Organic thin film transistor sensors

Abstract

The present disclosure relates to sensors including organic thin film transistors and the preparation and use thereof in sensing applications.

Description

1005587934Organic Thin Film Transistor sensorsField of the disclosure

[0001] This disclosure relates to organic thin film transistors for use in sensing applications, the preparation of said sensors, and uses thereof.Background of the disclosure

[0002] In recent years there has been rapid development of point-of-care (POC) devices which can be used by patients at home or medical professionals in a clinic for rapid detection or diagnosis without the need to deliver samples for pathological analysis. Electrochemical sensors and transistors such as organic thin film transistors are ideal for POC devices because of their compatibility with biological fluid and potential to interface with electronics without requiring further analytical equipment to analyse the signal. This is in contrast to absorbance, fluorescence or luminescence based assays, where a separate equipment is needed for signal analysis.

[0003] One of the obstacles in the development of electrochemical sensors, such as those in POC devices, is the rapid accumulation of proteins from biological fluids on the conductive surfaces of the sensor. This weakens the sensor signal and can deactivate the sensor.

[0004] There is a need for point-of-care diagnostic devices conducting an assay in a biological fluid contacting the surface of a sensor or transistor. Preferably, the device minimises the loss of signal to the sensor or transistor electrode. This is often achieved by the addition of a coating or antifouling layer to a device. Most antifouling strategies rely on an antifouling layer acting as a passive barrier that prevents the build-up of debris or other contamination that, for example, interferes with the assay or the generation of charge or the receipt of the charge, and reduces the sensitivity of the sensor. On some occasions, biological fouling essentially incapacitates a sensor shortly after the assay commences. This significantly reduces the value and potential uses of such sensors. However, the need to include antifouling technology increases the complexity of sensors as the deposition of any antifouling coating should be uniform and reproducible so that it does not variably impact electrical signal.1005587934

[0005] There is therefore a need for sensors and transistors that can function in biological fluids with improved signal sensitivity or improved maintenance of signal sensitivity. Preferably, the sensors and transistors (i) do not impede the function of enzymes or probes, (ii) do not impede the molecular / chemical interactions resulting in the generation of charge, (iii) minimise non-specific interactions, and / or (iv) preserve the sensitivity of the electrical sensor / transducer.

[0006] There is also a need for rapid POC diagnostic devices capable of molecular assays. Further there is a need for inexpensive and easy to manufacture diagnostic tools for POC diagnosis.

[0007] There is a need for OTFT devices with improved signal sensitivity and / or for sensing biologies such as proteins, antigens and antibodies. Such a device may make commercially viable biological sensors that allow estimation of blood levels of biologies and / or detection of infection such as viral infection. Such a device may be a rapid POC diagnostic device.

[0008] Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and / or combined with other pieces of prior art by a skilled person in the art.Summary of the disclosure

[0009] The present inventors have successfully fabricated an organic transistor based sensor device that is capable of detecting analytes in biological fluid. The transistor is straightforward and relatively cheap to manufacture. The transistor may enable commercially viable rapid and / or POC diagnosis of various conditions including viral infections in a biological fluid such as blood or saliva. Surprisingly, the disclosure provides a sensor without an additional antifouling layer that functions with sufficient sensitivity.

[0010] The present disclosure provides an organic thin film transistor (OTFT) comprising an organic semiconductor and a probe for facilitating generation of a charge carrier from an analyte, wherein the organic semiconductor is adapted for contact with an analyte.1005587934

[0011] Typically, OTFT sensors of the present disclosure are required to have an antifouling layer to minimise degradation of the sensor. Surprisingly, the inventors have found that the antifouling layer can be removed from the sensor and still provide a working sensor.

[0012] Optionally, the probe is at least partially embedded in or attached to the surface (top) of the organic conducting or semiconducting layer, wherein, when the probe is at least partially embedded or attached to the surface (top) of the organic conducting or semiconducting layer, the probe is surrounded by the antifouling layer. In this disclosure the probe is not an enzyme.

[0013] Optionally, the OTFT further comprises a substrate. Optionally, the substrate is on the opposite side of the electrode to the conducting or semiconducting layer.

[0014] In some embodiments, the OTFT further comprises a conducting polymer gating layer directly or indirectly in contact with the organic semiconducting layer. Optionally, the conducting polymer gating layer is a tetrafluoroethylene-based fluoropolymer-copolymer. The tetrafluoroethylene-based fluoropolymer-copolymer may be a copolymer of tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octene- sulfonic acid. The tetrafluoroethylene-based fluoropolymer-copolymer may be a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer. Preferably the conducting polymer gating layer is nation.

[0015] In a further aspect, the present disclosure provides an OTFT comprising:(i) a source electrode,(ii) a drain electrode,(iii) an organic semiconducting layer, the organic semiconducting layer connecting the source electrode to the drain electrode, wherein either:(a) the organic semiconductor is adapted for contact with the analyte; or(b) a conducting or semiconducting surface layer coats at least a portion of the surface of the organic semiconducting layer and the surface (or outermost) layer is adapted for contact with the analyte,1005587934(iv) either the surface layer or the organic semiconductor is configured to be connected to an ohmic conductor for applying a gate voltage to said organic semiconducting layer and / or said organic semiconducting layer via the surface layer, and(v) a probe or enzyme for facilitating generation of a charge carrier from an analyte, wherein the probe or enzyme is at least partially embedded or attached to the surface (top) of the surface layer or the organic semiconducting layer, wherein when the probe or enzyme is at least partially embedded or attached to the surface (top) of the organic semiconducting layer the probe or enzyme is surrounded by the surface layer.

[0016] Optionally, the surface layer is a conducting layer such as a porous wicking layer.

[0017] Optionally, the OTFT further comprises an ohmic conductor for applying a gate voltage in contact with said organic semiconducting layer or said surface layer such as a porous wicking layer. Optionally, the ohmic conductor for applying a gate voltage is a gate electrode.

[0018] Optionally, a voltage is applied from the ohmic conductor to the organic semiconducting layer. Optionally, a voltage is applied from the ohmic conductor to the organic semiconducting layer via the surface layer.

[0019] The present disclosure provides an OTFT comprising:(i) a source electrode,(ii) a drain electrode,(iii) an organic semiconducting layer, the organic semiconducting layer connecting the source electrode to the drain electrode,(iv) a polymer gating layer, the polymer gating layer being conducting to the charge carrier and connecting to the organic semiconducting layer,1005587934(v) the polymer gating layer is configured to be connected to an ohmic conductor for applying a gate voltage to said organic semiconductor via said polymer gating layer, and(vi) a probe for facilitating generation of a charge carrier from an analyte, wherein the probe is at least partially embedded or attached to the surface (top) of the polymer gating layer.

[0020] Optionally, the polymer gating layer is configured to be connected to the ohmic conductor. Optionally, the polymer gating layer is at least partially covered by a porous wicking layer.

[0021] Optionally, the OTFT further comprises an ohmic conductor for applying a gate voltage in contact with the polymer gating layer (possibly indirectly via the porous wicking layer). Optionally, the ohmic conductor for applying a gate voltage is a gate electrode.

[0022] Optionally, a voltage is applied from the ohmic conductor to the organic semiconducting layer. Optionally, a voltage is applied from the ohmic conductor to the organic semiconducting layer via the polymer gating layer or the porous wicking layer or both.

[0023] Optionally, the ohmic conductor is located at the top of the OTFT ie opposite the source and drain electrodes. Ohmic conductors in this location can contact the polymer gating layer or the porous wicking layer.

[0024] Optionally, the ohmic conductor is in contact with the polymer gating layer and separated from the porous wicking layer and the analyte ie a) at the bottom of the OTFT when the porous wicking layer is at the top of the OTFT and offset from the source and drain electrode, or b) on the side of the OTFT when the porous wicking layer is at the top and the source and drain electrodes at the bottom.

[0025] Unless otherwise stated, the following embodiments apply to a device in accordance with any one of the above aspects of the disclosure.

[0026] Optionally, the OTFT is suitable for point-of-care analysis or diagnostics (or point-of-sample collection analysis) ie it is not necessary to send the sample to a1005587934 pathology centre or other diagnostic / analytical chemistry facility. Optionally, the OTFT is portable.

[0027] Optionally, the OTFT is at least a partially printed OTFT. Optionally, one or more layers of the OTFT are printed on a substrate (preferably all layers). Optionally, the organic semiconductor, porous wicking layer and optionally the conducting polymer gating layer of the OTFT are printed directly or indirectly on a substrate. Optionally, the porous wicking layer and optionally the conducting polymer gating layer are printed directly or indirectly onto the organic semiconductor (ie indirectly refers to printing on an intermediate layer between the organic semiconductor and the printed layer). Irrespective of the printing or non-printing of the organic semiconductor, conducting polymer gating layer, and porous wicking layer, optionally, the enzyme or probe is printed onto the OTFT. Optionally, one or more layers of the OTFT and the enzyme or probe are printed on a substrate. The electrodes are optionally printed on the substrate, for example, prior to printing of the semiconductor. Optionally, one or more electrode is printed using silver ink. Optionally, the OTFT comprises one or more of a dielectric layer, and the dielectric layer is printed directly or indirectly onto a substrate or the organic semiconductor.

[0028] In all embodiments comprising a polymer gating layer and a porous wicking layer, the polymer gating layer is not a porous wicking layer.Methods of making the OTFT

[0029] In one aspect, the present disclosure provides a method for preparing an OTFT in accordance with this disclosure, the method comprising: a) providing a substrate for depositing thereon components of the device; b) depositing the source electrode and the drain electrode onto the substrate; c) depositing the organic semiconductor; d) optionally depositing a dielectric layer; e) optionally depositing a polymer gating layer; f) optionally depositing a porous wicking layer; and1005587934 g) depositing the enzyme or probe on the organic semiconductor layer and / or optional polymer gating layer or porous wicking layer.

[0030] In one aspect, the present disclosure provides a method for preparing an OTFT in accordance with this disclosure, the method comprising: a) providing an organic semiconductor for depositing thereon components of the device; b) depositing the source electrode and the drain electrode onto the organic semiconductor; d) optionally depositing a dielectric layer; e) optionally depositing a polymer gating layer; f) optionally depositing a porous wicking layer; and g) depositing the enzyme or probe on the organic semiconductor layer and / or optional polymer gating layer or porous wicking layer.

[0031] Preferably, the source electrode and the drain electrode are deposited on the substrate.

[0032] In at least one embodiment step b) precedes step c), step c) precedes step f), and step f) precedes step g). Optionally, a polymer gating layer is deposited and step c) precedes step e) and step e) precedes step f). Optionally, a dielectric layer is deposited and step c) precedes step d) and step d) precedes step f).

[0033] Preferably the method also includes depositing the ohmic conductor / gate electrode. Optionally, the ohmic conductor / gate electrode is in contact with said polymer gating layer to control an electric potential of said polymer gating layer. Optionally, the ohmic conductor / gate electrode is in contact with said conducting porous wicking layer to control an electric potential of said conducting antifouling layer. Preferably, in this case, the ohmic conductor is deposited before the polymer gating layer and / or porous wicking layer.

[0034] In other embodiments, the ohmic conductor may be connected to said polymer gating layer and / or conducting porous wicking layer in use, to control an electric1005587934 potential of said polymer gating layer and / or conducting porous wicking layer, whereby the ohmic conductor is not integrated into OTFT during manufacture of the OTFT.

[0035] In at least one embodiment, the source electrode and the drain electrode are deposited over the substrate. In at least one embodiment, the organic semiconductor layer is deposited over source electrode and the drain electrode.

[0036] In at least one embodiment, the polymer gating layer is deposited over the organic semiconductor. In some embodiments, no dielectric layer is deposited.Alternatively, a dielectric layer may be deposited over the organic semiconductor, with said polymer of the polymer gating layer then being deposited over the organic dielectric layer. In this case, the dielectric layer may be deposited by spin coating or screenprinting.

[0037] Preferably, the enzyme or probe is introduced by screen-printing.

[0038] Step b) may comprise depositing the source electrode and the drain electrode over the substrate such that the source electrode and the drain electrode are disposed above, and in contact with, the substrate.

[0039] Step c) may comprise depositing the organic semiconductor over the source electrode and the drain electrode such that at least part, but preferably a majority, of the semiconductor is disposed above and in between the source electrode and the drain electrode.

[0040] Preferably, in step c), the semiconductor is deposited such that it is in contact with the source electrode and the drain electrode.

[0041] In at least one embodiment, the semiconductor layer is deposited by spin coating.

[0042] In at least one embodiment the polymer gating layer is deposited by spin coating.

[0043] Devices in accordance with the present disclosure may be fabricated by low- cost spin-coating and printing techniques, thereby offering the potential for affordable and disposable non-reversible devices. All of the components of the device are capable of being printed onto an (optionally removable) substrate.1005587934

[0044] The organic semiconducting layer and / or the dielectric layer (for embodiments in which such a dielectric layer is included) may be deposited in accordance with methods well known to those skilled in the art, including, but not limited to: electroplating, vapour phase deposition, spin coating, screen printing, ink-jet printing, slot-dye printing, spray coating, draw bar coating or derived coating / printing techniques thereof, painting, gravure, roller and embossing.

[0045] The organic semiconducting layer may be deposited so as to achieve a thickness between about 5 nm and about 500 nm, or between about 75 nm and about 125 nm, or about 100 nm.

[0046] Where the probe is attached to the OTFT via a connector, optionally, the connector is deposited on the OTFT and the remainder of the probe attached to the connector subsequently. Alternatively, the probe with the connector is deposited on the OTFT.

[0047] In another aspect the present disclosure provides a device prepared by any of the above methods of making the OTFT.Methods of using the OTFT

[0048] In another aspect, the present disclosure provides use of the sensor / OTFT of the disclosure for sensing an analyte in a sample. Optionally, the analyte is a target for a probe.

[0049] The analyte is optionally a biological analyte. The analyte may be glucose. In an embodiment the analyte / target for the probe is an antibody, antigen, protein, peptide or chemical. The chemical is optionally glucose. The antibody is optionally a coronavirus antibody. The antibody is optionally a SARS-CoV-2 antibody.

[0050] The sample may be any aqueous solution but is preferably a biological fluid, more preferably a bodily fluid, and still more preferably, blood or saliva.

[0051] In a further aspect, the present disclosure provides a method for detecting an analyte in a sample, the method comprising the following steps:- providing an OTFT of the present disclosure;1005587934- contacting the sample to the OTFT, preferably the portion of the OTFT adapted for contact with an analyte; and- detecting the analyte based on an electrical parameter of the device.

[0052] Optionally, the method further comprises interaction between the analyte and probe or enzyme to facilitate generation of a charge carrier. Preferably, the analyte is detected by detecting the charge carrier.

[0053] Optionally, the method further comprises determining a concentration or an amount of the analyte. Preferably, the concentration or amount is determined by detecting the amount of charge carrier and / or the change in voltage.

[0054] The method may comprise applying a voltage to the drain electrode. The method may comprise grounding the source electrode. The method also comprises applying a voltage to the ohmic conductor. Preferably the voltage applied to the ohmic conductor (ie the “gate voltage”) and the voltage to the drain electrode have the same polarity with respect to the source electrode.

[0055] The method may include detecting drain current through the OTFT, wherein the concentration or amount of the analyte is determined based on a magnitude of the drain current.

[0056] The determination of the concentration or amount may be performed by reference to an appropriate calibration curve.

[0057] Step b) may comprise contacting the sample with the polymer gating layer and / or porous wicking layer.

[0058] The gate voltage and drain voltage applied may be voltages greater than that required to liberate H+ from H2O2, and lower than that required to cause electrolysis of water.

[0059] The gate voltage and drain voltage applied may be between about 0 V and -2 V, or about -1 V. Optionally, about -0.7 V and -2V or -0.7 V and -1 .5 V or -0.7 and -1 V. Alternatively, about -0.55 V and -2V or -0.55 V and -1 .5 V or -0.55 and -1 V or -0.6V and -2V or -0.6 V and -1 .5 V or -0.6 and -1 V or -0.65V and -2V or -0.65 V and -1 .5 V or -0.65 and -1 V.1005587934

[0060] The analyte is optionally a biological analyte. The analyte may be glucose. In an embodiment the analyte / target for the probe is an antibody, antigen, protein, peptide or chemical. The chemical is optionally glucose. The antibody is optionally a coronavirus antibody. The antibody is optionally a SARS-CoV-2 antibody.

[0061] The sample may be any aqueous solution but is preferably a biological fluid, more preferably a bodily fluid, and still more preferably, blood, urine or saliva.

[0062] In another aspect, the present disclosure provides a method for detecting presence of one or more analyte in a sample, the method comprising:- contacting a sample with the one or more probe of an OTFT of this disclosure; and- detecting binding of the analyte to the compound.

[0063] Optionally, the one or more analyte is a coronavirus analyte. Optionally, the one or more coronavirus analyte is one or more coronavirus particle, protein, peptide, nucleic acid, or antibody specific to a coronavirus antigen.

[0064] In another aspect, the present disclosure provides a method for detecting one or more analyte comprising:- contacting a sample comprising one or more analyte to the surface of an OTFT of this disclosure (such as an organic semiconducting layer, a polymer gating layer, or a porous wicking layer);- allowing the analyte to bind with the probe, thereby forming a complex comprising the analyte and the probe;- labelling the complex with a detection agent to form a detectable complex, wherein the a portion of the detection agent binds specifically with the complex and a portion of the detection agent comprises at least one reporter; and- contacting the detectable complex with a substrate for the reporter enzyme , wherein the contact results in reaction of the substrate for the reporter with the at least one reporter to form a charge carrier.

[0065] In a further aspect, the present disclosure provides a method comprising:1005587934(i) selecting a sample in need of determination of the presence or absence of an analyte;(ii) contacting the sample to the surface of an OTFT, wherein the probe specifically binds with an analyte and the analyte is connected directly or indirectly to one or more electrode(s);(iii) allowing any analyte present in the sample to bind with the probe, thereby forming a complex comprising the analyte and the probe;(iv) labelling the analyte or any complex formed between the analyte and the probe with a detection agent to form a detectable complex, wherein a portion of the detection agent binds specifically with the complex and a portion of the detection agent comprises at least one reporter; and(v) contacting any detectable complex with a substrate for the reporter, wherein the contact results in reaction of the substrate for the reporter with any reporter in the detectable complex to form a charge carrier.

[0066] Optionally, the method is for detecting whether a subject has an infection (preferably a coronavirus infection, more preferably COVID-19). Optionally, the sample is a biological sample from a subject selected as in need of determination of the presence or absence of an infection. Optionally, the method is for detecting the presence of an analyte in a non-biological sample (for example drinking water or sewerage water).

[0067] Optionally, the method further comprises (vi) determining whether the sample comprised the analyte. Optionally, the method further comprises (vii) determining whether the subject has the infection.

[0068] Optionally, the subject is selected for a SARS-CoV-2 or COVID-19 test.

[0069] Optionally, the subject is suspected of having an infection. A subject suspected of having COVID-19 infection is optionally identified as a close contact of a person with confirmed COVID-19 infection, exhibiting COVID-19 symptoms or has any other common indications of COVID-19 infections. Optionally, the sample is from a subject for the purpose of routine monitoring of a known COVID-19 infection.1005587934

[0070] In a further aspect, the present disclosure provides a method comprising:(ia) selecting at least a first sample and a second sample in need of determination of the presence or absence of an analyte;(i) contacting the first sample to the surface of an OTFT of this disclosure, wherein the probe specifically binds with an analyte; and contacting the second sample to the surface of a second conducting layer with a probe at least partially embedded or attached, wherein the probe specifically binds with an analyte and the probe is connected directly or indirectly to one or more electrode(ii) allowing any analyte present in the first sample to bind with the first probe, thereby forming a complex comprising the analyte and the first probe; allowing any analyte present in the second sample to bind with the second probe, thereby forming a complex comprising the analyte and the second probe;(iii) labelling any analyte or complex formed between analyte and probe of the first a first detection agent to form a detectable complex, wherein a portion of the first detection agent binds specifically with the analyte / complex and a portion of the first detection agent comprises at least one first reporter; labelling any analyte or complex formed between analyte and second probe with a second detection agent to form a detectable complex, wherein a portion of the second detection agent binds specifically with the analyte / complex and a portion of the second detection agent comprises at least one second reporter;(iv) contacting any first detectable complex with a substrate for the first reporter, wherein the contact results in reaction of the substrate for the first reporter with any first reporter in the detectable complex to form a charge carrier; contacting any second detectable complex with a substrate for the second reporter, wherein the contact results in reaction of the substrate for the second1005587934 reporter with any second reporter in the detectable complex to form a charge carrier;(vi) determining that the first sample includes the analyte;(vii) determining that the second sample does not include the analyte.

[0071] Optionally, the method is for detecting whether a plurality of subjects have an infection (preferably a coronavirus infection, more preferably COVID-19). Optionally, a first subject and a second subject are identified as in need of determination of the presence or absence of an infection (preferably a coronavirus infection).

[0072] Optionally, the method further comprises (viii) determining the first subject has the infection and the second subject does not have the infection.Options for all methods of use

[0073] Optionally, the method is conducted at the point-of-care or point-of-sample collection ie it is not necessary to send the sample to a pathology centre or other diagnostic / analytical chemistry facility.

[0074] In some embodiments, the coronavirus is a beta-coronavirus. Optionally, the coronavirus is a beta-coronavirus of lineage A. Optionally, the coronavirus is a betacoronavirus of lineage B.

[0075] Optionally, the one or more analyte is one or more coronavirus analyte.

[0076] Optionally, the reporter is a reporter enzyme.

[0077] Optionally, charge carrier precipitates on the gating layer or porous wicking layer. Optionally, the charge carrier adsorbs on the gating layer or porous wicking layer.

[0078] Optionally, the OTFT has a plurality of probes. Optionally, the probes are all of the same type. Alternatively, the OTFT includes multiple probe types, for example, antibodies to more than one antigen or multiple antigens. Optionally, the method further comprises (v) applying a voltage to the one or more electrodes, wherein the current is impacted by the charge carrier, thereby facilitating detection of the analyte.1005587934

[0079] Optionally, the method further comprises (vi) measuring the current to detect the presence or determine the absence of the charge carrier.

[0080] Optionally, the sample is removed following binding of the analyte with the probe to form the complex. Optionally, the method comprises contacting a fluid comprising the detection agent to the surface of polymer gating or porous wicking layer with the probe. Optionally, the polymer gating or porous wicking layer is washed before addition of the fluid comprising the detection agent.

[0081] In some embodiments, the detection agent is added to the sample. The detection agent is optionally in a fluid. This can occur following or prior to binding of the analyte to the probe.

[0082] Optionally, the sample or fluid comprising the detection agent is removed following labelling the complex with the detection agent. Optionally, the method comprises contacting a fluid comprising the substrate for the reporter enzyme to the surface of the layer with the probe. Optionally, the surface of the conductive layer or semiconductive layer with the probe is washed before the addition of a fluid comprising the substrate for the reporter enzyme. This washing removed unbound detection agent.

[0083] In some embodiments, the substrate for the reporter enzyme is added to the sample or the fluid comprising the detection agent. This can occur following or prior to labelling of the complex. This can occur prior to binding of the probe to the complex.

[0084] Optionally, the charge carrier is adsorbed at the surface of the layer comprising the probe. Optionally, following adsorption of the charge carrier and before applying a voltage, the fluid including the substrate for the reporter enzyme is washed from the surface of the layer with the probe. This washing removes the substrate for the reporter enzyme molecule and non-adsorbed charge carrier.Kits

[0085] In another aspect, the present disclosure provides a kit for detection of an analyte in a sample comprising:(i) an OTFT of this disclosure;1005587934(ii) detection agent comprising a first portion that binds the complex of the probe and analyte and a second portion comprising at least one reporter enzyme; and(iii) a substrate for the reporter enzyme, wherein reaction of the substrate for the reporter enzyme with the at least one reporter enzymes forms charge carrier.

[0086] Optionally, charge carrier precipitates on the top, surface or outermost layer. Optionally, the charge carrier adsorbs on the top, surface or outermost layer. Optionally, the kit further comprises a means for applying voltage to the OTFT.

[0087] Further aspects of the present disclosure and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.Brief description of the drawings

[0088] Figure 1 : Current-time characteristics for solution based tests on ITO / P3HT / Nafion devices. Long dashed line indicates addition of analyte, short dashed line indicates addition of TMB. The fourth inset (bottom right) shows the overlays of the first three insets.

[0089] Figure 2: Summary of results for solution based tests on ITO / P3HT / Nafion devices.

[0090] Figure 3: Current-time characteristics for solution based tests on ITO / P3HT devices. Long dashed line indicates addition of analyte, short dashed line indicates addition of TMB.

[0091] Figure 4: shows the structure of a device in accordance with one embodiment of the disclosure.

[0092] Figure 5: shows the structure of an alternative sensor including a dielectric layer in accordance with one embodiment of the disclosure.

[0093] Figure 6: Schematic depicting sensor device architecture (a) layer 1 , electrodes, ITO; (b) layer 2, polymer semiconductor, P3HT; (c) layer 3, polymer gating1005587934 layer, Nation; (d) layer 4, porous wicking layer, PAN; (e) layer 5, antibody or enzyme probe (enzyme shown). Each substrate pictured contains two sensors.

[0094] Figure 7: Scanning electron micrographs (SEM) of poly(acrylonitrile) (PAN) porous membranes. The scale bar in (a) is 100 pm and the scale bar in (b) is 1 pm.

[0095] Figure 8: Photograph depicting the contact angle of water on a glucose sensor (a) with poly(acrylonitrile) (PAN) and (b) without PAN.

[0096] Figure 9: (a) XPS survey scan of pristine Nation film, (b) XPS region scans of pristine PAN membrane (solid line), Nafion / PAN bilayer (dashed line) and Nafion / PAN bilayer exposed to analyte solution (dotted line).

[0097] Figure 10: (a) Photograph of sensors placed on inkjet printer platen following printing of GOX layer, the sensors on the left contain a PAN porous membrane and the sensors on the right do not contain a PAN porous membrane, (b) Sensor response to a 10 mM glucose solution added at t = 180 s to a device containing a PAN membrane (solid line) and a device with no PAN membrane (dashed line).Detailed description of the embodiments

[0098] The development of organic thin film transistors (OTFTs) has grown rapidly in recent years motivated primarily by the unique physical properties of polymer devices, including their flexibility and ability to be fabricated using low-cost, solution-based techniques. Work on developing OTFTs for new and existing applications has focussed on two main areas. First, there have been systematic improvements in the materials and fabrication processes which have led to an improvement in the conventional performance parameters of organic devices making them comparable to their inorganic counterparts. Second, improvements in film morphology of the organic semiconducting layer have been made with the goal of eliminating electron and / or hole traps and enhancing free carrier transport in the polymer semiconducting materials. Progress has also been made in developing high capacitance organic dielectric layers and large improvements in OTFT performance have been reported.

[0099] The inherent compatibility of organic materials with biological molecules makes OTFTs suitable for use in biosensing applications. However, to help prevent OTFT degradation, antifouling layers are often required. The inventors have surprisingly1005587934 found a sensor architecture that allows the removal of the antifouling layer while still producing a working sensor. This provides the advantage of fewer components needed in the manufacturing process.

[0100] An OTFT device without an antifouling layer has been fabricated that is capable of detecting analyte levels across a broad range of concentrations and which is straightforward and relatively cheap to manufacture.

[0101] The following are definitions may be helpful in understanding the description of the present disclosure. These are intended as general definitions only and in no way limit the scope of the present disclosure to those terms alone.

[0102] As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps.

[0103] In the context of this specification, the term "about" is understood to refer to a range of numbers that a person of skill in the art would consider equivalent to the recited value in the context of achieving the same function or result.

[0104] In the context of this specification, the terms "a" and "an" refer to one or to more than one (i.e. to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.

[0105] In the context of this specification, the term "bodily fluid" is understood to include any liquid which originates within a human or animal body, including fluids that are secreted or excreted. Non-limiting examples of bodily fluids include: blood, saliva, sweat, urine, breast milk, bile and peritoneal fluid.

[0106] In the context of this specification, the term "top" means farthest away from the substrate, and the term "bottom" means closest to the substrate. Where a first layer is described as "disposed above" a second layer, the first layer is disposed farther away from the substrate. Furthermore, where a first layer is described as being "disposed above" a second layer, additional intermediate layers may be present in between the first and second layers, unless it is specified that the first layer is "in direct contact with" (ie physically contacting) the second layer.1005587934

[0107] In the context of this specification, the term “sensor” refers a device that senses the presence and / or amount of something. For example, the sensor could sense the presence of a chemical such as glucose, a protein such as an antigen, or an antibody in a biological fluid.

[0108] In the context of this specification, the term “transistor” refers to a device capable of converting physical quantities into an electrical signal. Preferably, the device is a semiconductor. Preferably, the physical quantities are physical quantities of a chemical produced by an assay. The assay is optionally enzymatic. The assay is optionally a molecular diagnostic and / or involved antibody binding. The assay may be an ELISA assay.

[0109] As used herein, "to cross link" means to form one or more bonds between polymer chains so as to form a network structure such as a gel or hydrogel. The polymers are then "crosslinked" polymers. The bonding can be through hydrogen bonding, covalent bonding or electrostatic. The "cross linking agent" can be a bridging molecule or ion, or it can be a reactive species such as an acid, a base or a radical producing agent.

[0110] In the context of this specification, the term “assay” refers to a method of detecting a biological sample suspected of having a target analyte, wherein the biological sample is contacted and incubated with the probe so that the probe binds to the analyte, if present, which can be subsequently detected in a detection step. The detection step involves the use of a labelled probe, which, when contacted with any of the bound analyte, binds to the target, and a detection means which is used to detect the label on the antibody and confirm the presence or amount of the target analyte. The assay is optionally enzymatic. The assay is optionally a molecular diagnostic, optionally involves antibody binding.

[0111] In the context of this specification, the term “coated” means that a layer of is present on a surface. For example, a layer of probe on the semiconducting, polymer gating or porous wicking layer. The amount of the probe used to coat the semiconducting, polymer gating or porous wicking layer can vary with a number of factors such as surface area, coating density, types of probe, and binding performance.1005587934

[0112] As used herein, like reference numerals in different figures are intended to refer to the same features.

[0113] The OTFT may have a channel length, between the source and drain of electrodes, of between about 5 m and about 50 pm, or between about 10 pm and about 30 pm, or about 20 pm, and a channel width of between about 1 mm and about 20 mm, or between about 1 mm and about 10 mm, or about 3 mm.

[0114] The OTFT may be for sensing an analyte in a sample. The analyte is optionally a biological analyte. In an embodiment the analyte is an antibody, antigen, protein, peptide or chemical. The sample may be any aqueous solution but is preferably a biological fluid, more preferably a bodily fluid, and still more preferably, saliva. The chemical is optionally glucose.Electrodes

[0115] As used herein, an “electrode” is an electrical conductor used to make contact with a non-metallic part of a circuit (i.e., it emits or collects electrons or electron “holes”). Electrodes can comprise electrically conducting or semi-conducting material, including but not limited to metals, alloys and polymers.

[0116] Suitable electrodes are commercially available, for example pre-patterned ITO, In some embodiments, the electrodes may be fabricated by low-cost spin-coating and printing techniques.

[0117] The source and / or drain electrodes may comprise, consist, or consist essentially of an ohmic material, such as metals (eg gold or silver) or metal oxides or graphene. Preferably the source and / or drain electrodes are tin oxide. Preferably the source and / or drain electrodes are indium tin oxide (ITO), for example pre-patterned ITO. Preferably each of said source and drain electrodes consist of an ohmic material. In at least one embodiment, source electrode and drain electrode each comprise, consist, or consist essentially of ITO, for example pre-patterned ITO. In alternate preferred embodiments, the ohmic conductor is a metal based ink such as silver based ink.1005587934Ohmic conductor for applying gate voltage

[0118] In some embodiments, the ohmic conductor comprises, consists, or consists essentially of an ohmic material, such as metals (eg gold or silver) or metal oxides or graphene. Preferably the source and / or drain electrodes are tin oxide. Preferably the source and / or drain electrodes are indium tin oxide (ITO), for example pre-patterned ITO. In alternate preferred embodiments, the ohmic conductor is a metal based ink such as silver based ink. In some embodiments the silver based ink comprises silver nanoparticles (AgNPs).Offset ohmic conductors / gate electrodes

[0119] The ohmic conductor or gate electrode is optionally laterally offset from the source and drain electrodes, as is part of the polymer layer. When the gate voltage is applied via the ohmic conductor I gate electrode to the polymer gating layer, a substantial electric field results in a vertical plane (ie in a plane perpendicular to the top surface of the semiconductor layer).Organic semiconducting layer

[0120] In at least one embodiment, the organic semiconducting layer consists of one organic semiconductor.

[0121] The organic semiconducting layer may be disposed above and in between the source electrode and the drain electrode. In an embodiment, the organic semiconducting layer is connected to and between a source electrode and a drain electrode. The organic semiconducting layer may be disposed above and in between the source electrode and the drain electrode, and in direct contact with, the source electrode and the drain electrode.

[0122] The organic semiconducting layer is preferably in contact with, the source electrode and the drain electrode. At least part of the organic semiconducting layer is disposed above the source electrode and the drain electrode. Preferably a majority of the organic semiconducting layer is disposed above the source electrode and the drain electrode.1005587934

[0123] The organic semiconducting layer is configured to enable flow of electrical current between the source electrode and the drain electrode as a result of the generation of these charge carriers.

[0124] The organic semiconducting layer includes one or more organic compounds. Any organic compound having semiconducting properties is suitable for use. However, it is preferred that the one or more organic compounds are selected from the group consisting of: polyacetylenes, porphyrins, phthalocyanins, fullerenes, polyparaphenylenes, polyphenylenevinylenes, polyfluorenes, polythiophenes, polypyrroles, polypyridines, polycarbazoles, polypyridinevinylenes, polyarylvinylenes, poly (p-phenylmethylvinylenes), including derivatives and co-polymers thereof, and further including combinations thereof. More preferably, the one or more organic compounds are selected from the group consisting of: poly(9,9-dioctylfluorene-2,7-diyl- co-bis-N,N-(4-butylphenyl)-bis-N,N-phenyl-1 ,4-phenylenediamine), poly(9,9- dioctylfluorene-2,7-diyl-co-benzothiadiazole), poly(3-hexylthiophene), (6,6)-phenyl-C61 - butyric acid methyl ester, poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1 ,4-phenylene vinylene), and combinations thereof.

[0125] Most preferably, the semiconducting layer includes, consists of, or consists essentially of poly(3-hexyl-thiophene) (P3HT).

[0126] Optionally, the semiconducting layer does not include poly(4-vinylphenol) (PVP).

[0127] The organic semiconducting layer may have a thickness between about 5 nm and about 500 nm, or between about 75 nm and about 125 nm, or about 100 nm. In at least one embodiment, the organic semiconductor layer has a thickness of less than about 390 nm. In at least one embodiment, the organic semiconductor layer has a thickness of between about 36 nm and about 9 nm. In at least one embodiment, the organic semiconductor layer has a thickness of between about 22 nm and about 9 nm. In at least one embodiment, the organic semiconductor layer has a thickness between about 22 nm and about 390 nm. In at least one embodiment, the organic semiconductor layer has a thickness between about 74 nm and about 108 nm (such as between 75 nm and 100 nm).1005587934

[0128] In embodiments with a polymer gating layer, preferably, said thickness spans at least between the polymer gating layer and inner ends of the respective source and drain electrodes, the inner ends being at opposite ends of a channel between the source and drain electrodes. However, preferably said thickness is a minimum thickness between the polymer gating layer and all of the source electrode and drain electrode.Polymer gating layer

[0129] In aspects of the disclosure not requiring a polymer gating layer there is optionally a polymer gating layer. In one embodiment, the organic semiconductor layer is in contact with said polymer gating layer. In at least one embodiment, at least part of the polymer gating layer is disposed above the semiconductor layer. Optionally, at least part of the ohmic conductor may be beneath another part of the polymer gating layer.

[0130] In at least one embodiment, a layer of the probe is formed on a surface of the polymer gating layer. In at least one embodiment, a porous wicking layer is on top of the polymer gating layer. In that embodiment, the probe may be embedded within or on the surface of the porous wicking layer.

[0131] In at least one embodiment, said polymer gating layer does not include poly(4- vinylphenol) (PVP).

[0132] Preferably said polymer gating layer forms a proton-conductive membrane. Preferably the polymer gating layer has a conductivity to protons that is greater than a conductivity to protons that is possessed by said organic semiconductor layer.

[0133] In at least one embodiment, at least part of the polymer gating layer is disposed above the semiconductor layer. Optionally, at least part of the ohmic conductor may be beneath another part of the polymer gating layer.

[0134] Preferably the polymer gating layer is not covered by the organic semiconductor. In at least one embodiment this is achieved by having the polymer gating layer as a top-most layer of the device, ie furthest from the substrate (other than the probe). In another embodiment this is achieved by having the polymer gating layer beneath the organic semiconductor, but extending laterally beyond the organic1005587934 semiconductor so that a portion of the polymer gating layer is not covered by the semiconductor.

[0135] Optionally, the polymer gating layer is 10 nm to 750 nm, 100 to 600 nm or about 400 nm thickness between the organic semiconductor or dielectric layer and the polymer gating layer.

[0136] The polymer gating layer may comprise, consist, or consist essentially of a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer, for example a copolymer comprising a tetrafluoroethylene backbone and perfluoroalkyl ether groups terminated with sulfonate groups.

[0137] The sulfonated tetrafluoroethylene-based fluoropolymer-copolymer may be a copolymer of tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid. It is preferred that the sulfonated tetrafluoroethylene-based fluoropolymer- copolymer is a tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer which is commonly referred to as Nation.

[0138] In an embodiment, the tetrafluoroethylene-based fluoropolymer-copolymer has the following structure:

[0139] In an embodiment, the tetrafluoroethylene-based fluoropolymer-copolymer has the following structure:1005587934Organic dielectric layer

[0140] In some embodiments, the sensor or OTFT of the disclosure further comprises a dielectric layer intermediate the polymer gating layer and the organic semiconductor layer.

[0141] In an embodiment, the ohmic conductor is in contact with the dielectric layer and configured to apply a gate voltage to the dielectric layer.

[0142] The dielectric layer may comprise, consist of, or consist essentially of an organic dielectric material. Preferably, the organic dielectric material has a conductivity to protons that is greater than the conductivity of said semiconductor layer. Preferably the dielectric layer intermediate said polymer gating layer and said semiconductor layer is a homogenous layer. Preferably the organic dielectric material is a hygroscopic insulator, such as for example polyvinyl phenols. More specifically, the dielectric layer may comprise, consist of, or consist essentially of, poly(4-vinylphenol).

[0143] Alternative dielectric materials that may be used in the devices will be readily apparent to those skilled in the art. Non-limiting examples include polyimide and poly(methyl methacrylate) (PMMA). In alternative embodiments the dielectric layer may comprise a doped dielectric material, for example lithium perchlorate doped poly(4- vinylpyridine).

[0144] The dielectric layer intermediate said polymer gating layer and said semiconductor layer may be in contact with the organic semiconductor. Additionally or alternatively the dielectric layer may be in contact with said polymer gating layer.

[0145] The gate electrode / ohmic conductor may be disposed above the dielectric layer. The gate electrode may be disposed above, and in direct contact with, the1005587934 dielectric layer or disposed above the dielectric layer, and in indirect contact with the dielectric layer via the polymer gating layer.

[0146] The gate electrode / ohmic conductor may be offset with respect to the dielectric layer.

[0147] The dielectric layer may be disposed above the semiconducting layer. The dielectric layer may be disposed above, and in direct contact with, the semiconducting layer. The dielectric layer may be disposed below the polymer gating layer. The dielectric layer may be disposed below, and in direct contact with, the polymer gating layer. The dielectric layer may comprise, consist of, or consist essentially of, poly(4- vinylphenol). The dielectric layer may have a thickness between about 50 nm and 750 nm, or between about 300 nm and about 500 nm, or about 400 nm.Porous wicking layer

[0148] The porous wicking layer exhibits a wicking effect which improves incorporation of a liquid sample into the device, this wicking effect has the potential to ensure delivery of a standard volume of liquid sample to within the device. Additionally, the wicking effect results in excellent wetting of the internal porous structure of the porous wicking layer which results in a high degree of exposure of an analyte within the liquid sample to the enzyme retained within the porous wicking layer. This is beneficial as it results in efficient generation of charge carriers within the device, and consequently the rapid detection of the analyte if present within the liquid sample.

[0149] The skilled person will appreciate that the porous wicking layer may be formed from a range of different materials, including: porous ceramics, porous metals, porous protein fibres, or porous polymers. However, generally porous polymers are preferred for ease of sensor fabrication. Suitable polymers include, but are not limited to: polyacrylonitrile, polysulfone, polyethersulfone, polystyrene, polybutadiene, polyisoprene, polyimides, polyamides, and fluoropolymers. Typically, the porous wicking layer is formed from a material that is not the same as the material that the polymer gating layer is formed from. Where the polymer gating layer is formed from Nation, the porous wicking layer is not formed from Nation. Preferably the porous wicking layer is not formed from Nation.1005587934

[0150] Ideally the porous wicking layer is formed from a material that has a low contact angle with the liquid of the liquid sample to ensure that the liquid sample is rapidly taken into the porous wicking layer and that there is good wetting of pore surfaces of the porous wicking layer.

[0151] Preferably the porous wicking layer takes the form of a layer that enables the rapid formation of a droplet, preferably an aqueous droplet, more preferably a biological fluid droplet, more preferably a saliva droplet, such as a neat saliva droplet or a processed or diluted saliva droplet, on the porous wicking layer that has a low contact angle with the porous wicking layer.

[0152] Preferably the porous wicking layer is formed from a layer having a high degree of wettability by an aqueous droplet, more preferably a biological fluid droplet, more preferably a saliva droplet, more preferably a neat saliva droplet or a processed or diluted saliva droplet.

[0153] Notwithstanding the above, it is preferred that the porous wicking layer is a porous poly(acrylonitrile) (PAN) layer. PAN has physical properties that make it particularly useful as the porous wicking layer. PAN is thermally stable with a glass transition temperature (Tg) of ~95 °C and melting temperature (Tm) > 300 °C. Given this, PAN exhibits good thermal stability, which is desirable in a sensor as this means that during typical use, the Tg is unlikely to be exceeded. If the Tg is exceeded, the porous structure may collapse. PAN also has high strength, a high modulus of elasticity, and a low density. Furthermore, from a fabrication point of view, PAN is soluble in dimethyl sulfoxide (DMSO) and can be used to prepare porous polymer membranes via the phase inversion technique-immersion precipitation.

[0154] In a preferred embodiment, the porous wicking layer has a sufficiently low surface energy to enable a body fluid, preferably saliva, preferably undiluted or otherwise unprocessed saliva, or processed saliva to rapidly wet and penetrate the porous wicking layer.

[0155] As discussed above, the porous wicking layer includes an enzyme or probe. The enzyme or probe may be disposed on a surface of the porous wicking layer and / or disposed throughout the porous wicking layer, such that the enzyme or probe is exposed on pore surfaces within the porous wicking layer.1005587934Enzyme

[0156] For embodiments involving an enzyme probe, the enzyme is selected to facilitate generation of charge carriers when an analyte contacts the device. The charge carriers are typically electrons, anions, or cations (e.g. hydrogen ions / protons). The generation of the charge carriers may be further facilitated by the presence of an electric field. As will be described, these generated charge carriers can then contribute to electric current through the device. It will be recognised that a range of enzymes could be used for any one particular analyte. Further given the diversity of enzymes available, the device, by following the disclosure herein can be adapted or developed for detection of a range of analytes.

[0157] A particularly preferred class of enzyme is an oxidoreductase. An oxidoreductase for use in the device may act on any one of the following donor groups: the CH-OH group of donors (alcohol oxidoreductases), the aldehyde or oxo group of donors, the CH-CH group of donors (CH-CH oxidoreductases), the CH-NH2 group of donors (amino acid oxidoreductases, monoamine oxidase), CH-NH group of donors, NADH or NADPH, other nitrogenous compounds as donors, a sulfur group of donors, a heme group of donors, diphenols and related substances as donors, peroxide as an acceptor (peroxidases), hydrogen as donors, single donors with incorporation of molecular oxygen (oxygenases), paired donors with incorporation of molecular oxygen, superoxide radicals as acceptors, CH or CH2 groups, iron-sulfur proteins as donors, reduced flavodoxin as a donor, phosphorus or arsenic in donors, X-H and Y-H to form an X-Y bond, or oxidoreductases that oxidize metal ions.

[0158] The enzyme may be glucose oxidase.

[0159] In some embodiments, the enzyme is printed, eg ink-jet printed, on the polymer gating layer. Printing methods include gravure, flexographic, screen-printing and doctor blade. Alternatively, non-printing methods known to those skilled in the art may used, such as drop casting, vapour deposition and sputtering.Probe

[0160] For embodiments involving a probe, the probe is selected to bind the analyte.1005587934

[0161] As used herein, a "probe” is a natural or synthetic receptor (eg, a molecular receptor) that binds to a target molecule such as an analyte. In some embodiments, the probe is an "antibody probe." The probe is optionally attached to the sensor via a connector such as a connector protein.

[0162] In some embodiments, the binding is a specific binding such that it is selective to that target above non-targets.

[0163] For example, a probe may be, but is not limited to an antibody, an antigen, an antibody mimetic, a peptide, protein or nucleic acid (eg, an RNA or DNA aptamer) or enzyme. The probe may be a sugar, oligosaccharide, polysaccharide, lipopolysaccharides. The probe may be a receptor, for example a hormone receptor, cytokine receptor, or a synthetic receptor. Additionally or alternatively the probe may be a small molecule such as a pharmacological active substance, alkaloid, steroids, vitamins, or amino acids.

[0164] In the context of this specification, the term “antibody” includes a protein comprising an antigen binding domain and capable of specifically binding to an antigen. Preferably, the antigen binding domain is contained within a Fv. An antibody can be a polyclonal antibody, monoclonal antibody, humanized or chimeric antibody. Antibody fragments include single chain Fv antibody fragments, Fab fragments, and F(ab)2 fragments.

[0165] In some embodiments, the probe is printed, eg ink-jet printed, on the polymer gating layer and / or porous wicking layer. Printing methods include gravure, flexographic and doctor blade. Alternatively, non-printing methods known to those skilled in the art may used, such as drop casting, vapour deposition and sputtering.

[0166] Optionally, the OTFT has a plurality of probes. Optionally, the probes are all of the same type. Alternatively, the OTFT includes multiple probe types, for example, antibodies to more than one coronavirus antigen or multiple coronavirus antigens.

[0167] The probe is selective to a specific analyte or class of analyte.1005587934Detection agent and generation of charge carrier

[0168] If the analyte is not a charge carrier or able to generate a charge carrier the analyte bound probe can be further bound to a detection agent that can generate a charge carrier. Optionally, the detection agent includes a first portion that binds to the analyte or analyte and probe and a second portion for generation of a charge carrier. Optionally, the second portion is an enzyme. Preferably, the enzyme is a redox active enzyme, for example, a peroxidase such as horseradish peroxidase (HRP) that will generate a charge carrier in the presence of a the substrate for the reporter enzyme such as 3,3'-diaminobenzidine (DMB), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS); o-orthophenylenediamine (OPD); amplexred; 3,3'-diaminobenzidine (DAB); 4-chloro-1 -naphthol (4CN); AEC; 3,3',5,5'-tetramethylbenzidine (TMB); homovanilllic acid; lumininol; nitro blue tetrazolium (NBT); hydroquinone; benzoquinone; or mixtures of these.

[0169] The probe / target / detection agent and substrate for the reporter enzyme facilitate generation of charge carriers when the target contacts the sensor in the presence of detection agent and substrate for the reporter enzyme and a minimum electric potential (ie gate voltage or potential) is applied via the ohmic conductor, the voltage being selected relative to at least one of the drain and source electrodes. As for embodiments of the sensor with an enzyme, the charge carrier impacts the current in the device allowing detection of the target.

[0170] In some embodiments the probe facilitates generation of a charge carrier indirectly. For example, following binding of the analyte to the probe, the analyte can be detected by binding with a detection agent such as an antibody, protein or other molecule that generates a charge carrier by catalyzing, directly or indirectly, a redox reaction close to the surface of the OTFT. Optionally, the detection agent, antibody, protein or other molecule in the presence of a substrate for the reporter enzyme causes deposition of a charge carrier on the sensor surface (eg, on the polymer gating layer and / or porous wicking layer of the sensor). The charge carrier alters the charge applied by the ohmic conductor / gate electrode. The difference in the charge (eg voltage and / or current) is detected by the sensor. For example, the detection agent can be conjugated with a redox catalyst and, in the presence of the substrate for the reporter enzyme,1005587934 substrate for the reporter enzyme is oxidized or reduced and precipitated onto the OTFT surface, thereby generating a charge carrier.

[0171] Embodiments include known immunoassays or modifications of these to be detectable by an OTFT.

[0172] In some embodiments, the detection agent is used at a concentration between about 1 and about 500 mg / mL. In embodiments, the detection agent is used at a concentration between about 10 and 100 mg / mL, such as between about 20 and 100 mg / mL, or between about 20 and about 100 p / mL. In some embodiments, the detection agent is (eg, detection antibody) is used at a concentration between about 0.1 and 100 mg / mL, such as between about 0.5 and 50 mg / mL, between about 1 and 30 mg / mL, between about 10 and 30 mg / mL, or between about 15 and 25 mg / mL.

[0173] In embodiments, the substrate for the reported enzyme includes rabbit antihuman IgG-HRP, HPR:AB, or a similar molecule for signal augmentation. In embodiments, the HRP concentration is between about 0.1 and about 100 pg / mL, such as between about 1 and 50 p / mL, or between about 5 and 20 p / mL. The ranges of concentrations of substrate for the reported enzyme and detection agent can be used in any combination, such as about 20 mg / mL of substrate for the reported enzyme in combination with 10 pg / mL of detection agent. The ranges of concentrations of substrate for the reported enzyme, detection agent and HRP may also be used in any combination, such as 10 pg / mL of probe, 20 mg / mL of detection agent and 10 pg / mL HRP.Charge carrier

[0174] The charge carrier may be any one or more of the following charge carrier types: anions, cations or electrons. However, in at least one embodiment the charge carriers are cations, and more preferably hydrogen ions (eg protons).

[0175] Preferably, the organic semiconductor is doped by interaction with said charge carriers, preferably protons, to increase an electrical conductivity between the drain electrode and the source electrode.1005587934Substrate layer

[0176] In one or more embodiments, the OTFT further comprises a substrate layer. Preferably, at least the source electrode and drain electrode are disposed on the substrate. In at least one form, the source electrode, drain electrode and organic semiconductor are each in contact with the substrate. The substrate may be glass, or any other suitable substrate known to those skilled in the art, for example metal, paper or a low-cost plastic, such as polyethylene terephthalate (PET).

[0177] The source electrode and the drain electrode may be disposed above the substrate. The source electrode and the drain electrode may be in direct contact with the semiconductor layer.Analyte

[0178] The one or more probe and one or more analyte in each embodiment are compatible ie each probe specifically binds an analyte.

[0179] The analyte can be an ion, molecule, oligomer, polymer, protein, peptide, antigen, antibody, nucleic acid, toxin, biological threat agent such as spore, viral, cellular and protein toxin, carbohydrate (eg, monosaccharide, disaccharide, oligosaccharide, polyol, and polysaccharide), lipid, fatty acid, or combinations of these. The analyte is optionally an antigen or antibody indicative of infection or resistance to infection. The analyte is optionally a clinical chemistry analyte.

[0180] In some embodiments the analyte can be redox active and the probe / enzyme directly responsible for generation of the charge carrier that is detected by an electrode. For example, the binding of the analyte to the probe facilitates generation of the charge carrier near the conducting polymer layer surface, the conducting polymer layer conducts the charge carrier and this impacts the applied voltage and / or current resulting in detection of the analyte by the sensor. In some embodiments, the electrode is a gate electrode of an OTFT.

[0181] In some embodiments, the analyte is immunological or serological, for example an antigen or antibody. In preferred embodiments the analyte is an antigen or antibody a coronavirus, Hepatitis A, Hepatitis B, Hepatitis C, or HIV.1005587934

[0182] Preferably the analyte indicates a coronavirus infection or immunity, more preferably COVID-19 infection or immunity.

[0183] In some embodiments, the analyte is a coronavirus antigen. Preferably, the coronavirus antigen is a SARS-CoV-2 antigen. Examples of SARS-CoV-2 antigens include, but are not limited to, nucleocapsid, glycoprotein spike including individually the S1 and S2 subunits and the RBD domain, membrane glycoprotein, small envelope protein, accessory proteins, non-structural proteins and any combinations thereof.

[0184] In some embodiments, the analyte is a coronavirus antibody. Optionally, a SARS-CoV-2 antibody. Optionally, the SARS-CoV-2 antibody is an immunoglobulin M (IgM), immunoglobulin A (IgA) or immunoglobulin G (IgG) antibody. Examples of IgG subtypes are IgG 1 , lgG2, lgG3 and lgG4. Optionally, the analyte is anti-SARS-CoV-2 nucleocapsid IgG.

[0185] In some embodiments multiple probes may be used to detect multiple analytes, for example, multiple antigens for the same infection or an antigen and antibody for the same infection.

[0186] In some embodiments the probes are selected to cover one or more analytes for one or more diseases of the TORCH Screen ie for detecting one or more of Toxoplasmosis, HIV, hepatitis A, B or C, varicella, parvovris, rubella, cytomegalovirus, herpes simplex and syphilis.

[0187] In some embodiments the analyte is a hormone, for example a gynaecological hormone such as luteinizing hormone (LH), progesterone, estradiol or follicle-stimulating hormone. In preferred embodiments the probe detects LH. In some embodiments the probe is a LH specific antibody. In some embodiments the probe is an LH monoclonal antibody. Additionally or alternatively the hormone may be a pregnancy hormone such as human chorionic gonatropin (hCG).

[0188] In some embodiments the analyte is a clinical chemistry analyte such as an ion, salt, mineral, metabolite, therapeutic drug, toxicology marker, drug of abuse, transport protein, enzyme, specific protein, lipoprotein or marker, for example diabetes or myocardial infarction markers. In some embodiments the analyte is a metabolite selected from the group of glucose, cholesterol, urea, lactic acid, bilirubin, creatinine,1005587934 triglycerides. In preferred embodiments the probe is selected to detect glucose or cholesterol.

[0189] In some embodiments, the analyte is a tumour marker. Tumour markers can be used in guiding treatment decisions, monitoring treatment, predicting the change of recovery and to predict or monitor for tumour recurrence.

[0190] Once the analyte is selected, a probe is selected to bind the analyte. Many combinations of analyte and probe are known in the art.Coronaviruses

[0191] Coronaviruses, belong to the Coronaviridae family in the Nidovirales order, are minute in size (65-125 nm in diameter) and contain a single-stranded RNA as a nucleic material, ranging from 26 to 32kbs in length. The subgroups of coronaviruses family are alpha (a), beta (|3), gamma (y) and delta (5) coronavirus. The beta-coronaviruses are of the greatest clinical importance concerning humans. Beta-coronavirus of lineage A include OC43 and HKU1 (which can cause the common cold). Beta-coronaviruses of Lineage B include the severe acute respiratory syndrome coronaviruses SARS-CoV and SARS-CoV-2 (which causes the disease COVID-19). Middle East respiratory syndrome coronavirus (MERS-CoV) is a beta-coronavirus from lineage C. These viruses cause acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) which leads to pulmonary failure and death.Voltage

[0192] The gate voltage VG and drain voltage VD provide a sufficiently strong electric field to liberate H+ from H2O2, but not strong enough to cause electrolysis of water, as electrolysis of water may lead to a decrease in the signal-to-noise ratio of the sensor (ie below -1 .23 V). Typically, the gate voltage and drain voltage applied are between about 0 V and -2 V, e.g. about -1 V. Where a simple sensor is used, low voltages can be used including 250 to 500 mV to 300-400 mV. The voltage range can then be -0.25 to -2V or - 0.25 to -0.1 V.

[0193] When the sensor is an OTFT with an organic semiconductor with a conducting layer (eg nation), the voltage applied (eg by an ohmic conductor / gate electrode) is at1005587934 least -0.55 V, -0.6 V, -0.65 V or -0.7V (ie -0.55 V to -2 V). -0.6 to -0.8V and -0.65 to - 0.75 V are preferred ranges.

[0194] The voltage applied by the ohmic conductor / gate electrode is optionally at least 0.7 V.Printing

[0195] Printing methods include gravure, flexographic, screen-printing and doctor blade. Alternatively, non-printing methods known to those skilled in the art may used, such as drop casting, vapour deposition and sputtering.Sample

[0196] In accordance with various embodiments described herein, a sample, including any fluid or specimen (processed or unprocessed) that is intended to be evaluated for the presence of an analyte can be subjected to methods, compositions, kits and systems described herein. The sample or fluid can be liquid, supercritical fluid, solutions, suspensions, gases, gels, slurries, and combinations thereof. The sample or fluid can be aqueous or non-aqueous.

[0197] In some embodiments, the sample can be an aqueous fluid. An aqueous fluid includes biological fluids as described below. Optionally, if the sample is water-based but not fluid, an aqueous solution can be added to produce a fluid sample.

[0198] In some embodiments, the sample can include a biological fluid obtained from a subject. Exemplary biological fluids obtained from a subject can include, but are not limited to, blood (including whole blood, plasma, cord blood and serum), lactation products (e.g., milk), amniotic fluids, sputum, saliva, urine, semen, cerebrospinal fluid, bronchial aspirate, perspiration, mucus, liquefied stool sample, synovial fluid, lymphatic fluid, tears, tracheal aspirate, and any mixtures thereof. In some embodiments, a biological fluid can include a homogenate of a tissue specimen (e.g., biopsy) from a subject. In one embodiment, a test sample can comprises a suspension obtained from homogenization of a solid sample or a fragment thereof obtained from a subject.

[0199] In some embodiments, the sample can include a fluid or specimen obtained from an environmental source. For example, the fluid or specimen obtained from the1005587934 environmental source can be obtained or derived from food products or industrial food products, food produce, poultry, meat, fish, beverages, dairy products, water (including wastewater), surfaces, ponds, rivers, reservoirs, swimming pools, soils, food processing and / or packaging plants, agricultural places, hydrocultures (including hydroponic food farms), pharmaceutical manufacturing plants, animal colony facilities, and any combinations thereof.

[0200] In some embodiments, the sample can be a non-biological fluid. As used herein, the term “non-biological fluid” refers to any fluid that is not a biological fluid as the term is defined herein. Exemplary non-biological fluids include, but are not limited to, water, salt water, brine, drinking water, industrial water, brown water, sewerage, and mixtures thereof. Preferred non-biological fluids are drinking or industrial water or sewerage.Determining concentrations

[0201] The impact of a specific concentration of analyte on the current in the semiconductor in a specific sensor can be calibrated and the sensor used to identify the concentration of analyte in a sample.Exemplary devices

[0202] An exemplary organic thin film transistor based sensor 100 in accordance with one embodiment of the disclosure is illustrated in Figure 4, which provides a conceptual representation of the structure of the sensor 100. Sensor 100 includes a drain electrode 102 and source electrode 104 disposed on the surface of a substrate 106. The sensor includes a two or three-layered structure that includes: a porous wicking layer 108 in the three-layered structure, a polymer gating layer 120, and an organic semiconducting layer 122. The organic semiconducting layer 122 covers a portion of the drain and source electrodes, with the organic semiconducting layer 108 in contact with, and extending between the drain electrode 102 and the source electrode 104. The polymer gating layer 120 is disposed on a surface of the organic semiconducting layer 122. An ohmic conductor 132 is in contact with polymer gating layer 120 to enable a gate voltage to be applied to the polymer gating layer 120. A porous wicking layer 108 is optionally disposed on the surface of the polymer gating layer 120. The surface of the porous wicking layer 108 or the polymer gating layer 120 is exposed to receive a fluid1005587934 sample. An enzyme or probe is on the surface of or within the porous wicking layer 108 or on the surface of or within the polymer gating layer 120. The porous wicking layer 108 is not located between gate and drain electrodes.

[0203] The polymer gating layer 120 is disposed between the porous wicking layer 108 and the organic semiconducting layer 122. The function of polymer gating layer 120 is to facilitate transport of charge carriers generated above or within the porous wicking layer 108 or the polymer gating layer 120 from an analyte on application of a gate voltage and transported via the conducting polymer gating layer. A range of different polymers may be used to form the polymer gating layer 120 depending on the nature of the analyte, enzyme, and / or charge carrier. In a preferred form, the charge carriers are protons (such as hydrogen ions) and the polymer gating layer 120 is proton conducting. Preferably the polymer gating layer has a conductivity to protons that is greater than a conductivity to protons of the organic semiconductor layer 122. The conductivity may be due to permeability of the polymer gating layer 120 to charge carriers, such as where conduction occurs via migration of the charge carriers; alternatively, conduction may occur via another mechanism, such as the Grotthuss mechanism. Where a charge carrier is a proton, or is an electron, the polymer gating layer may be proton conducting or electron conducting.

[0204] The organic semiconducting layer 122 is configured to enable flow of electrical current between the source electrode and the drain electrode as a result of the generation of these charge carriers.

[0205] The use of the OTFT 100 will now be described below in relation to a preferred embodiment in which the OTFT 100 is for detecting the presence of glucose in a saliva sample.

[0206] In use, a gate voltage VG and a drain voltage VD are applied to the OTFT 100. The gate voltage applied by via ohmic conductor or gate electrode. The drain voltage applied via the drain electrode. The voltages being with respect to the source electrode 104. A liquid sample comprising an analyte, for example a bodily fluid such as saliva, is contacted with the porous wicking layer 108 or polymer gating layer 120 upon which the probe or enzyme has been deposited / attached. If the analyte is glucose, the glucose is degraded via an enzymatic reaction with the enzyme GOX thereby producing H2O2. The gate voltage VG and drain voltage VD provide a sufficiently strong electric field to1005587934 liberate charge ie H+ from H2O2, but not strong enough to cause electrolysis of water, as electrolysis of water may lead to a decrease in the signal-to-noise ratio of the sensor (ie below -1 .23 V). Typically, the gate voltage and drain voltage applied are between about 0 V and -2 V, e.g. about -1 V.

[0207] When the OTFT is an organic semiconductor with a conducting layer ie polymer gating layer (eg nation), the voltage applied (eg by an ohmic conductor / gate electrode) is at least 0.55 V, 0.6 V, 0.65 V or 0.7V (ie -0.55 V to -2 V). -0.6 to -0.8V and -0.65 to -0.75 V are preferred ranges.

[0208] The H+ ions are conducted though the polymer gating layer 120 (e.g. Nation) to the organic semiconducting layer. This results in doping of the semiconductor (from the Nation), and consequentially, current between the drain and the source electrodes. Without wishing to be bound by theory, the inventors are of the view that the gate potential controls the doping and de-doping of the semiconducting compound(s) via ion migration from the site of ion generation to the active channel in the organic semiconductor. Thus, the increase in H+ ions results in an increase in drain current, such that a relationship is established between the amount of analyte present in the sample and the magnitude of the drain current. The drain current is then measured which provides an indication of the presence and optionally concentration of analyte within the sample.

[0209] The skilled person will be aware that a similar outcome can be achieved using different probe or enzyme, analyte and charge carrier options.

[0210] In an alternative form of the disclosure, as illustrated in Figure 5, the OTFT 200 is similar to OTFT 100 of Figure 4, but further comprises a dielectric layer 234 between and in contact with polymer gating layer 220 and organic semiconductor layer 222.

[0211] The dielectric layer 234 comprises, consists of, or consists essentially of an organic dielectric material. Preferably, the organic dielectric material has a conductivity to protons that is greater than the conductivity of organic semiconductor layer 222. Preferably the organic dielectric material is a hygroscopic insulator, such as for example polyvinyl phenols. More specifically, the dielectric layer may comprise, consist of, or consist essentially of, poly(4-vinylphenol).1005587934

[0212] The device operates at least for an organic semiconductor layer thickness of less than about 390 nm. Further, there is advantageous device behaviour when the organic semiconducting layer has a thickness in the range of about 75 nm and about 100 nm, between the polymer gating layer and the source and drain electrodes. The advantage is that in this range the device has a calibration curve that has a one-to-one correspondence between a calibration parameter and glucose concentration for concentrations between 0.1 mM and 100mM. Further their results have shown the calibration curve as being is essentially linear over that range.

[0213] Further, there is also advantageous behaviour when the organic semiconducting layer instead has a thickness in the range of about 36 nm or less, between the polymer gating layer and the source and drain electrodes. The advantage in this case is a faster response time for the device.

[0214] It will be understood that the disclosure disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the disclosure.ExamplesExample 1 - Preparation of the OTFT substratesMaterials and Reagents

[0215] Glutaraldehyde (GA), N-hydroxysuccinimide (NHS), 2-(N- morpholino)ethanesulfonic acid hydrate (MES), 3,3',5,5'-tetramethylbenzidine (TMB) colorimetric substrate, ethanolamine, Tween 20, 0.01 M phosphate buffer saline (PBS, pH 7.4) were purchased from Sigma-Aldrich. 1 -ethyl-3-(3- dimethylamonipropyl)carbodiimide (EDC), blocker blotto blocking buffer were purchased from Thermo Scientific. Recombinant SARS-CoV-2 Nucleocapsid Protein (His-tag) (230-30164) (SARS-CoV-2 N protein) was purchased from Raybiotech. SARS-CoV-2 Spike S1 -His Recombinant Protein (HPLC-verified) (40591 -V08H) (SARS-CoV-2 S1 protein) was purchased from Sino Biological. SARS-CoV-2 Spike S1 antibody (hlgM2001 ), human chimeric (A02046) (SARS-CoV-2 IgM) and SARS-CoV-2 Spike S1 antibody (HC2001 ), human chimeric (A02038) (SARS-CoV-2 IgG) were purchased from GenScript. Rabbit anti-human Prostate Specific Antigen antibody (IgG) (ab53774) (PSA1005587934IgG) and rabbit anti-human IgG H&L (HRP) (ab6759) (anti-human IgG-HRP or HRP:AB) were purchased from Abeam.Preparation of substrates

[0216] Patterned indium tin oxide (ITO) on glass substrates were cleaned using liquid Pyroneg solution, deionised water, acetone and isopropanol. The ITO pattern consists of two sets of three electrodes: two of which are separated by a 20 pm long and 3 mm wide channel and the third offset by 2 mm orthogonal to the channel.Preparation of Thin Films

[0217] Where required, P3HT (synthesised in accordance with the method of Pappenfus et al. Macromol. Chem. Phys., 2018, 219: 1800272; section 2.2.2 GRIM Synthesis of Poly(3-hexylthiophene), 20 mg / mL or 10 mg / mL in chloroform) was spin coated on to ITO-on-glass substrates at 2000 rpm and 1596 rpm / s for 60 seconds to produce a thin film approximately 150 nm in thickness. Nation (N-(3-acetylphenyl)-4-(2- phenylethyl)thieno[3,2-b]pyrrole-5-carboxamide) solution (Sigma Aldrich, part number 274704) was used as received and spin coated on to P3HT films as appropriate at 550 rpm and 399 rpm / s for 120 seconds to produce a thin film approximately 400 nm in thickness.Preparation of porous wickinq layer

[0218] Porous polymer membranes can be fabricated using the phase inversion (immersion precipitation) technique. Firstly, a viscous solution of polyacrylonitrile (PAN) polymer in DMSO solvent is coated on a flat, rigid substrate, such as glass, to form a uniform ‘wet’ film. The ‘wet’ film can be coated by either spin coating, drop-casting or with the use of a printing technique such as slot-die coating. The ‘wet’ film is not a solid, dry film, it is a composite film, comprising a polymer network with liquid solvent molecules existing in the voids between polymer chains. The ‘wet’ film upon the rigid substrate is then submerged in water (the non-solvent), the porous polymer membrane forming as the DMSO solvent diffuses out of the polymer network into the surrounding water bath and the water diffuses into the polymer network. It is this solvent exchange with non-solvent that induces precipitation of the polymer. The selection of solvent and non-solvent is highly dependent on the chosen polymer, the solvent needs to be capable of dissolving the polymer whereas the non-solvent is one in which the polymer1005587934 is insoluble. The solvent and non-solvent combination should be miscible, otherwise the solvent will not diffuse into the non-solvent and the porous polymer membrane will not form, instead remaining as a ‘wet’ solvent-containing film. The fabrication is a two-step process, it is during the second step that the ‘wet’ film transforms into a solid film. Once the solid film has been formed, it is processed into individual layers of the desired size and thickness and applied to the device as a porous wicking layer.Example 2 - Design of an antigen integrated OTFT architecture and characterisation of antibody response

[0219] On a P3HT / Nafion bilayer, the initial conductivity of the channel material was measured to be relatively high and the P3HT / Nafion interface is doped. Addition of plain PBS or antibody solutions in PBS (at t = 30 s) results in a lowered current due to dedoping of the P3HT / Nafion interface due to removal of protons from the interface. The subsequent addition of the TMB solution (at t = 60 s) resulted in a further reduction in current. This reduction is attributed to a reaction between doped P3HT and the neutral TMB. This reaction results in oxidation of the TMB to TMB2+ and dedoping of the P3HT was observed in all cases. In the absence of HRP, this dedoping continues during the testing period until approximately t = 200 s at which point the current stabilises (Figure 1 (a) and (b)). This indicates that performance of the devise is impacted in the presence of a biological sample.

[0220] When the HRP-conjugated antibody is present in solution, a competitive reaction occurs. The TMB is partially oxidised by the HRP (again to form TMB2+ which aggregates on the film surface as a blue precipitate). Consequently, less TMB is available in solution to dedope the P3HT and the current remains higher (Figure 1 (c)), indicating a positive response for the presence of HRP as shown in the composite plot of representative data in Figure 1 (d).

[0221] The ratio of lt=200s / lt=55s was chosen as a calibration parameter to compare the response of devices to the applied analyte. The choice of 55 s for the calibration reference point was made in order to provide a reference where the hydration level of devices has had time to equilibrate (accounting for any difference due to storage or testing conditions) but prior to the addition of TMB. Figure 2 shows the average value of this calibration parameter for devices with either PBS, COVID antibody or a HRP- conjugated antibody (HRP:AB) and a TMB developer solution used in all cases as the1005587934 secondary addition. The graph clearly shows that the addition of the HRP:AB results in a four-fold higher normalised current value indicating a positive response (i.e. less dedoping of the P3HT / Nafion interface) in comparison to the other two analytes. This means that the device functions well in the presence of the detection agent, specifically for the generation of a charge carrier even without an antifouling layer.

[0222] Due to the similarity in the responses of the devices to PBS and COVID antibody additions, in subsequent experiments PBS was judged to be a suitable negative control.

[0223] In order to further probe the mechanism of device operation, a film of P3HT without the addition of Nation was used in the device. The initial conductivity of the undoped P3HT is much lower than the P3HT / Nafion devices, and hence the current for the same applied voltage (50 mV) is also lower. Upon addition of PBS solutions (t = 30 s), an initial increase in current as the buffer partially dopes the low conductivity P3HT was observed. Upon addition of the TMB (at t = 60 s), a current pulse was observed which is attributed to ionic solution-based conductivity and then a current drop as TMB dedopes the P3HT and forms TMB2+ on the film surface. When HRP is present in solution the competing oxidation of the TMB was again observed. The amount of neutral TMB in solution is lowered (having already formed TMB2+) and therefore the P3HT is less dedoped. Indeed, for the native P3HT films used here with a low initial doping level, it is likely that TMB2+ on the surface of the film may even further dope the P3HT, as evidenced by the slowly increasing current observed for the 1 pg / mL HRP:AB devices (Figure 3(a)). Consequently, even this simple sensor is expected to be functional without an antifouling layer.

[0224] Due to the large difference between the responses to 1 pg / mL HRP:AB solution and the negative PBS control, the response to a lower concentration of HRP:AB (chosen to be 0.1 pg / mL) was also recorded (Figure 3 (b)). Encouragingly, there is a distinct difference between the response to 0.1 pg / mL HRP:AB solution and the negative control (Figure 3 (c)) indicating that the devices are currently operating well above the limit of detection. A composite plot of representative data for each analyte is presented in Figure 3 (d).1005587934Example 3 - Benefits of the porous wicking layer

[0225] The porosity of PAN membranes prepared via the phase inversion technique were investigated using scanning electron microscopy (SEM) (see Figure 7) on a Zeiss ZP FESEM operating at an accelerating voltage of 2 kV. DMSO was used as the solvent and water as the non-solvent in the membrane preparation process. SEM revealed PAN membrane pore size to be in the 200 - 800 nm size range.

[0226] To investigate the potential for wicking of PAN membranes, the contact angle of water on PAN compared to water on Nation was measured. Figure 8 presents photographs of water droplets on (a) PAN and (b) Nation from which the contact angle was extracted. The contact angle of water on PAN was measured to be ~35 °, this increased to ~70 ° on Nation. The decreased contact angle of water on PAN indicates that PAN is a more hydrophilic surface than Nation. This reduced contact angle on PAN is beneficial for a wicking effect.

[0227] X-ray photoelectron spectroscopy (XPS) was performed to probe any potential redistribution of Nation throughout the PAN porous membranes following analyte addition. XPS spectra were collected by illuminating the samples with a non- monochromatic X-ray source (Omnivac) using Al Ka (1486.6 eV) radiation, and the photoemission collected by an SES2002 analyser (Scienta). The F 1s peak was utilised as a marker for Nation as Nation contains fluorine atoms attached to the carbon atoms of the polymer backbone whereas PAN only contains the elements carbon, nitrogen and hydrogen. Structures for (a) PAN and (b) Nation are provided below:(a) PAN (b) Nation1005587934

[0228] An XPS survey scan (Figure 9(a)) of a pristine Nation film identified the F 1 s peak at a binding energy of 691 eV. XPS region scans were then performed of a pristine PAN membrane, a Nafion / PAN bilayer and a Nafion / PAN bilayer following exposure to analyte solution. The pristine PAN membrane had no F 1 s peak (Figure 9(b)). The Nafion / PAN bilayer XPS spectrum contains a peak for F 1 s, the Nafion / PAN bilayer following exposure to analyte solution XPS spectrum also contains a peak for F 1 s, and this peak is quite invariant compared to the Nafion / PAN bilayer indicating that the analyte solution does not cause solvation and redistribution of the underlying Nation film. This is a positive result for the biosensors indicating that the Nation film is quite robust.

[0229] Glucose sensors were fabricated with the architecture depicted in Figure 6. Sensors with PAN and without PAN were fabricated and the GOX layer was inkjet printed with a Dimatix DMP 2831 inkjet printer with a 10 pL nozzle printing head (Figure 10).

[0230] The sensors were exposed to glucose analyte solutions and the difference in response of sensors with and without PAN porous membranes was analysed. Figure 10(b) presents representative plots of a sensor with PAN and a sensor without PAN following exposure to a 10 mM glucose solution. Here an improvement was observed in the drain current (ID) response time as well as the maximum current when porous PAN membranes were utilised. The rate of ID increase changes from 0.04 pA / s without PAN to 0.93 pA / s with PAN, and a more than three-fold improvement in total ID for the PAN- containing sensor was observed. The superior response time suggests that glucose is oxidised at a faster rate and / or the hydrogen peroxide is able to travel to the Nation layer more quickly.1005587934STATEMENTS OF DISCLOSURE1 . An organic thin film transistor (OTFT) comprising an organic semiconductor and a probe or enzyme for facilitating generation of a charge carrier from an analyte, wherein either(i) the organic semiconductor is adapted for contact with an analyte; or(ii) a conducting surface layer coats the surface of the OTFT and is adapted for contact with the analyte.2. The OTFT of statement 1 , wherein the surface layer is a polymer gating layer or a porous wicking layer above a polymer gating layer.3. The OTFT of statement 1 or statement 2, wherein the probe or enzyme is at least partially embedded in or attached to the surface (top) of the organic semiconducting layer, the polymer gating layer or the porous wicking layer.4. The OTFT of any one of the preceding statements, wherein the OTFT further comprises a substrate, optionally on the opposite side of the electrode to the semiconducting layer.5. The OTFT of any one of the preceding statements, wherein the OTFT is an at least partially printed sensor.6. The OFTF of any one of the preceding statements, wherein the OTFT further comprises a conducting polymer gating layer directly or indirectly in contact with the organic semiconducting layer.7. The OFTF of statement 6, wherein the conducting polymer gating layer is a tetrafluoroethylene-based fluoropolymer-copolymer, preferably the tetrafluoroethylenebased fluoropolymer-copolymer is a copolymer of tetrafluoroethylene and perfluoro-3,6- dioxa-4-methyl-7-octene-sulfonic acid or a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer.8. The OFTF of statement 6 or statement 7, wherein the conducting polymer gating layer is nation.10055879349. An OTFT comprising:(i) a source electrode,(ii) a drain electrode,(iii) an organic semiconducting layer, the organic semiconducting layer connecting the source electrode to the drain electrode, wherein either:(a) the organic semiconductor is adapted for contact with the analyte; or(b) a porous wicking layer coats at least a portion of the surface of the organic semiconducting layer (directly or indirectly) and is adapted for contact with the analyte,(iv) either the porous wicking layer or the organic semiconductor is configured to be connected to an ohmic conductor for applying a gate voltage to said organic semiconducting layer and / or said organic semiconducting layer via the porous wicking layer, and(v) a probe or enzyme for facilitating generation of a charge carrier from an analyte, wherein the probe or enzyme is at least partially embedded or attached to the surface (top) of the porous wicking layer or the organic semiconducting layer.10. The OTFT of statement 9, wherein the OTFT further comprises an ohmic conductor for applying a gate voltage in contact with said organic semiconducting layer and / or said porous wicking layer.11. An OTFT comprising:(i) a source electrode,(ii) a drain electrode,(iii) an organic semiconducting layer, the organic semiconducting layer connecting the source electrode to the drain electrode,1005587934(iv) a polymer gating layer, the polymer gating layer being conducting to the charge carrier and connecting directly or indirectly to the organic semiconducting layer,(v) the polymer gating layer is configured to be connected to an ohmic conductor for applying a gate voltage to said organic semiconductor via said polymer gating layer, and(vi) a probe or enzyme for facilitating generation of a charge carrier from an analyte, wherein the probe or enzyme is at least partially embedded or attached to the surface (top) of the polymer gating layer.11 The OTFT of statement 10, wherein the polymer gating layer is configured to be connected to the ohmic conductor.12. The OTFT of statement 10 or statement 11 , wherein the OTFT further comprises an ohmic conductor for applying a gate voltage in contact with the polymer gating layer.13. The OTFT of any one of statements 10 or 12, wherein the ohmic conductor for applying a gate voltage is a gate electrode.14. The OTFT of any one of statements 10, 12 or 13, wherein a voltage is applied from the ohmic conductor to the organic semiconducting layer optionally via the polymer gating layer.15. The OTFT of any one of statements 10 and 12-14, wherein the ohmic conductor is located at the top of the OTFT ie opposite the source and drain electrodes, optionally contacting the polymer gating layer.16. The OTFT of any one of the preceding statements, wherein the at least one electrode or the source and / or drain electrodes comprise, consist, or consist essentially of an ohmic material.17. The OTFT of any one of the preceding statements, wherein the ohmic material is metal, metal oxide or graphene (preferably tin oxide such as indium tin oxide or metal based ink such as silver based ink).100558793418. The OTFT of any one of the preceding statements, wherein the organic semiconducting layer may be disposed above and in between the source electrode and the drain electrode (and optionally in direct contact with the source electrode and the drain electrode).19. The OTFT of any one of the preceding statements, the organic semiconducting layer including one or more organic compounds having semiconducting properties optionally the one or more organic compounds are selected from the group consisting of: polyacetylenes, porphyrins, phthalocyanins, fullerenes, polyparaphenylenes, polyphenylenevinylenes, polyfluorenes, polythiophenes, polypyrroles, polypyridines, polycarbazoles, polypyridinevinylenes, polyarylvinylenes, poly (p- phenylmethylvinylenes), including derivatives and co-polymers thereof, and further including combinations thereof.20. The OTFT of statement 19, wherein the one or more organic compounds are selected from the group consisting of: poly(9,9-dioctylfluorene-2,7-diyl-co-bis-N,N-(4- butylphenyl)-bis-N,N-phenyl-1 ,4-phenylenediamine), poly(9,9-dioctylfluorene-2,7-diyl- co-benzothiadiazole), poly(3-hexylthiophene), (6,6)-phenyl-C61 -butyric acid methyl ester, poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1 ,4-phenylene vinylene), and combinations thereof.21 . The OTFT of any one of the preceding statements, wherein the semiconducting layer includes, consists of, or consists essentially of poly(3-hexyl-thiophene) (P3HT).22. The OTFT of any one of the preceding statements, wherein the semiconducting layer does not include poly(4-vinylphenol) (PVP).23. The OTFT of any one of the preceding statements, wherein the organic semiconducting layer may have a thickness between about 5 nm and about 500 nm.24 The OTFT of any one of the preceding statements, wherein the ohmic conductor comprises, consists, or consists essentially of an ohmic material, such as a metals, metal oxide or graphene (preferably tin oxide such as indium tin oxide or metal based ink such as silver based ink).100558793425. The OTFT of any one of the preceding statements, wherein the OTFT further comprises a polymer gating layer and optionally the organic semiconductor layer is in contact with said polymer gating layer.26. The OTFT of any one of the preceding statements, wherein at least part of the polymer gating layer is disposed above the semiconductor layer.27. The OTFT of any one of the preceding statements, wherein at least part of the ohmic conductor may be beneath another part of the polymer gating layer.28. The OTFT of any one of the preceding statements, wherein the polymer gating layer may comprise, consist, or consist essentially of a sulfonated tetrafluoroethylenebased fluoropolymer-copolymer, for example a copolymer comprising a tetrafluoroethylene backbone and perfluoroalkyl ether groups terminated with sulfonate groups.29. The OTFT of statement 28, wherein the sulfonated tetrafluoroethylene-based fluoropolymer-copolymer is a copolymer of tetrafluoroethylene and perfluoro-3,6-dioxa- 4-methyl-7-octene-sulfonic acid, preferably a tetrafluoroethylene-perfluoro-3,6-dioxa-4- methyl-7-octenesulfonic acid copolymer, more preferably nation.30. The OTFT of statement 28 or 29, wherein the polymer gating later has a thickness of 10 nm to 750 nm between the organic semiconductor or the dielectric layer and the polymer gating layer.31 . The OTFT of any one of statements 28 to 30, wherein the tetrafluoroethylenebased fluoropolymer-copolymer has the following structure:100558793432. The OTFT of statement 31 , wherein the tetrafluoroethylene-based fluoropolymercopolymer has the following structure:33. The OTFT of any one of the preceding statements, wherein the OTFT further comprises a dielectric layer intermediate the polymer gating layer and the organic semiconductor layer.34. The OTFT of any one of the preceding statements, wherein the dielectric layer is intermediate said polymer gating layer and said semiconductor layer is a homogenous layer.35. The OTFT of any one of the preceding statements, wherein the dielectric layer comprises, consists of, or consists essentially of an organic dielectric material optionally polyimide or poly(methyl methacrylate).36. The OTFT of any one of the preceding statements, wherein the organic dielectric material is a hygroscopic insulator, optionally polyvinyl phenols.37. The OTFT of any one of the preceding statements, wherein the dielectric layer comprises, consists of, or consists essentially of, poly(4-vinylphenol).38. The OTFT of any one of the preceding statements, wherein the dielectric layer comprises doped dielectric material, for example, lithium perchlorate doped poly(4- vinylpyridine).39. The OTFT of any one of the preceding statements, wherein the organic dielectric material has a conductivity to protons that is greater than the conductivity of said semiconductor layer.100558793440. The OTFT of any one of the preceding statements, wherein the dielectric layer may have a thickness between about 50 nm and 750 nm, or between about 300 nm and about 500 nm, or about 400 nm.41 . The OTFT of any one of the preceding statements, wherein the probe is attached to the polymer gating layer via a connector.42. The OTFT of any one of the preceding statements, wherein the probe is an antibody, an antigen, an antibody mimetic, a peptide, protein or nucleic acid (eg, an RNA or DNA aptamer) or enzyme, sugar, oligosaccharide, polysaccharide, lipopolysaccharides, a receptor, hormone receptor, cytokine receptor, synthetic receptor, small molecule, pharmacological active substance, alkaloid, steroids, vitamins, or amino acids.43. The OTFT of any one of the preceding statements, wherein the probe is printed, eg ink-jet printed, on the polymer gating layer.44. OTFT of any one of the preceding statements, wherein the probe is capable of binding a target and binding of the target facilitates generation of a charge carrier, optionally indirectly following binding of a detection agent to the target bound probe and the detection agent catalyses a redox reaction that generates a charge carrier.45. The OTFT of any one of the preceding statements, wherein the detection agent is an enzyme, for example, a redox active catalyst such as a peroxidase such as horseradish peroxidase (HRP) and the substrate for the reported enzyme is 3,3'- Diaminobenzidine (DMB); 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS); o-orthophenylenediamine (OPD); AmplexRed; 3,3'-Diaminobenzidine (DAB); 4- chloro-1 -naphthol (4CN); AEC; 3,3',5,5'-Tetramethylbenzidine (TMB); homovanilllic acid; lumininol; Nitro blue tetrazolium (NBT); Hydroquinone; benzoquinone; or mixtures of these.46. The OTFT of any one of the preceding statements, wherein the enzyme is glucose oxidase.47. The OTFT of any one of the preceding statements, wherein the enzyme is printed, eg ink-jet printed, on the polymer gating layer.100558793448. The OTFT of any one of the preceding statements, wherein the charge carrier is one or more of the following charge carrier types: anions, cations or electrons.49. The OTFT of any one of the preceding statements, wherein the charge carriers are cations, preferably hydrogen ions (eg protons).50. The OTFT of any one of the preceding statements, wherein the organic semiconductor is doped by interaction with said charge carriers, preferably protons, to increase an electrical conductivity between the drain electrode and the source electrode.51 . The OTFT of any one of the preceding statements, wherein the OTFT further comprises a substrate layer.52. The OTFT of any one of the preceding statements, wherein at least the source electrode and drain electrode are disposed on the substrate or the source electrode, drain electrode and organic semiconductor are each in contact with the substrate.53. The OTFT of any one of the preceding statements, wherein the substrate is glass, metal, paper or plastic, such as polyethylene terephthalate (PET).54. The OTFT of any one of the preceding statements, wherein the sensor or OTFT has a channel length, between the source and drain electrodes, of between about 5 pm and about 50 pm.55. The OTFT of any one of the preceding statements, wherein the OTFT is for sensing an analyte in a sample, preferably a biological analyte.56. The OTFT of any one of the preceding statements, wherein the sample is an aqueous solution, preferably a biological fluid such as blood or saliva.57. The OTFT of any one of the preceding statements, wherein the analyte is glucose or a SARS-CoV-2 antibody.58. The OTFT of any one of the preceding statements, wherein a voltage of at least 0.7 V is applied to the ohmic conductor / gate electrode.100558793459. The OTFT of any one of the preceding statements, wherein one or more of the organic semiconductor, or the conducting polymer gating layer are printed directly or indirectly on a substrate.60. The OTFT of any one of the preceding statements, wherein the conducting polymer gating layer is printed onto the organic semiconductor.61 . The OTFT of any one of the preceding statements, wherein the enzyme or probe is printed onto the OTFT.62. The OTFT of any one of the preceding statements, wherein the OTFT comprises a porous wicking layer.63. The OTFT of statement 62, wherein the porous wicking layer has a thickness of from 50 nm up to about 500 pm.64. The OTFT of statement 62 or 63, wherein the porous wicking layer is formed from a material such that the contact angle of the liquid on the first surface of the porous wicking layer is 60° or less.65. The OTFT of any one of statements 62 to 64, wherein the contact angle is 50° or less.66. The OTFT of statement 65, wherein the contact angle is 40° or less.67. The OTFT of any one of statements 62 to 66, wherein the pore size is from 50 nm to 2000 nm.68. The OTFT of statement 67, wherein the pore size is from 100 nm to 1000 nm.69. The OTFT of any one of statements 62 to 68, wherein the porous wicking layer has a void ratio of from about 30% up to about 95%.70. The OTFT of any one of statements 62 to 69, wherein the porous wicking layer is a porous polymer layer.71 . The OTFT of statement 70, wherein the porous polymer wicking layer is formed from a polymer that has a glass transition temperature of at least 80 °C.10055879341 . The OTFT of statement 71 , wherein the glass transition temperature is at least 90°C.73. The OTFT of any one of statements 62 to 72, wherein the porous polymer wicking layer is formed from a polymer that is soluble in dimethyl sulfoxide.74. The OTFT of any one of statements 62 to 73, wherein the porous polymer wicking layer is formed from a polymer that is formed from a one or more repeating monomer units, wherein the one or more repeating monomer units do not include a halide atom.75. The OTFT of statement 74, wherein the one or more repeating monomer units consist of C, N, O, and H atoms.76. The OTFT of any one of statements 62 to 75, wherein the porous layer is a porous polyacrylonitrile (PAN) layer.77. The OTFT of any one of statements 1 to 76, wherein the concentration of the reporter agent (such as HRB) is from about 0.01 to about 10 mg / mL, or from about 0.05 to about 10 mg / mL, or from about 0.1 to about 10 mg / mL, or from about 0.01 to about 5 mg / mL, or from about 0.01 to about 0.1 mg / mL, or from about 0.05 to about 5 mg / mL, or from about 0.05 to about 0.1 mg / mL.78. The OTFT of any one of statements 1 to 77, wherein the OTFT is capable of facilitating generation of a charge carrier from an analyte when the concentration of the analyte is from about 0.01 to about 100 pg / mL, or from about 0.1 to about 100 pg / mL, or from about 1 to about 100 pg / mL, or from about 10 to about 100 pg / mL.79. A method for preparing an OTFT of any one of the preceding statements, the method comprising: a) optionally providing a substrate for depositing thereon components of the device; b) depositing the source electrode and the drain electrode onto the substrate or connecting the source electrode and the drain electrode to an organic semiconductor;1005587934 c) depositing an organic semiconductor or providing an organic semiconductor for depositing thereon components of the device; d) optionally depositing a dielectric layer; e) optionally depositing a polymer gating layer; f) optionally depositing a porous wicking layer; and g) depositing the enzyme or probe on the organic semiconductor layer and / or optional polymer gating layer or porous wicking layer.80. The method of statement 79, wherein the source electrode and the drain electrode are deposited on the substrate.81 . The method of statement 79 or 80, wherein step b) precedes step c), step c) precedes step f).82. The method of any one of statements 79 - 81 , wherein a polymer gating layer is deposited and step c) precedes step e) and step e) precedes step f).83. The method of any one of statements 79 - 82, wherein a dielectric layer is deposited and step c) precedes step d) and step d) precedes step f).84. The method of any one of statements 79 - 83, wherein the method further comprises depositing a gate electrode.85. The method of statement 84, wherein the gate electrode is in contact with said polymer gating layer to control an electric potential of said polymer gating layer.86. The method of any one of statements 79 - 85, wherein the ohmic conductor is deposited before the polymer gating layer and / or porous wicking layer.87. The method of any one of statements 79 - 86, wherein the ohmic conductor is not integrated into the OTFT during manufacture of the OTFT but the ohmic conductor is connected to said polymer gating layer in use, to control an electric potential of said polymer gating layer.88. The method of any one of statements 79 - 87, wherein the polymer gating layer is deposited over the organic semiconductor.100558793489. The method of any one of statements 79 - 88, wherein no dielectric layer is deposited.90. The method of any one of statements 79 - 88, wherein a dielectric layer is deposited over the organic semiconductor, with said polymer of the polymer gating layer then being deposited over the organic dielectric layer.91 . The method of any one of statements 79 - 89, wherein the enzyme or probe is introduced by screen-printing.92. The method of any one of statements 79 - 91 , wherein step b) comprises depositing the source electrode and the drain electrode over the substrate such that the source electrode and the drain electrode are disposed above, and in contact with, the substrate.93. The method of any one of statements 79 - 92, wherein step c) comprises depositing the organic semiconductor over the source electrode and the drain electrode such that at least part, but preferably a majority, of the semiconductor is disposed above and in between the source electrode and the drain electrode.94. The method of any one of statements 79 - 93, wherein in step c), the semiconductor is deposited such that it is in contact with the source electrode and the drain electrode.95. The method of any one of statements 79 - 94, wherein the semiconductor layer is deposited by spin coating.96. The method of any one of statements 79 - 95, wherein the polymer gating layer is deposited by spin coating.97. The method of any one of statements 79 - 96, wherein a substrate is used and the substrate is removed following at least part of the manufacture.98. The method of any one of statements 79 - 97, wherein the organic semiconducting layer and / or the dielectric layer are be deposited by electroplating, vapour phase deposition, spin coating, screen printing, ink-jet printing, slot-dye printing, spray coating, draw bar coating or derived coating / printing techniques thereof, painting, gravure, roller and embossing.100558793499. An OTFT prepared by any one of the methods of statements 79 to 98.100. Use of the OTFT of any one of statements 1 -78 for sensing an analyte in a sample.101. A method for detecting an analyte in a sample, the method comprising the following steps: a) providing an OTFT of any one of statements 1 to 78; b) contacting a sample to the OTFT preferably the portion of the OTFT adapted for contact with an analyte; and c) detecting the analyte based on an electrical parameter of the device.102. The use or method of statements 100 or 101 , wherein the analyte is a biological analyte.103. The use or method of any one of statements 100-102, wherein the analyte is glucose.104. The use or method of any one of statements 100-102, wherein the analyte is the target for the probe.105. The use or method of any one of statements 100-104, wherein the target is an antibody, antigen, protein, peptide or chemical.106. The use or method of statement 105, wherein the antibody is a coronavirus antibody, optionally a SARS-CoV-2 antibody.107. The use or method of any one of statements 100-106, wherein the sample is an aqueous solution, is a biological fluid, more preferably a bodily fluid, and still more preferably, blood or saliva.108. The use or method of any one of statements 100-107, wherein the method further comprises interaction between the analyte or target and probe or enzyme to facilitate generation of a charge carrier.109. The use or method of any one of statements 100-108, wherein the analyte is detected by detecting the charge carrier.1005587934110. The use or method of any one of statements 100-109, wherein the method further comprises determining a concentration or an amount of the analyte.111. The use or method of any one of statements 100-110, wherein the concentration or amount is determined by detecting the amount of charge carrier and / or the change in voltage.112. The use or method of any one of statements 100-111 , wherein the method comprises applying a voltage to the drain electrode and grounding the source electrode.113. The use or method of any one of statements 100-112, wherein the method comprises applying a voltage to the ohmic conductor or gate electrode.114. The use or method of any one of statements 100-113, wherein the voltage applied to the ohmic conductor / gate electrode and the voltage applied to the drain electrode have the same polarity with respect to the source electrode.115. The use or method of any one of statements 100-114, wherein the method further includes detecting drain current through the OTFT, wherein the concentration or amount of the analyte is determined based on a magnitude of the drain current.116. The use or method of any one of statements 100-115, wherein the gate voltage and drain voltage applied are voltages greater than that required to liberate H+ from H2O2, and lower than that required to cause electrolysis of water.117. The use or method of any one of statements 100-116, wherein the gate voltage and drain voltage applied are between about 0 V and -2 V, or about -1 V.118. The use or method of any one of statements 100-117, wherein following contacting the sample to the OTFT the analyte binds the enzyme or the probe and this facilitates generation of a charge carrier.119. The use or method of any one of statements 100-118, wherein a detection agent is included in the sample or a fluid present after the sample and following binding of a target analyte to the probe, the target and probe are detected by binding with a detection agent that generates a charge carrier by catalysing a redox reaction close to the surface of the OTFT.1005587934120. The use or method of any one of statements 100-119, wherein a substrate for the reported enzyme is included in the sample or in a fluid present after the sample (either the same or different fluid to that including the detection agent) and in the presence of a substrate for the reported enzyme the detection agent generate a charge carrier.121 . The use or method of any one of statements 100-120, wherein the charge carrier alters the charge applied by the ohmic conductor / gate electrode.122. The use or method of any one of statements 100-121 , wherein the detection agent is at a concentration of about 10 to about 5000 p / ml.123. The use or method of any one of statements 100-122, wherein the substrate for the reporter enzyme concentration is about 0.1 to about 100 p / ml.

Claims

1005587934CLAIMS1 . An organic thin film transistor (OTFT) comprising:(i) a source electrode,(ii) a drain electrode,(iii) an organic semiconducting layer, the organic semiconducting layer connecting the source electrode to the drain electrode,(iv) a polymer gating layer, the polymer gating layer being conducting to the charge carrier and connecting directly or indirectly to the organic semiconducting layer,(v) the polymer gating layer is configured to be connected to an ohmic conductor for applying a gate voltage to said organic semiconductor via said polymer gating layer, and(vi) a probe for facilitating generation of a charge carrier from an analyte, wherein the probe is at least partially embedded or attached to the surface (top) of the polymer gating layer and the probe is not an enzyme.

2. The OTFT of claim 1 , wherein the polymer gating layer is configured to be connected to the ohmic conductor.

3. The OTFT of claim 1 or claim 2, wherein the OTFT further comprises an ohmic conductor for applying a gate voltage in contact with the polymer gating layer.

4. The OTFT of any one of claims 1 , 2 or 3, wherein a voltage is applied from the ohmic conductor to the organic semiconducting layer optionally via the polymer gating layer.

5. The OTFT of any one of claims 1 to 4, wherein the ohmic conductor is located at the top of the OTFT ie opposite the source and drain electrodes, optionally contacting the polymer gating layer.10055879346. The OTFT of any one of the preceding claims, wherein the organic semiconducting layer may be disposed above and in between the source electrode and the drain electrode (and optionally in direct contact with the source electrode and the drain electrode).

7. The OTFT of any one of the preceding claims, the organic semiconducting layer including one or more organic compounds having semiconducting properties optionally the one or more organic compounds are selected from the group consisting of: polyacetylenes, porphyrins, phthalocyanins, fullerenes, polyparaphenylenes, polyphenylenevinylenes, polyfluorenes, polythiophenes, polypyrroles, polypyridines, polycarbazoles, polypyridinevinylenes, polyarylvinylenes, poly (p- phenylmethylvinylenes), including derivatives and co-polymers thereof, and further including combinations thereof.

8. The OTFT of any one of the preceding claims, wherein the semiconducting layer includes, consists of, or consists essentially of poly(3-hexyl-thiophene) (P3HT).

9. The OTFT of any one of the preceding claims, wherein the OTFT further comprises a polymer gating layer and optionally the organic semiconductor layer is in contact with said polymer gating layer.

10. The OTFT of any one of the preceding claims, wherein at least part of the polymer gating layer is disposed above the semiconductor layer.11 . The OTFT of any one of the preceding claims, wherein at least part of the ohmic conductor may be beneath another part of the polymer gating layer.

12. The OTFT of any one of the preceding claims, wherein the polymer gating layer may comprise, consist, or consist essentially of a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer, for example a copolymer comprising a tetrafluoroethylene backbone and perfluoroalkyl ether groups terminated with sulfonate groups.

13. The OTFT of claim 12, wherein the sulfonated tetrafluoroethylene-based fluoropolymer-copolymer is a copolymer of tetrafluoroethylene and perfluoro-3,6-dioxa- 4-methyl-7-octene-sulfonic acid, preferably a tetrafluoroethylene-perfluoro-3,6-dioxa-4- methyl-7-octenesulfonic acid copolymer, more preferably nation.100558793414. The OTFT of any one of the preceding claims, wherein the OTFT further comprises a dielectric layer intermediate the polymer gating layer and the organic semiconductor layer.

15. The OTFT of any one of the preceding claims, wherein the dielectric layer comprises, consists of, or consists essentially of, poly(4-vinylphenol).

16. The OTFT of any one of the preceding claims, wherein the dielectric layer comprises doped dielectric material, for example, lithium perchlorate doped poly(4- vinylpyridine).

17. The OTFT of any one of the preceding claims, wherein the probe is attached to the polymer gating layer via a connector.

18. The OTFT of any one of the preceding claims, wherein the probe is an antibody, an antigen, an antibody mimetic, a peptide, protein, nucleic acid, sugar, oligosaccharide, polysaccharide, lipopolysaccharides, a receptor, hormone receptor, cytokine receptor, or synthetic receptor.

19. OTFT of any one of the preceding claims, wherein the probe is capable of binding a target and binding of the target facilitates generation of a charge carrier, optionally indirectly following binding of a detection agent to the target bound probe and the detection agent catalyses a redox reaction that generates a charge carrier.

20. The OTFT of any one of the preceding claims, wherein the detection agent is an enzyme, for example, a redox active catalyst such as a peroxidase such as horseradish peroxidase (HRP) and the substrate for the reported enzyme is 3,3'-Diaminobenzidine (DMB); 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS); o- orthophenylenediamine (OPD); AmplexRed; 3,3'-Diaminobenzidine (DAB); 4-chloro-1 - naphthol (4CN); AEC; 3,3',5,5'-Tetramethylbenzidine (TMB); homovanilllic acid; lumininol; Nitro blue tetrazolium (NBT); Hydroquinone; benzoquinone; or mixtures of these.21 . The OTFT of any one of the preceding claims, wherein the OTFT further comprises a substrate layer.100558793422. The OTFT of any one of the preceding claims, wherein the substrate is glass, metal, paper or plastic, such as polyethylene terephthalate (PET).

23. The OTFT of any one of the preceding claims, wherein the OTFT is for sensing an analyte in a sample, preferably a biological analyte.

24. The OTFT of any one of the preceding claims, wherein the sample is an aqueous solution, preferably a biological fluid such as blood or saliva.

25. The OTFT of any one of the preceding claims, wherein a voltage of at least 0.7 V is applied to the ohmic conductor / gate electrode.

26. The OTFT of any one of the preceding claims, wherein the probe is an antibody.

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