Multichannel Potentiostat Research Articles

A multiplexed sensing system with multimodal readout electronics and thread-based electrochemical sensors for high throughput screening

High throughput screening (HTS) based on microwell (or bioreactor) arrays is a well-established approach for rapid screening and identification of lead molecules or target analytes for drug discovery and other applications in biotechnology. However, it has been challenging to scale up these platforms due to the lack of integrated sensors to monitor the microenvironment of each microwell in the array needed. In this work, we present a practical solution for a miniaturized multiplexed sensing system with integrated circuitry capable of performing continuous electrochemical potentiometric and amperometric measurements. The platform uses lightweight multiplexed electrochemical sensors implemented on thin textile threads, all of which share a single operational amplifier (op-amp) and a switch network for both voltage and current measurements. The resulting platform forgoes the need for large-area sensors or bulky multichannel potentiostat with a simple readout circuitry capable of multimodal measurements. The design and validation of the multiplexed sensing system have been reported in the context of measuring pH and oxygen (O2), which are crucial biomarkers for any HTS application. The thread-based pH and O2 sensors possess sensitivities of ∼65.87 mV/pH for the pH sensor (n = 3) and 0.6621 nA/mg L-1 for the O2 sensor (n = 3). This architecture is modular such that it can be easily extended to monitoring multiple biomarkers employing thread-based sensors and sharing the same readout circuitry, making it a practical and versatile tool for biotechnology research.

Nanomaterials Synthesis Discovery via Parallel Electrochemical Deposition.

Electrodeposition of nanoparticles is investigated with a multichannel potentiostat in electrochemical and chemical arrays. De novo deposition and shape control of palladium nanoparticles are explored in arrays with a two-stage strategy. Initial conditions for electrodeposition of materials are discovered in a first stage and then used in a second stage to logically expand chemical and electrochemical parameters. Shape control is analyzed primarily with scanning electron microscopy. Using this approach, optimized conditions for the electrodeposition of cubic palladium nanoparticles were identified from a set of previously untested electrodeposition conditions. The parameters discovered through the array format were then successfully extrapolated to a traditional bulk three-electrode electrochemical cell. Electrochemical arrays were also used to explore electrodeposition parameters reported in previous bulk studies, further demonstrating the correspondence between the array and bulk systems. These results broadly highlight opportunities for electrochemical arrays, both for discovery and for further investigations of electrodeposition in nanomaterials synthesis.

A highly sensitive electrochemical magneto-genosensing assay for the specific detection of a single nucleotide variation in the KRAS oncogene in human plasma

Liquid biopsy is a non-invasive and efficient technique for the detection of tumor biomarkers in biological fluids, which currently represents a new frontier in theranostics and precision medicine. Among mutations of the KRAS oncogene, p.G12D single nucleotide variation in the KRAS gene plays a central role in the early diagnosis and therapeutic treatment of colorectal cancer. In this context, we developed a highly sensitive magneto-genosensing assay based on PNA capture probes immobilized on magnetic microbeads. To detect the mutation of the KRAS oncogene, two capture probe sequences recognizing wild-type and p.G12D tumor DNA were used in association with a DNA signaling probe allowing for electrochemical detection using an enzyme conjugate. The assay conditions were optimized using a 32 full-factorial design, obtaining an outstanding specificity, evidenced by a remarkably lower (>95%) signal of the singly-mismatched- compared to that of fully-complementary-DNA. Ultra-high sensitivity was achieved in 10-fold diluted human plasma reaching detection limits of 818 fM for the p.G12D and 1.8 pM for the wild-type targets. The genosensing assay was tested on genomic tumor DNA samples provided by IRCCS-Regina Elena National Cancer Institute and finally integrated into a smart portable multichannel potentiostat capable of performing up to four simultaneous acquisitions. The developed magneto-genosensing assay demonstrated portability, simplicity, and high sensitivity, showing good potential as theranostic tool for personalized medicine in oncology.

High-Throughput Activity Screening of Oxygen Reduction and Oxygen Evolution Catalysts

High-throughput techniques are being actively studied to expedite the evaluation of the electrocatalytic activity of newly developed materials. These techniques include the use of optical sensing or electrochemical array cells in stagnant or hydrodynamic aqueous electrolytes [1-2]. A new high-throughput electrochemical cell has been developed utilizing multiple glassy carbon working electrodes with dimensions comparable to those of a conventional ring-disk electrode (RDE) that are inserted into a channel flow cell (Figure 1) comprised of two PEEK blocks separated by a gasket that defines the electrolyte channel depth. This cell enables evaluation of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) activity as a function of the potential of multiple catalyst samples simultaneously that are deposited on the glassy carbon electrodes using standard methods used for RDE electrodes (e.g., using a hand-held micropipette). As shown in Figure 1, a common reference electrode is located in the lower cell block across an electrolyte channel from the working electrodes and a common counter electrode is located in the electrolyte outlet. Electrolyte flow has been simulated to ensure that the electrolyte is evenly distributed throughout the shallow flow channel with uniform laminar electrolyte flow and identical flow rate for all working electrodes. The new cell is coupled with a Bio-logic multichannel Potentiostat (VSP) that allows the use of multiple working electrodes simultaneously with a common counter electrode and common reference electrode. The catalyst activity and stability results obtained with the new cell have been verified by comparison with RDE measurements for the same catalysts. Acknowledgments This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office under the auspices of the Electrocatalysis Consortium (ElectroCat). Argonne National Laboratory is managed for the U.S Department of Energy by the University of Chicago Argonne, LLC, also under contract DE-AC-02-06CH11357.

Electrochemical interference study of manganese and iron by multiplex method and the application for manganese analysis in drinking water

AbstractManganese is an emerging concern in drinking water, due to its potential health and aesthetic effects. Although accurate and sensitive, spectroscopic techniques for Mn2+ detection are costly and not capable of rapid detection. Electrochemical methods, such as cathodic stripping voltammetry, have been intensively explored as portable low‐cost methods for Mn2+ detection. Challenges of reliability and matrix interference are difficult to overcome with current electrochemical methods. Among the interference reagents, Fe2+ is one of the biggest challenges for Mn2+ detection. Herein, a new method based on multiplex chronoamperometry at potentials between 0.9 and 1.4 V by a multichannel potentiostat is explored for its ability for interference resistance and applicability for Mn2+ detection in real drinking water samples. Compared to conventional one‐channel electrochemical techniques, the multiplex method generates a reliable pattern that is unique to the sample components. The interference between Mn2+ and Fe2+ is investigated and the results are promising even at 100:1 Fe2+:Mn2+ concentrations. The detection limit determined for the multiplex method was 25.3 μM, and the optimum recovery rate in a real drinking water sample was 99.8%.

SnO2-QDs/Rgo Nanocomposites for Lithium Ion Battery Anodes

SnO2 is one of the most efficient materials for lithium ion battery (LIBs) anodes as it can theoretically provide a reversible capacity of 790 mAh/g (graphite, 372 mAh/g) for alloying reaction with lithium ion [(i) SnO 2 + 4 Li+ + 4e - = 2Li 2 O + Sn, (ii) Sn + xLi+ + xe- = LixSn (0 ≤ x ≤ 4.4)] during charge-discharge process [1]. In addition, SnO2 shows lowest operating potentials (average charge and discharge potentials: 0.3 V and 0.5 V vs. Li/Li+, respectively) in comparison with other transition metal oxides, facilitating a higher energy density when a full cell is constructed [2]. However, two issues: (1) poor electric conductivity, and (2) high volume fluctuation during lithiation-delithiation process (about 200-300%), limit its direct use as the anode material. To bit these issues, various carbon materials are employed to load the SnO2 [3].Graphene, a carbon allotrope, which possesses high electrical conductivity (106 s/cm), excellent mechanical flexibility (Young’s modulus up to 1.0 TPa) and high surface area (2630 m2/g) and in addition, lithium storage capacity of a single layer graphene is theoretically found to be 744 mAh/g. Consequently, graphene can be most suitable host to incorporate the SnO2 [3]. We have tailored SnO2 quantum dots (TOQDs) encapsulated reduced graphene oxide (RGO) nanocomposite (TOQDs/RGO) by in-situ growth of the TOQDs in the RGO flakes. A nanofluidic synthesis approach has been developed using 1D-Sn(OH)4 nanofluid [4] and graphene oxide (GO) nanofluid [5] as prim precursors for the homogeneous encapsulation of the TOQDs in RGO flakes. The 1D-Sn(OH)4 nanofluid was dropwise added to the graphene oxide (GO) nanofluid with continuous stirring. Then the resultant mixture was sonicated to get a nanofluidic mixture which was freeze-dried followed by calcination at 600 °C for 6 hrs under nitrogen gas. During these processes, in-situ growth of the TOQDs was proceeded on the RGO plane, leading to give their homogeneous distribution with encapsulation on the RGO plane. The cyclic voltammetry (CV) and glavanostatic charge-discharge (GCD) were performed on an Iviumstat Multichannel Potentiostat using a three-electrode cell and two-electrode cell, respectively. It is found that the developed TOQDs/RGO nanocomposite provides high reversible specific capacity with excellent rate capability. The results of these electrochemical studies implied that the developed TOQDs/RGO nanocomposite could be utilized for high-performance LIBs. References Lu et al., Porous SnO2/Graphene composites as anode materials for lithium-ion batteries: morphology control and performance improvement. Energy Fuels 2020, 34 (10), 13126-13136.Deng et al.,The developments of SnO2/graphene nanocomposites as anode materials for high performance lithium ion batteries: a review. J. Power Sources 2016, 304, 81-101.Han et al., Caging tin oxide in three-dimensional graphene networks for superior volumetric lithium storage. Nat. commun. 2018, 9 (1), 1-9.I. U. Hoque et al., One-dimensional Sn (iv) hydroxide nanofluid toward nonlinear optical switching. Mater. Horiz. 2020, 7 (4), 1150-1159.A. Khan et al., Synthesis of graphene oxide nanofluid based micro-nano scale surfaces for high-performance nucleate boiling thermal management systems. Case Stud. Therm. Eng. 2021, 28, 101436.

A compact, low-cost, and binary sensing (BiSense) platform for noise-free and self-validated impedimetric detection of COVID-19 infected patients

Electrochemical immuno-biosensors are one of the most promising approaches for accurate, rapid, and quantitative detection of protein biomarkers. The two-working electrode strip is employed for creating a self-supporting system, as a tool for self-validating the acquired results for added reliability. However, the realization of multiplex electrochemical point-of-care testing (ME-POCT) requires advancement in portable, rapid reading, easy-to-use, and low-cost multichannel potentiostat readers. The combined multiplex biosensor strips and multichannel readers allow for suppressing the possible complex matrix effect or ultra-sensitive detection of different protein biomarkers. Herein, a handheld binary-sensing (BiSense) bi-potentiostat was developed to perform electrochemical impedance spectroscopy (EIS)-based signal acquisition from a custom-designed dual-working-electrode immuno-biosensor. BiSense employs a commercially available microcontroller and out-of-shelf components, offering the cheapest yet accurate and reliable time-domain impedance analyzer. A specific electrical board design was developed and customized for impedance signal analysis of SARS-CoV-2 nucleocapsid (N)-protein biosensor in spiked samples and alpha variant clinical nasopharyngeal (NP) swab samples. BiSense showed limit-of-detection (LoD) down to 56 fg/mL for working electrode 1 (WE1) and 68 fg/mL for WE2 and reported with a dynamic detection range of 1 pg/mL to 10 ng/mL for detection of N-protein in spiked samples. The dual biosensing of N-protein in this work was used as a self-validation of the biosensor. The low-cost (∼USD$40) BiSense bi-potentiostat combined with the immuno-biosensors successfully detected COVID-19 infected patients in less than 10 min, with the BiSense reading period shorter than 1.5 min, demonstrating its potential for the realization of ME-POCTs for rapid and hand-held diagnosis of infections.

GEOGRAPHICAL ORIGIN AUTHENTICITY DISCRIMINATION OF MILK BASED ON SMART ELECTRONIC TONGUE

The aim work was to evaluate the capacity of a smart electronic tongue in the geographical origin discrimination of milk samples of different provenance. The analysis was carried out with a smart electronic tongue formed by a polypyrrole voltammetric sensor array doped with different doping agents, a multichannel potentiostat, and an Android app installed on a smartphone for signal recording, data storage, and device control. The analyzed samples were collected in different localities belonging to different agroclimatic and environmental zones in Cordoba - Colombia. The registered voltammetric signals showed particular responses to each one of the milk samples, evidencing crosssensitivity, which constituted a "fingerprint" of the samples with information about their characteristics. The pattern recognition analysis showed that the smart electronic tongue was able to discriminate each sample. In addition, the spatial distribution of the samples showed a certain correlation with the subregions of origin. The results made it possible to establish that the smart electronic tongue could be capable of discriminating milk samples of different geographical origins and that its classification may be related to the particularities of the areas of origin

The multi-channel potentiostat: Development and evaluation of a scalable mini-potentiostat array for investigating electrochemical reaction mechanisms.

A potentiostat is an essential piece of analytical equipment for studying electrochemical devices and reactions. As the design of electrochemical devices evolve, applications for systems with multiple working electrodes have become more common. These applications drive a need for low-cost multi-channel potentiostat systems. We have developed a portable, low-cost and scalable system with a modular design that can support 8 to 64 channels at a cost as low as $8 per channel. This design can replace the functionality of commercial potentiostats which cost upwards of $10k for certain applications. Each channel in the multi-channel potentiostat has an independent adjustable voltage source with a built-in ammeter and switch, making the device flexible for various configurations. The multi-channel potentiostat is designed for low current applications (nA range), but its purpose can change by varying its shunt resistor value. The system can either function as a standalone device or remotely controlled. We demonstrate the functionality of this system for the control of a 24-channel bioelectronic ion pump for open- and closed- loop control of pH.

Temperature glass and conductivity behavior of epoxy deproteinized natural rubber in ternary blend of EDPNR/PMMA/LiCF3SO3

The temperature glass behavior of epoxy deproteinized natural rubber/polymethylmethacrylate/lithium trifluoromethanesulfonate (EDPNR/PMMA/LiCF3SO3) and the conductivity behavior of EDPNR in the ternary blends were studied by DSC and multichannel potentiostat. The DSC result revealed the temperature glass of the EDPNR was shifted to the right with the increase of lithium salt amount in these binary blends composition. However, in the ternary blends of EDPNR/PMMA/LiCF3SO3 the temperature glass revealed the miscibility of these ternary blends. Two different temperature glass values were obtained when the ratio of EDPNR in EDPNR/PMMA was less than 80 wt.%. The ionic conductivity of EDPNR could be improved by increasing the amount of lithium salt up to 35 wt.%, after this amount the ionic conductivity of EDPNR was significantly decreased. While in the ternary blends, the highest ionic conductivity value was found at the ratio 80/20 of EDPNR/PMMA. Furthermore, the factors influencing the temperature glass and conductivity behavior of EDPNR were systematically studied in this work. The results demonstrated an intimate correlation between temperature glass and conductivity behavior of EDPNR.

Multiplexing neurochemical detection with carbon fiber multielectrode arrays using fast-scan cyclic voltammetry.

Carbon fiber microelectrodes (CFMEs) have been extensively used to measure neurotransmitters with fast-scan cyclic voltammetry (FSCV) due to their ability to adsorb cationic monoamine neurotransmitters. Although FSCV, in tandem with CFMEs, provides high temporal and spatial resolution, only single-channel potentiostats and electrodes have been primarily utilized. More recently, the need and use of carbon fiber multielectrode arrays has risen to target multiple brain regions. Previous studies have shown the ability to detect dopamine using multielectrode arrays; however, they are not readily available to the scientific community. In this work, we interfaced a carbon fiber multielectrode array (MEA or multielectrode array), to a commercially available four-channel potentiostat for multiplexing neurochemical measurements. The MEA's relative performance was compared to single CFMEs where dopamine detection was found to be adsorption controlled to the electrode's surface. Multiple waveforms were applied to each fiber of the multielectrode array simultaneously to detect different analytes on each electrode of the array. A proof of concept ex vivo experiment showed that the multielectrode array could record redox activity in different areas within the mouse caudate putamen and detect dopamine in a 3-mm2 area. To our knowledge, this is the first use of the multielectrode array paired with a commercially available multichannel potentiostat for multi-waveform application and neurotransmitter co-detection. This novel array may aid in future studies to better understand complex brain heterogeneity, the dynamic neurochemical environment, and how disease states or drugs affect separate brain areas concurrently. Graphical abstract.

On the electrocatalytic symbiotic synergism between Pt, Ni and Al in plasma vapour deposited PtxNiyAlz thin metal films for water electrolysis

This work highlights the fact that the activity of an already active metal/surface, i.e. Ni, can be increased even further by combining it with metals/surfaces that exhibit low activity, i.e. Pt and Al, when used on their own. Combinatorial screening was conducted on plasma vapour deposited PtxNiyAlz thin-film ratios for the oxygen evolution reaction in alkaline medium. All co-deposited thin films were simultaneously evaluated employing a multichannel potentiostat with Pt9Ni56Al35 exhibiting the highest current at 1.39 V (SHE). Subsequent deposition on a glassy carbon insert followed by electrochemical characterization revealed that Pt9Ni56Al35 performed better than its constituent components in that it exhibited an overpotential of 487 mV at 10 mA cm−2 compared to 590 mV, 941 mV, and 1379 mV for the overpotentials of vapour deposited Ni, Pt and Al respectively. Subsequent evaluation of co-deposited Pt9Ni56Al35, as an electrocatalyst on a nickel woven mesh anode inside a membraneless divergent electrode-flow-through (DEFT™) alkaline electrolyser, resulted in a current density of 1198 mA cm−2 at a cell potential of 2 VDC. This represents the highest current density to date for a membraneless alkaline electrolyser.

Novel platinum group metal-free catalyst ink deposition system for combinatorial polymer electrolyte fuel cell performance evaluation

A new system for rapid and precise fabrication of polymer electrolyte fuel cell (PEFC) membrane-electrode assemblies (MEAs) is introduced to facilitate rapid testing and characterization of platinum group metal-free (PGM-free) catalysts, with minimal waste of materials, using commercial combinatorial hardware and multi-channel potentiostat. The commercial combinatorial system, designed for high-throughput catalyst activity evaluation (i.e., low overpotential and current densities) using gas-diffusion electrodes (GDEs), has been further developed to enable simultaneous evaluation of the high current density performance on air of twenty-five cathodes prepared by coating catalyst-ionomer inks directly onto the membrane using a newly-developed deposition system. A nanopipette or micropipette coupled to a precise peristaltic pump is being used for precise and even catalyst ink deposition onto the membrane in each of twenty-five circular electrodes with areas of <1 cm2 and in the precise locations required by the commercial combinatorial MEA hardware. The automated ink deposition system is coupled with a custom-designed heated vacuum table mounted on a computer-controlled XY stage to prevent deformation of the membrane and electrode layers during ink deposition onto the membrane. This system was utilized to evaluate the impact of ionomer to catalyst ratio on the hydrogen-air fuel cell performance of the PGM-free catalyst.

Design of multichannel potentiostat for remote and longtime monitoring of glucose concentration during yeast fermentation.

This paper presents the design of a wireless portable and multichannel potentiostat for remote monitoring in enclosed environments for long-time applications. In this paper, the proposed potentiostat is tested for monitoring the glucose concentration during the fermentation of yeast in real time for more than 24 h. The potentiostat is powered by a USB-connected battery and operated through a Bluetooth using a LabVIEW designed data monitoring and control panel. The potentiostat is capable of performing cyclic voltammetry or chronoamperometry on six biosensors simultaneously and gives the real-time response using Bluetooth connection. The potentiostat has a common counter electrode and reference electrode connection to all biosensors and independent working electrodes for all biosensors. The potentiostat was tested and validated by comparing the results obtained by a commercial potentiostat. The tests performed for monitoring the glucose concentration during the fermentation process showed a current detection limit of 180 nA and reported a standard deviation of ±2% for anodic and cathodic current peaks for cyclic voltammetry measurements when compared with the commercially available device. This study enables the novel method of monitoring the fermentation process wirelessly for days.

A Scalable Multi-Channel Software Potentiostat

Electronic hardware is a major cost driver when scaling bio-electrical systems (BES) for biological methanation. Many academic publications reporting BES experiments lack statistical power because such experiments are seldom carried out in replicates. One reason is that conventional electronic potentiostats often lack sufficient independent channels required for replication. Nonetheless, replication is necessary for any statistical analysis. Here, I developed a simple, easy-to-scale multi-channel software potentiostat which solves these problems. The software controls off-the-shelf hardware saving up to 80% of the hardware cost spent otherwise for electronic potentiostats. The difference between the setpoint and the measured working electrode potential was comparable to that of hardware potentiostats. Chronoamperomtric experiments were carried out in parallel for ten days at +0.300 V and −0.800 V. A scaling experiment using a tubular wastewater treatment reactor demonstrated that the software can be used to scale BES. The results show that a simple proportional controller can replace expensive potentiostats for chronoamperometry.

Reliability of a Method of Electrochemical Impedance for the Determination of Milk Adulteration

The objective of this research work was to determine the reliability of a electrochemical impedance spectroscopy method to determine the percentage of adulteration of milk with tap water. To measure the adulteration, the resistance in ohms was correlated with respect to the concentration of water in the milk. For this, a multichannel potentiostat was used. The milk was maintained at a temperature of 24 ° C. Five concentrations of tap water were used with respect to pure cow's milk, with values of 10, 15, 20, 25 and 30% v / v. A calibration curve was constructed from a sample of pure milk (unadulterated) as the reference standard. All readings were made by four repetitions at frequencies between 1 and 10000 hertz (Hz). From this, for each concentration of water in the milk through the Bode diagrams, a response of the resistance in ohms (Ω) was obtained as a function of the frequency (Hz). To determine the reliability of the method, linearity, precision, limit of detection and limit of quantification were determined. The linearity of the method was demonstrated from the coefficient of proportionality of 0.9975. The coefficient of variation (CV) had a value of 0.04%, which indicates that the accuracy of the method is acceptable. On the other hand, the limit of detection and limit of quantification correspond to values of 2.22 and 0.44% v / v respectively.

Design of a multichannel potentiostat and its application to corrosion testing of a nickel‐aluminum bronze

A setup for potentiostatic testing of eight specimens at different potentials in a common electrolyte pool was developed. The potentiostat requires only one reference electrode and one counter electrode to control all working electrodes and its design is easily scalable with respect to the number of channels. The system is applied to assess the effect of chloride, sulfate, and bicarbonate in fresh water‐typical concentration on a nickel‐aluminum bronze, assuming some anodic polarization by stainless steel with and without microbially induced ennoblement. Chloride and sulfate activate corrosion, bicarbonate has a passivating effect, and its combination with chloride and sulfate promotes localized corrosion. The susceptibility of nickel‐aluminum bronze to localized corrosion may be high in fresh water when polarized anodically. Potentiostatic corrosion testing may yield practically relevant results for systems with slow kinetics.

(Invited) Point-of-Care Diagnostics with Inkjet-Printed Microchips

Point-of-Care (POC) diagnostics grows currently in importance. Portable devices with electrochemical detection are very attractive for the rapid and low cost identification of diseases, especially when centralized laboratories with well-equipped, automatized analytical setups are either not available or results need to be obtained rapidly on site. There is a need for portable POC devices in developing and emerging countries, but also in developed countries. Electroanalysis, often in combination with immunoassay-based detection, provides sensing platforms with high sensitivity and reproducibility without suffering from optical interferences as optical detection methods can often do. For electroanalytical sensors, the selection and costs of the electrode materials and sensor fabrication strategies play major roles. Such considerations need to be made for the complete development chain from designing a sensor, fabricating and optimizing prototypes until reaching the industrial production scale. We found that inkjet printing, which is a digital and mask-less material deposition technique where picoliter droplets of functional inks are jetted with high precision, is the ideal tool for process development of commercial electroanalytical platforms. Herein, we demonstrate the large-scale fabrication of electrochemical microchips with up to eight parallel 50 µL wells containing each carbon nanotube working and counter electrodes, silver/silver chloride quasi-reference electrodes and a dielectric layer to define accurately the dimensions of the electrodes. The employed carbon nanotubes show a superior electrochemical behaviour and the multi-layer inkjet printing process provides highly reproducible electrode surfaces. We shall demonstrate the application as sensing platforms for antioxidants and hormones in several biological fluids using a portable, in-house made multichannel potentiostat.

Inkjet-printed microtiter plates for portable electrochemical immunoassays

Herein, we present the large-scale fabrication of multiplexed three-electrode sensors used in a point-of-care device platform that couples a magnetic bead-based immunoassay strategy with amperometric detection for rapid and highly sensitive analysis. The multiplexed sensors consisted of eight independent electrochemical cells, each with a carbon nanotube (CNT) working electrode, CNT counter electrode and a silver-silver chloride quasi-reference electrode. The microchips were fabricated on flexible polyethylene terephthalate (PET) sheets by sequential multilayer inkjet printing (IJP) of silver, CNT and insulator inks that were either simultaneously or subsequently post-processed (e.g. through UV photo-polymerization or photonic curing). Finally, plastic wells were mounted on top of the inkjet-printed patterns to obtain an eight-well microtiter plate where each well had a solution capacity of 50μL. Due to the high precision of the IJP process, the microtiter plates showed high reproducibility among the individual electrochemical cells (1–2% of deviation). Furthermore, the microchips can be reusable for at least up to 20 times as demonstrated herein. In a customized multichannel potentiostat with eight implemented magnets matching the positions of the working electrodes, the electrochemical readout of magnetic bead based sandwich and competitive immunoassays was successfully realized for the detection of thyroid-stimulating hormone (TSH) and atrazine (ATR) in aqueous and urine samples, respectively. The achieved limits of detection for ATR (i.e. 0.01μg/L) and TSH (i.e. 0.5μIU/mL) demonstrated the potential of the IJP microtiter plates for the environmental and biological quantification of analytes in a very reliable high throughput platform. This work shows that IJP has certainly reached the status of a batch production tool for electroanalytical sensing platforms.

An Inkjet-Printed Non-Enzymatic Hydrogen Peroxide Sensor on Paper

This paper reports a novel disposable non-enzymatic hydrogen peroxide sensor fabricated using an inkjet printing method on paper. An electrochemical cell based on carbon nanotubes was patterned and printed on a paper substrate. Silver nanoparticles have been used as the catalyst for electrochemical reduction of H2O2. Moreover, a handheld multichannel potentiostat was developed in order to on-site determination of hydrogen peroxide. The device was characterized by performing simultaneous cyclic voltammetry measurements utilizing separate working electrodes at various scan rates. Using the presented system, we successfully measured the hydrogen peroxide concentration in an alkaline solution with the linear range of 1 μM–700 μM. Incorporating the paper-based enzyme-free sensor and portable readout system will result in accurate, reliable, cost effective, and on-site measurement of hydrogen peroxide in concentration as low as 1 μM.