ELECTROCHEMICAL SENSOR FOR ANALYTICAL TESTS

Abstract

An electrochemical sensor for analytical applications comprising a two-electrode system or electrochemical cell, characterized by comprising one or more pseudo-1D filaments (2), each of which constitutes a single filament with two conductive parts, containing a reference electrode (3) and a working electrode (4), which constitute respective conductive regions at the ends or intermediate sections of the filament (2), and a space between them defining a non-conductive region (5) that separates said two conductive regions.

Description

ELECTROCHEMICAL SENSOR FOR ANALYTICAL TESTS OBJECT OF THE INVENTION The invention, as stated in the present descriptive memorandum, refers to an electrochemical sensor for analytical purposes that provides advantages and characteristics, which are described in detail below, that represent an improvement over the current state of the art. The object of the present invention is an electrochemical sensor device for detecting analyticals comprising one or more filaments, each of which constitutes a single filament, which may be conductive or non-conductive, modified to contain two electrodes, one reference (RE) and one working (WE), which are dielectrically separated parts of said filament, specifically such that the electrodes are conductive ends or sections of the filament and are separated from each other by a non-conductive space or a non-conductive region of the filament itself, forming an electrochemical cell, which allows for greater control of the sensor parameters, since each electrode can be modified separately, one of the main advantages being that said single filament can be used to reduce sample volumes without affecting the detection limit and sensitivity of the sensor.The reduced size allows for measurements below the micrometer level, providing precise data for the analyses of interest (the sensors are adjustable). Simultaneously, the use of multiple single-filament sensors can yield more reliable results (multiple parallel measurements). Furthermore, a single sensor with multiple single filaments can be used to detect multiple analytes. FIELD OF APPLICATION OF THE INVENTION The field of application of the present invention falls within the sector of the industry dedicated to the manufacture of measuring and detection devices, focusing particularly on the field of electrochemical sensors for analytics, including safe and non-destructive continuous analysis of industrial and biological samples. BACKGROUND OF THE INVENTION Electrochemical sensors are widely known for converting the chemical interaction of a specific species (the analyte) into an electrical signal. Typically, this type of sensor operates through the reaction of a working electrode, coated with a material selective for the analyte, generating an electrochemical reaction that produces the electrical signal. This signal is measured, quantified, and used to determine the presence and quantity of the analyte in a medium, proving useful in applications such as environmental monitoring, biological analysis, and chemical process monitoring. Most electrochemical sensor designs are characterized by the construction of electrodes as separate filaments, even when they do not use a conductive filament as the sensor base. Separate electrodes and filaments are less frequently used compared to rods, wires, etc. As a reference to the current state of the art, it is worth mentioning that, as the closest related to the field of electrochemical sensors for analytics, several documents are known, among which the following stand out: The publication by Possanzini et al., "Textile sensors platform for the selective and simultaneous detection of chloride ion and pH in sweat," Scientific Reports, 2020 Oct 14; 10(1): 17180, describes a sensor based on the electrochemical transduction phenomenon, which requires the application of a potential. Specifically, it measures conductivity. A single thread (cotton, silk, polyester) made from bundles of fibers is used to measure the concentration of chloride ions and pH in sweat. The filaments for pH measurement are modified with PEDOT:BTB and used to form a single substrate in contact with the human body. - Patent WO2016166343A1 relating to amperometry and voltammetry with classic cell design, which proposes a biosensor based on a double electrode cell with a working electrode a support filament based on carbon fibers modified with a metallic layer by vacuum deposition techniques and where the working electrode can be formed by several layers. - In WO2019094966, a constrained ion-sensing electrode is disclosed, based on a filament comprising bundles of fibers treated with a conductive polymer, a portion of which is modified to interact with an analyte. Unlike the present invention, the sensor is not a single wire that acts as both the working and reference electrode. US Patent No. 11547358 discloses a classic cell-based, strand-based sensor for determining oxygen concentration in biological tissues. This sensor utilizes modified conductive threads, most of whose surface is coated with a dielectric material. The sensor includes a pair of filaments in various configurations, acting as a cathode and anode, connected to a device that records a potential difference. The difference from the present invention is that it features two separate filaments that act as electrodes in the electrochemical cell. According to document US2024377347, a sensor with a two- or three-electrode structure based on a wire-shaped core covered with several alternating conductive and non-conductive cups is known. Document PCT / US2024 / 014995 discloses a sensor comprising at least three conductive filaments, one of which is modified to detect the target substance and the other two to act as a reference electrode and counter electrode. And by document WO2019204483, a sensor for measuring sweat levels is disclosed, comprising conductive figures interwoven with non-conductive fibers. However, it does not appear that any of the documents mentioned, taken independently or in combination, describe the present invention, that is, an electrochemical sensor with two electrodes based on a filament, conductive or non-conductive, sections of which are modified to act as a working electrode and a reference electrode, separated from each other by a non-conductive space or non-conductive region of the filament itself, and whose essential objective is to achieve greater control of the sensor parameters, since with this each electrode can be modified separately. EXPLANATION OF THE INVENTION The electrochemical sensor for analytical purposes proposed by the invention represents an improvement over the current state of the art, with the characterizing details that make it possible and that conveniently distinguish it being included in the final claims that accompany this description. Specifically, the invention proposes, as previously mentioned, an electrochemical sensor device for detecting analytical components. This device comprises one or more filaments, each of which constitutes a single filament. This filament may be made of conductive or non-conductive material and may or may not be modified to contain two electrodes: a reference electrode (RE) and a working electrode (WE). These electrodes are dielectrically separated from each other. More specifically, the filament may be conductive, with the two electrodes being either ends or sections of the filament separated by a non-conductive space. Alternatively, the filament may be made of non-conductive material and modified at the ends or electrode sections to create conductive regions separated by a non-conductive region of the filament itself, thus forming an electrochemical cell. Thus, in an alternative embodiment, the sensor filament or filaments can be made of any non-conductive material, e.g., cotton or nylon sewing thread for hydrophilic or hydrophobic samples, respectively, or nanofibers such as Al2O3 nanotubes with diameters of tens of nanometers. And, in other embodiments, the sensor filament or filaments can be a conductive yarn, including industrially manufactured yarns comprising a non-conductive base interwoven with a conductive yarn; or a conductive yarn itself, i.e., carbon fiber. In any case, each single filament of the sensor serves as the basis for the reference electrode (ER) and the working electrode (WE), separated by a non-conductive section of the filament. Nanofibers, such as pretreated Al2O3 nanotubes, allow adaptation to hydrophilic / hydrophobic samples, drastic miniaturization, compatibility with modification procedures (e.g., immersion / painting / impregnation, metallization, electrochemical deposition ALD, PVD), and the use of specific material properties, such as luminescence, for hybrid electrochemical and luminescence analytical methods (e.g., electrochemiluminescence, photoelectrochemical-luminescence). In embodiments of the invention, multiple filaments can be combined in the same sensor to multiply the electrochemical response by the number of filaments, improving sensitivity and performance, and configured with different detection materials in the electrodes (WE) to form a multichannel sensor that allows simultaneous detection of multiple analytes. The multichannel configuration can amplify the electrochemical response by combining the filament outputs or perform parallel measurements with basic statistical methods (e.g., average EMF (electromotive force), standard deviation, median EMF, coefficient of variation) to improve accuracy, reduce manufacturing or human errors, and enable online data processing. In this option, each micro-filament operates with sub-microliter volumes, which reduces the amount of sample approximately 1000 times compared to conventional electrochemical cells (~1 mL) and 50 times compared to screen-printed electrodes (~50 L). The RE region or filament zone that defines the reference electrode is coated with a conductive material, mostly chemically inert to the analyte, for example, carbon inks, graphene, graphite or carbon nanotubes, which chemically does not react with the analyte, thus ensuring stability. For its part, the WE region or filament zone that defines the working electrode is coated with a material specific to the target analyte, for example transition metals, noble metals and their compounds and analogues, manganese dioxide or Prussian blue for hydrogen peroxide, platinum nanoparticles specifically for human chorionic gonadotropin, glucose oxidase for glucose, and other enzymes in the case of enzyme-based sensors, or (1) (2, 3-diazabuta-1, 3-diene) ferrocenophane for glutamate etc., which generates an electromotive force (EMF) measurable by means of Faradaic (redox with charge transfer) or Nernstian (sorption / desorption (Redox reaction / concentration gradient of charged particles in equilibrium states under zero current conditions)) mechanisms.For example, commercially available conductive sewing threads can be used as a sensor material against hydrogen peroxide, as they provide electrochemical responses comparable to those of noble metal electrodes. Each filament is wetted through capillary forces (or equivalent for nanofibers), adsorbing the analyte solution and distributing the sample along the porous sensing portion, minimizing the sample volume by increasing the interface surface area, and remaining stable without requiring total and permanent immersion, unlike paper-based electrodes which become unstable without sufficient analyte solution coverage; however, immersion does not affect the stability of the cell. In an improved configuration, an adsorbent, for example for aqueous samples, such as polyacrylamide or modified PAM, can be used, applied by dripping onto the filament or by any convenient technique. As an adsorbent material with good affinity to prevent sample evaporation and stabilize the detection area by defining the cell volume and surface, it stabilizes the electrochemical response, while the basic design is based solely on the natural adsorption of the filament. Hydrophobic barriers (e.g., silanes, polymers, or oils) define precise reactive regions, ensuring the electrode surface area (filament diameter, reactive region length) and preventing electrode connectors from affecting the cell's electrochemical response. The electromotive force (EMF) is measured with a potentiometer and correlated with the analyte concentration using a calibration curve, enabling accurate detection. In any case, all the described designs can be used for different electrochemical measurements, such as ultra-low volume voltammetry. However, in these cases, the cell must undergo corresponding modifications to adapt to the requirements of the applied method. The sensor of this invention is environmentally friendly and cost-effective, providing a portable sensor for applications such as medical diagnostics, environmental monitoring, and biofluid analysis (especially for non-destructive testing methods, as no potential is applied). It offers high sensitivity, stability, reproducibility, and adaptability thanks to customizable working electrode (WE) materials, scalable multi-channel multi-filament configurations with error-reducing statistical analysis, flexible filament materials, and hybrid nanofiber-based detection methods. The preferred detection method, FME (electromotive force), allows the invention to be used for in vivo measurements, as it does not apply any potential, resulting in less impact on the object of interest. The customization of the working electrode or WE can be done according to the analyte of interest and the available or preferred techniques. In short, the electrochemical sensor of the present invention is based on a single-filament design, which, among other advantages, allows for reduced sample volumes without affecting the detection limit or sensitivity. The reduced dimensions enable measurements below the micrometer level, providing precise readings for the analyses of interest. Simultaneously, the use of multiple single-filament sensors allows for more reliable results (multiple parallel measurements), and a single sensor with multiple single filaments can be used to detect multiple analytes. It should be mentioned that the concept of a single filament in the sensor that is the subject of the invention means that it is a pseudo 1-D (pseudo one-dimensional) sensor, in which the two electrodes are located on a single filament, separated by a non-conductive region, which defines an electrochemical cell. This simplifies sensor production; the controllable shape of the space (size and volume) means that sensor parameters can be controlled. Each electrode can be modified separately, making the process flexible and easy to control. It's referred to as "pseudo 1D" because every filament has thickness, and most filaments are porous materials. The porosity of the material means that the required sample volume is reduced, as it is adsorbed by the sensor array, thus reducing the desired sensor length. Capillary forces carry the sample directly to the sensor array. By adjusting the physical properties of the filaments, the wettability can be changed, which means the detection region can be adjusted. For example, if we compare low-porosity or non-porous materials like GC (Glassy Carbon), a surface area comparable to that of a 10 mm diameter GC electrode can be replaced by a sewing thread 7.5 mm long and 0.3 mm thick. The use of mesoporous materials drastically reduces the dimensions. DESCRIPTION OF THE DRAWINGS To complement the description being made and in order to help a better understanding of the characteristics of the invention, this descriptive document is accompanied, as an integral part thereof, by sheets of drawings in which the following has been represented for illustrative and non-limiting purposes: Figure 1 shows a schematic elevation representation of a portion of the filament structure comprising the electrochemical sensor that is the subject of the invention; Figure 2 shows a representation of the cross-section of the sensor filament structure shown in Figure 1; and Figure number 3.- Shows another perspective representation of the structure of the filament of the electrochemical sensor that is the object of the invention. PREFERRED EMBODIMENT OF THE INVENTION In view of the aforementioned figures, and in accordance with the numbering adopted, one can observe in them an example of a non-limiting embodiment of the electrochemical sensor for analytical purposes of the invention, which comprises what is described in detail below. Thus, as can be seen in said figures, the sensor (1) of the invention comprises one or more pseudo 1D or "linear" structure filaments (2), each of which, in turn, constitutes a single filament, of conductive or non-conductive material and modified or not, with two conductive parts, containing a reference electrode (3) and a working electrode (4) respectively, which constitute respective conductive regions, at the ends or in intermediate sections of the filament (2) itself, and a space between them that defines a non-conductive region (5) that separates said two conductive regions from each other, forming together a two-electrode system or electrochemical cell, without a conventional reference electrode (e.g., Ag / AgCl, calomels). In one embodiment, the filament (2) or filaments (2) are made of a conductive material, such as a conductive sewing thread or a carbon filament, in which case it has two conductive regions of the thread itself, containing respectively the reference electrode (3) and the working electrode (4), and a space between them defined by a non-conductive region (5) that is modified by physical, chemical or mechanical engraving to give it such a non-conductive character. And, in another alternative embodiment, the filament or filaments (2) are made of a non-conductive material, in this case modified in the two parts mentioned above to contain a reference electrode (3) or RE and a working electrode (4) or WE, so that they constitute respective regions, at the ends and / or intermediate sections of the filament (2) itself, for which they are coated with a conductive material, both parts being separated from each other by a non-conductive region (5) in this case as part of the filament itself. Preferably, the conductive material with which the region of the filament (2) that defines the reference electrode (3) is coated is a mostly electrochemically inert conductive material [towards the analyte], such as carbon ink, graphene, graphite, carbon nanotubes, or the carbon fiber itself, and may even be a non-conductive metallized thread, such as a sewing thread interwoven with a conductive wire / fiber / filament. Preferably, the working electrode region (4) is a conductive base that can be self-detecting, such as a conductive filament, rod, or sewing thread, or modified to support at least one detector material. Such modification can be physical, mechanical, chemical, or electrochemical. Preferably, the working electrode region (4) comprises a protective layer that improves adhesion, adsorption, and chemical and electrochemical stability in the working or non-working state. In any case, preferably, each filament (2) of the sensor (1), which may consist of a conventional filament, such as sewing thread in the case of being non-conductive, but not limited to it, is moistened by capillary forces to adsorb and distribute the analyte solution in submicroliter volumes (~1 pl_), which reduces the need for sample approximately 1000 times compared to conventional electrochemical cells and 50 times compared to erygraphed electrodes. To this end, although in a basic sensor design option, this wetting is based solely on the natural adsorption of the filament, in one embodiment option, it incorporates an adsorption unit (not shown in the figures), for example, crosslinked polyacrylamide, for water-soluble analytes, deposited or applied on the filament (2) as an adsorbent material with good affinity with the parts of the filament, to prevent evaporation of the sample and stabilize the electrochemical response. Additionally, to further improve stability, the sensor (1) is incorporated inside a tube, for example, a capillary of the corresponding diameter, not only to protect the sample from evaporation, but also to improve wetting, since the capillary has its intrinsic capillary effect. In any case, in other embodiment options, the sensor (1) comprises the combination of multiple filaments (2) of identical configuration to multiply the electrochemical response by the number of said filaments (2), improving sensitivity and performance, while maintaining submicroliter sample volumes (~1 pl_). And, in other embodiments, the sensor (1) comprises the combination of multiple filaments (2) with different sensing materials in their respective working electrodes (4), to form a multichannel sensor, allowing the simultaneous detection of multiple analytes with customized electrochemical responses, enabling amplification of the response by combining the outputs of the filaments (2) or performing parallel measurements with basic statistical methods (e.g., average FME, standard deviation, median FME, coefficient of variation) to improve accuracy, reduce manufacturing errors or human errors, and enable online data processing, maintaining submicroliter sample volumes (~1 _). In any case, the filament material (2) can be any suitable material of any diameter, such as cotton for hydrophilic samples, nylon for hydrophobic samples; or materials specially treated to provide hydrophobicity / hydrophilicity properties or affinity towards a solution or an analyte, being designed to adapt to the properties of the sample, thus improving adaptability to various analytes and sample types. Furthermore, the filament (2) can be a nanofiber, such as, among others, Al2O3 nanotubes with diameters of tens of nanometers, which allows adaptation to hydrophilic / hydrophobic samples through appropriate pretreatment, miniaturization and compatibility with modification procedures (e.g., painting / dipping, metallizing, electrochemical deposition). Furthermore, the use of specific properties of the filament material (2), such as luminescence (in the case of Al2O3), can be employed for hybrid analytical methods of electrochemistry and luminescence (e.g., electrochemiluminescence, photoelectrochemistry-luminescence). Having sufficiently described the nature of the present invention, as well as the manner of putting it into practice, it is not considered necessary to make its explanation more extensive so that any expert in the field can understand its scope and the advantages that derive from it.

Claims

1. An electrochemical sensor for analytical purposes comprising a two-electrode system or electrochemical cell, characterized by comprising one or more pseudo-1D filaments (2), each of which constitutes a single filament with two conductive parts, containing a reference electrode (3) and a working electrode (4), which constitute respective conductive regions at the ends or intermediate sections of the filament (2), and a space between them defining a non-conductive region (5) that separates said two conductive regions. 2.An electrochemical sensor for analytical applications comprising a two-electrode system or electrochemical cell, according to claim 1, characterized in that one or more of the filaments (2) are made of a conductive material, with two conductive regions containing the reference electrode (3) and the working electrode (4), and a non-conductive region (5) modified by physical, chemical, or mechanical etching.

3. An electrochemical sensor for analytical applications comprising a two-electrode system or electrochemical cell, according to claim 1, characterized in that one or more of the filaments (2) are made of a non-conductive material, with two regions modified to be coated with a conductive material and containing the reference electrode (3) and the working electrode (4), and a non-conductive region (5) of the filament itself. 4.An electrochemical sensor for analytical purposes, according to claim 3, characterized in that the conductive material coating the region of the filament (2) that defines the reference electrode (3) is a material that is electrochemically inert towards the analyte.

5. An electrochemical sensor for analytical purposes, according to claim 4, characterized in that the conductive material of the reference electrode region (3) is carbon ink, graphene, graphite, carbon nanotubes, or carbon fiber, or a non-conductive metallized thread, such as sewing thread interwoven with a conductive wire / fiber / filament.

6. An electrochemical sensor for analytical purposes, according to any of the preceding claims, characterized in that the working electrode region (4) is a self-detecting conductive base, such as a conductive filament, rod, or sewing thread. 7.An electrochemical sensor for analytical purposes, according to any of claims 3 to 5, characterized in that the working electrode region (4) is modified physically, mechanically, chemically, or electrochemically to support at least one detector material.

8. An electrochemical sensor for analytical purposes, according to any of claims 3 to 7, characterized in that the working electrode region (4) comprises a protective layer.

9. An electrochemical sensor for analytical purposes, according to any of claims 3 to 8, characterized in that each filament (2) is configured with a capillary structure capable of adsorbing and distributing the analyte solution in submicroliter volumes (approximately 1 μL).

10. An electrochemical sensor for analytical purposes, according to claim 9, characterized in that it incorporates an adsorption unit, crosslinked polyacrylamide, deposited or applied onto the filament (2) as an adsorbent material. 11.An electrochemical sensor for analytical purposes, according to claim 9 or 10, characterized in that it is incorporated within a tube, consisting of a capillary of the corresponding diameter, to protect the sample from evaporation and improve wetting.

12. An electrochemical sensor for analytical purposes, according to any of the preceding claims, characterized in that it comprises the combination of multiple filaments (2) of identical configuration to multiply the electrochemical response by the number of said filaments (2).

13. An electrochemical sensor for analytical purposes, according to any of claims 1 to 11, characterized in that it comprises the combination of multiple filaments (2) with different sensing materials in their respective working electrodes (4), to form a multichannel sensor. 14.An electrochemical sensor for analytical purposes, according to any of claims 3 to 13, characterized in that the filament material (2) is cotton for hydrophilic samples or nylon for hydrophobic samples.

15. An electrochemical sensor for analytical purposes, according to any of the preceding claims, characterized in that the filament (2) is an Al2O3 nanotube nanofiber.