Screen-printed electrodes: Transitioning the laboratory in-to-the field

This short article overviews the use of screen-printed electrodes (SPEs) in the field of electroanalysis and compares their application against traditional laboratory based analytical techniques. Electroanalysis coupled with SPEs can offer low-cost, precise, sensitive, rapid, quantitative information and laboratory equivalent results. The combined use of SPEs and electroanalysis reduces the need of sample transportation and preparation to a centralised laboratory allowing experimentalists to perform the measurements where they are needed the most. We first introduce the basic concepts and principles of analytical techniques to the reader, with particular attention to electroanalysis, and then discuss the application of SPEs to common analytical targets such as food, environmental, forensics, cancer biomarkers and pathogenic monitoring and sensing

Electroanalytical Overview: Electrochemical Sensing Platforms for Food and Drink Safety

Robust, reliable, and affordable analytical techniques are essential for screening and monitoring food and water safety from contaminants, pathogens, and allergens that might be harmful upon consumption. Recent advances in decentralised, miniaturised, and rapid tests for health and environmental monitoring can provide an alternative solution to the classic laboratory-based analytical techniques currently utilised. Electrochemical biosensors offer a promising option as portable sensing platforms to expedite the transition from laboratory benchtop to on-site analysis. A plethora of electroanalytical sensor platforms have been produced for the detection of small molecules, proteins, and microorganisms vital to ensuring food and drink safety. These utilise various recognition systems, from direct electrochemical redox processes to biological recognition elements such as antibodies, enzymes, and aptamers; however, further exploration needs to be carried out, with many systems requiring validation against standard benchtop laboratory-based techniques to offer increased confidence in the sensing platforms. This short review demonstrates that electroanalytical biosensors already offer a sensitive, fast, and low-cost sensor platform for food and drink safety monitoring. With continued research into the development of these sensors, increased confidence in the safety of food and drink products for manufacturers, policy makers, and end users will result

2D‐Hexagonal Boron Nitride Screen‐Printed Bulk‐Modified Electrochemical Platforms Explored towards Oxygen Reduction Reactions

A low‐cost, scalable and reproducible approach for the mass production of screen‐printed electrode (SPE) platforms that have varying percentage mass incorporations of 2D hexagonal boron nitride (2D‐hBN) (2D‐hBN/SPEs) is demonstrated herein. These novel 2D‐hBN/SPEs are explored as a potential metal‐free electrocatalysts towards oxygen reduction reactions (ORRs) within acidic media where their performance is evaluated. A 5% mass incorporation of 2D‐hBN into the SPEs resulted in the most beneficial ORR catalysis, reducing the ORR onset potential by ca. 200 mV in comparison to bare/unmodified SPEs. Furthermore, an increase in the achievable current of 83% is also exhibited upon the utilisation of a 2D‐hBN/SPE in comparison to its unmodified equivalent. The screen‐printed fabrication approach replaces the less‐reproducible and time‐consuming dropcasting technique of 2D‐hBN and provides an alternative approach for the large‐scale manufacture of novel electrode platforms that can be utilised in a variety of application

MoO2 Nanowire Electrochemically Decorated Graphene Additively Manufactured Supercapacitor Platforms

Additively manufactured (AM) supercapacitor platforms are fabricated from bespoke filaments, which are comprised of electro-conductive graphene (20 wt%) incorporated polylactic acid (80 wt%), via fused deposition modeling and denoted as G/AMEs. The G/AMEs are shown to be capable of acting as a template for the electrodeposition of metals/metal oxides, in particular MoO2 nanowires (MoO2-G/AMEs), which are subsequently explored as a capacitor within 1 m H2SO4, 1-butyl-3-methylimidazolium hexafluorophosphate, and 1-butyl-3-methylimidazolium tetrafluoroborate. Optimization of the MoO2-G/AMEs demonstrates capacitance up to 1212 F g–1 when used in a symmetric arrangement. The material science described herein represents a significant enhancement in unlocking AMs potential as a valid manufacturing route for device level capacitance architectures

The effect of water ingress on additively manufactured electrodes

Additive Manufacturing (AM), otherwise known as 3D printing, is becoming increasingly popular in the field of electrochemistry since it allows affordable, on-demand production of bespoke devices. Provided a suitably conductive polymer composite material is used, this can include working electrodes. However, while a number of publications have shown such Additively Manufactured Electrodes (AMEs) to be effective, there remain several fundamental areas which must be understood to continue the development of AM for electrochemistry. One such area is the effect of solvent ingress on AME performance, with water probably representing the most important solvent for study considering the amount of electrochemical sensing directed towards biological and environmental systems. Therefore, in this work we study the effect of up to 28 days of water immersion on the physical properties and electrochemical performance of AMEs made from a commonly used conductive material, Protopasta. It is shown that water immersion leads to water uptake of around 1-1.5% by mass for our specific electrode design, which in turn causes a decrease in measured peak current, but an increase in the heterogeneous electron transfer rate constant, k0. These observations are rationalised in terms of Ohmic drop and conductive filler surface chemistry, respectively. Overall, it can be concluded that water ingress is likely to be a concern for any application where AMEs are expected to have extended contact with water, although we note that more work is required to fully understand the extent of the issue

Electrochemical properties of vertically aligned graphenes: tailoring heterogeneous electron transfer through manipulation of the carbon microstructure

The structure of vertically aligned graphene electrodes is shown to directly affect heterogeneous electron transfer kinetics in terms of the density of active edge plane sites of the microstructure, where greater edge content results in favourable electrochemical behaviour

Novel Additive Manufactured Multielectrode Electrochemical Cell with Honeycomb Inspired Design for the Detection of Methyl Parathion in Honey Samples

The development and increase in the number of crops recently have led to the requirement for greater efficiency in world food production and greater consumption of pesticides. In this context, the widespread use of pesticides has affected the decrease in the population of pollinating insects and has caused food contamination. Therefore, simple, low-cost, and quick analytical methods can be interesting alternatives for checking the quality of foods such as honey. In this work, we propose a new additively manufactured (3D-printed) device inspired by a honeycomb cell, with 6 working electrodes for the direct electrochemical analysis of methyl parathion by reduction process monitoring in food and environmental samples. Under optimized parameters, the proposed sensor presented a linear range between 0.85 and 19.6 μmol L–1, with a limit of detection of 0.20 μmol L–1. The sensors were successfully applied in honey and tap water samples by using the standard addition method. The proposed honeycomb cell made of polylactic acid and commercial conductive filament is easy to construct, and there is no need for chemical treatments to be used. These devices based on 6 working electrodes array are versatile platforms for rapid, highly repeatable analysis in food and environment, capable of performing detection in low concentrations

Toward the Rapid Diagnosis of Sepsis: Detecting Interleukin-6 in Blood Plasma Using Functionalized Screen-Printed Electrodes with a Thermal Detection Methodology

This paper reports the detection of the inflammatory and sepsis-related biomarker, interleukin-6 (IL-6), in human blood plasma using functionalized screen-printed electrodes (SPEs) in conjunction with a thermal detection methodology, termed heat-transfer method (HTM). SPEs are functionalized with antibodies specific for IL-6 through electrodeposition of a diazonium linking group and N'-ethylcarbodiimide hydrochloride (EDC) coupling, which was tracked through the use of cyclic voltammetry and Raman spectroscopy. The functionalized SPEs are mounted inside an additively manufactured flow cell and connected to the HTM device. We demonstrate the ability to detect IL-6 at clinically relevant concentrations in PBS buffer (pH = 7.4) with no significant interference from the similarly sized sepsis-related biomarker procalcitonin (PCT). The limit of detection (3s) of the system is calculated to correspond to 3.4 ± 0.2 pg mL-1 with a working range spanning the physiologically relevant concentration levels in both healthy individuals and patients with sepsis, indicating the sensitivity of the sensor is suitable for the application. Further experiments helped provide a proof-of-application through the detection of IL-6 in blood plasma with no significant interference observed from PCT or the constituents of the medium. Due to the selectivity, sensitivity, straightforward operation, and low cost of production, this sensor platform has the potential for use as a traffic light sensor for the multidetection of inflammatory biomarkers for the diagnosis of sepsis and other conditions in which the rapid testing of blood biomarkers has vital clinical application

Exploration of defined 2-dimensional working electrode shapes through additive manufacturing

In this work, the electrochemical response of different morphologies (shapes) and dimensions of additively manufactured (3D-printing) carbon black (CB)/poly-lactic acid (PLA) electrodes are reported. The working electrodes (WE) are printed using standard non-conductive PLA based filament for the housing and commercial Protopasta (carbon black/PLA) filament for the electrode and connection parts. Discs, squares, equilateral triangles and six-point stars with varying working electrode (WE) widths from 2 to 10 mm are evaluated herein towards the well-known near-ideal outer sphere redox probe hexaamineruthenium(III) chloride (RuHex). The results obtained show that triangular and squared electrodes exhibit a faster heterogeneous electron transfer (HET) rate constant (k°) than those of discs and stars, the latter being the slowest one. The results reported here also show a trend between the WE dimension and the reversibility of the electrochemical reaction, which decreases as the WE size increases. It is also observed that the ratio of the geometrical and electroactive area (%realarea) decreases as the overall WE size increases. On the other hand, these four WE shapes were applied toward the well-known and benchmarking detection of ascorbic acid (AA), uric acid (UA), β-nicotinamide adenine dinucleotide (NADH) and dopamine (DA). Moreover, electroanalytical detection of real acetaminophen (ACOP) samples is also showcased. The different designs for the working electrode proposed in this manuscript are easily changed to any other desired shapes thanks to the additive manufacturing methodology, these four shapes being just an example of what additive manufacturing can offer to experimentalists and to electrochemists in particular. Additive manufacturing is shown here as a versatile and rapid prototyping tool for the production of novel electrochemical sensing platforms, with scope for this work to be able to impact a wide variety of electroanalytical applications

All-in-One Single-Print Additively Manufactured Electroanalytical Sensing Platforms

This manuscript provides the first report of a fully additively manufactured (AM) electrochemical cell printed all-in-one, where all the electrodes and cell are printed as one, requiring no post-assembly or external electrodes. The three-electrode cell is printed using a standard non-conductive poly(lactic acid) (PLA)-based filament for the body and commercially available conductive carbon black/PLA (CB/PLA, ProtoPasta) for the three electrodes (working, counter, and reference; WE, CE, and RE, respectively). The electrochemical performance of the cell is evaluated first against the well-known near-ideal outer-sphere redox probe hexaamineruthenium(III) chloride (RuHex), showing that the cell performs well using an AM electrode as the pseudo-RE. Electrochemical activation of the WE via chronoamperometry and NaOH provides enhanced electrochemical performances toward outer-sphere probes and for electroanalytical performance. It is shown that this activation can be completed using either an external commercial Ag|AgCl RE or through simply using the internal AM CB/PLA pseudo-RE and CE. This all-in-one electrochemical cell (AIOEC) was applied toward the well-known detection of ascorbic acid (AA) and acetaminophen (ACOP), achieving linear trends with limits of detection (LODs) of 13.6 ± 1.9 and 4.5 ± 0.9 μM, respectively. The determination of AA and ACOP in real samples from over-the-counter effervescent tablets was explored, and when analyzed individually, recoveries of 102.9 and 100.6% were achieved against UV–vis standards, respectively. Simultaneous detection of both targets was also achieved through detection in the same sample exhibiting 149.75 and 81.35% recoveries for AA and ACOP, respectively. These values differing from the originals are likely due to electrode fouling due to the AA oxidation being a surface-controlled process. The cell design produced herein is easily tunable toward different sample volumes or container shapes for various applications among aqueous electroanalytical sensing; however, it is a simple example of the capabilities of this manufacturing method. This work illustrates the next step in research synergising AM and electrochemistry, producing operational electrochemical sensing platforms in a single print, with no assembly and no requirements for exterior or commercial electrodes. Due to the flexibility, low-waste, and rapid prototyping of AM, there is scope for this work to be able to span and impact a plethora of research areas