduced into a 1 mM hydrogen peroxide and 342 μM ascorbic acid solution;

[0044] Fig.11 is a graph of Isd current when an exemplary FET sensor according to some embodiments of the disclosure is introduced into a 1 mM hydrogen peroxide and 342 μM ascorbic acid solution, the sensor being tuned to tune out an ascorbic acid redox signal;

[0045] Fig.12 is a flow chart of an exemplary process for calibrating a FET sensor according to some embodiments of the disclosure;

[0046] Fig.13 is a graph of calibration response of a SiNW FET glucose sensor under in vitro conditions according to some embodiments of the disclosure;

[0047] Fig.14 is a graph showing the response of a SiNW FET sensor to phosphate buffer at different working electrode voltages according to some embodiments of the disclosure;

[0048] Fig.15 is a graph showing the response of the SiNW FET sensor to hydrogen peroxide at different working electrode voltages;

[0049] Fig.16is a schematic diagram of a multi-microprobe sensor chip according to some embodiments of the disclosure;

[0050] Fig.17 is a perspective view of a multi-microprobe sensor chip according to some embodiments of the disclosure;

[0051] Fig.18 is an enlarged view of a microprobe of a multi-microprobe sensor chip according to some embodiments of the disclosure;

[0052] Fig.19 is a schematic diagram of microprobes of a multi-microprobe sensing microchip according to some embodiments of the disclosure;

[0053] Fig. 20 is a schematic diagram of a SiNW FET sensor setup for a working electrode of a multi-microprobe sensing microchip according to some embodiments of the disclosure;

[0054] Fig.21 is a schematic diagram of a silicon-on-insulator wafer before producing a multi-microprobe sensing microchip according to some embodiments of the disclosure;

[0055] Fig. 22 is a schematic diagram of the first step of an exemplary method for producing a multi-microprobe sensor microchip according to some embodiments of the disclosure;

[0056] Fig.23 is a schematic diagram of the second step of an exemplary method for producing a multi-microprobe sensor microchip according to some embodiments of the disclosure;

[0057] Fig.24 is a schematic diagram of the third step of an exemplary method for producing a multi-microprobe sensor microchip according to some embodiments of the disclosure;

[0058] Fig.25 is a schematic diagram of the fourth step of an exemplary method for producing a multi-microprobe sensor microchip according to some embodiments of the disclosure;

[0059] Fig.26 is a schematic diagram of the fifth step of an exemplary method for producing a multi-microprobe sensor microchip according to some embodiments of the disclosure;

[0060] Fig. 27 is a schematic diagram of the sixth step of an exemplary method for producing a multi-microprobe sensor microchip according to some embodiments of the disclosure;

[0061] Fig.28 is a schematic diagram of the seventh step of an exemplary method for producing a multi-microprobe sensor microchip according to some embodiments of the disclosure;

[0062] Fig.29 is a schematic diagram of the eighth step of an exemplary method for producing a multi-microprobe sensor microchip according to some embodiments of the disclosure;

[0063] Fig.30 is a schematic diagram of the ninth step of an exemplary method for producing a multi-microprobe sensor microchip according to some embodiments of the disclosure;

[0064] Fig.31 is a schematic diagram of the tenth step of an exemplary method for producing a multi-microprobe sensor microchip according to some embodiments of the disclosure;

[0065] Fig.32 is a schematic diagram of the eleventh step in an exemplary method for producing a multi-microprobe sensor microchip according to some embodiments of the disclosure;

[0066] Fig.33 is a graph depicting current from a SiNW FET sensor versus time according to some embodiments of the disclosure;

[0067] Fig.34 is an enlarged view of a multi-microprobe sensor chip according to some embodiments of the disclosure;

[0068] Fig.35 is a schematic diagram of a microprobe sensing system according to some embodiments of the disclosure;

[0069] Fig.36 is a perspective view of a patch portion of a microprobe sensing system according to some embodiments of the disclosure. DETAILED DESCRIPTION

[0070] The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its application or use. As used throughout, ranges are used as shorthand for describing each value and all values ​​of the range. Any value of the range can be selected as the endpoint of the range. In addition, all references cited herein are incorporated herein by reference in their entirety. In the event of a conflict between the definition in the open text and the definition of the reference cited, the open text shall prevail.

[0071] It is intended that the description of the illustrative embodiments according to the principles of the present invention be read in conjunction with the accompanying drawings, which are considered to be part of the entire written description. In the description of the embodiments of the present invention disclosed herein, any reference to direction or orientation is merely for convenience of description and is not intended to limit the scope of the present invention in any way.

[0072] Relative terms such as "lower", "upper", "horizontal", "vertical", "above", "below", "up", "down", "left", "right", "top", and "bottom" and their derivatives (e.g., "horizontally", "downward", "upward", etc.) should be interpreted as referring to the direction shown in the drawings being described or discussed at the time. These relative terms are only for convenience of description and do not require that the device be constructed or operated in a particular orientation unless explicitly stated.

[0073] Terms such as “attached,” “fixed,” “connected,” “coupled,” “interconnected,” “mounted” and the like refer to a relationship wherein structures are fixed or attached to one another either directly or indirectly through intermediate structures and refer to either removable or rigid attachments or relationships unless expressly stated otherwise.

[0074] As used in the specification and claims, the singular form of "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0075] Spatial or directional terms such as "left", "right", "inner", "outer", "upper", "lower" and the like should not be considered limiting as the invention may assume various alternative orientations.

[0076] All numbers used in the specification and claims are to be understood as being modified in all instances by the term “about.” The term “about” means a range of plus or minus ten percent of the stated value.

[0077] Unless otherwise indicated, all ranges or ratios disclosed herein should be understood to include any and all sub-ranges or sub-ratios contained therein. For example, a specified range or ratio of "1 to 10" should be considered to include any and all sub-ranges between a minimum value of 1 and a maximum value of 10 (including 1 and 10); that is, all sub-ranges or sub-ratios starting with a minimum value of 1 or greater and ending with a maximum value of 10 or less, such as, but not limited to, 1 to 6.1, 3.5 to 7.8, and 5.5 to 10.

[0078] The terms "first", "second", etc. do not refer to any particular order or sequence, but rather to different conditions, properties or elements.

[0079] All documents mentioned herein are "incorporated by reference" in their entirety.

[0080] The term "at least" means "greater than or equal to." The term "not greater than" means "less than or equal to."

[0081] The term "comprising" is synonymous with "including."

[0082] As used herein, the term "BGM" refers to blood glucose monitoring.

[0083] As used herein, the term "CGM" refers to continuous glucose monitoring.

[0084] As used herein, the term “working electrode” or “WE” is also referred to as a “front gate electrode” or a “water gate electrode.” The working electrode is typically a metal (eg, gold) deposited electrode connected to a voltage source.

[0085] As used herein, the term "working electrode voltage" or "WE voltage" is the potential applied to the WE by a voltage source meter / potentiometer.

[0086] As used herein, the term "work function" or "WF" describes the energy required to transfer an electron from a solid to a vacuum point outside the solid surface. The WF presents an electrical potential that is present at a surface / interface, such as the surface / interface potential of a WE in solution. The WF is measured in electron volts, eV.

[0087] As used herein, the term “Isd” or “source-drain current” refers to a current flowing through a semiconductor transistor from a source electrode to a drain electrode of the semiconductor transistor.

[0088] As used herein, the term "back gate" or "Bg" refers to the more distant (relative to the WE or front gate) electrically biased voltage gate, which in most cases is located at the bottom (handle) of a silicon SOI (silicon on insulator) wafer. In biological and electrochemical applications, the FET Bg is electrically separated from the solution / analyte.

[0089] As used herein, the term "trans-conductance graph" refers to an electrical characteristic that relates the current through the output of a device to the voltage at the input of the device. The trans-conductance value is obtained by measuring Isd while continuously changing (sweeping) the front / back gate potential.

[0090] As used herein, the term "threshold voltage" or "Vth" of a field effect transistor (FET) refers to the minimum gate-drain voltage required to create a conductive path between the source terminal and the drain terminal.

[0091] As used herein, the term "wire" refers to any material that is conductive, ie, has the ability to pass an electrical charge through, onto, and / or into itself. In some embodiments, hollow structures defined as nanotubes may be used.

[0092] As used herein, the term "nanowire" refers to a nanoscale, elongated semiconductor wire-like structure, most often formed from a silicon precursor by etching a solid or by catalytic growth from a gas or liquid phase. For example, in some embodiments, the nanowire may be a "silicon nanowire" or "SiNW."

[0093] As used herein, the term "PB" refers to phosphate buffered saline.

[0094] As used herein, the term "glucose oxidase" or "GOX" refers to an enzyme that is an oxidoreductase that catalyzes the oxidation of glucose to hydrogen peroxide and D-glucono-delta-lactone.

[0095] As used herein, the term "lactate oxidase" or "LOX" refers to FMN (flavin mononucleotide)-dependent alpha hydroxy acid oxidase. This enzyme catalyzes the oxidation of L-lactate to pyruvate in the presence of dissolved oxygen, forming hydrogen peroxide.

[0096] As used herein, the term "interstitial fluid" or "interstitial fluid" or "ISF" refers to the solution that bathes and surrounds the cells of multicellular animals. Interstitial fluid is present in the interstitial spaces, also called tissue spaces.

[0097] As used herein, the term "field effect transistor" or "FET" refers to an electronic device that uses an electric field to control the flow of current. This is achieved by applying a voltage to the gate terminal, which in turn changes the conductivity between the drain terminal and the source terminal. FETs are also known as unipolar transistors because they involve a single carrier type of operation. There are many different types of field effect transistors. Field effect transistors generally show very high input impedance at low frequencies.

[0098] As used herein, the term "metal oxide semiconductor field effect transistor" or "MOSFET" refers to a type of field effect transistor, most commonly made by controlled oxidation of silicon. It has an insulating gate whose voltage determines the conductivity of the device.

[0099] As used herein, the term "complementary metal oxide semiconductor field effect transistor" or "CMOS-FET" refers to a typical design style using complementary and symmetrical pairs of p-type and n-type MOSFETs.

[0100] As used herein, the term "ion sensitive field effect transistor" or "ISFET" refers to a field effect transistor used to measure the concentration of ions in a solution; when the ion concentration (e.g., H+, see pH scale) changes, the current flowing through the transistor will also change accordingly. Here, the solution acts as a gate electrode. The voltage between the substrate and the oxide surface increases due to the ion sheath.

[0101] As used herein, the term "electrochemical detection" refers to an analytical method that can detect the current or potential changes resulting from redox reactions or interactions among test compounds.

[0102] As used herein, the term "oxidation-reduction reaction" or "redox reaction" refers to a chemical reaction involving the transfer of electrons between two species. Oxidation refers to the loss of electrons or increase in oxidation state of a molecule, atom or ion, and "reduction" refers to the gain of electrons or decrease in oxidation state of a molecule, atom or ion.

[0103] As used herein, the term "amperometry" or "voltammetry" when used in chemical applications refers to the detection of chemical species in solution based on an electric current or a change in an electric current. For example, amperometry is used in electrophysiology to study vesicle release events using carbon fiber electrodes.

[0104] As used herein, the term "potentiometric" when used in chemical applications refers to the detection of chemical species in solution based on changes in electrical potential.

[0105] As used herein, the term "amperometric titration" refers to a type of titration in which the equivalence point is determined by measuring the current produced by the titration reaction. Amperometry can be used to estimate the equivalence point and endpoint of a titration.

[0106] As used herein, the term "potentiometric titration" is a technique similar to direct titration of a redox reaction. This is a useful means of characterizing acids. No indicator is required; instead the potential across the analyte (usually an electrolyte solution) is measured.

[0107] As used herein, the term "nonspecific sensor" or "calibrated microneedle" describes a FET sensor with or without a hydrogel layer that does not contain an enzyme or analyte-specific membrane. The purpose of such a sensor is to detect the background (basal level) of the chemical in the analyte. Such nonspecific sensors are used to perform substructure analysis of environmental changes in tissues, such as intrinsic redox and temperature effects that are not actually measured by specific measurements recorded by different sensors.

[0108] As used herein, the phrase "chemical substance" describes atoms, molecules, molecular fragments, ions, etc., that are subjected to a chemical process or measurement. In general, a chemical substance can be defined as a collection of chemically identical molecular entities that can explore the same set of molecular energy levels on a defined time scale.

[0109] As used herein, the phrase "redox-reactive species" describes a moiety or compound that can participate in a redox or redox reaction as an oxidant or reductant and is capable of changing the oxidation number of one or more atoms of another species. This phrase is used to describe both oxidants and reductants.

[0110] As used herein, "oxidant," also interchangeably referred to as "oxidizing agent / oxidizing agent" or "oxidizing / oxidizing moiety" or "oxidizing / oxidizing species," describes a moiety, substance, or compound that is capable of increasing the oxidation number of one or more atoms of another substance. Typically, such a change involves the conversion of a proton from another substance to the oxidized moiety or compound. Exemplary oxidants suitable for detection using the sensing system include, but are not limited to, reactive oxygen species (ROS) or compounds generated by reactive oxygen species.

[0111] Reactive oxygen species include oxygen-containing molecules and / or ions in which the oxygen atom is in free radical form (having unpaired electrons) or molecules or ions that readily produce species characterized by one or more oxygen free radicals or singlet oxygen. Examples include, but are not limited to, ozone, peroxides, RO- and ROO-, where R is an organic moiety or hydrogen. In the presence of water or any other protic solvent, ROS typically produce hydrogen peroxide. Therefore, according to some embodiments of the present invention, hydrogen peroxide or any other peroxide is an exemplary oxidant.

[0112] As used herein, "reducing agent" may also be referred to interchangeably as "reducing / reducing reagent" or "reducing / reducing moiety" or "reducing / reducing substance", and describes a moiety, substance or compound that is capable of reducing the oxidation state of another substance. Typically, this change involves the transfer of a proton from the reducing agent to the other substance.

[0113] Reducing agents include, for example, moieties or substances that form stable anions upon release of one or more protons. Exemplary such agents include, for example, hydroxyl-containing agents that form stable enolate anions upon release of one or more protons. Compounds or moieties containing amine oxide groups are provided herein as examples. N-alkyl- or N,N-dialkyl-hydroxylamines (e.g., DMHA) are provided as representative examples. Any other known reducing agents may also be considered.

[0114] As used herein, "Debye length" describes the distance over which significant charge separation occurs.

[0115] As used herein, the term "hydrogel" describes a three-dimensional fiber network containing at least 20%, usually at least 50%, or at least 80% and up to about 99.99% (mass) water. A hydrogel can be considered to be a material that is mainly water, but due to a three-dimensional cross-linked solid-like network made of natural and / or synthetic polymer chains in a liquid dispersion medium, its behavior is similar to a solid or semi-solid. According to some embodiments of the present invention, a hydrogel can contain polymer chains of various lengths and chemical compositions, depending on the precursor used to prepare it. The polymer chain can be composed of monomers, oligomers, and block polymer units, which are interconnected (cross-linked) by chemical bonds (covalent bonds, hydrogen bonds, and ionic / complex / metal bonds, usually covalent bonds). Network-forming materials include small aggregated molecules, particles, or polymers that form extended elongated structures with interconnections (cross-linking) between segments. Cross-linking can be in the form of covalent bonds, coordination interactions, electrostatic interactions, hydrophobic interactions, or dipole-dipole interactions or chain entanglements between network segments. In the context of this embodiment, the polymer chain is preferably hydrophilic in nature.

[0116] According to embodiments of the present invention, the hydrogel may be of biological origin or synthetically prepared.

[0117] According to some embodiments of the present invention, the hydrogel is biocompatible and maintains the activity of the biological moiety when the biological moiety is immersed or accumulated therein, that is, the activity of the biological moiety does not change by more than 30%, or by more than 20%, or by more than 10% compared to the activity of the biological moiety in a physiological medium. The biological moiety can be a sensing moiety or an analyte.

[0118] According to this embodiment, exemplary polymers or copolymers that can be used to form hydrogels include polyacrylates, polymethacrylates, polyacrylamides, polymethacrylamides, polyvinylpyrrolidone, and copolymers of any of the foregoing. Other examples include polyethers, polyurethanes, and poly(ethylene glycol), functionalized with crosslinking groups or used in combination with compatible crosslinking agents.

[0119] Some specific non-limiting examples include: poly(2-vinylpyridine), poly(acrylic acid), poly(methacrylic acid), poly(N-isopropylacrylamide), poly(N,N'-enediacrylamide), poly(N-(N-propyl)acrylamide, poly(methacrylic acid), poly(2-hydroxyacrylamide), poly(ethylene glycol) acrylate, poly(ethylene glycol) methacrylate, and polysaccharides (e.g., dextran, alginate, agarose, etc.), and copolymers of any of the foregoing.

[0120] In some embodiments, hydrogel precursors that form such polymer chains are contemplated, including any combinations thereof.

[0121] Hydrogels are typically formed from or in the presence of difunctional or trifunctional or polyfunctional monomers, oligomers or polymers having two, three or more polymerizable groups, which are collectively referred to as hydrogel precursors or hydrogel formers. The presence of more than one polymerizable group makes such precursors crosslinkable and allows the formation of a three-dimensional network.

[0122] Exemplary crosslinkable monomers include, but are not limited to, diacrylate and triacrylate monomer families, which have two or three polymerizable functional groups, one of which can be considered as a crosslinkable functional group. Exemplary diacrylate monomers include, but are not limited to, methylene diacrylate and poly(ethylene glycol) n dimethacrylic acid (nEGDMA) families. Exemplary triacrylate monomers include, but are not limited to, trimethylolpropane triacrylate, pentaerythritol triacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, isocyanuric acid tris(2-acryloyloxyethyl) ester, ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate and glycerol triacrylate, phosphoryl tris(oxyethylene) triacrylate.

[0123] Hydrogels can take physical forms ranging from soft, brittle, and weak to hard, elastic, and tough materials. Soft hydrogels are characterized by rheological parameters, including elastic and viscoelastic parameters, while hard hydrogels are suitably characterized by tensile strength parameters, elastic, storage, and loss moduli, as these terms are known in the art.

[0124] The softness / hardness of a hydrogel is determined, inter alia, by the chemical composition of the polymer chains, the "degree of cross-linking" (the number of links between the chains), the content and composition of the aqueous medium, and the temperature.

[0125] According to some embodiments of the present invention, hydrogel can include macromolecular polymer and / or fiber element, and it is not chemically connected with main cross-linked network, but mechanically entangled and / or immersed therein with it.This macromolecular fiber element can be woven (for example, in mesh structure) or non-woven, and in some embodiments, can be used as the reinforcing material of hydrogel fiber network.The non-limiting example of this macromolecule includes polycaprolactone, gelatin, gelatin methacrylate, alginate, alginate methacrylate, chitosan, chitosan methacrylate, glycol chitosan, glycol chitosan methacrylate, hyaluronic acid (HA), HA methacrylate and other non-crosslinked natural or synthetic polymer chains etc.According to some in any embodiment of the present invention, the amount of this non-crosslinked additive is seldom, is usually no more than 100mg in 1ml hydrogel formation precursor solution.

[0126] In some embodiments, the hydrogel is porous, and in some embodiments, at least a portion of the pores in the hydrogel are nanopores, having an average volume in the nanometer range.

[0127] In some embodiments of any of the embodiments described herein, the hydrogel is covalently attached to the nanostructure surface either directly or via a linking group through covalent bonds formed between compatible reactive groups on the hydrogel and the nanostructure surface.

[0128] As used herein, the term "analyte" is also interchangeably referred to as "target analyte" or "target molecule" and includes chemical and biological substances, including small molecules and biomolecules, such as but not limited to peptides, proteins, nucleotides, oligonucleotides and polynucleotides.

[0129] In some embodiments, as described herein, the sample is a biological sample and the analyte is a biological analyte, ie, a chemical or biological substance present in a biological system (eg, a biological system of a subject), as defined herein.

[0130] In some embodiments, the term analyte may refer to explosives, narcotics, and other hazardous materials.

[0131] In some embodiments, the biological analyte is a biomarker.

[0132] As used herein, the term "biomarker" describes a chemical or biological substance that indicates the presence and / or severity of a disease or disorder in a subject. Exemplary biomarkers include small molecules (e.g., metabolites), biomolecules (e.g., antigens, hormones, receptors, and any other proteins), and polynucleotides. Any other substance that indicates the presence and / or severity of a medical condition may be considered.

[0133] As used herein, the term "affinity moiety" refers to a molecule that binds with a predetermined affinity, preferably with specificity for a marker or biomarker.

[0134] As used herein, the term "amine oxide" describes a -N(OR')(R") or -N(OR')- group, wherein R' and R" are as defined herein. Where the amine oxide is a terminal group, the term refers to the -N(OR')(R") group, as the phrase is defined above; where the amine oxide is a terminal group, the term refers to the -N(OR')- group, as the phrase is defined above.

[0135] Whenever a group, moiety or compound described herein is substituted, the substituent can be, for example, one or more of hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, heterocycloalkyl, amine, halide, sulfonate, sulfoxide, phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate, O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea, N-carbamate, O-carbamate, C-amide, N-amide, carbamimidyl, guanidine and hydrazine as defined herein.

[0136] As used herein, the term "ligand" refers to an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The binding to the metal generally involves the formal donation of one or more ligand electron pairs.

[0137] As used herein, the term "peroxide" describes a group of compounds with the structure ROOR. [1] The OO group in a peroxide is called a peroxide group or a peroxy group. In contrast to an oxide ion, the oxygen atom in a peroxide ion has an oxidation state of -1.

[0138] As used herein, the term "calomel" describes the mineral mercuric chloride with the chemical formula Hg2Cl2. Calomel is used as an interface between metallic mercury and chloride solution in a saturated calomel electrode, which is used in electrochemistry to measure pH and potential in solution. In most electrochemical measurements, it is necessary to keep one of the electrodes in the electrochemical cell at a constant potential. This so-called reference electrode allows the potential of the working electrode to be controlled.

[0139] As used herein, the term "Pt electrode" describes a platinum electrode that is used because it can readily absorb hydrogen and is an inert metal that does not participate in redox reactions during cell operation.

[0140] As used herein, the terms "halide" and "halogen" describe fluorine, chlorine, bromine, or iodine.

[0141] As used herein, the term "haloalkyl" describes an alkyl group as defined above, further substituted with one or more halides.

[0142] As used herein, the term "sulfate" describes a terminal -O-S(=O)2-OR' group, as that term is defined above, or a linking group -O-S(=O)2-O-, as such phrases are defined above, wherein R' is as defined above.

[0143] As used herein, the term "thiosulfate" describes a -O-S(=S)(=O)-OR' terminal group or a -O-S(=S)(=O)-O- linking group, as these phrases are defined above, wherein R' is as defined above.

[0144] As used herein, the term "sulfite" describes an -O-S(=O)-O-R' terminal group or an -O-S(=O)-O- group linking group, as these phrases are defined above, wherein R' is as defined above.

[0145] As used herein, the term "thiosulfite" describes an -O-S(=S)-O-R' terminal group or an -O-S(=S)-O- group linking group, as these phrases are defined above, wherein R' is as defined above.

[0146] As used herein, the term "sulfinate" describes a -S(=O)-OR' terminal group or a -S(=O)-O- group linking group, as these phrases are defined above, wherein R' is as defined above.

[0147] As used herein, the term "sulfoxide" or "sulfinyl" describes a terminal -S(=O)R' group or a -S(=O)- linking group, as these phrases are defined above, wherein R' is as defined above.

[0148] As used herein, the term "sulfonate" describes a -S(=O)2-R' terminal group or a -S(=O)2- linking group, as these phrases are defined above, wherein R' is as defined herein.

[0149] As used herein, the term "S-sulfonamide" describes a -S(=O)2-NR'R" terminal group or a -S(=O)2-NR' linking group, as these phrases are defined above, wherein R' and R" are as defined herein.

[0150] As used herein, the term "N-sulfonamide" describes a R'S(=O)2-NR" terminal group or a -S(=O)2-NR'- linking group, as these phrases are defined above, wherein R' and R" are as defined herein.

[0151] As used herein, the term "disulfide" refers to an -S-SR' terminal group or an -S-S- linking group, as these phrases are defined above, wherein R' is as defined herein.

[0152] As used herein, the term "carbonyl" or "carbonate" describes a -C(=O)-R' terminal group or a -C(=O)- linking group, as these phrases are defined above, wherein R' is as defined herein.

[0153] As used herein, the term "thiocarbonyl" as used herein describes a -C(=S)-R' terminal group or a -C(=S)- linking group, as these phrases are defined above, wherein R' is as defined herein.

[0154] As used herein, the term "oxime" describes a terminal =N-OH group or a =NO- linking group, as these phrases are defined above.

[0155] As used herein, the term "hydroxy" describes an -OH group.

[0156] As used herein, the term "alkoxy" describes both -O-alkyl and -O-cycloalkyl groups, as defined herein.

[0157] As used herein, the term "aryloxy" describes both -O-aryl and -O-heteroaryl groups, as defined herein.

[0158] As used herein, the term "thiol" describes a -SH group.

[0159] As used herein, the term "thioalkoxy" describes both -S-alkyl and -S-cycloalkyl groups, as defined herein.

[0160] As used herein, the term "thioaryloxy" describes both -S-aryl and -S-heteroaryl groups, as defined herein.

[0161] As used herein, the term "cyano" describes a -C≡N group.

[0162] As used herein, the term "isocyanate" describes a -N=C=O group.

[0163] As used herein, the term "nitro" describes a -NO2 group.

[0164] As used herein, the term "acyl halide" describes a -(C=O)R"" group, wherein R"" is a halide, as defined above.

[0165] As used herein, the term "azo" or "diazo" describes a terminal -N=NR' group or a -N=N- linking group, as these phrases are defined above, wherein R' is as defined above.

[0166] As used herein, the term "C-carboxylate" describes a -C(=O)-OR' terminal group or a -C(=O)-O- linking group, as these phrases are defined above, wherein R' is as defined herein.

[0167] As used herein, the term "O-carboxylate" describes an -OC(=O)R' terminal group or an -OC(=O)- linking group, as these phrases are defined above, wherein R' is as defined herein.

[0168] As used herein, the term "C-thiocarboxylate" describes a -C(=S)-OR' terminal group or a -C(=S)-O- linking group, as these phrases are defined above, wherein R' is as defined herein.

[0169] As used herein, the term "O-thiocarboxylate" describes a terminal -OC(=S)R' group or a -OC(=S)- linking group, as these phrases are defined above, wherein R' is as defined herein.

[0170] As used herein, the term "N-carbamate" describes an R"OC(=O)-NR'- terminal group or a -OC(=O)-NR'- linking group, as these phrases are defined above, wherein R' and R" are as defined herein.

[0171] As used herein, the term "O-carbamate" describes an -OC(=O)-NR'R" terminal group or a -OC(=O)-NR'- linking group, as these phrases are defined above, wherein R' and R" are as defined herein.

[0172] As used herein, the term "O-thiocarbamate" describes an -OC(=S)-NR'R" terminal group or a -OC(=S)-NR'- linking group, as these phrases are defined above, wherein R' and R" are as defined herein.

[0173] As used herein, the term "N-thiocarbamate" describes an R"OC(=S)NR'-terminal group or an -OC(=S)NR'-linking group, as these phrases are defined above, wherein R' and R" are as defined herein.

[0174] As used herein, the term "S-dithiocarbamate" describes a -SC(=S)-NR'R" terminal group or a -SC(=S)NR'- linking group, as these phrases are defined above, wherein R' and R" are as defined herein.

[0175] As used herein, the term "N-dithiocarbamate" describes a R"SC(=S)NR'-terminal group or a -SC(=S)NR'- linking group, as these phrases are defined above, wherein R' and R" are as defined herein.

[0176] As used herein, the term "urea", also referred to herein as a "urea group", describes a -NR'C(=O)-NR"R"' terminal group or a -NR'C(=O)-NR"- linking group, as these phrases are defined above, wherein R' and R" are as defined herein and R"' is as defined herein for R' and R".

[0177] As used herein, the term "thiourea", also referred to herein as "thiourea group", describes a -NR'-C(=S)-NR"R"' terminal group or a -NR'-C(=S)-NR"- linking group, wherein R', R" and R'" are as defined herein.

[0178] As used herein, the term "C-amide" describes a -C(=O)-NR'R" terminal group or a -C(=O)-NR'- linking group, as these phrases are defined above, wherein R' and R" are as defined herein.

[0179] As used herein, the term "N-amide" describes an R'C(=O)-NR"-terminal group or an R'C(=O)-N-linking group, as these phrases are defined above, wherein R' and R" are as defined herein.

[0180] As used herein, the term "amidino" describes an R'R"NC(=N)-terminal group or an -R'NC(=N)- linking group, as these phrases are defined above, wherein R' and R" are as defined herein.

[0181] As used herein, the term "guanidine" describes a -R'NC(=N)-NR"R"' terminal group or a -R'NC(=N)-NR"- linking group, as these phrases are defined above, wherein R', R" and R'" are as defined herein.

[0182] As used herein, the term "hydrazine" describes a -NR'-NR"R"' terminal group or a -NR'-NR"- linking group, as these phrases are defined above, wherein R', R", and R'" are as defined herein.

[0183] As used herein, the term "silyl" describes a -SiR'R"R"' terminal group or a -SiR'R"- linking group, as these phrases are defined above, wherein each of R', R", and R'" are as defined herein.

[0184] As used herein, the term "siloxy" describes a -Si(OR')R"R"' terminal group or a -Si(OR')R"- linking group, as these phrases are defined above, wherein each of R', R", and R"' are as defined herein.

[0185] As used herein, the term "silazane" describes a -Si(NR'R")R"' terminal group or a -Si(NR'R")- linking group, as these phrases are defined above, wherein each of R', R", and R"' are as defined herein.

[0186] As used herein, the term "tetraorthosilicate" describes an —O—Si(OR')(OR") (OR"') terminal group or an —O—Si(OR')(OR")— linking group, as these phrases are defined above, wherein R', R" and R'" are as defined herein.

[0187] As used herein, the term "hydrazide" describes a -C(=O)-NR'-NR"R"' terminal group or a -C(=O)-NR'-NR"- linking group, as these phrases are defined above, wherein R', R", and R'" are as defined herein.

[0188] As used herein, the term "thiohydrazide" describes a -C(=S)-NR'-NR"R"' terminal group or a -C(=S)-NR'-NR"-linking group, as these phrases are defined above, wherein R', R" and R'" are as defined herein.

[0189] As used herein, the term "methyleneamine" describes a -NR'-CH2-CH=CR"R"' terminal group or a -NR'-CH2-CH=CR"- linking group, as these phrases are defined above, wherein R', R" and R'" are as defined herein.

[0190] In some embodiments, the disclosure relates to sensing, more specifically, to methods and systems for determining the presence and / or amount of an analyte (such as, but not limited to, a biological analyte) in a sample (e.g., a biological sample) and uses thereof. It will be appreciated by those skilled in the art that the application of the disclosure is not necessarily limited to the details of the construction and arrangement of the components and / or methods set forth in the following description and / or shown in the accompanying drawings and / or examples. The disclosure can have other embodiments, or can be practiced or executed in various ways.

[0191] The present invention relates to the use of field effect transistors (FETs), wherein the electrode of the transistor gate directly serves as a working electrode. In the present invention, the use of a gate electrode as a working electrode allows the sensitivity, specificity and selectivity to be increased by applying a varying electrode potential and / or any combination thereof. Thus, the applied potential can be adjusted to match the potential of a specific redox species to be analyzed. According to some embodiments of the disclosure, the analyte-gate interaction is eliminated by isolating the gate oxide material from direct interaction with the redox species using a chemically inert passivation layer. The passivation layer can significantly reduce ionic, pH and other solution effects and prevent signal drift due to gate surface degradation. In addition, according to some embodiments of the disclosure, superior sensor sensitivity has been demonstrated by using a silicon nanowire (SiNW)-based FET in this setting. According to some embodiments of the disclosure, superior sensor sensitivity is achieved due to the high surface to volume ratio of SiNW.

[0192] Typically, commercially available sensors rely on current measurement and therefore require sufficient electrons to be collected at the working electrode to allow the current to be above the noise level. In contrast, in the present nanowire-sensitive FET setup, according to some embodiments of the disclosure, a small potential change at the working electrode produces a considerable and detectable current change in the adjacent FET, as will be described in further detail below. Therefore, according to some embodiments of the disclosure, the nanowire-sensitive FET has a miniaturized footprint compared to commercially available electrochemical sensors, allowing the FET to be placed in a compact device, such as but not limited to a microprobe or minimally invasive microprobe designed to sense arrays of metabolites and other chemicals in interstitial fluid. According to some embodiments of the disclosure, the sensitivity of such a small footprint sensor is unmatched compared to existing electrochemical sensors. Furthermore, according to some embodiments of the disclosure, another advantage of using such a small sensor is the ability to form an area less than 0.1 mm 2 , or 0.5mm 2 , or 1.0mm 2 or 2.0mm 2 The sensor array allows for parallel sensing of multiple different analytes.

[0193] In another embodiment, MOSFET-based technology can be used to replace the nanowire sensing element, with the metal gate of the MOSFET acting as the working electrode in contact with the analyte solution. In yet another embodiment, CMOSFET-based technology can be used to replace the nanowire sensing element, with the metal gate of the CMOSFET acting as the working electrode in contact with the analyte solution.

[0194] FET Sensors:

[0195] According to one aspect of some embodiments of the disclosure, a mediator-free, redox-tunable electrochemical FET amplified sensing system (FET sensing system) is provided, comprising a working electrode, an insulator, and a FET amplifier. According to an embodiment of the disclosure, the FET sensing system is configured to detect the presence and / or amount of an analyte in a sample (e.g., a biological sample).

[0196] Now referring to the accompanying drawings, Figure 1 is a schematic diagram of an adjustable potential redox-FET sensor 100 according to an exemplary embodiment of the disclosure. The FET sensor 100 includes a gate electrode used as a working electrode 102 and a FET amplifier 104, which includes a source terminal 106 connected to a drain terminal 108 through at least one nanowire 110. Figure 1As shown, the FET amplifier 104 is isolated from the working electrode 102 and the analyte solution 120 by a chemical and electrical insulator 114. As shown, the analyte solution 120 is located in a well 144 defined by well walls 143. This separation of the working electrode 102 from the FET amplifier 104 allows the working electrode 102 to be located within the analyte solution 120 in the well 144 without any contact between the FET amplifier 104 and the analyte solution 120. Physically and chemically isolating the FET amplifier 104 from the analyte solution 120 by the insulator 114, leaving only the working electrode 102 exposed to the analyte solution 120, enhances the specificity of the FET sensor 100, and at least reduces undesirable FET potential drift, which will be described in further detail below.

[0197] In some embodiments of the invention, working electrode 102 is a single working electrode connected to voltage source 124. In some embodiments of the invention, working electrode 102 comprises a noble metal, such as gold, platinum, ruthenium, rhodium, palladium, silver, osmium, iridium, or a similar noble metal that is very corrosion resistant, such as titanium, tantalum, and / or carbon.

[0198] In some embodiments of the present invention, the major dimension of the exposed working electrode 102 is about 200 microns in length. The major dimension is the longest dimension in the observation plane. For example, the major dimension of a round wire cross section is the circular diameter of the cross section. The major dimension of a rectangular cross section of an element is the length of the diagonal of the rectangle. The major dimension of a triangular cross section of an element is the length of the base of the triangle. In other embodiments, the major dimension of the working electrode 102 is 1 micron to 10,000 microns, or 100 microns to 10,000 microns, or 750 microns to 10,000 microns, or 1,500 microns to 10,000 microns, or 2,500 microns to 10,000 microns, or 5,000 microns to 10,000 microns, or 7,500 microns to 10,000 microns.

[0199] In some embodiments, the major dimension of the working electrode 102 is from 1 micron to 12,000 microns. In other embodiments, the major dimension of the working electrode 102 is from 1 micron to 10,000 microns, or from 1 micron to 7,500 microns, or from 1 micron to 5,000 microns, or from 1 micron to 2,500 microns, or from 1 micron to 1,000 microns, or from 1 micron to 500 microns, or from 1 micron to 250 microns.

[0200] In other embodiments, the major dimension of the working electrode 102 is 50 microns to about 250 microns. In other embodiments, the major dimension of the working electrode 102 is 100 microns to 750 microns, or 750 microns to 5000 microns, or 250 microns to 7000 microns, or 2500 microns to 3000 microns, or 1000 microns to 3000 microns, or 150 microns to 8000 microns.

[0201] The working electrode 102 is configured to interact with the analyte 118 in the analyte solution 120. Specifically, there is an electron transfer from the analyte 118 to the working electrode 102, which generates an electric field that is detected by the FET amplifier 104. In some embodiments of the present invention, the electron transfer is the result of a redox reaction between the working electrode 102 and the analyte 118.

[0202] In some embodiments of the present invention, a redox reaction occurs because the enzyme-containing sensing hydrogel 116 is deposited on the working electrode 102, such as Figure 3 Specifically, the sensing hydrogel 116 and the amount of enzyme in the hydrogel are selected so that upon contact with the analyte 118 in the analyte solution 120, redox molecules are generated, resulting in a shift in the working electrode potential.

[0203] As defined herein, a "hydrogel" is a three-dimensional fiber network comprising at least 20%, or at least 50%, or at least 80% and up to about 99.99% (mass) water. A hydrogel can be considered to be a material that is primarily water, but behaves like a solid or semisolid due to a three-dimensional cross-linked solid network made of natural and / or synthetic polymer chains in a liquid dispersion medium. According to some embodiments of the disclosure, a hydrogel can include polymer chains of varying lengths and chemical compositions, depending on the precursor used to prepare it. The polymer chain can be composed of monomers, oligomers, block polymer units, which are interconnected (cross-linked) by chemical bonds (covalent bonds, hydrogen bonds, and ionic / complex / metal bonds, typically covalent bonds).

[0204] Exemplary polymers or copolymers that can be used to form the sensing hydrogel 116 according to the present embodiment include polyacrylates, polyhydroxyethyl methacrylates, polymethacrylates, polyacrylamides, polymethacrylamides, polyvinyl pyrrolidone, and copolymers of any of the foregoing. Other examples include polyethers, polyurethanes, functionalized polyethylene glycols, redox hydrogels (e.g., redox hydrogels based on Os complexes), and macromonomers.

[0205] In some embodiments of the invention, the sensing hydrogel 116 is adhered to the working electrode 102 via an optional adhesive layer (not shown). Some examples of adhesive layers include, but are not limited to, polyurethane, a self-assembled monolayer, or a combination thereof.

[0206] In some embodiments of the present invention, the sensing hydrogel 116 includes at least one type of enzyme 128 that interacts with a specific corresponding analyte 118 to be sensed in the analyte solution 120. For example, in some embodiments of the present invention, the enzymes within the sensing hydrogel 116 include glucose oxidase, lactate oxidase, cholesterol oxidase, pyruvate oxidase, glycerol oxidase, alcohol oxidase, glutaminase oxidase, L-glutamate oxidase, xanthine oxidase, L-glutamate oxidase, choline oxidase, sarcosine oxidase and ascorbate oxidase or creatinase, creatinase, peroxidase, laccase, tyrosinase or 3-hydroxybutyrate dehydrogenase, glucose dehydrogenase, lactate dehydrogenase, alcohol dehydrogenase, glutamate dehydrogenase. The enzyme is selected so that the enzyme interacts with a specific analyte 118, for example, β-d-glucose, L-lactate, glutamine, cholesterol, glycerol, pyruvate, ethanol L-glutamate, choline acetylcholine, L-ascorbic acid, cortisol, creatine, creatinine, 2-hydroxybutyrate or 3-hydroxybutyrate to form an electron transport cofactor, for example, hydrogen peroxide, nicotinamide adenine dinucleotide (NADH), flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) and a quinone cofactor. The cofactor can be inorganic (e.g., iron-sulfur clusters) or organometallic, for example, heme. Therefore, in these embodiments, the formation of the electron transport cofactor produces an electrical shift in the working electrode potential, resulting in changes in the surrounding electric field that affect the FET amplifier 104. Mediators such as ferrocyanide and ferrocene, methylene blue, phenazine, methyl violet, alizarin yellow, Prussian blue, thionin, azure A and C, toluidine blue, and inorganic redox ions can be added to the sample or immobilized on the electrode surface.

[0207] In some embodiments of the present invention, additional limiting membranes may also be deposited on the working electrode 102 to provide control of the diffusion rate and / or concentration of the analyte 118. In some embodiments of the present invention, the limiting membrane is a semipermeable membrane 119, for example, perfluorosulfonic acid, cellulose acetate, polypyrrole, polyurethane, chitosan, poly(2-hydroxyethyl methacrylate), HAs / poly(diallyldimethylammonium chloride) (PDDA) and poly(styrene sulfonate) (PSS) / PDDA. These semipermeable membranes 119 may also reduce the detection of interfering substances, for example, uric acid, lactic acid, ascorbic acid, acetaminophen and oxygen.

[0208] In some embodiments of the present invention, antifouling layers (e.g., cellulose acetate biocide embedded in a copolymer matrix), polymers containing methacrylate units substituted with phosphorylcholine (PC), antimicrobial N-halamine polymers, polyurethanes containing fluoroalkyl glycols, poly(ether) grafted poly(urethanes) and plasma polymers of hexamethyldisiloxane / O2, epoxy resins, perfluorosulfonic acids, polypeptides, poly(ethylene glycol PEG), polyglycerol (PG), polysaccharides, polyoxazolines, poly(propylene sulfoxide), 2-methacryloyloxyethyl phosphorylcholine (MPC), poly(phosphates), vinyl pyrrolidone, poly(vinyl alcohol) (PVA) and zwitterionic polymers (e.g., phosphorylcholine), poly(carboxybetaine acrylamide) (pCBAA) and sulfobetaine or carboxybetaine polymers can be used to prevent clogging and damage to the analyte diffusion into the sensing hydrogel 116.

[0209] Back to Figure 1 , the FET amplifier 104 includes a source terminal 106 and a drain terminal 108 connected by at least one nanowire 110. In the vicinity of the electric field of the working electrode 102, there is a continuous current across the at least one nanowire 110 from the source terminal 106 to the drain terminal 108. However, for example, changes in the surrounding electric field caused by redox species produced by an enzymatic redox reaction of a biological analyte by an enzyme 128 contained in a sensing hydrogel 116 on top of the working electrode 102 and in contact with a semipermeable membrane 119 and an analyte 118 may cause the current flowing through the at least one nanowire 110 to increase or decrease.

[0210] In some embodiments of the present invention, a plurality of nanowires may be used. When a plurality of nanowires are employed, in some embodiments of the present invention, the nanowires are arranged in an array. For example, the nanowires may be arranged substantially parallel to each other. In some embodiments of the present invention, the FET amplifier may include from 1 nanowire to 100 nanowires, or from 1 nanowire to 90 nanowires, or from 1 nanowire to 75 nanowires, or from 1 nanowire to 60 nanowires, or from 1 nanowire to 45 nanowires, or from 1 nanowire to 25 nanowires, or from 1 nanowire to 10 nanowires, or from 1 nanowire to 5 nanowires.

[0211] In some embodiments of the present invention, the FET amplifier may include from 5 nanowires to 100 nanowires, or from 15 nanowires to 100 nanowires, or from 30 nanowires to 100 nanowires, or from 40 nanowires to 100 nanowires, or from 55 nanowires to 100 nanowires, or from 70 nanowires to 100 nanowires, or from 85 nanowires to 100 nanowires, or from 95 nanowires to 100 nanowires.

[0212] In some embodiments of the invention, the FET amplifier may include from 15 nanowires to 65 nanowires, or from 2 nanowires to 7 nanowires, or from 10 nanowires to 15 nanowires, or from 12 nanowires to 25 nanowires, or from 35 nanowires to 55 nanowires.

[0213] In some embodiments of the invention, the average diameter of the circular cross-section of at least one nanowire 110 is 1 nm to 500 nm, or 50 nm to 500 nm, or 150 nm to 500 nm, or 200 nm to 500 nm, or 250 nm to 500 nm, or 375 nm to 500 nm, or 450 nm to 500 nm.

[0214] In some embodiments, the average diameter of the circular cross-section is 1 nm to 450 nm, or 1 nm to 400 nm, or 1 nm to 300 nm, or 1 nm to 250 nm, or 1 nm to 200 nm, or 1 nm to 150 nm, or 1 nm to 100 nm, or 1 nm to 50 nm.

[0215] In some embodiments, the average diameter of the circular cross-section is from 10 nm to 50 nm, or from 150 nm to 400 nm, or from 50 nm to 300 nm, or from 100 nm to 250 nm, or from 200 nm to 250 nm, or from 100 nm to 150 nm, or from 400 nm to 450 nm, or from 350 nm to 450 nm.

[0216] In some embodiments of the present invention, at least one nanowire 110 may have a non-circular cross-section. For example, the cross-section of at least one nanowire 110 may have any arbitrary shape, including but not limited to circular, square, rectangular, elliptical, and tubular. In some embodiments of the present invention, at least one nanowire 110 may have a cross-section of a regular or irregular shape. Figure 2 Some exemplary cross-sections of at least one nanowire 110 according to embodiments of the disclosure are depicted. For example, the nanowire may include, but is not limited to, an ellipse 111, a semi-ellipse 113, a rectangle 115, a hexagon 117, or a trapezoid 119.

[0217] In some embodiments of the invention, the non-circular cross-section of at least one nanowire 110 has a major dimension of 5 nm to 1000 nm, or 25 nm to 1000 nm, or 50 nm to 1000 nm, or 75 nm to 1000 nm, or 100 nm to 1000 nm, or 150 nm to 1000 nm, or 200 nm to 1000 nm, or 300 nm to 1000 nm, or 500 nm to 1000 nm, or 700 nm to 1000 nm, or 800 nm to 1000 nm, or 900 nm to 1000 nm.

[0218] In some embodiments, the non-circular major dimension of at least one nanowire 110 is from 5 nm to 900 nm, or from 5 nm to 800 nm, or from 5 nm to 700 nm, or from 5 nm to 600 nm, or from 5 nm to 500 nm, or from 5 nm to 400 nm, or from 5 nm to 300 nm, or from 5 nm to 200 nm, or from 5 nm to 150 nm, or from 5 nm to 100 nm, or from 5 nm to 50 nm, or from 5 nm to 25 nm, or from 5 nm to 10 nm.

[0219] In some embodiments, the non-circular major dimension of at least one nanowire 110 is from 10 nm to 100 nm, or from 25 nm to 75 nm, or from 250 nm to 750 nm, or from 300 nm to 500 nm, or from 100 nm to 400 nm, or from 50 nm to 150 nm.

[0220] In some embodiments of the invention, at least one nanowire 110 has a length in the range of 1 micron to 500 microns. As defined herein, length is the dimension of at least one nanowire extending from a first end connected to source terminal 106 to a second end connected to drain terminal 108. In some embodiments of the invention, at least one nanowire 110 has a length in the range of 10 microns to 500 microns, or 50 microns to 500 microns, or 100 microns to 500 microns, or 150 microns to 500 microns, or 200 microns to 500 microns, or 250 microns to 500 microns, or 300 microns to 500 microns, or 400 microns to 500 microns.

[0221] In some embodiments of the invention, the length of at least one nanowire 110 ranges from 1 micron to 400 microns, or from 1 micron to 300 microns, or from 1 micron to 250 microns, or from 1 micron to 200 microns, or from 1 micron to 100 microns, or from 1 micron to 50 microns, or from 1 micron to 25 microns, or from 1 micron to 10 microns.

[0222] In some embodiments of the invention, the length of at least one nanowire 110 ranges from 10 microns to 50 microns, or from 50 microns to 150 microns, or from 25 microns to 100 microns, or from 300 microns to 400 microns, or from 75 microns to 200 microns, or from 5 microns to 75 microns.

[0223] To increase the electric field sensitivity, in some embodiments of the disclosure, the FET amplifier 104 includes a silicon nanowire (SiNW). In some embodiments of the disclosure, due to its significantly high surface area to volume ratio, the SiNW responds to small changes in the surrounding electric field. For example, assuming a semi-cylindrical nanowire, where the flat portion of the nanowire is in contact with the substrate, the semi-cylinder radius R is 50 nanometers (nm), and the nanowire length L is 10 microns, i.e., 10,000 nanometers. The volume of the semi-cylindrical nanowire is V=Pi / 2*R 2 *L, the surface area of ​​the semi-cylinder is S = 2*Pi / 2*R*L, the ratio of surface area to volume is (surface area / volume) = 2 / R = 1 / 25 = 0.04nm -1 .

[0224] In another example, assume that the nanowire has a square cross-section, where the side length SL of the square is 50 nanometers and the nanowire length L is 10 micrometers, or 10,000 nm. The volume of the nanowire is V = SL 2 *L, the surface area of ​​the nanowire that is not in contact with the substrate (i.e., the three faces of the rectangular element) is S = 3*SL*L. The ratio of surface area to volume is (surface area / volume) = 3 / SL = 3 / 50 = 0.06 nm -1 .

[0225] In one embodiment, the surface area to volume ratio (surface area / volume) is less than 1.000 nm -1 , or less than 0.800nm -1 , or less than 0.500nm -1 , or less than 0.250nm -1 , or less than 0.100nm -1 , or less than 0.080nm -1 , or less than 0.040nm -1 , or less than 0.020nm -1 , or less than 0.010nm -1 , or less than 0.005nm -1 , or less than 0.003nm -1 , or less than 0.002nm -1 Therefore, the change in source-drain current (Isd) occurs with minimal losses, providing excellent sensor sensitivity.

[0226] In some embodiments of the present invention, at least one nanowire 110 may be suspended above the substrate, such as Figure 2 shown.

[0227] In some embodiments of the present invention, unlike typical FET sensors, at least one nanowire 110 of the current FET sensor 100 is not in contact with the analyte 118, which will be described in further detail below, providing many performance advantages and flexibility in system design. In some embodiments of the present invention, the surface of at least one nanowire 110 is chemically passivated. In some embodiments of the present invention, the surface of at least one nanowire 110 is chemically passivated and reduces the electrical noise generated by the analyte solution 120. In other embodiments, at least one nanowire is encapsulated. In other embodiments, at least one nanowire is encapsulated and electrically and chemically isolated and protected from the environment or solution. In other embodiments, at least one nanowire 110 is encapsulated with a coating of a metal oxide, a polymer and / or other insulator. In some embodiments, the encapsulation of at least one nanowire 110 results in the separation of the signal of the working electrode 102 and the bypass signal that may be generated due to direct contact of the analyte 118 with the at least one nanowire 110 and the chemical modification of the sensitive surface of at least one nanowire 110. Furthermore, since at least one nanowire 110 is packaged in a stacked configuration, the working electrode 120 can be placed on top of the at least one nanowire 110, allowing for a reduction in the form factor, such as Fig. 9 shown and described below.

[0228] In one embodiment, encapsulation is achieved by covering at least one nanowire with an insulator. In one embodiment, at least one covered nanowire is embedded in an insulator.

[0229] like Figure 1 As shown, in some embodiments of the present invention, the FET sensor 100 also includes a back gate electrode 126, which allows the voltage applied to the working electrode 102 to be adjusted. In this embodiment, the back gate electrode 126 is a silicon-based electrode. Figure 1 As shown, the back gate electrode 126 is separated from the FET amplifier 104 by a dielectric oxide layer 130, which is located below and provides support for the FET amplifier 104. The selectivity of the FET sensor 104 can be adjusted using the back gate electrode 126 to specifically sense different redox species by applying different voltage settings to the working electrode 102. In addition, the physical and chemical isolation of the back gate electrode 126 from the analyte solution 120 by the dielectric oxide layer 130 further enhances the specificity of the FET sensor 100 and eliminates undesirable redox potential drift.

[0230] In some embodiments of the present invention, Figure 4-Figure 7The general mechanism of action of the FET sensor 100 is depicted. Specifically, the interaction of the redox species with the disclosed device forms a specific work function (WF) in eV relative to the working electrode 102. This leads to one of three possible results, depending on the initial potential bias of the working electrode. When the WF and the applied working electrode potential are equal The first possible outcome occurs when . Here, the overall potential does not change, resulting in no change in the adjacent FET Isd.

[0231] When WF is higher than the applied working electrode potential The second possible result occurs when . In this case, the total potential will increase, resulting in a decrease in Isd of the P-type semiconductor and an increase in Isd of the N-type semiconductor. Figure 4-Figure 5 A second case is depicted, where Isd is reduced in the P-type semiconductor, i.e., at least one nanowire 110. In this configuration, analyte A causes positive polarization of the working electrode, resulting in a depletion of free charge carriers (+) at the adjacent P-type silicon nanowire 110, thereby reducing the current flowing through the drain terminal 108. Figure 5 This reduction in current is shown in the graph of .

[0232] At WF below the applied working electrode potential A third possible outcome occurs when . In this case, the total potential will represent the difference between the working electrode 102 and the WF, resulting in an increase in Isd in the P-type semiconductor and a decrease in Isd in the N-type semiconductor. Figure 6-Figure 7 A third case is depicted, where Isd increases in the P-type semiconductor, i.e., silicon nanowire 110. In this configuration, analyte B causes negative polarization of the working electrode 102, resulting in accumulation of free charge carriers (+) at the adjacent silicon nanowire 110, thereby increasing the current flowing through the drain terminal 108. Figure 7 This increase in current is shown in the graph of .

[0233] As previously described, the disclosed FET sensor 100 arrangement has superior sensor sensitivity, in part due to the use of silicon nanowires. While commercially available sensors rely on current measurements, in which a sufficient number of electrons need to be collected at the working electrode to provide a current signal above the electrical noise level. In addition, commercially available sensors typically require at least two electrodes to be in contact with the analyte solution, which results in increased electrical noise and also increases the size of the sensor. For example, a typical commercially available sensor is about 10 mm in length. In contrast, in the silicon nanowire sensitive FET sensor 100, a small potential change at the working electrode 102 produces a considerable current rise in the adjacent FET amplifier 104. Due to this increased current rise, in some embodiments of the present invention, the FET sensor 100 can have a current rise of approximately 0.0025 mm compared to current-type sensors. 2 (0.05 x 0.05 mm). In other embodiments, the FET sensor 100 has a miniaturized footprint of 0.00005 mm 2 To 0.005mm 2 , or 0.00006mm 2 To 0.005mm 2 , or 0.0001mm 2 To 0.005mm 2 , or 0.0005mm 2 To 0.005mm 2 , or 0.001mm 2 To 0.005mm 2 Small footprint.

[0234] In other embodiments, the FET sensor 100 may have a 0.00005 mm 2 To 0.001mm 2 , or 0.00005mm 2 To 0.0005mm 2 , or 0.00005mm 2 To 0.0001mm 2 , or 0.00005mm 2 To 0.00006mm 2 Small footprint.

[0235] In other embodiments, the FET sensor 100 may have a range of 0.0001 to 0.001 mm 2 , or 0.0025 to 0.0005 mm 2 , or 0.0006 to 0.001 mm 2 Small footprint.

[0236] In some embodiments, the miniaturized major length of the FET sensor 100 is about 0.2 mm. In other embodiments, the miniaturized major length of the FET sensor 100 is 0.1 mm to 1.5 mm, or 0.1 mm to 1.3 mm, or 0.1 mm to 1.1 mm, or 0.1 mm to 0.9 mm, or 0.1 mm to 0.7 mm, or 0.1 mm to 0.5 mm, or 0.1 mm to 0.3 mm.

[0237] In some embodiments, the FET sensor 100 has a miniaturized primary length of 0.3 mm to 1.5 mm, or 0.5 mm to 1.5 mm, or 0.7 mm to 1.5 mm, or 0.9 mm to 1.5 mm, or 1.1 mm to 1.5 mm, or 1.3 mm to 1.5 mm.

[0238] In other embodiments, the FET sensor 100 has a miniaturized major length of 0.3 mm to 1.1 mm, or 0.7 mm to 0.9 mm, or 0.9 mm to 1.3 mm, or 0.5 mm to 1.1 mm, or 0.3 mm to 0.5 mm, or 0.5 mm to 1.1 mm, or 0.7 mm to 1.3 mm. The major length of the FET sensor 100 allows the FET sensor 100 to be placed in a compact device, for example, a microprobe or minimally invasive microprobe designed to sense a variety of different metabolites and other chemicals in interstitial fluid. Figure 8 The miniaturized size of the current FET sensor 100 can be seen in FIG.

[0239] Fig. 9 A compact layered design of an adjustable potential redox-FET sensor 200 in some embodiments of the present invention is depicted, which has a reduced form factor due to the covering of at least one nanowire 210 with a chemical and electrical insulator 214. In this embodiment, at least one silicon nanowire (SiNW) 210 is connected to a source terminal and a drain terminal to form a FET amplifier 204, similar to the FET amplifier 104. However, in this embodiment, the FET amplifier 204, the working electrode 202, and the chemical and electrical insulator 214 are in a stacked configuration. Specifically, the working electrode 202 is stacked on the insulator 214, and the insulator is stacked on the FET amplifier 204. The insulator 214 separates the FET amplifier 204 from the working electrode 202 and the analyte solution 220 in the well 244. As shown in the figure, the well is defined by a polymer well wall 243. In addition, as shown in the figure, Fig. 9 As shown, in this embodiment, the FET sensor 200, back gate electrode 226 and dielectric oxide layer 230 are located below the FET amplifier 204, providing a more compact sensor design and form factor reduction.

[0240] Calibration of FET Sensors

[0241] One purpose of the calibration process in the present invention is to identify a voltage value or voltage value range within which the performance of the working electrode will be robust and sensitive enough. In some cases, the calibration process also identifies a voltage value or voltage value range of the back gate electrode that will support this performance level of the working electrode.

[0242] In some embodiments of the present invention, a calibration process may be required for various reasons. For example, in some cases where multiple FET sensors are used, there may be differences between devices from different manufacturing batches. In addition, there may be differences in sensor performance within the same production batch. In other cases, calibration may be required when multiple sensors are used, and the performance curves of these sensors have similar shapes but may be offset in some way. In addition, in some cases, sensor performance may drift due to natural material degradation or environmental or external factors, which can be addressed by calibration.

[0243] In one aspect of the invention, robust sensor performance results in a sensor that can repeatedly and consistently identify a target analyte and is insensitive to other materials and noise. In another aspect of the invention, the calibration process is based on identifying a single point in the sensor performance graph for a given analyte. The single point can be a voltage value or a small voltage range where the sensor response (i.e., change in Isd current) to a particular analyte is minimized or becomes insignificant.

[0244] In some embodiments of the present invention, as the voltage level increases or decreases from the voltage value at a single point, the sensitivity of the sensor to a specific analyte will increase. In one example, a single point can be identified as a peak or valley in a response curve graph. The response is highly sensitive to both sides of the peak or valley. This can be seen, for example, from an analysis of the first-order derivative of the response curve graph. In a peak or valley, the value of the first-order derivative is zero. On both sides of the peak or valley, the absolute value of the first-order derivative is greater than zero. In other words, the response of the sensor is enhanced. Therefore, for high sensitivity, the working electrode voltage will preferably be set at a value equal to the single point voltage + / - offset voltage level.

[0245] In an exemplary embodiment, the calibration process includes two modes. A "coarse calibration mode" in which the identification of a single point voltage is achieved by changing the back gate voltage for a given working electrode voltage; and a "fine calibration mode" in which the identification of a single point voltage is achieved by changing the working electrode voltage for a given fixed back gate voltage. However, there may be interactions between the two modes, so the order of the calibration modes is important. For a given fixed back gate voltage, the single point voltage should be finally determined by the fine tuning mode.

[0246] Once a single point potential is determined, an offset voltage is applied to the back gate voltage and the working electrode voltage. The offset voltage level and direction are also analyte specific and are determined empirically through experimentation. For example, in one embodiment of the present invention, in the case of hydrogen peroxide sensing, a typical working electrode offset is about + / -0.2 to 0.5 v and a typical back gate offset is about + / -0.5 to 1 v. These offsets will provide robustness and sensitivity to the sensor performance, i.e., a consistently high response to the desired analyte.

[0247] In some embodiments of the present invention, Figure 10-11 Examples are provided of how appropriate tuning of the sensor provides filtering of possible interfering substances or chemicals so that only substances of interest are detected in the analyte solution. Specifically, in one example, Figure 10-11 It is shown how to prevent interference with ascorbic acid redox. Fig.10 and Fig.11 The meta-figure shows the Isd current recorded for the same device when 1 mM hydrogen peroxide and 342 μM ascorbic acid solution were introduced. However, the back gate voltage (VBg) and working electrode voltage (VWE) were different. Fig.10 In the experiment, VBg = -1 V, VWE = -0.2. Using these settings, the presence of hydrogen peroxide resulted in an increase in the current level, while the sensor's response to ascorbic acid was reduced.

[0248] Fig.12 Flowchart of an exemplary calibration process in some embodiments of the present invention. In Mode I (coarse backgate calibration mode), the backgate voltage is changed while the working electrode voltage remains unchanged. At each backgate voltage setting, the response is checked until a single point is identified. The backgate working voltage is then set to equal the voltage level of the identified single point + / - the voltage level of the voltage offset. Once the coarse backgate calibration is completed, the fine tuning calibration of the working electrode voltage can be started.

[0249] Through the horizontal dotted line Fig.12 In Mode II, separate from Mode I, a fine-tuning calibration of the working electrode is performed by varying the working electrode voltage while the back gate voltage is held constant. At each working electrode voltage setting, the response is analyzed until a single point is identified. The working electrode voltage is then set to a voltage level equal to the voltage level at which the single point was identified + / - a voltage offset.

[0250] In some cases, a partial calibration (including only the working electrode fine-tune calibration) may be sufficient. For example, if the sensor has been calibrated in the past and should be calibrated regularly, if there is an operational motivation to verify the performance of a working sensor, or if there is a concern about functional degradation of the sensor components. A backgate coarse calibration can be applied mainly to new sensors or in cases where the working electrode fine-tune calibration procedure cannot identify a single point.

[0251] Fig.13 Depicted is a graph of the calibration response of a glucose sensor under in vitro conditions for different glucose concentrations (in phosphate buffer) in some embodiments of the present invention. It can be seen that the glucose concentration log 2 The graph is linear, with the current increasing as the concentration increases, indicating that the sensor signal is normalized.

[0252] Fig.14 1 shows a graph of current (Isd) versus working electrode voltage (WE) as the working electrode voltage is swept over a range of -0.7 V to 0.7 V in some embodiments of the invention. Each trace represents the current level recorded repeatedly by the same sensor unit as described above. Fig.14 In the sample shown, the current was recorded when the sensor was exposed to phosphate buffer (PB), so that no redox reaction occurred at the working electrode. Fig.14 The current curve shown follows a relatively smooth curve. In a similar experiment, the current was recorded when the same sensor was exposed to a 1 mM hydrogen peroxide solution, causing a redox reaction. As a result, a change in the measured current was induced. It can be seen that there is an inflection point at an equilibrium voltage of approximately -0.2V, a maximum current rise response at approximately 0.05V, and a maximum current rise response at approximately -0.45V. As a result, this voltage scan can identify -0.2V as an inflection point, which is a voltage setting that reduces (e.g., tunes out) the response of the sensor to hydrogen peroxide. These findings correlate well with the exemplary discrete fixed voltage experiments, whose results are shown in Figure 2. Fig.15 shown.

[0253] As can be seen from the figure, three different states can be observed when the analyte switches between PB and hydrogen peroxide at different WE potentials. As can be seen from the figure, at a WE voltage of -0.2 V, the net change in Isd in response to the introduction of hydrogen peroxide is negligible, which correlates with the inflection point observed in the voltage sweep experiment ( Fig.15 ). At WE voltages of approximately 0-0.1 V, there is a visible net Isd current rise in response to hydrogen peroxide, which is consistent with Fig.15The maximum current rise response is related to that seen at 0.05 V in Figure 1. At WE voltages of approximately -0.3 V to -0.4 V, there is a net Isd current decrease in response to hydrogen peroxide.

[0254] Multi-microprobe sensor chip

[0255] Figure 16-Figure 20 A multi-microprobe sensor chip 132 according to an exemplary embodiment of the disclosure is depicted. Figure 16-Figure 19 As shown, the sensor chip 132 includes at least one sensor microprobe 136 extending outward from the bridge portion 134 of the sensor chip 132. At least one sensor microprobe 136 has a body 140 that connects the tip of the microprobe 142 to the bridge portion 134. The tip 142 of the microprobe can have any shape, including but not limited to conical, cylindrical, tubular and pyramidal. In one embodiment, the tip 142 of at least one microprobe 136 is sharp so that a minimally invasive skin penetration microprobe will be formed. In some embodiments of the present invention, at least one microprobe 136 is straight, but non-straight shapes (e.g., curved microprobes, hooked microprobes or semi-hooked microprobes) can also be considered. At least one microprobe 136 can extend vertically from the bridge portion 134 of the microprobe array. In some embodiments of the present invention, at least one microprobe 136 has a base 138 attached to the bridge portion 134 of the sensor chip 132 or integrated with the bridge portion of the sensor chip, wherein the body 140 extends away from the bridge portion 134 of the sensor chip 132. The tip 142 is distal to the body 140 , which is distal to the base 138 .

[0256] In some embodiments of the present invention, at least one microprobe 136 is hollow or has a well 144 embedded therein and includes at least one opening for allowing the at least one microprobe 136 to exchange fluid with a medium external to the at least one microprobe 136 . Fig. 20 is an enlarged schematic diagram showing a portion of a sensing microprobe 136 having a well 144 at its distal portion. In another embodiment of a distal well structure, the FET sensing element can be located in another environment / compartment, for example, embedded in a dielectric material that allows sensing of the WE potential as a result of analyte redox activity at the well portion of the sensor.

[0257] The term "well" as used herein refers to a fluid compartment having a circular, rectangular or elliptical opening in cross section in some embodiments. In some embodiments, the opening is elliptical and its major dimension is less than 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.9 mm, 1.1 mm, 1.3 mm or 1.5 mm. In some embodiments, the minor dimension of the elliptical opening is less than 90%, 80%, 70%, 60%, 50%, 40%, 30% or 20% of the major dimension.

[0258] In some embodiments, the opening is substantially rectangular and has a major dimension less than 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.9 mm, 1.1 mm, 1.3 mm, or 1.5 mm. In some embodiments, the minor dimension of the substantially rectangular opening is less than 90%, or 80%, or 70%, or 60%, or 50%, or 40%, or 30%, or 20% of the major dimension.

[0259] In some embodiments of the invention, at least one microprobe has an opening at the tip. In some embodiments of the invention, at least one microprobe or a portion thereof can be porous. Alternatively, at least one microprobe can be nonporous, with only one or several openings formed in its body. In some embodiments of the invention, at least one microprobe comprises a non-degradable material.

[0260] In some embodiments of the present invention, the diameter of at least one microprobe is selected to leave a residual hole less than about 1 μm (after the microprobe is inserted and removed), thereby avoiding the formation of holes that allow bacteria to enter the penetration wound. In some embodiments of the present invention, the length of the penetration portion is selected to allow the penetration portion to penetrate the skin, for example, beyond the stratum corneum. In some embodiments of the present invention, the length of the penetration portion is selected to position the tip in the viable epidermis, rather than in the dermis. In an exemplary embodiment, the length of the penetration portion is 0.05mm to 1mm, or 0.05mm to 0.8mm, or 0.05mm to 0.75mm, or 0.05mm to 0.6mm, or 0.05mm to 0.5mm, or 0.05mm to 0.4mm, or 0.05mm to 0.3mm, or 0.05mm to 0.25mm, or 0.05mm to 0.15mm.

[0261] In some embodiments of the invention, the length of the penetrating portion is 0.05 mm to 1 mm, or 0.15 mm to 1 mm, or 0.2 mm to 1 mm, or 0.35 mm to 1 mm, or 0.45 mm to 1 mm, or 0.5 mm to 1 mm, or 0.75 mm to 1 mm, or 0.85 mm to 1 mm, or 0.9 mm to 1 mm.

[0262] In some embodiments of the invention, the length of the penetration portion is 0.35 mm to 0.75 mm, or 0.55 mm to 0.65 mm, or 0.75 mm to 0.95 mm. In other embodiments, the length of the penetration portion is less than 1 mm, or less than 2 mm, or less than 3 mm, or less than 4 mm, or less than 5 mm.

[0263] Sensor chips can be made of a variety of materials, including but not limited to metals, ceramics, semiconductors, organics, polymers, and composites.

[0264] In some embodiments of the present invention, the microprobe array includes microprobes of various lengths, base portion materials, body portion diameters (ie, gauges), tip portion shapes, spacing between microprobes, coatings, and the like.

[0265] In some embodiments of the present invention, each microprobe 136 includes a FET sensor 100 located at, but not limited to, a distal portion of the microprobe 136 . Fig. 20 An enlarged schematic diagram of a FET sensor 100 located on at least one microprobe 136 according to some embodiments of the present invention is shown. As shown, each microprobe 136 includes a working electrode 102 located at a well 144 so as to contact the analyte solution 120 collected therein when the microprobe 136 is immersed in the analyte. The working electrode 102 includes a trace 137 that extends at least a portion of the length of at least one microprobe 136 to the main portion 134 of the sensor chip 132. In some embodiments, the working electrode 102 and the trace 137 are formed of the same material. In some embodiments, a portion of the working electrode 102 and / or the trace 137 can be covered or encapsulated. As shown in FIG. Fig. 20 As shown, on the main part 134 of the sensor chip 132, at least one FET amplifier 104 is located near the working electrode 102. As described above, the FET amplifier 104 includes a source terminal 106, a drain terminal 108, and at least one nanowire 110 connecting the source terminal 106 and the drain terminal 108. In an exemplary embodiment, each FET sensor 100 is designed to be functionalized with a different analyte-specific material, for example, a sensing hydrogel 116 embedded with the above-mentioned enzyme, so as to achieve multi-metabolite sensing capabilities. For example, in some embodiments of the present invention, each FET sensor can include a sensing hydrogel 116 attached to a working electrode 102 embedded in at least one microprobe 136.

[0266] In some embodiments, at least one microprobe 136 may each include two FET sensors 100. In some embodiments of the present invention, the FET sensor 100 includes more than one FET amplifier 104 that detects electrical changes in the working electrode 102.

[0267] In some embodiments of the present invention, the chip includes one or more microprobes for calibration, which also protrude outward from the main part, similar to at least one sensing microprobe. The calibration microprobe can have the same structure as at least one sensing microprobe, but in some embodiments of the present invention, there is no hydrogel, which contains enzymes or is configured to react with any part of the analyte in the analyte solution. However, in some embodiments of the present invention, the calibration microprobe includes a hydrogel having a part with affinity for substances other than biological analytes. Alternatively, the calibration microprobe can have a hydrogel with a non-sensing part or an enzyme.

[0268] Figure 21-Figure 32 An exemplary method of microchip production in some embodiments of the present invention is shown. Fig.21 As shown, in an exemplary embodiment, a silicon-on-insulator (SOI) wafer 148 is used with a buried oxide layer 150 and an ultra-thin silicon device layer (eg, <100 nm) 152. The device layer may have, for example, 10 15 -10 17 Atom / cm 3 of dopant concentration.

[0269] In step 1, if Fig. 22 As shown, the silicon device layer 152 is patterned by electron beam, stepper or scanner lithography or other equivalent nanolithography techniques. The device layer 152 can then be etched with reactive species via wet anisotropic chemical etching or dry plasma-based silicon etching to form at least one nanowire 110 or a nanowire array.

[0270] In step 2, after forming at least one nanowire 110, the back gate 126 is etched through the buried oxide layer 150, such as Fig.23 Specifically, the back gate 126 is photolithographically patterned and then etched through the buried oxide layer 150 via photolithography, stepper or scanner lithography. The buried oxide layer 150 is then etched using a reactive species via wet isotropic chemical etching or dry plasma-based silicon dioxide etching.

[0271] exist Fig.24 In step 3 shown, photolithography, stepper or scanner lithography is used to pattern the resist for the working electrode 102 and the bonding pad 190. Specifically, a metal stack is deposited in the photolithographically patterned resist via evaporation, sputtering or electrodeposition. The metal stack includes an initial layer for adhesion and silicide formation and a noble metal layer for exposure to the environment. In some embodiments of the present invention, the initial layer is one of titanium, nickel or TiN.

[0272] exist Fig.25In step 4 shown, native silicon dioxide is etched via wet isotropic etching or dry etching, and a metal stack 194 is deposited in a photolithographically patterned resist via evaporation, sputtering, or electrodeposition to form a nanowire contact 196 between the metal stack and the nanowire (in this embodiment, SiNW 110). In some embodiments, the metal stack 194 includes an initial layer (Ti, Ni, or TiN) for adhesion and silicide formation, a second metal layer (Al, AlSi, AlSiCu, Pd, Au, Cu, or Ag) with lower resistance, and a third top layer (Ti, Al, Cr) for improved adhesion to subsequent passivation layers.

[0273] exist Fig.26 At least one nanowire contact (not shown) may be subjected to rapid thermal annealing (RTA) in an inert nitrogen or argon atmosphere or with a forming gas in step 5. RTA-induced silicide formation results in the nanowire contact being transformed into an interface volume 197.

[0274] exist Fig. 27 In step 6 shown, a passivation layer 188 is deposited via atomic layer deposition (ALD), inductively coupled plasma-chemical vapor deposition (ICP-CVD) or tetraethyl orthosilicate (TEOS) for electrical isolation. In some embodiments of the present invention, the passivation layer 188 includes one of aluminum oxide, silicon nitride, silicon dioxide or silicon oxynitride.

[0275] exist Fig.28 In step 7 shown, resist is patterned on the back side of the wafer via photolithography, stepper or scanner lithography. A back gate handle 198 is etched from silicon via wet anisotropic silicon etching or plasma-based anisotropic deep silicon etching (DSE).

[0276] exist Figure 29-Figure 30 In step 8 shown, openings 174 are photolithographically patterned on the passivation layer 188. The openings 174 are then etched through the passivation layer 188 using an active material via an isotropic wet chemical etch or a plasma-based dry etch to expose the working electrode 102, the back gate electrode 126, and the at least one nanowire 110. This etching exposes the noble metal of the at least one nanowire 110 to the environment.

[0277] exist Fig.31 In step 9 shown, a thick permanent photoresist 192 is photolithographically patterned via photolithography, stepper or scanner lithography to form well 144. In some embodiments of the present invention, photoresist 192 is in the range of 5 to 50 microns. In some embodiments of the present invention, photoresist 192 is formed of SU-8 or polyimide.

[0278] exist Fig.31In step 10 shown, the resist is photolithographically patterned via photolithography, stepper or scanner lithography to define wells 144 and well walls 143 on at least one microprobe and microchip. The passivation layer is then etched with active material via wet chemical etching or plasma-based dry etching. The buried oxide layer is also etched with active material by wet chemical etching or plasma-based dry etching, while the handle layer silicon is etched via plasma-based anisotropic deep silicon etching (DSE).

[0279] Finally, in Fig.32 In step 11 shown, a single microchip 132 is removed from the silicon wafer by breaking off the tabs connecting the microchip 132 to the wafer.

[0280] Fig.33 It is described how a microchip 132 having a single FET sensor 100 in use in some embodiments of the present invention can measure different concentrations of, for example, a chemical substance over time. In this embodiment, the FET sensor 100 is tuned to measure hydrogen peroxide. Fig.33 The current from a single FET sensor 100 is recorded over time. The measurements were taken at a fixed working electrode voltage. As can be seen from the figure, changing the hydrogen peroxide concentration results in a change in the current level flowing through the FET amplifier 104. Specifically, an increase in the hydrogen peroxide concentration results in a decrease in the current level, while a decrease in the hydrogen peroxide concentration results in an increase in the current level. For example, changing the hydrogen peroxide concentration from 10 μM to 1 mM can reduce the current level from about 150 nA to 70 nA.

[0281] Fig.34An exemplary arrangement of a multi-microprobe sensor chip 132 configured to monitor glucose, lactate, and ascorbic acid (AA) in an analyte solution in some embodiments of the present invention is depicted. In this embodiment, the multi-microprobe sensor chip includes six microprobes, each of which includes a FET sensor. The exemplary embodiment includes a specific discussion of a device configured to detect glucose, lactate, and ascorbic acid, but it will be apparent to one skilled in the art that the device can be configured to detect glucose, lactate, and ascorbic acid without departing from the broader principles described herein by using enzymes (i.e., glucose oxidase, lactate oxidase, cholesterol oxidase, pyruvate oxidase, glycerol oxidase, ethanol oxidase, glutaminase oxidase, L-glutamate oxidase, xanthine oxidase, L-glutamate oxidase, choline oxidase, creatine oxidase, acetylcholine ... Other analytes with enzyme substrates such as oxidase and ascorbate oxidase or creatinase, creatinase, peroxidase, laccase, tyrosinase or 3-hydroxybutyrate dehydrogenase, glucose dehydrogenase, lactate dehydrogenase, alcohol dehydrogenase, glutamate dehydrogenase) to detect other analytes (i.e., β-d-glucose, L-lactate, glutamine, cholesterol, glycerol, pyruvate, ethanol, L-glutamate, choline, acetylcholine, L-ascorbic acid, cortisol, creatine, creatinine, 2-hydroxybutyrate or 3-hydroxybutyrate)

[0282] Specifically, the multi-microprobe sensing microchip 132 includes a first microprobe 154 having a first FET sensor 156. In this embodiment, the working electrode of the first FET sensor 156 is embedded with a hydrogel containing GOX. GOX reacts with GOX in the analyte solution to produce hydrogen peroxide (H2O2). The second microprobe 158 of the microchip 132 includes a second FET sensor 160. In this embodiment, the working electrode of the second FET sensor 160 is embedded with a hydrogel containing LOX. LOX reacts with lactate in the analyte solution to produce H2O2. The third microprobe 162 of the multi-microprobe sensing chip 132 includes a third FET sensor 164. However, the working electrode of the third FET sensor 164 is embedded with a hydrogel that does not contain any enzyme. Therefore, the third FET sensor 164 detects all background analytes in the analyte solution to allow correction of the measured values ​​from the first and second FET sensors 156, 160. In this embodiment, each of the first, second and third FET sensors 156, 160, 164 has the same voltage setting, so that the third FET sensor 164 acts as a blank sensor to compensate for background noise. Therefore, by subtracting the third FET sensor output from the first FET sensor output, the amount of glucose in the analyte solution can be calculated. Similarly, by subtracting the third FET sensor output from the second FET sensor output, the amount of lactate in the analyte solution can be calculated.

[0283] Turning to the fourth microprobe 166 of the multi-microprobe sensor chip 132, the fourth FET sensor 168 located thereon is designated as an ascorbic acid sensor in this embodiment. In this embodiment, the working electrode of the fourth FET sensor 166 is embedded with an enzyme-free hydrogel, and its voltage is adjusted to maximize ascorbic acid (AA) sensing. For example, the back gate / working electrode voltage can be set to a more negative value. The fifth microprobe 170 of the multi-microprobe sensor chip 132 includes a fifth FET sensor 172. In this embodiment, the working electrode of the fifth FET sensor 172 is embedded with ascorbic acid oxidase (AAOX), which does not produce hydrogen peroxide, but only produces dehydroascorbic acid and water. Therefore, AAOX is used to eliminate AA, and by subtracting the fifth FET sensor output from the fourth sensor output, the AA concentration can be calculated. The sixth microprobe 173 of the multi-pin sensor chip 132 includes a sixth FET sensor 175. In this embodiment, the working electrode of the sixth FET sensor 175 is embedded with an ion-specific ionophore membrane to allow measurement of specific ions, for example, beauvericin (Ca2+, Ba2+), calcimycin or A23187 (Mn2+, Ca2+, Mg2+), cezomycin, carbonyl cyanide m-chlorophenylhydrazone (CCCP) (H+), enfusin (ammonium), gramicidin A (H+, Na+, K+), ronumacin (Ca2+), lasalocid (K+, Na+, Ca2+, Mg2+), monensin (Na+, H+), nigericin (K+, H+, Pb2+), inactivin (ammonium ionophore I), salinomycin (K+), tenesin, valinomycin (potassium ionophore I), methyl narasin, or a combination thereof.

[0284] Microprobe sensing system

[0285] In some embodiments of the present invention, Figure 35-Figure 36 As shown, the multi-microprobe sensor chip 132 is incorporated into the sensor system 180. In some embodiments of the present invention, the sensor system 180 is configured as a patch or a removable implant, which allows monitoring of the presence, absence or amount of multiple biological analytes. Fig.35As shown, in some embodiments of the present invention, the sensing system 180 includes a sensor patch 182 having a skin contact surface 184 for contacting the skin of a subject (human or animal). In some embodiments of the present invention, the sensor patch 182 is configured to hold the multi-microprobe sensor chip 132 so that one or more sensing microprobes 136 protrude outward from the skin contact surface. In an exemplary embodiment, at least one microprobe 136 can protrude vertically from the surface 184 of the sensor patch 182, or protrude from the surface 184 at an acute angle. In some embodiments of the present invention, the circuit is attached to the sensor patch 182. In some embodiments of the present invention, the circuit is located on the opposite side of the substrate relative to the microprobes.

[0286] Fig.36 A sensor patch 182 according to an exemplary embodiment of the disclosure is depicted. In some embodiments of the present invention, the sensor patch surface 184 is an adhesive surface that allows the substrate to be attached to the skin. For example, the surface may include or be coated with a skin adhesive material. In some embodiments of the present invention, the sensor patch 182 also includes a substance selected to prevent or reduce skin irritation, such as but not limited to itching, flushing, rash, pain, eczema, and skin inflammation. In some embodiments of the present invention, the sensor patch 182 is flexible. For example, the sensor patch 182 may be at least partially made of woven fabrics, nonwoven fabrics, plastic films, etc. Parts of the sensor patch 182 are made of, for example, elastic polymers. Suitable elastic polymer substrate materials are typically selected based on their compatibility with manufacturing processes (soft lithography, stereolithography, and three-dimensional jet printing, etc.). Considering the huge differences in polymer chemistry, precursors, synthesis methods, reaction conditions, and potential additives, a large number of materials are considered. Representative examples of elastomeric polymers include, but are not limited to, polydimethylsiloxane (PDMS), polyisoprene, polybutadiene, polychloroprene, polyisobutylene, poly(styrene-butadiene-styrene), polyurethanes, and silicones. Generally non-elastomeric polymers are also contemplated.

[0287] Representative examples of such polymers include, but are not limited to, PMMA and polycarbonate.

[0288] Embodiments are also contemplated in which the sensor patch 182 is made of two or more materials. For example, a portion of the sensor patch 182 may be made of a woven or non-woven fabric or film, i.e., coated with a skin-adhesive material in some embodiments of the invention, while another portion serves as a microfluidic interface, wherein the microprobes 136 are formed on or integral with the microfluidic interface. The microfluidic interface may be more rigid than the fabric or film.

[0289] The transverse dimensions of the sensor patch 182 may vary, depending on the size of the subject's organ receiving the surface 14. Typical transverse diameters of the sensor patch 182 are, but are not limited to, about 10 mm to about 50 mm.

[0290] As described above, in some embodiments of the present invention, the response of the FET sensor to the redox species in the analyte solution can be processed and measured by, for example, a circuit. In some embodiments of the present invention, the circuit can be configured to, for example, measure the current through the drain terminal of the FET amplifier.

[0291] In some embodiments of the present invention, the FET amplifier on the sensor chip is directly or indirectly connected to the circuit. The circuit applies voltage to the FET amplifier. The circuit generally includes a power supply and a voltmeter or an ammeter. When the reaction between the sensing hydrogel and the analyte in the solution is a redox reaction, in some embodiments of the present invention, the circuit is configured to control the voltage setting from the back gate to the working electrode.

[0292] It should be understood that, for the sake of clarity, certain features of the disclosure described in the context of separate embodiments may also be provided in a single embodiment. Conversely, for the sake of brevity, various features of the disclosure described in the context of a single embodiment may also be provided separately, or in any suitable subcombination, or as appropriate for any other described embodiment of the disclosure. Certain features described in the context of various embodiments are not considered essential features of those embodiments, unless the embodiment does not function without those elements.

Claims

1. A sensor, comprising: a working electrode configured to be positioned in contact with an analyte solution; a voltage source coupled to the working electrode; A field effect transistor amplifier, the field effect transistor amplifier comprising: source terminal; a drain terminal; and Multiple nanowires, wherein each of the plurality of nanowires electrically connects the source terminal to the drain terminal; Back gate electrode; a dielectric layer, the dielectric layer being located between the back gate electrode and the field effect transistor amplifier; and an insulator having a first side and a second side opposite to the first side, wherein the working electrode is located on a first side of the insulator, wherein the field effect transistor amplifier is located on the second side of the insulator, whereby the insulator is configured to prevent direct electrical contact between the working electrode and the field effect transistor amplifier, and whereby the insulator is configured to prevent direct contact between the analyte solution and the field effect transistor amplifier, wherein the sensor is configured so that only the working electrode contacts the analyte solution, and The working electrode is configured so that when a chemical substance is present in the analyte solution, a change in the electric field at the location of the field effect transistor amplifier is induced, and the field effect transistor amplifier is configured so that when the electric field changes, a corresponding current change is induced between the source terminal and the drain terminal. 2 . The sensor of claim 1 , wherein the working electrode, the field effect transistor amplifier, and the insulator are in a stacked configuration.

3. The sensor of claim 1, wherein the working electrode, the field effect transistor amplifier, and the insulator are in a side-by-side configuration.

4. The sensor of claim 1, wherein the working electrode material comprises at least one noble metal.

5. The sensor of claim 1, wherein the working electrode material comprises a metal oxide.

6. The sensor according to claim 1, wherein the sensor has a 0.00005 mm 2 To 0.005mm 2 coverage area.

7. The sensor of claim 1, wherein the exposed portion of the working electrode has a major dimension of 1 micron to 1000 microns.

8. The sensor of claim 1, wherein the plurality of nanowires comprises 1 to 100 nanowires.

9. The sensor of claim 1, further comprising a hydrogel disposed on the working electrode, the hydrogel comprising at least one enzyme configured to interact with an analyte in the analyte solution.

10. The sensor according to claim 9, wherein the enzyme comprises one of glucose oxidase, lactate oxidase, cholesterol oxidase, pyruvate oxidase, glycerol oxidase, alcohol oxidase, glutamine oxidase, L-glutamate oxidase, xanthine oxidase, choline oxidase, sarcosine oxidase and ascorbate oxidase or creatininase, creatinase, peroxidase, laccase, tyrosinase or 3-hydroxybutyrate dehydrogenase, glucose dehydrogenase, lactate dehydrogenase, alcohol dehydrogenase or glutamate dehydrogenase.

11. The sensor of claim 9, wherein the hydrogel is configured to interact with at least one of β-d-glucose, L-lactate, glutamine, cholesterol, glycerol, pyruvate, ethanol L-glutamate, choline, acetylcholine, L-ascorbic acid, cortisol, creatine, creatinine, 2-hydroxybutyrate, or 3-hydroxybutyrate.

12. The sensor of claim 9, wherein the chemical is one of hydrogen peroxide, nicotinamide adenine dinucleotide, ascorbic acid, caffeine, acetaminophen, flavin adenine dinucleotide and flavin mononucleotide, or a quinone cofactor.

13. A microprobe sensing device, comprising: A plurality of microprobes, each microprobe comprising a tip configured to be inserted into an analyte solution and a sensor located at the tip, each sensor comprising: a working electrode configured to be positioned in contact with the analyte solution; a voltage source coupled to the working electrode; A field effect transistor amplifier, the field effect transistor amplifier comprising: source terminal; a drain terminal; and Multiple nanowires, wherein each of the plurality of nanowires electrically connects the source terminal to the drain terminal; wherein each of the plurality of nanowires has a major cross-sectional dimension in the range of 1 to 500 nanometers; Back gate electrode; a dielectric layer, the dielectric layer being located between the back gate electrode and the field effect transistor amplifier; and an insulator having a first side and a second side opposite to the first side, wherein the working electrode is located on a first side of the insulator, wherein the field effect transistor amplifier is located on the second side of the insulator, whereby the insulator is configured to prevent direct electrical contact between the working electrode and the field effect transistor amplifier, and whereby the insulator is configured to prevent direct contact between the analyte solution and the field effect transistor amplifier, wherein the sensor is configured such that only the working electrode contacts the analyte solution; wherein the working electrode is configured so that when a chemical species is present in the analyte solution, a change in the electric field at the location of the field effect transistor amplifier is induced, and The field effect transistor amplifier is configured such that when the electric field changes, a corresponding current change between the source terminal and the drain terminal is induced.

14. The device of claim 13, wherein the plurality of microprobes are configured to detect at least two analytes.

15. The device of claim 13, wherein at least one of the plurality of microprobes is a non-specific sensor.

16. A method of determining the amount of glucose in an analyte solution, the method comprising: Inserting a tip of a first microprobe and a tip of a second microprobe of a sensing device into the analyte solution, each of the first microprobe and the second microprobe comprising a sensor at the tip, each sensor comprising: a working electrode configured to be positioned in contact with an analyte solution; a voltage source coupled to the working electrode; A field effect transistor amplifier, the field effect transistor amplifier comprising: source terminal; a drain terminal; and Multiple nanowires, wherein each nanowire electrically connects the source terminal to the drain terminal; Back gate electrode; a dielectric layer, the dielectric layer being located between the back gate electrode and the field effect transistor amplifier; and an insulator having a first side and a second side opposite to the first side, wherein the working electrode is located on a first side of the insulator, wherein the field effect transistor amplifier is located on the second side of the insulator, whereby the insulator is configured to prevent direct electrical contact between the working electrode and the field effect transistor amplifier, and whereby the insulator is configured to prevent direct contact between the analyte solution and the field effect transistor amplifier, wherein the sensor is configured such that only the working electrode contacts the analyte solution; wherein the working electrode of the sensor of each of the first microprobe and the second microprobe comprises a hydrogel embedded therein, wherein the hydrogel of the first microprobe comprises glucose oxidase; By inducing a first change in a first electric field at the location of a field effect transistor amplifier of the sensor of the first microprobe as follows: (a) the glucose oxidase reacts with glucose in the analyte solution to form hydrogen peroxide; and (b) the redox interaction between the working electrode of the sensor of the first microprobe and the following substances: (1) redox species present in the analyte solution, and (2) hydrogen peroxide formed by the reaction of the glucose oxidase and the glucose; Inducing a second change in a second electric field at the location of a field effect transistor amplifier of the second microprobe sensor through a redox interaction between a working electrode of the second microprobe sensor and a redox species present in the analyte solution; inducing a first change in a first current between the source terminal of the sensor of the first microprobe and the drain terminal of the sensor of the first microprobe, the first change in the first current corresponding to a first change in the first electric field; inducing a second change in a second current between the source terminal of the sensor of the second microprobe and the drain terminal of the sensor of the second microprobe, the second change in the second current corresponding to a second change in the second electric field; and Based on a difference between the first change in the first current and the second change in the second current, an amount of glucose present in the analyte solution is determined.

17. A method for the undesired detection of interfering chemicals present in an electrochemically filtered analyte solution, the method comprising: A sensor at the tip of a sensing device is inserted into the analyte solution, the sensor comprising: a working electrode configured to be positioned in contact with the analyte solution; a voltage source coupled to the working electrode; A field effect transistor amplifier, the field effect transistor amplifier comprising: source terminal; a drain terminal; and Multiple nanowires, wherein each of the plurality of nanowires electrically connects the source terminal to the drain terminal; Back gate electrode; a dielectric layer, the dielectric layer being located between the back gate electrode and the field effect transistor amplifier; and an insulator having a first side and a second side opposite to the first side, wherein the working electrode is located on a first side of the insulator, wherein the field effect transistor amplifier is located on the second side of the insulator, whereby the insulator is configured to prevent direct electrical contact between the working electrode and the field effect transistor amplifier, and whereby the insulator is configured to prevent direct contact between the analyte solution and the field effect transistor amplifier, wherein the sensor is configured so that only the working electrode contacts the analyte solution, wherein the working electrode is configured so that when a chemical species is present in the analyte solution, a change in the electric field at the location of the field effect transistor amplifier is induced, The field effect transistor amplifier is configured so that when the electric field changes, a corresponding current change is induced between the source terminal and the drain terminal, and (a) the back gate voltage of the back gate electrode, (b) the working electrode voltage and (c) the source voltage are adjusted so that the minimum current change between the source terminal and the drain terminal is induced by the presence of undesirable chemicals.

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