EP4314795A1 - Device for electrical signal transduction comprising electrolyte-gated organic transistor - Google Patents

Device for electrical signal transduction comprising electrolyte-gated organic transistor

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Publication number
EP4314795A1
EP4314795A1 EP22717654.2A EP22717654A EP4314795A1 EP 4314795 A1 EP4314795 A1 EP 4314795A1 EP 22717654 A EP22717654 A EP 22717654A EP 4314795 A1 EP4314795 A1 EP 4314795A1
Authority
EP
European Patent Office
Prior art keywords
thin film
channel
source
electrode
electrolyte
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22717654.2A
Other languages
German (de)
French (fr)
Inventor
Luciano FADIGA
Michele DI LAURO
Fabio Biscarini
Michele Bianchi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fondazione Istituto Italiano di Tecnologia
Original Assignee
Fondazione Istituto Italiano di Tecnologia
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by Fondazione Istituto Italiano di Tecnologia filed Critical Fondazione Istituto Italiano di Tecnologia
Publication of EP4314795A1 publication Critical patent/EP4314795A1/en
Pending legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/414—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
    • G01N27/4146—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS involving nanosized elements, e.g. nanotubes, nanowires
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/316—Modalities, i.e. specific diagnostic methods
    • A61B5/369—Electroencephalography [EEG]
    • A61B5/37—Intracranial electroencephalography [IC-EEG], e.g. electrocorticography [ECoG]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7225—Details of analogue processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/414—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y15/00—Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors

Definitions

  • TITLE DEVICE FOR ELECTRICAL SIGNAL TRANSDUCTION COMPRISING
  • the present invention relates o a device for transducing electrical signals, namely bioelectrical signals.
  • the device comprises an Electrolyte-Gated Organic Transistor EGOT, also known in the art as Electrolyte-Gated Organic Field-Effect transistor - EGOFET - or Organic Electro-Chemical Transistor - OECT - according to the nature of the channel, particularly suitable for label-free biosensor applications, but also as a digital logic device, such as an inverter or a switch, for circuit modulation, or for actuation of drug or active species release devices, or as an energy conversion device.
  • EGOT Electrolyte-Gated Organic Transistor
  • EGOFET Electrolyte-Gated Organic Field-Effect transistor
  • OECT Organic Electro-Chemical Transistor
  • Electrocorticography (ECOG) and microelectrocorticography (pECoG) techniques are known to be used to reduce the invasiveness of measurements in various applications, such as in detection of bioelectrical signals of the brain.
  • ECOG Electrocorticography
  • pECoG microelectrocorticography
  • Electrocorticography (ECOG) and pECoG have certain limitations due to the detection of the signals being carried out at a greater distance from the signal source.
  • pECoG suffers from an increase in impedance, and hence noise, due to the miniaturization of the electrode.
  • bioelectrical brain signal detection techniques that are minimally invasive while also being reliable and having a high performance, for example by having improved conformability to the surface of the brain and similar mechanical properties, such as flexural strength and elastic modulus, between the probe and the neural tissue, as well as a different transduction mode that affords in situ amplification of the first stage signal.
  • transistor technology has been used in neurophysiology.
  • Inorganic field effect transistors have been successfully used as in vitro bioelectrical activity transducers. Nevertheless, their application in vivo has been strongly limited due to poor biocompatibility of the main materials that form them, i.e. silicon and silicon oxides, which restrict their use to the role of integrated multiplexers of microelectrodes.
  • EGOT Organic Electrolytic Transistors Due to their ability to operate in a liquid environment, to their inherent biocompatibility in combination with their peculiar operating principle, Organic Electrolytic Transistors (EGOT) have been successfully employed to obviate various drawbacks and limitations of inorganic transistors.
  • EGOTs are electronic devices based on a film of semi conductive organic material whose electrical conductivity may be regulated by an external agent, via the gate electrode G, based on the chemical-physical variables of an electrolytic solution in contact with the material. In the prior art, this is achieved by having the organic film contacted by two metal contacts, i.e.
  • the source electrode S connected to ground, and the drain electrode D, and by exposing the film to a liquid, a gel or a polymer electrolyte containing a third gate electrode G which controls the electrochemical potential of the electrolyte.
  • the above-discussed EGOT configuration is known as common-source/common-ground.
  • a voltage VDS is applied to the drain electrode D with respect to the source electrode S, connected to ground, a current IDS is obtained in the film of semi conductive organic material which is proportional to conductance.
  • the conductance of organic materials exposed to electrolytes varies according to the proximal concentration of the ionic species, which may be modulated through the electrochemical potential of the electrolyte, i.e. by applying a voltage VGS to the gate electrode with respect to the source electrode S.
  • VGS voltage YDS of the electrode D with respect to S
  • a negative current IDS is detected at the electrode D.
  • the material of the organic film is reversibly and continuously oxidized at the electrode S and reduced at the electrode D. Therefore, by applying a negative voltage VGS, a higher negative current IDS is obtained, because the transistor switches to the ON state in which charge carriers accumulate in the channel.
  • a variation in positive voltage VGS results in a lower negative current IDS, with the transistor switching to its OFF state by ejection of charge carriers.
  • This property is the main functional characteristic of EGOTs and allows such devices to be used as amplifiers of small fluctuations of the voltage VGS, which can be due to electrophysiological activity or chemical modifications of the electrolyte, in high current variations IDS.
  • One electrical signal transduction device is disclosed in WO 2010/033087 Al.
  • One electrochemical organic transistor is disclosed in the document Limiting Bai ET AL: “Biological applications of Organic Electrochemical Transistors: Electrochemical Biosensors and Electrophysiology Recording”.
  • the object of the present invention is to provide a platform, hereinafter referred to as device, for transduction of electrical signals, namely bioelectrical signals, comprising a biosensor, that can obviate the drawbacks of the prior art.
  • a further object of the present invention is to provide a method of making the device for transduction of electrical, especially bioelectrical signals.
  • An additional object of the present invention is to provide a method of amplifying a bioelectrical and/or biochemical signal by means of the device.
  • bioelectrical signal transduction device comprising the technical features as disclosed in one or more of the accompanying claims.
  • One embodiment may provide a device for transducing electrical, namely bioelectrical signals in which the prior art configuration known as common- source/common-ground configuration is converted to a common-drain/grounded- source configuration.
  • the current in the organic semiconductor is driven with a voltage value VDS between drain D and positive source S, applied to the drain electrode D with respect to the source electrode S, whereas the value of the current IDS reaching the drain D from the source S is positive.
  • the gate-drain voltage value VGD may be controlled and the device may be switched between its ON and OFF states with a negative and positive V GD value, respectively.
  • One embodiment may provide a bioelectrical signal transduction device that may be employed in any EGOT transistor-based architecture for signal amplification and transduction in amperometric techniques, in applications ranging from electrophysiology to biochemical sensors.
  • FIG. 1 shows a schematic view of an EGOT transistor as a component of the device of the present invention
  • FIG. 3 shows: A) a schematic view of a possible in vivo application of the device of the present invention in electrophysiology; B) a diagram of the in vivo transfer characteristics of the device as provided; C) a diagram showing the curve of drain-source current IDS with respect to the drain-source voltage value VDS, as the gate- drain voltage value VGD changes.
  • the present invention relates to a device 1 for transducing electrical and namely bioelectrical signals, such as for applications in the detection of the bioelectrical and biological activity of the brain.
  • the device is particularly suitable for label-free biosensor applications, but also as a digital logic device, such as an inverter or switch, for circuit modulation, or for the actuation of drug or active species release devices, or also as an energy conversion device.
  • a digital logic device such as an inverter or switch
  • circuit modulation or for the actuation of drug or active species release devices
  • energy conversion device for brevity, reference will be particularly made herein to the preferred application of the device 1 for detection of bioelectrical signals, therefore to biosensor applications, without excluding the other fields of application as mentioned above.
  • the device 1 comprises a source measure unit (SMU) having two channels, each having a respective high terminal and a respective low terminal. It should be noted that the high terminal of the SMU is the one at which measurement is made, and the low terminal is the reference for such measurement.
  • SMU source measure unit
  • the device 1 further comprises an Electrolyte-Gated Organic Transistor (EGOT) 2.
  • EGOT Electrolyte-Gated Organic Transistor
  • the transistor 2 comprises a thin film (3) of semiconductive or conductive organic material designed to contact an electrolyte.
  • an electrolyte refers to an electrolyte in the form of ionic liquid, gel or polymer (polyanion or polycation) acting as a medium in which bioelectrical signals are to be detected.
  • the transistor 2 also comprises a source electrode S, also known as emitter electrode, and a drain electrode D, also known as collector electrode, both contacting the thin film 3.
  • the thin film 3 is made of a p-type, an n-type or an ambipolar semiconductor material.
  • the semiconductive thin film 3 is made of a biocompatible or biodegradable material.
  • the semiconductive thin film 3 is made of poly(3, 4-ethylene dioxy thiophene) doped with poly(stirene sulfonate), or more briefly PEDOT:PSS.
  • the thin film 3 is made of poly(3,4-ethylenedioxythiophene):X, PEDOT:X, where the anion X is preferably selected from: i) molecules such as perchlorate, tosylate, chloride, Nafion and other salts of perfluorinated and fluorinated acids, carboxylic acid salts, sulphonic acid salts, phosphonic acid salts, single-walled or multi-walled carbon nanotubes; and/or ii) negatively charged molecules, biomolecules and polymers such as dexamethasone, polydopamine, DNA, RNA; peptides, proteins, antibodies, enzymes.
  • anion X is preferably selected from: i) molecules such as perchlorate, tosylate, chloride, Nafion and other salts of perfluorinated and fluorinated acids, carboxylic acid salts, sulphonic acid salts, phosphonic acid salts, single-walled or multi-walled carbon nanotubes;
  • the thin film 3 comprises: i) conjugated organic molecules, preferably selected from the following species: oligoacenes, oligothienyls, oligophenyls, oligopyrroles, perylene diimide, whether or not substituted, oligotienothiophene, discotic liquid crystals, benzocoronenes; and/or ii) conjugated polymers, preferably selected from the following species: polythiophene glycolate (p(g2T-TT) or derivatives), poly-3- hexylthiophene-2,5-diyl), polyphenyl, polypyrrole, polyaniline, polyacetylene.
  • conjugated organic molecules preferably selected from the following species: oligoacenes, oligothienyls, oligophenyls, oligopyrroles, perylene diimide, whether or not substituted, oligotienothiophene, discotic liquid crystals, benzocoronenes
  • conjugated polymers
  • the thin film 3 comprises at least one of the following materials: graphene, graphene oxide (GO), reduced graphene oxide (RGO), single-walled and multi-walled C nanotubes.
  • the thin film 3 comprises: I) non- stoichiometric semiconductive metal oxides, preferably selected from MgOx, WxOy, VOX, SnOx, SnOxF, AlxOy, TiOx, IrOx, activated IrOx; and/or ii) organic/inorganic hybrid compounds, preferably selected from cyclometalated complexes of a metal, metal/organic frameworks (MOF), covalent-organic frameworks (COF), polyoxometalated compounds (POM).
  • MOF metal/organic frameworks
  • COF covalent-organic frameworks
  • POM polyoxometalated compounds
  • the thin film 3 is made of a semiconductor material
  • the thin film 3 is made of a p-type, an n-type o an ambipolar conductor material with modulable conductivity.
  • the transistor 2 further comprises a gate electrode G, also known as a base electrode, which is intended to contact the electrolyte.
  • the drain electrode D is shared by the low terminal of the first channel of the SMU and the high terminal of the second channel of the SMU.
  • the gate electrode G is electrically connected to the high terminal of the first channel of the SMU.
  • the source electrode S is electrically connected to the low terminal of the second channel of the source measure unit and is grounded. In other words, the source electrode S is the ground of the transduction device 1.
  • the current in the organic semiconductor may be guided by a positive drain-source voltage value VDS, applied to the drain electrode D with respect to the source electrode S, and the value of the drain-source current value IDS is positive.
  • the gate-drain voltage value VGD may be controlled and the device 1 may be switched between its ON and OFF states with a negative and positive VGD value, respectively.
  • the gate electrode G isopotential with the source electrode S and no parasitic voltage is formed in the electrolyte resulting in a much safer configuration that does not affect the amplification capacity of the EGOT transistor 2 and produces an output signal substantially free of undesired
  • the gate electrode G is coated with a film of organic material 4, preferably made of materials similar to those used for the thin film 3.
  • the Electrolyte-Gated Organic Transistor 2 comprises a substrate 5 made of an insulating material, preferably comprising one or more of glass, quartz, silicon wafer, non-biodegradable polymeric film such as for example polyimide, parylene C, polydimethylsiloxane, or bio resorbable polymeric film such as for example PLA, PGA, PLGA, PCL, hyaluronic acid, collagen, chitosan, fibrin, gelatin, polyacrylates, PEG, PVA, PPF.
  • non-biodegradable polymeric film such as for example polyimide, parylene C, polydimethylsiloxane, or bio resorbable polymeric film such as for example PLA, PGA, PLGA, PCL, hyaluronic acid, collagen, chitosan, fibrin, gelatin, polyacrylates, PEG, PVA, PPF.
  • the device 1 affords detection of bioelectrical signals while minimizing invasiveness and providing in situ amplification of the first stage signal.
  • the device 1 ensures that no current will be injected in the brain between the gate electrode G and the conductive channel between the drain D and the source S. This provides the safety required by the tissue. Furthermore, unlike the prior art, the current signal that flows through the channel between the drain D and the source S is cleaned from the leakage current between the gate G and the drain D, which is thus free of uncontrolled contributions. This results in clean, uniquely interpretable signals that do not require analytical post-treatment to remove any undesired contributions.
  • the present invention also relates to a method of making the device 1 of the present invention.
  • the method comprises the step of providing a dual-channel source measure unit, also known as dual SMU.
  • the method also comprises the step of sharing the drain electrode D by electrically connecting it between the low terminal of the first channel of the SMU and the high terminal of the second channel of the SMU.
  • the method comprises the additional step of electrically connecting the gate electrode G to the high terminal of the first channel of the source measure unit.
  • the method comprises the step of electrically connecting the source electrode S to the low terminal of the second channel, which is grounded.
  • the current at the common drain electrode D may thus be measured on the second channel, while monitoring the zero leakage current on the other channel.
  • the device 1 provides a new operating mode for the common- drain/grounded-source EGOT transistor 2, to avoid the application of parasitic voltages in the biological tissue of interest, while affording the amplification characteristics of this particular architecture.
  • the EGOT transistor 2 in the common- drain/grounded-source configuration is particularly suitable for electrophysiological applications.
  • a positive voltage VDS is applied to the drain electrode D with respect to the grounded source electrode S, to drive a positive current in the p- type semiconductor.
  • the potential of the gate electrode G in the electrolyte is related to the drain D and not to the source S.
  • the device 1 can provide the maximum transconductance in the EGOT transducer 2 when equal and opposite voltages are applied to the drain electrode D (positive bias) and to the gate G (negative bias), resulting in net zero bias between the gate G and the source S.
  • the present invention also relates to a biosensor comprising the device 1 of the present invention.
  • the biosensor is configured to detect and transduce bioelectrical signals by means of the device 1.
  • the biosensor thus obtained may be used in a large number of applications for detection of bioelectrical signals.
  • the present invention also relates to a method of amplifying an electrical, namely bioelectrical signal by means of the device 1 of the present invention.
  • the method of amplifying an electrical signal includes applying a positive or negative voltage V DS to the drain electrode D with respect to the grounded source electrode S to generate a positive or negative current I DS in the thin film 3 between the drain D and source S electrodes, according to the nature of the material that forms the thin film 3.
  • the method of amplifying a bioelectrical signal includes applying a negative or positive voltage VGD to the gate electrode G with respect to the drain electrode D, which has the same intensity as the positive or negative voltage VSD applied to the drain electrode D with respect to the grounded source electrode S, to thereby obtain the maximum transconductance value of the transistor 2.
  • Figure 3 A shows a schematic view of a possible in vivo application of the device 1 of the present invention in electrophysiology, specifically in the somatosensory cortex of the rat.
  • Figure 3B shows a diagram of the in vivo transfer characteristics of the device 1 of Figure 3 A, illustrating the curve of the current IDS between the drain D and source S electrodes and of the (zero) current IGD between the gate G and drain D electrodes as the voltage value VGD between the gate G and drain D electrodes.
  • Figure 3C shows a diagram illustrating the curve of the current IDS between the drain D and source S electrodes with respect to the voltage value VDS between the drain D and source S electrodes, as the voltage value VGD varies between the gate G and drain D electrodes.

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Abstract

A device (1) for transducing electrical and especially bioelectrical signals, comprising: a source measurement unit SMU having two channels, each having a respective high terminal and a respective low terminal; an Electrolyte-Gated Organic Transistor EGOT 2, comprising: a thin film (3) of molecular or polymeric conjugated semiconductive or conductive organic material; a source electrode (S) and a drain electrode (D) both in contact with the thin film (3); a gate electrode (G) designed to contact the electrolyte; wherein the drain electrode (D) is shared between the low terminal of the first channel of the SMU and the high terminal of the second channel of the SMU; the gate electrode (G) is connected to the high terminal of the first channel of the SMU, the source electrode (S) is electrically connected to the low terminal of the second channel of the SMU and constitutes the ground of the transduction device (1).

Description

TITLE: DEVICE FOR ELECTRICAL SIGNAL TRANSDUCTION COMPRISING
ELECTROLYTE-GATED ORGANIC TRANSISTOR
DESCRIPTION
FIELD OF THE INVENTION
The present invention relates o a device for transducing electrical signals, namely bioelectrical signals. In detail, the device comprises an Electrolyte-Gated Organic Transistor EGOT, also known in the art as Electrolyte-Gated Organic Field-Effect transistor - EGOFET - or Organic Electro-Chemical Transistor - OECT - according to the nature of the channel, particularly suitable for label-free biosensor applications, but also as a digital logic device, such as an inverter or a switch, for circuit modulation, or for actuation of drug or active species release devices, or as an energy conversion device.
Discussion of the related art
Electrocorticography (ECOG) and microelectrocorticography (pECoG) techniques are known to be used to reduce the invasiveness of measurements in various applications, such as in detection of bioelectrical signals of the brain. As compared to the more invasive intracortical devices, both ECoG and pECoG have certain limitations due to the detection of the signals being carried out at a greater distance from the signal source. Furthermore, pECoG suffers from an increase in impedance, and hence noise, due to the miniaturization of the electrode. Therefore, the need is felt for bioelectrical brain signal detection techniques that are minimally invasive while also being reliable and having a high performance, for example by having improved conformability to the surface of the brain and similar mechanical properties, such as flexural strength and elastic modulus, between the probe and the neural tissue, as well as a different transduction mode that affords in situ amplification of the first stage signal. In order meet this need, transistor technology has been used in neurophysiology. Inorganic field effect transistors have been successfully used as in vitro bioelectrical activity transducers. Nevertheless, their application in vivo has been strongly limited due to poor biocompatibility of the main materials that form them, i.e. silicon and silicon oxides, which restrict their use to the role of integrated multiplexers of microelectrodes.
Due to their ability to operate in a liquid environment, to their inherent biocompatibility in combination with their peculiar operating principle, Organic Electrolytic Transistors (EGOT) have been successfully employed to obviate various drawbacks and limitations of inorganic transistors. EGOTs are electronic devices based on a film of semi conductive organic material whose electrical conductivity may be regulated by an external agent, via the gate electrode G, based on the chemical-physical variables of an electrolytic solution in contact with the material. In the prior art, this is achieved by having the organic film contacted by two metal contacts, i.e. the source electrode S, connected to ground, and the drain electrode D, and by exposing the film to a liquid, a gel or a polymer electrolyte containing a third gate electrode G which controls the electrochemical potential of the electrolyte. The above-discussed EGOT configuration is known as common-source/common-ground. When a voltage VDS is applied to the drain electrode D with respect to the source electrode S, connected to ground, a current IDS is obtained in the film of semi conductive organic material which is proportional to conductance.
The conductance of organic materials exposed to electrolytes varies according to the proximal concentration of the ionic species, which may be modulated through the electrochemical potential of the electrolyte, i.e. by applying a voltage VGS to the gate electrode with respect to the source electrode S. For p-type semiconductor organic materials, the voltage YDS of the electrode D with respect to S is negative, and therefore a negative current IDS is detected at the electrode D. In practice, the material of the organic film is reversibly and continuously oxidized at the electrode S and reduced at the electrode D. Therefore, by applying a negative voltage VGS, a higher negative current IDS is obtained, because the transistor switches to the ON state in which charge carriers accumulate in the channel. Conversely, a variation in positive voltage VGS results in a lower negative current IDS, with the transistor switching to its OFF state by ejection of charge carriers.
The relationship between IDS and VGS with the voltage VDS being fixed, is quantitatively expressed by the transconductance gm of the device:
This property is the main functional characteristic of EGOTs and allows such devices to be used as amplifiers of small fluctuations of the voltage VGS, which can be due to electrophysiological activity or chemical modifications of the electrolyte, in high current variations IDS.
One electrical signal transduction device is disclosed in WO 2010/033087 Al. One electrochemical organic transistor is disclosed in the document Limiting Bai ET AL: “Biological applications of Organic Electrochemical Transistors: Electrochemical Biosensors and Electrophysiology Recording”.
Prior art problem
In the prior art, when EGOTs are used as amplifiers their transconductance should be maximized, for example by tuning the voltage values VDS and VGS. With prior art organic semiconductors, this occurs for highly negative voltage values VDS and moderately positive voltage values VGS, which cause an uncontrolled increase of a parasitic potential in the electrolyte between the electrode G and the electrode D, VGD = |VGS| + |VDS|, typically exceeding the electrochemical stability range of the aqueous solutions and causing undesired Faradaic reactions in the electrolyte. The above constitutes a serious drawback for translational electrophysiology since, in this scenario, the Faradaic reactions might cause critical damage to tissues. This should be avoided, especially when the electrolyte of interest is a biological tissue, as is the case of in vivo applications of EGOT transistors.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a platform, hereinafter referred to as device, for transduction of electrical signals, namely bioelectrical signals, comprising a biosensor, that can obviate the drawbacks of the prior art. A further object of the present invention is to provide a method of making the device for transduction of electrical, especially bioelectrical signals.
An additional object of the present invention is to provide a method of amplifying a bioelectrical and/or biochemical signal by means of the device.
The aforementioned technical purpose and objects are fulfilled by a bioelectrical signal transduction device comprising the technical features as disclosed in one or more of the accompanying claims.
Benefits of the invention
One embodiment may provide a device for transducing electrical, namely bioelectrical signals in which the prior art configuration known as common- source/common-ground configuration is converted to a common-drain/grounded- source configuration. The current in the organic semiconductor is driven with a voltage value VDS between drain D and positive source S, applied to the drain electrode D with respect to the source electrode S, whereas the value of the current IDS reaching the drain D from the source S is positive. By relating the potential of the gate electrode G to the drain electrode D, and not to the source electrode S, the gate-drain voltage value VGD may be controlled and the device may be switched between its ON and OFF states with a negative and positive VGD value, respectively.
One embodiment may provide a bioelectrical signal transduction device that may be employed in any EGOT transistor-based architecture for signal amplification and transduction in amperometric techniques, in applications ranging from electrophysiology to biochemical sensors.
BIEF DESCRIPTION OF THE DRA WINGS
The characteristics and advantages of the present invention will result from the following detailed description of a possible practical embodiment, illustrated as a non limiting example in the set of drawings, in which:
- Figure 1 shows a schematic view of an EGOT transistor as a component of the device of the present invention,
- Figure 2 shows the electrical schematic of the electrical signal transduction device of the present invention,
- Figure 3 shows: A) a schematic view of a possible in vivo application of the device of the present invention in electrophysiology; B) a diagram of the in vivo transfer characteristics of the device as provided; C) a diagram showing the curve of drain-source current IDS with respect to the drain-source voltage value VDS, as the gate- drain voltage value VGD changes.
The device as shown in the accompanying figures shall be deemed to be schematically illustrated, not necessarily drawn to scale, and not necessarily representing the actual proportions of its parts.
DETAILED DESCRIPTION
Even when not expressly stated, the individual features as described with reference to the particular embodiments shall be intended as auxiliary to and/or interchangeable with other features described with reference to other exemplary embodiments.
The present invention relates to a device 1 for transducing electrical and namely bioelectrical signals, such as for applications in the detection of the bioelectrical and biological activity of the brain. The device is particularly suitable for label-free biosensor applications, but also as a digital logic device, such as an inverter or switch, for circuit modulation, or for the actuation of drug or active species release devices, or also as an energy conversion device. For brevity, reference will be particularly made herein to the preferred application of the device 1 for detection of bioelectrical signals, therefore to biosensor applications, without excluding the other fields of application as mentioned above.
The device 1 comprises a source measure unit (SMU) having two channels, each having a respective high terminal and a respective low terminal. It should be noted that the high terminal of the SMU is the one at which measurement is made, and the low terminal is the reference for such measurement.
The device 1 further comprises an Electrolyte-Gated Organic Transistor (EGOT) 2. The transistor 2 comprises a thin film (3) of semiconductive or conductive organic material designed to contact an electrolyte. As used herein, an electrolyte refers to an electrolyte in the form of ionic liquid, gel or polymer (polyanion or polycation) acting as a medium in which bioelectrical signals are to be detected.
The transistor 2 also comprises a source electrode S, also known as emitter electrode, and a drain electrode D, also known as collector electrode, both contacting the thin film 3.
According to the preferred embodiment of the invention, the thin film 3 is made of a p-type, an n-type or an ambipolar semiconductor material. Preferably, the semiconductive thin film 3 is made of a biocompatible or biodegradable material. Also preferably, the semiconductive thin film 3 is made of poly(3, 4-ethylene dioxy thiophene) doped with poly(stirene sulfonate), or more briefly PEDOT:PSS. Alternatively, the thin film 3 is made of poly(3,4-ethylenedioxythiophene):X, PEDOT:X, where the anion X is preferably selected from: i) molecules such as perchlorate, tosylate, chloride, Nafion and other salts of perfluorinated and fluorinated acids, carboxylic acid salts, sulphonic acid salts, phosphonic acid salts, single-walled or multi-walled carbon nanotubes; and/or ii) negatively charged molecules, biomolecules and polymers such as dexamethasone, polydopamine, DNA, RNA; peptides, proteins, antibodies, enzymes.
According to an embodiment that is alternative to the above, the thin film 3 comprises: i) conjugated organic molecules, preferably selected from the following species: oligoacenes, oligothienyls, oligophenyls, oligopyrroles, perylene diimide, whether or not substituted, oligotienothiophene, discotic liquid crystals, benzocoronenes; and/or ii) conjugated polymers, preferably selected from the following species: polythiophene glycolate (p(g2T-TT) or derivatives), poly-3- hexylthiophene-2,5-diyl), polyphenyl, polypyrrole, polyaniline, polyacetylene.
According to a preferred embodiment, the thin film 3 comprises at least one of the following materials: graphene, graphene oxide (GO), reduced graphene oxide (RGO), single-walled and multi-walled C nanotubes.
According to a further preferred embodiment, the thin film 3 comprises: I) non- stoichiometric semiconductive metal oxides, preferably selected from MgOx, WxOy, VOX, SnOx, SnOxF, AlxOy, TiOx, IrOx, activated IrOx; and/or ii) organic/inorganic hybrid compounds, preferably selected from cyclometalated complexes of a metal, metal/organic frameworks (MOF), covalent-organic frameworks (COF), polyoxometalated compounds (POM).
According to a preferred embodiment that is alternative to those in which the thin film 3 is made of a semiconductor material, the thin film 3 is made of a p-type, an n-type o an ambipolar conductor material with modulable conductivity. The transistor 2 further comprises a gate electrode G, also known as a base electrode, which is intended to contact the electrolyte.
The drain electrode D is shared by the low terminal of the first channel of the SMU and the high terminal of the second channel of the SMU. In addition, the gate electrode G is electrically connected to the high terminal of the first channel of the SMU. Furthermore, the source electrode S is electrically connected to the low terminal of the second channel of the source measure unit and is grounded. In other words, the source electrode S is the ground of the transduction device 1. In this configuration known as common-drain/grounded-source, the current in the organic semiconductor may be guided by a positive drain-source voltage value VDS, applied to the drain electrode D with respect to the source electrode S, and the value of the drain-source current value IDS is positive. By relating the potential of the gate electrode G to the electrode D, and not to the electrode S, the gate-drain voltage value VGD may be controlled and the device 1 may be switched between its ON and OFF states with a negative and positive VGD value, respectively. In particular, for VGD = - VDS, the device 1 is in its maximum transconductance state. Thus, the gate electrode G is isopotential with the source electrode S and no parasitic voltage is formed in the electrolyte resulting in a much safer configuration that does not affect the amplification capacity of the EGOT transistor 2 and produces an output signal substantially free of undesired
Faradaic contributions.
According to a preferred embodiment of the invention, the gate electrode G is coated with a film of organic material 4, preferably made of materials similar to those used for the thin film 3.
According to a preferred solution of the invention, the Electrolyte-Gated Organic Transistor 2 comprises a substrate 5 made of an insulating material, preferably comprising one or more of glass, quartz, silicon wafer, non-biodegradable polymeric film such as for example polyimide, parylene C, polydimethylsiloxane, or bio resorbable polymeric film such as for example PLA, PGA, PLGA, PCL, hyaluronic acid, collagen, chitosan, fibrin, gelatin, polyacrylates, PEG, PVA, PPF.
Advantageously, the device 1 affords detection of bioelectrical signals while minimizing invasiveness and providing in situ amplification of the first stage signal.
Advantageously, the device 1 ensures that no current will be injected in the brain between the gate electrode G and the conductive channel between the drain D and the source S. This provides the safety required by the tissue. Furthermore, unlike the prior art, the current signal that flows through the channel between the drain D and the source S is cleaned from the leakage current between the gate G and the drain D, which is thus free of uncontrolled contributions. This results in clean, uniquely interpretable signals that do not require analytical post-treatment to remove any undesired contributions.
The present invention also relates to a method of making the device 1 of the present invention.
The method comprises the step of providing a dual-channel source measure unit, also known as dual SMU.
The method also comprises the step of sharing the drain electrode D by electrically connecting it between the low terminal of the first channel of the SMU and the high terminal of the second channel of the SMU. The method comprises the additional step of electrically connecting the gate electrode G to the high terminal of the first channel of the source measure unit.
In addition, the method comprises the step of electrically connecting the source electrode S to the low terminal of the second channel, which is grounded. Advantageously, the current at the common drain electrode D may thus be measured on the second channel, while monitoring the zero leakage current on the other channel.
Advantageously, the device 1 provides a new operating mode for the common- drain/grounded-source EGOT transistor 2, to avoid the application of parasitic voltages in the biological tissue of interest, while affording the amplification characteristics of this particular architecture. The EGOT transistor 2 in the common- drain/grounded-source configuration is particularly suitable for electrophysiological applications. In particular, a positive voltage VDS is applied to the drain electrode D with respect to the grounded source electrode S, to drive a positive current in the p- type semiconductor. The potential of the gate electrode G in the electrolyte is related to the drain D and not to the source S. Therefore, the device 1 can provide the maximum transconductance in the EGOT transducer 2 when equal and opposite voltages are applied to the drain electrode D (positive bias) and to the gate G (negative bias), resulting in net zero bias between the gate G and the source S. The present invention also relates to a biosensor comprising the device 1 of the present invention. The biosensor is configured to detect and transduce bioelectrical signals by means of the device 1. Advantageously, the biosensor thus obtained may be used in a large number of applications for detection of bioelectrical signals.
The present invention also relates to a method of amplifying an electrical, namely bioelectrical signal by means of the device 1 of the present invention. The method of amplifying an electrical signal includes applying a positive or negative voltage VDS to the drain electrode D with respect to the grounded source electrode S to generate a positive or negative current IDS in the thin film 3 between the drain D and source S electrodes, according to the nature of the material that forms the thin film 3.
Preferably, the method of amplifying a bioelectrical signal includes applying a negative or positive voltage VGD to the gate electrode G with respect to the drain electrode D, which has the same intensity as the positive or negative voltage VSD applied to the drain electrode D with respect to the grounded source electrode S, to thereby obtain the maximum transconductance value of the transistor 2.
Figure 3 A shows a schematic view of a possible in vivo application of the device 1 of the present invention in electrophysiology, specifically in the somatosensory cortex of the rat. Figure 3B shows a diagram of the in vivo transfer characteristics of the device 1 of Figure 3 A, illustrating the curve of the current IDS between the drain D and source S electrodes and of the (zero) current IGD between the gate G and drain D electrodes as the voltage value VGD between the gate G and drain D electrodes. Figure 3C shows a diagram illustrating the curve of the current IDS between the drain D and source S electrodes with respect to the voltage value VDS between the drain D and source S electrodes, as the voltage value VGD varies between the gate G and drain D electrodes. In the example that is generally shown in Figure 3, the constant transconductance state was selected as an operating range, with VDS = 0.7 V and VGD = -0.7 V, with a resulting voltage VGS = 0V.
Those skilled in the art will obviously appreciate that a number of changes and variants as described above may be made to fulfill particular requirements, without departure from the scope of the invention, as defined in the following claims.

Claims

1. A device (1) for electrical signal transduction, comprising:
- a source measure unit having two channels, each having a respective high terminal and a respective low terminal; - an Electrolyte-Gated Organic Transistor (2), comprising:
- a thin film (3) of semiconductive or conductive organic material designed to contact an electrolyte;
- a source electrode (S) and a drain electrode (D) both in contact with the thin film (3); - a gate electrode (G) designed to contact the electrolyte; characterized in that:
- the drain electrode (D) is shared by the low terminal of the first channel of the source measure unit and the high terminal of the second channel of the source measure unit;
- the gate electrode (G) is electrically connected to the high terminal of the first channel of the source measure unit;
- the source electrode (S) is electrically connected to the low terminal of the second channel of the source measure unit, with grounding.
2. A device (1) as claimed in claim 1, wherein:
- the thin film (3) is made of a p-type, an n-type or an ambipolar semiconductor material.
3. A device (1) as claimed in claim 2, wherein:
- the thin film (3) is made of a biocompatible or biodegradable material.
4. A device (1) as claimed in any of the preceding claims, wherein
- the thin film (3) is made of poly(3,4-ethylenedioxythiophene):poly(stirene sulfonate),
PEDOT:PSS.
5. A device (1) as claimed in any of the preceding claims 1- 3, wherein
- the thin film (3) is made of poly(3,4-ethylenedioxythiophene):X, PEDOT:X, where the anion X is preferably selected from
- molecules such as perchlorate, tosylate, chloride, Nafion and other salts of perfluorinated and fluorinated acids, carboxylic acid salts, sulphonic acid salts, phosphonic acid salts, single-walled or multi-walled carbon nanotubes;
- negatively charged molecules, biomolecules and polymers such as dexamethasone, polydopamine, DNA, RNA; peptides, proteins, antibodies, enzymes.
6. A device (1) as claimed in any of the preceding claims 1- 3, wherein - the thin film (3) comprises:
- conjugated organic molecules, preferably selected from the following species: oligoacenes, oligothienyls, oligophenyls, oligopyrroles, perylene diimide, whether or not substituted, oligothienothiophene, discotic liquid crystals, benzocoronenes; and/or
- conjugated polymers, preferably selected from the following species: poly-3- hexylthiophene-2,5-diyl, polythiophene glycolate, polyphenyl, polypyrrole, polyaniline, polyacetylene.
7. A device (1) as claimed in any of the preceding claims 1- 3, wherein
- the thin film (3) comprises at least one of the following materials:
- graphene, graphene oxide (GO), reduced graphene oxide (RGO), single-walled and multi-walled C nanotubes.
8. A device (1) as claimed in any of the preceding claims 1- 3, wherein
- the thin film (3) comprises:
- non-stoichiometric semiconductive metal oxides, preferably selected from MgOx, WxOy, VOX, SnOx, SnOxF, AlxOy, TiOx, IrOx, activated IrOx; and/or - organic/inorganic hybrid compounds, preferably selected from cyclometalated complexes of a metal, metal/organic frameworks (MOF), covalent-organic frameworks (COF), polyoxometalated compounds (POM).
9. A device (1) as claimed in claim 1, wherein: - the thin film (3) is made of a p-type, an n-type o an ambipolar conductor material with modulable conductivity.
10. A device (1) as claimed in any of the preceding claims, wherein:
- the gate electrode (G) is coated with a film of organic material (4), preferably made of materials similar to the thin film (3).
11. A device (1) as claimed in any of the preceding claims, wherein the transistor (2) comprises:
- a substrate (5) of insulating material, preferably comprising one or more of glass, quartz, silicon wafer, non-biodegradable or bio-absorbable polymeric film.
12. A method of making a device (1) as claimed in any of claims 1 to 11, comprising the steps of:
- providing a two-channel source measure unit;
- sharing the drain electrode (D) by the low terminal of the first channel of the source measure unit and the high terminal of the second channel of the source measure unit;
- electrically connecting the gate electrode (G) to the high terminal of the first channel of the source measure unit;
- electrically connecting the source electrode (S) to the low terminal of the second channel, which is grounded.
13. A biosensor comprising a device (1) as claimed in any of the preceding claims 1- 11 , configured for detecting and transducing bioelectrical signals.
14. A method of amplifying an electric signal using a device (1) as claimed in any of the preceding claims 1 to 11, comprising the steps of:
- applying a positive or negative voltage (VDS) to the drain electrode (D) with respect to the grounded source electrode (S) to generate a positive or negative current (IDS) in the semiconductive film (3) between the drain (D) and source (S) electrodes, according to the nature of the material that forms the thin film (3).
15. A method as claimed in claim 14, comprising the step of:
- applying a negative or positive voltage (VGD) to the gate electrode (G) with respect to the drain electrode (D), which has the same intensity as the positive or negative voltage (VSD) applied to the drain electrode (D) with respect to the grounded source electrode (S), to thereby obtain the maximum transconductance value of the transistor (2).
EP22717654.2A 2021-03-25 2022-03-18 Device for electrical signal transduction comprising electrolyte-gated organic transistor Pending EP4314795A1 (en)

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Title
DI LAURO MICHELE ET AL: "A Novel Biasing Scheme of Electrolyte-Gated Organic Transistors for Safe In Vivo Amplification of Electrophysiological Signals", ADVANCED MATERIALS INTERFACES, vol. 9, no. 11, 3 March 2022 (2022-03-03), DE, XP093264268, ISSN: 2196-7350, Retrieved from the Internet <URL:https://onlinelibrary.wiley.com/doi/full-xml/10.1002/admi.202101798> DOI: 10.1002/admi.202101798 *

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