Metal-coated screen-printed electrodes for trace element detection

Abstract

A system for detecting trace heavy metals in a solution is provided herein. The system includes a screen printed electrode comprising a working electrode, a counter electrode, and a reference electrode arranged on a substrate surface, a metal coating applied to the working electrode, a potentiostat connected to the screen printed electrode, and a processor. The processor is configured to control the potentiostat to perform anodic stripping voltammetry on the screen printed electrode and to analyze results of the voltammetry to detect presence of trace heavy metals in the solution.

Description

METAL-COATED SCREEN-PRINTED ELECTRODES FOR TRACE ELEMENTDETECTIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Application No. 63 / 637,333, titled METAL-COATED SCREEN-PRINTED ELECTRODES FOR TRACE ELEMENT DETECTION, filed April 22, 2024, which is hereby incorporated by reference in its entirety.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable.INTRODUCTION

[0003] Electrochemical detection methods have emerged as powerful analytical techniques for measuring trace levels of heavy metals and other elements in various sample matrices. These methods offer advantages such as high sensitivity, low detection limits, and the ability to analyze multiple analytes simultaneously. Stripping voltammetry in particular has found widespread use for trace metal analysis due to its ability to preconcentrate analytes on an electrode surface prior to measurement.

[0004] The choice of working electrode material is an important factor that influences the performance of electrochemical stripping techniques. Historically, mercury- based electrodes have been widely employed due to their wide cathodic potential range and low background currents. However, the toxicity of mercury and environmental concerns associated with its use have motivated research into alternative electrode materials.

[0005] Carbon-based electrodes have attracted significant interest as potential replacements for mercury electrodes in stripping analysis applications. Various forms of carbon electrodes have been investigated, including glassy carbon, carbon paste, and screen- printed carbon electrodes. Screen-printed electrodes in particular offer advantages of low cost, ease of mass production, and disposability.

[0006] While bare carbon electrodes can be used for some stripping voltammetry measurements, their performance is often limited compared to mercury. To enhance sensitivity and expand the range of detectable analytes, researchers have explored modifyingcarbon electrode surfaces with various metallic films or nanoparticles. This approach aims to combine the beneficial properties of metal electrodes with the practical advantages of carbonbased substrates.

[0007] Existing electrode materials and designs for trace element detection often suffer from one or more limitations. Some electrodes lack the sensitivity7required to detect ultra-trace levels of certain heavy metals that may be present in environmental or biological samples. Others may have poor selectivity, leading to interference from co-existing species in complex sample matrices. The stability and reproducibility of modified electrodes can also be challenging, with some coatings degrading over time or providing inconsistent results between measurements.

[0008] Many current heavy metal sensing systems rely on bulky, expensive laboratory instrumentation that is not suitable for on-site or field testing applications. Portable devices often compromise on performance to achieve miniaturization and lower costs. Additionally, some electrode modification procedures involve complex, multi-step processes that are difficult to scale up for mass production.

[0009] There remains a need for improved electrode materials and designs that can match or exceed the analytical performance of mercury while avoiding its drawbacks. Ideally, such electrodes would offer high sensitivity7, low detection limits, wide linear range, and good reproducibility for multiple metal analytes. Additionally, electrodes that are simple to fabricate, low-cost, and environmentally friendly are desirable for widespread adoption in routine analysis and field-portable applications.SUMMARY

[0010] According to an aspect of the present disclosure, a system for detecting trace heavy metals in a solution is provided. The system includes a screen-printed graphite electrode, a metal coating applied to the electrode, a potentiostat connected to the electrode, and a processor configured to control the potentiostat to perform anodic stripping voltammetry on the electrode and to analyze the results of the voltammetry to detect the presence of the trace heavy metals in the solution.

[0011] According to other aspects of the present disclosure, the system may include one or more of the following features. The metal coating may comprise gold or bismuth. The solution may comprise blood, water, or urine. The processor may be further configured to detect mercury, lead, or cadmium in the solution. The potentiostat may be configured to perform square-wave anodic stripping voltammetry. The system may further comprise awireless communication module configured to transmit the detected heavy metal concentrations to a remote device. The processor may be further configured to provide an alert when a detected heavy metal concentration exceeds a predetermined threshold. The screen-printed graphite electrode may comprise a graphite base formed from a compounding formula of graphite, carbon black, and styrene-ethylene-butylene-styrene (SEBS). The screen-printed graphite electrode may further comprise a conductive trace formed from Ag / AgCl conductive ink. The potentiostat may be a handheld device configured for portable use.

[0012] According to another aspect of the present disclosure, a method for detecting trace heavy metals in a solution is provided. The method includes providing a screen-printed graphite electrode, immersing the metal-coated electrode in the solution, and performing anodic stripping voltammetry on the electrode to detect the presence of heavy metals in the solution.

[0013] According to other aspects of the present disclosure, the method may include one or more of the following features. The solution may comprise blood, water, or urine. The anodic stripping voltammetry may be performed using a square-wave voltammetric stripping scan. The square-wave voltammetric stripping scan may use a frequency of 25 Hz, a potential step of 5 mV, and an amplitude of 25 mV. The method may further comprise quantitatively determining the concentration of the heavy metals in the solution based on a calibration curve correlating peak current to heavy metal concentration. The processor may be configured to detect mercury, lead, or cadmium in the solution. The potentiostat may be configured to perform square-wave anodic stripping voltammetry. The method may further comprise transmitting the detected heavy metal concentrations to a remote device using a wireless communication module. The method may further comprise providing an alert when a detected heavy metal concentration exceeds a predetermined threshold. The screen-printed graphite electrode may comprise a graphite base formed from a compounding formula of graphite, carbon black, and styrene-ethylene-butylene-styrene (SEBS).

[0014] According to another aspect of the present disclosure, a screen-printed graphite electrode for detecting trace heavy metals in a solution is provided. The screen- printed graphite electrode includes a graphite base, a metal coating applied to the graphite base, and a conductive trace connected to the graphite base. The metal coating enhances the sensitivity of the electrode to the trace heavy metals when the electrode is immersed in the solution and anodic stripping voltammetry is performed.

[0015] According to other aspects of the present disclosure, the screen-printedgraphite electrode may include one or more of the following features. The metal coating may comprise gold or bismuth. The metal coating may be applied to the graphite base by electrodeposition. The bismuth coating may be applied by immersing the electrode in a solution containing bismuth at a concentration between about 500 pg / L and about 1000 mg / L and maintaining the electrode at a potential of -0.8 V for a duration of 240 seconds.

[0016] In various aspects, the system can comprise: (a) a screen-printed electrode with a working electrode of graphite (60-80 wt%), carbon black (10-20 wt%), and SEBS (15- 25 wt%); (b) a bismuth / gold coating (50 nm-1 pm thickness) applied via electrodeposition (-0.8 V for 60-300 s); and (c) a potentiostat performing square-wave ASV (25 Hz, 5 mV step).

[0017] According to another aspect, the present disclosure provides methods and systems for manufacturing bismuth-modified screen-printed electrodes. The manufacturing process may involve preparing a graphite-based ink containing bismuth oxide, blending the ink components, and using an automated screen-printing system to print electrode layers onto a substrate. The method may include separate curing steps for the working electrode layer, counter and reference electrode layers, and an insulating layer. In some cases, the process may involve quality control checks and packaging of individual electrodes. The graphitebased ink may comprise specific quantities of graphite powder, carbon black, styrene- ethylene-butylene-styrene copolymer, toluene solvent, and bismuth oxide powder. The manufacturing system may include a mixing apparatus, an automated screen-printing system, a curing apparatus, and a cutting system. In some implementations, the system may also include a quality control station for performing various tests on the manufactured electrodes.

[0018] These and other features, aspects and advantages of the present teachings will become better understood with reference to the following description, examples and appended claims.DRAWINGS

[0019] Those of skill in the art will understand that the drawings, described below, are for illustrative purposes only. The drawings are not intended to limit the scope of the present teachings in any way.

[0020] FIG. 1 illustrates a screen printed electrode configuration, designed for efficient electrochemical sensing of trace metals.

[0021] FIG. 2 depicts an exploded view of an electrode testing assembly, showcasing the integrated components for portable analysis.

[0022] FIG. 3 shows a screen-printed electrode design, optimized for compact and disposable electrochemical sensing applications.

[0023] FIG. 4 presents a screen-printed electrode device layout, engineered for precise electrochemical measurements.

[0024] FIG. 5 demonstrates the operational comparison between a glucose meter and a heavy’ metals sensor, highlighting user interface similarities.

[0025] FIG. 6 illustrates a portable electronic device for displaying test results, designed for ease of use in field testing.

[0026] FIG. 7 shows another view7of the portable electronic device, emphasizing its ergonomic design for handheld operation.

[0027] FIG. 8 depicts the display screen of the testing device, showcasing clear presentation of measurement data.

[0028] FIG. 9 presents another view of the device display, highlighting the user- friendly interface for result interpretation.

[0029] FIG. 10 illustrates calibration analysis graphs for bismuth-coated electrodes, demonstrating optimization of sensing parameters.

[0030] FIG. 11 shows voltammetric measurements over time, validating the longterm stability7of the electrode performance.

[0031] FIG. 12 depicts voltammetric curves for lead detection in blood samples, showcasing the electrode's sensitivity in complex matrices.

[0032] FIG. 13 demonstrates the electrochemical response for lead detection in blood, highlighting the rapid analysis capability7.

[0033] FIG. 14 shows the effect of deposition time on electrode response, optimizing the sensing protocol for blood samples.

[0034] FIG. 15 illustrates the selectivity of the electrode for cadmium detection, demonstrating clear signal separation from lead.

[0035] FIG. 16 depicts the electrode's selectivity for zinc detection, showcasing its ability to distinguish between metal species.

[0036] FIG. 17 shows the electrode's response to varying lead concentrations, demonstrating its sensitivity and linear range.

[0037] FIG. 18 illustrates the electrode's selectivity’ for copper detection, highlighting its performance in multi-metal solutions.

[0038] FIG. 19 demonstrates the reproducibility of lead measurements, validating the electrode's reliability for repeated use.

[0039] FIG. 20 shows the electrode's sensitivity for low-level lead detection, emphasizing its capability for trace analysis.

[0040] FIG. 21 depicts the electrode's performance across a wider lead concentration range, showcasing its versatility in sensing.

[0041] FIG. 22 presents a comparison of different electrode materials, highlighting the superior performance of the developed graphite ink.

[0042] FIG. 23 illustrates the optimization of blood sample preparation, demonstrating the method's adaptability to complex matrices.DETAILED DESCRIPTION

[0043] All patents, applications, published applications and other publications cited herein are incorporated by reference in their entirety. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary7skill in the art to which the invention belongs. The chemical structures and formulae set forth herein are constructed according to the standard rules of chemical valency known in the chemical arts. Should a discrepancy exist between a depicted structure and a name given for that structure, the depicted structure is to be accorded more weight. Where the stereochemistry7of a structure or a portion of a structure is not indicated in a depicted structure or a portion of the depicted structure, the depicted structure is to be interpreted as encompassing all of its possible stereoisomers.

[0044] Any^ methods, devices and materials similar or equivalent to those described herein can be used in the practice of this invention. The following definitions are provided to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure. In the event that there is a plurality of definitions for a term herein, those in this section prevail unless stated otherwise. Headings used herein are for organizational purposes only and in no way limit the invention described herein.

[0045] Abbreviations and Definitions

[0046] To facilitate understanding of the invention, a number of terms and abbreviations as used herein are defined below as follows:

[0047] "Heavy metal": As used herein, the term "heavy metal" refers to metallic elements with relatively high atomic w eights and densities, typically having a specific gravity greater than 5.0. In the context of this disclosure, heavy metals may include but are not limited to lead (Pb), mercury (Hg), cadmium (Cd), arsenic (As), chromium (Cr), copper (Cu),and zinc (Zn).

[0048] "Trace metal": As used herein, the term "trace metal" refers to metals present in very low concentrations, typically in the parts per billion (ppb) or parts per trillion (ppt) range. In this disclosure, trace metals may include heavy metals and other metallic elements of interest at low concentrations.

[0049] "Screen-printed electrode" (SPE): As used herein, the term "screen-printed electrode" refers to an electrode fabricated using screen printing technology, where conductive inks are deposited onto a substrate through a patterned screen or stencil.

[0050] "Working electrode": As used herein, the term "working electrode" refers to the electrode in an electrochemical cell where the reaction of interest occurs and is typically where the analyte is oxidized or reduced.

[0051] "Counter electrode": As used herein, the term "counter electrode" refers to the electrode that completes the circuit in an electrochemical cell, allowing current to flow.

[0052] "Reference electrode": As used herein, the term "reference electrode" refers to the electrode that maintains a constant potential and serves as a reference point for measuring the potential of the working electrode.

[0053] "Anodic stripping voltammetry" (ASV): As used herein, the term "anodic stripping voltammetry" refers to an electrochemical method used for quantitative determination of specific ionic species, involving a preconcentration step followed by a stripping step.

[0054] "Square wave voltammetry" (SWV): As used herein, the term "square wave voltammetry" refers to a type of pulse voltammetric technique used in electrochemical analysis, characterized by a series of forward and reverse pulses superimposed on a staircase waveform.

[0055] "Deposition time": As used herein, the term "deposition time" refers to the duration of the preconcentration step in anodic stripping voltammetry, during which analyte ions are reduced and deposited onto the electrode surface.

[0056] "Deposition potential": As used herein, the term "deposition potential" refers to the applied potential during the preconcentration step in anodic stripping voltammetry.

[0057] "ppb": As used herein, the term "ppb" stands for parts per billion, a unit of measurement for very low7concentrations of analytes.

[0058] "ppt": As used herein, the term "ppt" stands for parts per trillion, a unit of measurement for extremely low concentrations of analytes.

[0059] Metal-Coated Screen-Printed Electrodes for Trace Element Detection

[0060] Metal-coated screen-printed electrodes for trace element detection represent an innovative approach to electrochemical sensing technology. This invention addresses the growing need for rapid, sensitive, and cost-effective methods to detect heavy metals and other trace elements in various sample matrices. The novel aspects of this technology' he in the combination of screen-printing techniques with carefully selected metal coatings to enhance electrode performance.

[0061] The screen-printed electrodes serve as the foundation for this sensing platform, offering advantages such as ease of mass production, low cost, and disposability'. These attributes make the technology' particularly suitable for widespread adoption in routine analysis and field-portable applications. The metal coating applied to the electrode surface further enhances the sensitivity and selectivity7for specific trace elements.

[0062] In some cases, the metal coating may comprise noble metals or other electrochemically active materials. The choice of coating material may be tailored to optimize detection for particular analytes of interest. This customization allows for versatile applications across diverse fields including environmental monitoring, food safety testing, clinical diagnostics, and industrial process control.

[0063] The invention provides a technical solution to the challenge of achieving low detection limits for trace elements while maintaining a practical and accessible sensing platform. By combining screen-printing technology with optimized metal coatings, the electrodes may offer performance comparable to more complex and expensive analytical techniques.

[0064] The novel combination of materials and fabrication methods in this invention may lead to unexpected improvements in electrode stability, reproducibility’, and resistance to interfering species. These advancements may expand the range of sample types and environmental conditions under which accurate trace element detection can be performed.

[0065] Those skilled in the art will recognize that various modifications and variations can be made without departing from the spirit and scope of the invention. The flexibility in electrode design and coating materials allows for continued optimization and adaptation to meet evolving analytical needs across multiple industries and applications.

[0066] Screen-Printed Graphite Electrode

[0067] The screen-printed graphite electrode may serve as the foundation for the trace element detection system. FIG. 1 illustrates an orthogonal view of a screen printedelectrode 100. The screen printed electrode 100 may be fabricated on a substrate surface 110, which may provide mechanical support and electrical insulation for the electrode components.

[0068] In some cases, the screen printed electrode 100 may comprise a graphite base formed from a compounding formula of graphite, carbon black, and styrene-ethylene- butylene-styrene (SEBS). This composition may offer a balance of conductivity, mechanical strength, and printability. The graphite component may provide the primary conductive matrix, while the carbon black may enhance overall conductivity and uniformity. The SEBS polymer may act as a binder, improving the adhesion and flexibility of the printed electrode.

[0069] The manufacturing process for the screen printed electrode 100 may involve preparing an ink formulation containing the graphite, carbon black, and SEBS components. In some cases, the ink may be prepared by mixing specific ratios of these materials with appropriate solvents to achieve the desired viscosity7for screen printing. The ink may then be deposited onto the substrate surface 110 through a patterned screen or stencil, creating the desired electrode geometry.

[0070] FIG. 3 shows a screen-printed electrode design with three parallel conductive tracks arranged vertically. These tracks may correspond to different functional areas of the screen printed electrode 100, such as the working electrode, counter electrode, and reference electrode. The spacing and dimensions of these tracks may be optimized for electrochemical performance and manufacturing considerations.

[0071] In some cases, the screen printed electrode 100 may comprise a conductive trace formed from Ag / AgCl conductive ink. FIG. 4 illustrates a screen-printed electrode device with conductive traces extending from contact points to their respective electrodes. These conductive traces may provide electrical connections between the electrode areas and external measurement instrumentation.

[0072] Alternative materials and compositions for the graphite base may be explored to further enhance electrode performance. For example, the graphite component may be replaced or supplemented with other carbon allotropes such as carbon nanotubes or graphene. The polymer binder may be varied to include materials such as polyvinyl chloride (PVC) or polyethylene terephthalate (PET) to modify the mechanical and chemical properties of the electrode.

[0073] The screen printing process allows for flexibility in electrode design and rapid prototyping. Various electrode geometries, thicknesses, and multi-layer structures may be explored to optimize sensing performance for specific trace element detectionapplications. Those skilled in the art will recognize that various modifications and variations can be made without departing from the spirit and scope of the invention.

[0074] Metal Coating

[0075] The metal coating applied to the screen-printed graphite electrode may play an important role in enhancing sensitivity and selectivity for trace element detection. In some cases, the metal coating may comprise gold or bismuth, each offering unique properties for specific analyte detection.

[0076] Bismuth coatings may be particularly effective for the detection of heavy metals such as lead and cadmium. In some cases, the bismuth coating may be applied by immersing the electrode in a solution containing bismuth at a concentration between about 500 pg / L and about 1000 mg / L. The deposition process may involve maintaining the electrode at a potential of -0.8V for a duration of 240 seconds. Those of skill in the art will recognize that the deposition time may range from about 60 to about 300 s to achieve appropriate thicknesses of the coating, and in some cases from about 120 to 240 s. This electrodeposition method may allow for precise control over the coating thickness and uniformity. For example, the working electrode’s bismuth coating thickness may range from 50 nm to 1 pm, with about 200 nm providing optimal signal -to-noise ratios for blood samples. Those of skill in the art w ould recognize other thicknesses which can be tested for sensitivity and specificity of the heavy metal being detected.

[0077] FIG. 10 illustrates the effect of various deposition parameters on electrode performance. The left graph in FIG. 10 show s multiple voltammetric curves at different applied potentials, demonstrating how the deposition potential may influence the resulting bismuth coating. The middle graph in FIG. 10 displays the electrode response at varying deposition times, which may be optimized to achieve the desired coating characteristics.

[0078] The thickness of the metal coating may range from a few nanometers to several micrometers, depending on the specific application requirements. In some cases, thinner coatings may offer faster response times, while thicker coatings may provide improved durability and higher sensitivity for certain analytes.

[0079] Gold coatings may be particularly suitable for the detection of mercury and arsenic. The deposition process for gold coatings may involve similar electrochemical methods as those used for bismuth, with adjustments to the deposition solution composition and electrochemical parameters.

[0080] Alternative coating materials may include silver, platinum, palladium, oralloys of these metals. Each coating material may offer specific advantages for certain trace element detection applications. For example, silver coatings may enhance sensitivity for halide ions, while platinum coatings may improve catalytic activity for certain electrochemical reactions.

[0081] FIG. 14 demonstrates the electrochemical response of a bismuth-coated screen-printed graphite electrode for detecting lead in blood samples. The graph displays multiple voltammetric curves corresponding to different deposition times, illustrating how the coating parameters may be optimized for specific sample matrices and analytes.

[0082] The choice of metal coating may significantly impact the electrode's performance characteristics. For instance, bismuth coatings may form alloys with certain heavy metals during the preconcentration step, enhancing sensitivity and selectivity. Gold coatings may facilitate the formation of amalgams with mercury, enabling ultra-low detection limits for this element.

[0083] In some cases, multi-layer or composite coatings may be employed to combine the advantageous properties of different metals. For example, a thin layer of gold over a bismuth coating may provide enhanced stability while maintaining high sensitivity for a broader range of analytes.

[0084] The metal coating process may be further optimized by adjusting factors such as solution pH, temperature, and the presence of additives or surfactants. These parameters may influence the morphology and electrochemical properties of the resulting coating, allowing for fine-tuning of electrode performance for specific analytical applications.

[0085] Moreover, prior systems such as US Pat. No. 6,682,647 and EP Pat. No. 0969281, require post-printing electrodeposition which increases manufacturing complexity. In various embodiments, the present invention integrates bismuth oxide directly into the electrode ink, eliminating post-processing while achieving a 0.05 ppb mercury detection limit - 10 times lower than EP0969281A2’s 0.5 ppb limit. In addition, unlike US Pat. No. 6,682,647, which uses toxic mercury', the integration of E^CE into the SEBS-graphite ink enables in-situ bismuth activation during printing, reducing manufacturing steps. In addition, the SEBS binder unexpectedly enhances conductivity by 30% compared to PVC-based electrodes.

[0086] Those skilled in the art will recognize that various modifications and variations can be made without departing from the spirit and scope of the invention. The metal coating composition, thickness, and deposition parameters may be adjusted to meet the specific requirements of different trace element detection scenarios, enabling a versatile andadaptable sensing platform.

[0087] Scaled-Up Manufacturing of Screen Printed Electrodes

[0088] In some aspects, a scaled-up manufacturing process for bismuth-modified screen-printed electrodes (SPEs) may be implemented by incorporating bismuth oxide (Bi20s) directly into the ink formulation. This process may offer advantages in terms of production efficiency and consistency of electrode performance. Alternative embodiments may explore the use of other bismuth compounds, such as bismuth nitrate or bismuth chloride, which may provide different electrochemical properties or improved dispersion characteristics in the ink matrix.

[0089] The process may begin with the preparation of a large batch of graphitebased ink. In one non-limiting example, the ink formulation may comprise:- 2400 g of graphite powder- 400 g of carbon black- 3696 g of styrene-ethylene-butylene-styrene (SEBS) copolymer- 970 g of toluene solvent- 100 g of bismuth oxide (Bi2O3) powder

[0090] Alternative ink formulations may adjust the ratios of these components or incorporate additional materials such as conductive polymers or metal nanoparticles to enhance electrode performance. In some embodiments, the graphite powder may be replaced or supplemented with carbon nanotubes or graphene to modify the electrical and mechanical properties of the printed electrodes.

[0091] These components may be thoroughly blended using a high-shear mixer for approximately 30 minutes. This mixing step may ensure uniform dispersion of the Bi20s particles throughout the ink matrix, which may be important for achieving consistent electrode performance. Alternative mixing methods may include ball milling, ultrasonic dispersion, or a combination of techniques to achieve optimal particle distribution.

[0092] The bismuth-modified ink may then be loaded into an automated screenprinting system. This system may be equipped with a large-format screen stencil designed to print multiple electrode patterns simultaneously. In some implementations, the printing system may be capable of producing hundreds of electrodes per minute, significantly increasing production throughput compared to manual methods. Alternative printing technologies such as inkjet printing or roll-to-roll printing may be explored for different production scales or specialized electrode designs.

[0093] The working electrode layer may be printed onto rolls of polyester substrate using the bismuth-modified ink. In some embodiments, alternative substrate materials such as paper, glass, or flexible polymers may be used to create electrodes with different physical or chemical properties. Following the printing step, the working electrode layer may be cured in a continuous belt oven. In some cases, the curing process may involve heating at approximately 80°C for about 10 minutes. Alternative curing methods may include UV curing, infrared heating, or plasma treatment, which may offer faster processing times or improved adhesion to certain substrates.

[0094] Subsequent printing steps may involve applying the counter and reference electrode layers using separate ink formulations. For example, a carbon-based ink may be used for the counter electrode, while an Ag / AgCl ink may be used for the reference electrode. In some embodiments, alternative materials such as platinum or gold may be used for the counter electrode, while iridium oxide or other stable reference materials may be explored for the reference electrode. These layers may be cured at a higher temperature, such as 90°C, for a longer duration, such as 30 minutes, in the continuous belt oven. The curing parameters may be adjusted based on the specific ink formulations and desired electrode characteristics.

[0095] An insulating layer may be applied to define the active electrode areas and protect the conductive traces. This step may involve an automated screen-printing process using a dielectric ink. In some cases, photopattemable polymers or laser ablation techniques may be used to create more precise electrode geometries or complex multi-layer structures. The insulating layer may be cured at an even higher temperature, such as 120°C, for approximately 20 minutes in the continuous belt oven. Alternative insulating materials with different chemical resistances or dielectric properties may be explored for specialized applications.

[0096] Once all layers have been printed and cured, an automated cutting system may be employed to separate individual electrodes from the printed rolls. This step may ensure precise and consistent dimensions for each electrode. In some embodiments, laser cutting or die-cutting techniques may be used to create electrodes with more complex shapes or integrated features such as microfluidic channels.

[0097] Quality control measures may be implemented throughout the manufacturing process. In some cases, a statistical sampling of electrodes from each production batch may undergo visual inspection, resistance measurements, and electrochemical performance testing. Advanced quality control methods may incorporate machine vision systems for automated defect detection or in-line electrochemical testing to ensure consistentperformance across all produced electrodes.

[0098] The finished electrodes may be packaged in moisture-resistant, sealed pouches for storage and distribution. This packaging step may help protect the electrodes from environmental factors that could affect their performance or shelf life. Alternative packaging methods may include individual blister packs or specialized containers with desiccants for extended shelf life in challenging environments.

[0099] By integrating B12O3 directly into the ink formulation, this manufacturing process may eliminate the need for post-production electrochemical deposition of bismuth. This integration may potentially reduce production time and complexity while maintaining or improving electrode performance for trace metal detection applications. In some embodiments, a hybrid approach may be explored where a base layer of bismuth-modified ink is printed, followed by an electrochemical deposition step to create a more uniform or thicker bismuth layer.

[0100] The automated nature of the printing, curing, and cutting steps may allow for high-throughput production, which may be advantageous for meeting large-scale demand for these electrodes. Additionally, the quality control measures implemented throughout the process may help ensure consistent performance across production batches, which may be important for reliable trace metal detection in various applications. In some cases, the manufacturing process may be integrated with automated packaging and labeling systems to create complete test kits or sensor arrays for specific analytical applications.

[0101] Electrode Configuration

[0102] The screen printed electrode 100 may comprise a working electrode 102, a counter electrode 103, and a reference electrode 101 arranged in a specific configuration on the substrate surface 110. FIG. 1 illustrates an orthogonal view of the screen printed electrode 100, showing the arrangement of these electrodes. The working electrode 102 may be positioned between the reference electrode 101 and the counter electrode 103, forming an electrode pattern 120 that optimizes electrochemical measurements.

[0103] In some cases, the working electrode 102 may sen e as the primary sensing surface where redox reactions occur. The counter electrode 103 may complete the electrical circuit, allowing current to flow, while the reference electrode 101 may provide a stable reference potential for accurate measurements.

[0104] The electrode pattern 120 may be designed to create distinct sensing regions for electrochemical measurements. FIG. 3 shows a screen-printed electrode design with threeparallel conductive tracks arranged vertically. These tracks may correspond to the working electrode 102, counter electrode 103, and reference electrode 101, respectively. The spacing between the electrodes may be optimized to minimize solution resistance and ensure accurate potential control. The electrodes may further be adapted to communicate with a receiver shown in the right panel of FIG. 3. Such receiver may communicate with a number of systems to interpret and display results of heavy metal detection.

[0105] Conductive traces may extend from each electrode to their respective contact points, facilitating electrical connections with external measurement instrumentation. FIG. 4 illustrates a screen-printed electrode device with conductive traces extending from contact points to their respective electrodes. These conductive traces may be covered by an insulating layer, leaving only the electrode areas and contact points exposed.

[0106] In some cases, the insulating layer may help prevent unintended electrical connections and define the active electrode areas. The insulating layer may be made of a polymer material that is compatible with the electrode fabrication process and resistant to the sample solutions used in electrochemical measurements.

[0107] Alternative electrode configurations may be explored to enhance performance for specific applications. For example, interdigitated electrode designs may increase the active surface area and improve sensitivity. Circular or spiral electrode patterns may offer advantages for certain sample types or measurement geometries.

[0108] The size and shape of the individual electrodes may be varied to optimize performance for different analytes or sample matrices. In some cases, the working electrode 102 may have a larger surface area compared to the counter electrode 103 and reference electrode 101 to enhance sensitivity and signal-to-noise ratio.

[0109] Multiple working electrodes may be incorporated into a single screen printed electrode 100 to enable simultaneous detection of multiple analytes or to provide redundancy in measurements. The arrangement and spacing of these multiple working electrodes may be optimized to minimize cross-talk and interference between measurements.

[0110] The thickness and composition of the conductive traces may be adjusted to balance conductivity and spatial constraints on the substrate surface 110. In some cases, the conductive traces may be fabricated using highly conductive materials, such as silver or gold inks, to minimize signal loss and ensure optimal electrical performance.

[0111] Those skilled in the art will recognize that various modifications and variations can be made without departing from the spirit and scope of the invention. The electrode configuration may be customized to meet specific analytical requirements, sampletypes, or measurement conditions, enabling a versatile and adaptable sensing platform for trace element detection.

[0112] Potentiostat and Measurement System

[0113] The screen printed electrode 100 may be connected to a potentiostat for performing electrochemical measurements. FIG. 2 illustrates an electrode testing assembly 200 that may incorporate a potentiostat for trace element detection. The electrode testing assembly 200 may comprise a circuit board 240 containing the electronic components necessary' for potentiostatic control and signal processing. In some cases, a sensor module 245 may be mounted on the circuit board 240 to provide specialized functionality' for electrochemical measurements.

[0114] The potentiostat may be configured to apply controlled potential waveforms to the working electrode 102 and measure the resulting current response. In some cases, the potentiostat may be a handheld device configured for portable use. FIG. 5 demonstrates a comparison between a glucose meter and a heavy metals sensor, both utilizing compact, handheld designs suitable for field testing applications.

[0115] Anodic stripping voltammetry may' be performed using the potentiostat to detect trace elements on the screen printed electrode 100. In some cases, the anodic stripping voltammetry may be performed using a square-wave voltammetric stripping scan. The square-wave voltammetric stripping scan may use a frequency of 25 Hz, a potential step of 5 mV, and an amplitude of 25 mV. These parameters may be optimized to achieve high sensitivity' and selectivity' for specific trace elements.

[0116] The anodic stripping voltammetry' process may involve two main steps: a deposition step and a stripping step. During the deposition step, the potentiostat may apply a negative potential to the working electrode 102, causing target metal ions to be reduced and deposited onto the electrode surface. The stripping step may involve scanning the potential in a positive direction, causing the deposited metals to be oxidized and stripped from the electrode surface. The resulting current response may be measured and analyzed to determine the concentration of trace elements in the sample.

[0117] FIG. 6 shows a portable electronic device that may be used for measuring and displaying test results from electrochemical measurements. The device may incorporate a display screen for showing numerical readouts of detected trace element concentrations. In some cases, the potentiostat and display functionality may be integrated into a single handheld unit for convenient field use.

[0118] Alternative measurement techniques may be explored to expand the capabilities of the trace element detection system. For example, differential pulse voltammetry may offer improved discrimination against background currents in certain sample matrices. Chronoamperometry may be suitable for continuous monitoring applications, allowing for real-time tracking of trace element concentrations over extended periods.

[0119] FIG. 7 illustrates another example of a portable electronic device for displaying test results. The device may include a test strip or sensor connector extending from the top, suggesting compatibility with disposable screen printed electrodes of the present invention. This configuration may allow for rapid sample analysis using pre-calibrated electrode strips.

[0120] The potentiostat and measurement system may be designed to accommodate various electrode configurations and sample types. In some cases, the system may include multiple measurement channels to enable simultaneous analysis of different trace elements or to provide redundancy in measurements. The electrode pattern 120 on the substrate surface 110 may be optimized to interface effectively with the potentiostat connections, ensuring reliable electrical contact and signal transmission.

[0121] Software algorithms may be implemented in the potentiostat system to perform data analysis and interpretation. These algorithms may include baseline correction, peak identification, and quantification routines tailored for specific trace element detection applications. In some cases, machine learning techniques may be employed to improve the accuracy and reliability of trace element concentration estimates across diverse sample matrices.

[0122] Those skilled in the art will recognize that various modifications and variations can be made without departing from the spirit and scope of the invention. The potentiostat and measurement system may be customized to meet specific analytical requirements, sample ty pes, or measurement conditions, enabling a versatile and adaptable platform for trace element detection in laboratory and field settings.

[0123] Data Processing and Analysis

[0124] The screen printed electrode 100 may be connected to a processor configured to control the potentiostat and analyze the results of voltammetry measurements. FIG. 8 illustrates a display screen 210 showing a test result from a diagnostic device. The display screen 210 may present measurement data such as detected heavy metalconcentrations.

[0125] In some cases, the processor may be programmed to perform data processing and analysis tasks to interpret the voltammetric responses obtained from the screen printed electrode 100. The processor may apply various algorithms for baseline correction, peak identification, and quantification of trace element concentrations.

[0126] FIG. 9 depicts a portable electronic device display showing test results from an electrochemical measurement. The device may incorporate a control interface 220 to allow user interaction and configuration of measurement parameters. The control interface 220 may enable selection of specific heavy metals for detection or adjustment of detection thresholds.

[0127] Calibration processes may be implemented to ensure accurate quantification of heavy metal concentrations. FIG. 11 shows a series of voltammetric measurements demonstrating the performance of a Bix2-coated SP-graphite electrode over different time periods. These calibration curv es may be used to correlate peak currents with known concentrations of target analytes.

[0128] The processor may be configured to detect different heavy metals based on their characteristic voltammetric responses. FIG. 12 depicts a graph showing the electrochemical response of a Bix2-coated SP-graphite electrode for detecting lead in blood samples. The distinct peaks corresponding to different lead concentrations may be analyzed by the processor to determine the lead content in the sample.

[0129] In some cases, the processor may employ machine learning algorithms to improve the accuracy and reliability of heavy metal detection across diverse sample matrices. These algorithms may be trained on large datasets of voltammetric responses to recognize patterns and compensate for matrix effects.

[0130] FIG. 13 illustrates a graph showing the electrochemical response of a Bix2- coated SP-graphite electrode for detecting lead in blood samples at different deposition times. The processor may analyze these time-dependent responses to optimize measurement parameters and enhance sensitivity for specific heavy metals.

[0131] The processor may be configured to provide an alert when a detected heavy metal concentration exceeds a predetermined threshold. This feature may enable rapid identification of potentially hazardous levels of contaminants in environmental or biological samples. The alert may be displayed on the display screen 210 or communicated through other means such as audible signals or wireless notifications.

[0132] Data interpretation methods implemented by the processor may include peak deconvolution techniques to resolve overlapping voltammetric signals from multiple heavymetals. These methods may enable simultaneous quantification of several trace elements in complex sample matrices.

[0133] The processor may also perform statistical analysis on measurement data to assess precision and reproducibility. This analysis may include calculation of standard deviations, relative standard deviations, and confidence intervals for reported heavy metal concentrations.

[0134] In some cases, the processor may be integrated with the electrode testing assembly 200, utilizing the circuit board 240 and sensor module 245 for data acquisition and processing. This integration may enable compact, portable systems for on-site heavy metal detection and analysis.

[0135] Those skilled in the art will recognize that various modifications and variations can be made without departing from the spirit and scope of the invention. The data processing and analysis capabilities may be customized to meet specific analytical requirements, regulatory standards, or end-user needs, enabling a versatile and adaptable platform for trace element detection in diverse applications.

[0136] System Integration and Operation

[0137] The screen printed electrode, working electrode, substrate surface, electrode pattern, electrode testing assembly, display screen, control interface, circuit board, and sensor module may be integrated into a comprehensive system for trace element detection. This integrated system may enable efficient sample analysis and result reporting across various applications.

[0138] In some cases, the screen printed electrode may be inserted into the electrode testing assembly to establish electrical connections. The electrode testing assembly may incorporate a measurement region where the screen printed electrode interfaces with liquid samples. FIG. 15 illustrates a graph showing the selectivity of a Bix2-coated SP-graphite electrode for detecting cadmium at 10 parts per billion (ppb) concentration. This graph demonstrates how the integrated system may distinguish between different heavy metals based on their characteristic voltammetric responses.

[0139] The sample preparation and measurement process may involve several steps. Initially, the liquid sample may be applied to the measurement region of the screen printed electrode. FIG. 23 depicts a graph showing the mixing of blood samples with hydrochloric acid (HC1) at different time intervals. This figure illustrates how sample preparation techniques may be optimized to enhance heavy metal detection in complex matrices likeblood.

[0140] Once the sample is prepared, the electrode testing assembly may initiate the electrochemical measurement sequence. The circuit board and sensor module may control the applied potential and current measurement. FIG. 16 shows a graph demonstrating the selectivity7of a Bix2-coated SP-graphite electrode for detecting zinc at a concentration of 10 ppb. This selective detection capability7may be achieved through precise control of measurement parameters by the integrated system.

[0141] The system may perform data processing and analysis to interpret the voltammetric responses. FIG. 17 depicts a graph showing the electrochemical response of a Bix2-coated SP-graphite electrode for detecting lead (Pb) concentrations from 0.5 to 5 parts per billion (ppb). The system may use calibration data like this to quantify heavy metal concentrations in unknown samples.

[0142] Results may be displayed on the display screen of the electrode testing assembly. The control interface may allow users to configure measurement settings and view detailed analysis reports. FIG. 18 illustrates a graph showing the selectivity of a Bix2-coated SP-graphite electrode for detecting copper ions in the presence of lead ions. This ty pe of multi-element analysis may be facilitated by the integrated system's data processing capabilities.

[0143] The system may include a wireless communication module configured to transmit the detected heavy metal concentrations to a remote device. This feature may enable real-time data sharing and remote monitoring of environmental or clinical samples. For example, field measurements of heavy metals in water sources may be immediately transmitted to a central database for analysis and reporting.

[0144] FIG. 19 demonstrates the reproducibility testing results for a Bix2-coated SP-graphite electrode detecting 3 parts per billion (ppb) of lead. The integrated system may leverage this reproducibility data to provide confidence interv als and statistical analysis of measurement results.

[0145] The system may be applied in various scenarios. For environmental monitoring, the portable nature of the electrode testing assembly may allow for on-site testing of water sources. FIG. 20 shows the sensitivity of a bismuth-coated screen-printed graphite electrode for detecting lead in solution at concentrations ranging from 0.05 ppb to 0.5 ppb. This high sensitivity may enable detection of trace contaminants in drinking water or natural water bodies.

[0146] In clinical applications, the system may be used for rapid screening of heavymetal exposure. FIG. 21 illustrates the sensitivity of a bismuth-coated screen-printed graphite electrode for detecting lead at parts per billion (ppb) concentrations in blood samples. The ability to perform these measurements quickly and with minimal sample preparation may facilitate point-of-care diagnostics.

[0147] Industrial quality control represents another potential application area. FIG. 22 presents a comparison of different electrodes for trace metal detection, showing the performance of carbon, graphene, and graphite electrodes. This comparison demonstrates how the system may be optimized for specific industrial processes or materials testing scenarios.

[0148] Those skilled in the art will recognize that various modifications and variations can be made without departing from the spirit and scope of the invention. The integration of components and operational steps may be customized to meet specific analytical requirements, sample types, or measurement conditions, enabling a versatile and adaptable platform for trace element detection across diverse applications.

[0149] EXAMPLES

[0150] Aspects of the present teachings may be further understood in light of the following examples, which should not be construed as limiting the scope of the present teachings in any way.

[0151] EXAMPLE 1: Detection of Lead in Blood Samples

[0152] The ability of the bismuth-coated screen-printed graphite electrode may be tested to detect lead in blood samples using the following protocol:

[0153] 1. Provide a bismuth-coated screen-printed graphite electrode. The electrode can be prepared by electrodepositing bismuth onto the graphite surface. The electrode is immersed in a solution containing 100 mg / L Bi(NO3)3 in 0.5 M HC1. A potential of -0.8 V is applied for 240 seconds to deposit the bismuth coating.

[0154] 2. Collect blood samples and prepare them for analysis by mixing 20 pL of blood with 20 pL of 0. 1 M HC1 in a 1 : 1 ratio. The mixture is vortexed for 1 minute to ensure thorough mixing and release of protein-bound lead.

[0155] 3. Apply 20 pL of the prepared blood sample to the bismuth-coated screen- printed graphite electrode, ensuring complete coverage of all three electrodes (working, counter, and reference).

[0156] 4. Perform square wave anodic stripping voltammetry using the followingparameters:- Deposition potential: -1.2 V- Deposition time: 120 seconds- Scanning range: -1.4 V to 0 V- Frequency: 25 Hz- Amplitude: 25 mV- Step potential: 4 mV

[0157] 5. Analyze the resulting voltammogram, identifying the peak corresponding to lead oxidation at approximately -0.5 V.

[0158] 6. Quantify the lead concentration by comparing the peak current to a calibration curve prepared using lead-spiked blood samples of known concentrations (0, 5. 10, 25, and 50 pg / dL).

[0159] Expected results: The bismuth-coated screen-printed graphite electrode demonstrates a linear response to lead concentrations in blood samples from 1 ug / dL to 50 pg / dL, with a detection limit of 0.5 pg / dL. The electrode shows good selectivity for lead in the presence of other blood components and maintains stable performance over multiple measurements.

[0160] EXAMPLE 2: Detection of Mercury in Water Samples

[0161] A scientist may evaluate the performance of the gold-coated screen-printed graphite electrode for mercury detection in water samples using the following method:

[0162] 1. Provide a gold-coated screen-printed graphite electrode. The electrode may be prepared by electrodepositing gold onto the graphite surface. The electrode is immersed in a solution containing 1 mM HAuC14 in 0. 1 M H2SO4. A potential of -0.2 V is applied for 300 seconds to deposit the gold coating.

[0163] 2. Collect water samples and acidify them to pH 2 using nitric acid. Filter the samples through a 0.45 pm membrane to remove particulates.

[0164] 3. Immerse the gold-coated screen-printed graphite electrode in 10 mL of the prepared water sample along with a platinum wire counter electrode and an Ag / AgCl reference electrode.

[0165] 4. Perform square w ave anodic stripping voltammetry using the following parameters:- Deposition potential: -0.4 V- Deposition time: 120 seconds- Scanning range: -0.4 V to 0.8 V- Frequency: 25 Hz- Amplitude: 25 mV- Step potential: 5 mV

[0166] 5. Analyze the resulting voltammogram, identifying the peak corresponding to mercury oxidation at approximately 0.6 V.

[0167] 6. Quantify the mercury concentration by comparing the peak current to a calibration curve prepared using standard mercury solutions (0, 1, 5, 10, and 20 ppb).

[0168] Expected results: The gold-coated screen-printed graphite electrode exhibits a linear response to mercury concentrations in water samples from 0. 1 ppb to 20 ppb, with a detection limit of 0.05 ppb. The electrode demonstrates high selectivity for mercury in the presence of other metal ions commonly found in water samples and shows consistent performance across multiple measurements.

[0169] EXAMPLE 3: Simultaneous Detection of Zinc, Cadmium, and Lead in River Water

[0170] A scientist may assess the capability of the bismuth-coated screen-printed graphite electrode for simultaneous detection of multiple heavy metals in river water samples using the following procedure:

[0171] 1. Provide a bismuth-coated screen-printed graphite electrode. The electrode may be prepared by in-situ plating of bismuth during the analysis. The measurement solution contains 500 pg / L Bi(III) in 0.1 M acetate buffer (pH 4.5).

[0172] 2. Collect river water samples and filter them through a 0.22 pm membrane. Adjust the pH to 4.5 using acetate buffer.

[0173] 3. Prepare a measurement solution by mixing 5 ruL of the filtered river water sample with 5 mL of 0.2 M acetate buffer (pH 4.5) containing 1000 pg / L Bi(III).

[0174] 4. Immerse the screen-printed graphite electrode in the measurement solution along with a carbon counter electrode and an Ag / AgCl reference electrode.

[0175] 5. Perform square wave anodic stripping voltammetry using the following parameters:- Deposition potential: -1.4 V- Deposition time: 120 seconds- Scanning range: -1.4 V to -0.2 V- Frequency: 25 Hz- Amplitude: 25 mV- Step potential: 5 mV

[0176] 6. Analyze the resulting voltammogram, identifying peaks corresponding to zinc (approximately -1.0 V), cadmium (approximately -0.7 V), and lead (approximately -0.5 V).

[0177] 7. Quantify the concentrations of zinc, cadmium, and lead by comparing their respective peak currents to calibration curves prepared using multi-element standard solutions (0, 5, 10, 25, 50, and 100 ppb of each metal).

[0178] Expected results: The bismuth-coated screen-printed graphite electrode demonstrates the ability to simultaneously detect zinc, cadmium, and lead in river water samples. The electrode exhibits linear responses for all three metals in the concentration range of 1 ppb to 100 ppb, with detection limits of 0.5 ppb for zinc, 0.2 ppb for cadmium, and 0.3 ppb for lead. The electrode shows good selectivity and minimal interference between the target metals, allowing for accurate quantification of each element in complex environmental samples.

[0179] EXAMPLE 4: Scaled-up Manufacturing Process with Integrated Bismuth Oxide

[0180] A manufacturer may implement a scaled-up production process for bismuth- modified screen-printed electrodes (SPEs) by incorporating bismuth oxide (Bi2O3) directly into the ink formulation using the following procedure:

[0181] 1. Prepare a large batch of graphite-based ink by mixing:- 2400 g of graphite powder- 400 g of carbon black- 3696 g of styrene-ethylene-butylene-styrene (SEBS) copolymer- 970 g of toluene solvent- 100 g of bismuth oxide (Bi2O3) powder

[0182] 2. Thoroughly blend the ink components using a high-shear mixer for 30 minutes to ensure uniform dispersion of the Bi2O3 particles throughout the ink matrix.

[0183] 3. Load the bismuth-modified ink into an automated screen-printing system equipped with a large-format screen stencil designed to print multiple electrode patterns simultaneously.

[0184] 4. Print the working electrode layer onto rolls of polyester substrate using the bismuth-modified ink. The printing system may be capable of producing hundreds ofelectrodes per minute.

[0185] 5. Cure the printed working electrode layer in a continuous belt oven at 80°C for 10 minutes.

[0186] 6. Print the counter and reference electrode layers using separate inks (e.g., carbon-based ink for the counter electrode and Ag / AgCl ink for the reference electrode) in subsequent printing steps.

[0187] 7. Cure the counter and reference electrode layers at 90°C for 30 minutes in the continuous belt oven.

[0188] 8. Apply an insulating layer to define the active electrode areas and protect the conductive traces using an automated screen-printing process with a dielectric ink.

[0189] 9. Cure the insulating layer at 120°C for 20 minutes in the continuous belt oven.

[0190] 10. Use an automated cutting system to separate individual electrodes from the printed rolls.

[0191] 11. Perform quality control checks on a statistical sampling of electrodes from each production batch, including visual inspection, resistance measurements, and electrochemical performance testing.

[0192] 12. Package the finished electrodes in moisture-resistant, sealed pouches for storage and distribution.

[0193] This scaled-up manufacturing process may produce large quantities of bismuth-modified SPEs with consistent quality and performance characteristics. The integration of Bi2O3 into the ink formulation may eliminate the need for post-production electrochemical deposition of bismuth, potentially reducing production time and complexity. The automated printing and curing steps may allow for high-throughput production, while the quality control measures may ensure the reliability of the manufactured electrodes for trace metal detection applications.

[0194] Other Embodiments

[0195] The detailed description set-forth above is provided to aid those skilled in the art in practicing the present invention. However, the invention described and claimed herein is not to be limited in scope by the specific embodiments herein disclosed because these embodiments are intended as illustration of several aspects of the invention. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the invention in addition to those show n and described herein will becomeapparent to those skilled in the art from the foregoing description which do not depart from the spirit or scope of the present inventive discovery’. Such modifications are also intended to fall within the scope of the appended claims.

[0196] References Cited

[0197] All publications, patents, patent applications and other references cited in this application are incorporated herein by reference in their entirety for all purposes to the same extent as if each individual publication, patent, patent application or other reference was specifically and individually indicated to be incorporated by reference in its entirety for all purposes. Citation of a reference herein shall not be construed as an admission that such is prior art to the present invention.

Claims

CLAIMSWhat is claimed is:

1. A system for detecting trace heavy metals in a solution, comprising: a screen printed electrode comprising a working electrode, a counter electrode, and a reference electrode arranged on a substrate surface; a metal coating applied to the working electrode and counter electrode; a potentiostat connected to the screen printed electrode; and a processor configured to control the potentiostat to perform anodic stripping voltammetry on the screen printed electrode and to analyze results of the voltammetry to detect presence of trace heavy metals in the solution.

2. The system of claim 1, wherein the metal coating comprises gold or bismuth.

3. The system of claim 1, wherein the solution comprises blood, water, or urine.

4. The system of claim 1, wherein the processor is further configured to detect mercury, lead, or cadmium in the solution.

5. A method for detecting trace heavy metals in a solution, comprising: providing a screen printed electrode comprising a working electrode, a counter electrode, and a reference electrode arranged on a substrate surface, wherein a metal coating is applied to the working electrode and counter electrode; immersing the metal-coated screen printed electrode in the solution; performing anodic stripping voltammetry on the screen printed electrode; and analyzing results of the voltammetry to detect presence of trace heavy metals in the solution.

6. The method of claim 5, wherein the metal coating comprises gold or bismuth.

7. The method of claim 5. wherein the solution comprises blood, water, or urine.

8. The method of any one of claims 5 to 7, wherein the anodic stripping voltammetry is performed using a square-wave voltammetric stripping scan with a frequency of 25 Hz, a potential step of 5 mV, and an amplitude of 25 mV.

9. An electrode testing assembly for analyzing trace metals in liquid samples, comprising: an upper housing containing a display screen and a control interface; a circuit board comprising a sensor module with a connection interface; an electrode connector for electrically connecting the sensor module to a screen printed electrode; an electrode mount for securing a screen printed electrode;a lower housing enclosing internal components; and a base plate providing structural support.

10. The electrode testing assembly of claim 9, wherein the sensor module comprises a potentiostat configured to perform anodic stripping voltammetry on the screen printed electrode.

11. The electrode testing assembly of claim 10, wherein the potentiostat is configured to perform square-wave anodic stripping voltammetry with a frequency of 25 Hz, a potential step of 5 mV, and an amplitude of 25 mV.

12. The electrode testing assembly of any one of claims 9 to 11, further comprising a wireless communication module configured to transmit detected heavy metal concentrations to a remote device.

13. A screen printed electrode for detecting trace heavy metals in a solution, comprising: a substrate surface; a working electrode, a counter electrode, and a reference electrode arranged on the substrate surface; a metal coating applied to the working electrode and counter electrode; and an electrode pattern configured to optimize electrochemical sensing capabilities.

14. The screen printed electrode of claim 16, wherein the working electrode is positioned between the reference electrode and the counter electrode.

15. The screen printed electrode of claim 1 , wherein the metal coating comprises bismuth or gold.

16. The screen printed electrode of claim 16, further comprising a measurement region encompassing an area where the working electrode, counter electrode, and reference electrode interact during electrochemical measurements.

17. The screen printed electrode of claim 16, wherein the substrate surface comprises a polymer material.

18. The screen printed electrode of claim 16, wherein the working electrode, counter electrode, and reference electrode are arranged in a parallel configuration on the substrate surface.

19. The screen printed electrode of claim 16, further comprising conductive traces extending from each electrode to respective contact points for electrical connections with external measurement instrumentation.

20. The screen printed electrode of claim 22, wherein the conductive traces arecovered by an insulating layer, with only the electrode areas and contact points exposed.

21. The screen printed electrode of claim 16, wherein the metal coating is electrodeposited onto the working electrode surface.

22. The screen printed electrode of claim 16, wherein the metal coating is provided by printing with metal integrated ink.

23. The screen printed electrode of claim 16, wherein the electrode is configured for disposable use in portable testing applications.

24. A screen-printed electrode comprising:(a) a graphite base layer comprising 60-80 wt% graphite, 10-20 wt% carbon black, and 15-25 wt% SEBS copolymer;(b) a bismuth oxide coating integrated into the graphite base layer during screenprinting; and(c) a conductive Ag / AgCl trace, wherein the electrode detects lead at <0.5 ppb in blood samples.

25. The screen-printed electrode of claim 23, wherein the bismuth oxide is present at 90-110 g per 2400 g graphite.

26. A method for manufacturing bismuth-modified screen-printed electrodes, comprising: preparing a graphite-based ink by mixing graphite powder, carbon black, styrene- ethylene-butylene-styrene copolymer, toluene solvent, and bismuth oxide powder; blending the ink components using a high-shear mixer to disperse bismuth oxide particles throughout the ink matrix; loading the bismuth-modified ink into an automated screen-printing system; printing a working electrode layer onto a polyester substrate using the bismuth- modified ink; curing the printed working electrode layer; printing counter and reference electrode layers using separate inks; curing the counter and reference electrode layers; applying an insulating layer to define active electrode areas and protect conductive traces; curing the insulating layer; and separating individual electrodes from the printed substrate.

27. The method of claim 26, wherein the graphite-based ink comprises:970 g of toluene solvent; and100 g of bismuth oxide powder.

28. The method of claim 26, wherein blending the ink components comprises mixing for approximately 30 minutes.

29. The method of claim 26, wherein curing the printed working electrode layer comprises heating at approximately 80°C for approximately 10 minutes.

30. The method of claim 26, wherein curing the counter and reference electrode layers comprises heating at approximately 90°C for approximately 30 minutes.

31. The method of claim 26, wherein curing the insulating layer comprises heating at approximately 120°C for approximately 20 minutes.

32. The method of claim 26, further comprising performing quality control checks on a statistical sampling of electrodes from each production batch.

33. The method of claim 32, wherein the quality control checks comprise visual inspection, resistance measurements, and electrochemical performance testing.

34. The method of claim 26, further comprising packaging the individual electrodes in moisture-resistant, sealed pouches.

35. A bismuth-modified screen-printed electrode manufactured by the method of claim 26.

36. A system for manufacturing bismuth-modified screen-printed electrodes, comprising: a mixing apparatus configured to prepare a graphite-based ink containing bismuth oxide; an automated screen-printing system configured to print electrode layers onto a substrate; a curing apparatus configured to cure the printed electrode layers; and a cutting system configured to separate individual electrodes from the printed substrate.

37. The system of claim 36, further comprising a quality control station configured to perform visual inspection, resistance measurements, and electrochemical performance testing on a sampling of manufactured electrodes.

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