Electrode Chip Research Articles

Predicting the risk of chronic kidney disease based on uric acid concentration in stones using biosensors integrated with a deep learning-based ANN system

Elevated levels of uric acid (UA) in the body may not only lead to the formation of stones but also increase the risk of developing chronic kidney disease (CKD). This study presents a biosensor for detecting UA concentration in stones and a deep learning-based artificial neural network (ANN) system for analyzing CKD risk. The biosensor is a screen-printed electrode (SPE) chip, whose surface was modified using oxygen plasma, enabling the detection of UA concentration via cyclic voltammetry. Experimental results show a good linear relationship between UA concentration and anodic peak current within the range of 0.15–5 mM. The surface modification method for this biosensor is simple and cost-effective. The ANN system took age and creatinine values as inputs, utilizing the Chronic_Kidney_Disease dataset and supplementary data from literatures for training. After detecting the UA concentration in stones using the biosensor, the result was converted into serum uric acid concentration, allowing the estimation of creatinine level, which was then used by the ANN to assess the risk of developing CKD. This system can assist urologists in determining whether patients should seek consultation with nephrologists for early diagnosis and treatment.

Efficient Oxygen Evolution Reaction on Catalyst‐Free Acid‐Functionalized Plastic Chip Electrodes

Innovative electrode design is critical for improving the oxygen evolution reaction (OER) and meeting rising global energy demands. Despite the development of numerous carbon materials for water splitting, their potential is hampered by sluggish kinetics, primarily due to high activation energy compounded by various smaller factors, including additives or binders used in electrode modification. To address these limitations, a catalyst‐free plastic chip electrode (PCE) for OER is developed. PCE is functionalized by oxidizing it in acidic media at 1.8 V versus Ag/AgCl and eliminates the need for additives, offering a more accurate industrial representation. The oxidation process enhances the electrode's surface area and introduces electrochemically active oxygen‐containing functional groups. Characterization of the modified PCE is conducted using scanning electron microscope, X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, Raman, and thermogravimetric analysis, while electrolyte analysis utilizes UV–vis spectroscopy and NMR. The PCE oxidized for 6 h (PCE@6) demonstrates improved OER performance, with an onset overpotential of 260 mV, an overpotential of 1.06 V versus reversible hydrogen electrode at 10 mA cm−2, and a Tafel slope of 494 mV decade−1. The modified PCE reduces overpotential and minimizes bubble formation, enhancing efficiency and showcasing its potential as a cost‐effective solution for alkaline water electrolysis systems.

PTC-NH2@MOFs-AuNCs: A novel bifunctional signal probe for ratiometric electrochemiluminescence/colorimetry dual-mode aptasensing of lead ion

The development of a dual-mode sensing method for lead ions (Pb2+) is crucial and desirable. Herein, a single component-based bifunctional signal probe (perylene derivative-modified MOFs-gold nanoclusters, PTC-NH2@MOFs-AuNCs), which was capable of simultaneously generating an electrochemiluminescence (ECL) signal and exhibiting nanoenzyme activity, was prepared to fabricate a novel ratiometric ECL/colorimetry dual-mode platform for the visual, reliable, and sensitive analysis of Pb2+. Specifically, the PTC-NH2@MOFs-AuNCs were firstly synthesized via the electrostatic adsorption of AuNCs on the surface of PTC-NH2@MOFs. Upon the addition of Pb2+, the ECL signal of PTC-NH2@MOFs-AuNCs, which had been quenched by the adsorbed aptamer, could be restored at both the anode and cathode. Simultaneously, the peroxidase-like activity of PTC-NH2@MOFs-AuNCs was also recovered, accompanied by a distinct color transition from light blue to dark blue. The linear ranges of ratiometric ECL/colorimetric dual-modal assay for Pb2+ were 1 pM ∼ 5 nM and 1 nM ∼ 2 μM, with the limits of detection of 0.1 pM and 0.31 nM, respectively. More importantly, by introducing the screen-printed electrode and paper chip as sensing platform, a portable sensor for the convenient detection of Pb2+ was further established, demonstrating its promising practicability of rapid visual screening and accurate quantitative analysis in farmland soils.

An integrated bipolar electrode with shared cathode for dual-mode detection and imaging of CEA

In this paper, we designed a novel shared cathode bipolar electrode chip based on Ohm 's law and successfully constructed a dual-mode dual-signal biosensor platform (DD-cBPE). The device integrates ELISA, ECL, and ECL imaging to achieve highly sensitive detection and visual imaging of carcinoembryonic antigen (CEA). The unique circuit structure of the device not only realizes the dual signal detection of the target, but also breaks the traditional signal amplification concept. The total resistance of the system is reduced by series-parallel connection of BPE, and the total current in the circuit is increased. In addition, Au@NiCo2O4@MnO2 nanozyme activity probe was introduced into the common cathode to enhance the conductivity of the material. At the same time, due to the excellent peroxidase (POD) activity of NiCo2O4@MnO2, the decomposition of H2O2 was accelerated, so that more electrons flowed to the BPE anode, and finally the dual amplification of the ECL signal was realized. The device affects the current in the circuit by regulating the concentration of the co-reactant TPrA, thereby affecting the resistance of the system. Finally, different luminescent reagents emit light at the same potential and the luminous efficiency is similar. In addition, the chip does not need external resistance regulation, which improves the sensitivity of the immunosensor and meets the needs of timely detection. It provides a new idea for the deviceization of bipolar electrodes and has broad application prospects in biosensors, clinical detection, and environmental monitoring.

Discriminative non-destructive imaging of flip chips based on photoacoustic remote sensing microscopy with layered elasto-optic models.

Discriminative internal imaging for different chip layers can pinpoint the location of critical defect in the flip chips, yet existing methods face challenges in in-line imaging to identify defects or structures from the sub-surface within the silicon substrate and their underlying coating. To address these challenges, we develop and verify layered elasto-optic models for photoacoustic remote sensing microscopy (PARS) that distinguish structures from multi-layers within a single device for in-line flip-chip wafer inspection. A finite-difference time-domain algorithm based on transparent source (TS-FDTD) accurately predicts different initial slopes of PARS signals within the silicon-metal and the silicon-air models. The initial slopes of PARS signals are experimentally validated and utilized for discriminative non-destructive imaging of the interdigital electrode chips and silicon cracks within the same region of interest. PARS with layered elasto-optic models and non-contact fast scanning has the potential for in-line detection of defects from various layered structures with different refractive indices, offering an approach for discriminative non-destructive testing (NDT) of flip-chip and layered structures.

Fabrication and bonding of In bumps on Micro-LED with 8 μm pixel pitch

Indium (In) is currently used to fabricate metal bumps on micro-light-emitting diode (Micro-LED) chips due to its excellent physical properties. However, as Micro-LED pixel size and pitch decrease, achieving high-quality In bumps on densely packed Micro-LED chips often presents more challenges. This paper describes the process of fabricating In bumps on micro-LEDs using thermal evaporation, highlighting an issue where In tends to grow laterally within the photoresist pattern, ultimately blocking the pattern and resulting in undersized and poorly dense In bumps on the Micro-LED chip. To address this issue, we conducted numerous experiments to study the height variation of In bumps within a range of photoresist aperture sizes (3 μm −7 μm) under two different resist thickness conditions (3.8 μm and 4.8 μm). The results showed that the resist thickness had a certain effect on the height of In bumps on the Micro-LED chip electrodes. Moreover, we found that, with the photoresist pattern size increasing under constant resist thickness conditions, the height and quality of the bumps significantly improved. Based on this finding, we rationalized the adjustment of the photoresist pattern size within a limited emission platform range to compensate for the height difference of In bumps caused by different resist thicknesses between the cathode and anode regions. Consequently, well-shaped and dense In bumps with a maximum height of up to 4.4 μm were fabricated on 8 μm pitch Micro-LED chips. Afterwards, we bonded the Micro-LED chip with indium bumps to the CMOS chip, and we found that we could successfully control the CMOS chip to drive the Micro-LED chip to display specific characters through the Flexible Printed Circuit (FPC). This work is of significant importance for the fabrication of In bumps on Micro-LED chips with pitches below 10 μm and subsequent bonding processes.

A wearable sensor device based on screen-printed chip with biofuel cell-driven electrochromic display for noninvasive monitoring of glucose concentration

Wearable flexible sensor devices have the characteristics of lightweight and miniaturization. Currently, power supply and detection components limit the portability of wearable flexible sensor devices. Meanwhile, conventional liquid electrolytes are unsuitable for the integration of sensing devices. To address these constraints, wearable biofuel cells and flexible electrochromic displays have been introduced, which can improve integration with other devices, safety, and color-coded display data. Meanwhile, electrode chips prepared through screen printing technology can further improve portability. In this work, a wearable sensor device with screen-printed chips was constructed and used for non-invasive detection of glucose. Agarose gel electrolytes doped with PDA-CNTs were prepared, and the mechanical strength and moisture retention were significantly improved compared with traditional gel electrolytes. Glucose in interstitial fluid was non-invasive extracted to the skin surface using reverse iontophoresis. As a biofuel for wearable biofuel cells, glucose drives self-powered sensor and electrochromic display to produce color change, allowing for visually measurement of glucose levels in body fluids. Accurate detection results can be visualized by reading the RGB value with a cell phone.

Electrochemical Evaluation of the Number of Viable Bacteria Using Carbon Electrode Chip

Electrochemical Evaluation of the Number of Viable Bacteria Using Carbon Electrode Chip

Graphene Electrode for Studying CO2 Electroreduction Nanocatalysts under Realistic Conditions in Microcells.

The ability to resolve the dynamic evolution of electrocatalytically induced processes with electrochemical liquid-phase electron microscopy (EM)is limited by the microcell configuration. Herein, a free-standing tri-layer graphene is integrated as a membrane and electrode material into the electrochemical chip and its suitability as a substrate electrode at the high cathodic potentials required for CO2 electroreduction (CO2ER) is evaluated. The three-layer stacked graphene is transferred onto an in-house fabricated single-working electrode chip for use with bulk-like reference and counter electrodes to facilitate evaluation of its effectiveness. Electrochemical measurements show that the graphene working electrode exhibits a wider inert cathodic potential range than the conventional glassy carbon electrode while achieving good charge transfer properties for nanocatalytic redox reactions. Operando scanning electron microscopy studies clearly demonstrate the improvement in spatial resolution but reveal a synergistic effect of the electron beam and the applied potential that limits the stability time window of the graphene-based electrochemical chip. By optimizing the operating conditions, in situ monitoring of Cu nanocube degradation is achieved at the CO2ER potential of -1.1V versus RHE. Thus, this improved microcell configuration allows EM observation of catalytic processes at potentials relevant to real systems.

Early diagnosis of autoimmune diseases through electrochemical biosensing using a modified plastic chip electrode.

Detecting chronic autoimmune disorders (ADs) early reduces the risk of morbidity, disability, and mortality and offers the possibility of significant therapeutic action in a timely manner. Developing low-cost, reliable, and sensitive sensors for ADs can ensure the efficient utilization of healthcare resources at earlier stages. Here, we report on the development of an electrochemical biosensor for sensing CXCL10, a chemokine protein that serves as a biomarker for autoimmune diseases. A self-assembly strategy is used for the immobilization of biorecognition elements on a plastic chip electrode (PCE). A homemade PCE offers a versatile and cost-effective scaffold for sensing applications. Gold nanoparticles were electrochemically deposited on the electrode via the reduction of gold ions on the PCE galvanostatically. The CXCL10 antibody and recognition elements were immobilized on the gold-deposited PCE. The attachment of recognition molecules was confirmed by energy-dispersive scanning electron microscopy, atomic force microscopy, infrared spectroscopy, and electrochemical techniques. Electrochemical impedance spectroscopy (EIS) was used for the detection of CXCL10 within a concentration range spanning from pico- to micro-molar levels. The sensor exhibited remarkable linearity in both buffer and plasma solutions, with a limit of detection (LOD) of up to 0.72 pg mL-1.

An eco-friendly polycaprolactone/graphite composite as a robust freestanding electrode platform for supercapacitive energy storage.

We present the successful development and characterization of a novel eco-friendly polycaprolactone-graphite (PCLGr) composite as a freestanding platform, serving as a bulk conducting chip electrode for supercapacitor applications. Notably, this is the first report of using this biodegradable polymer for making such a self-standing conductive platform. Traditional polymer and carbon-based electrodes often rely on insulating supports or non-eco-friendly materials, which we have addressed in our work. Direct deposition of the redox material, polyaniline (PANI), onto the electrode via the galvanostatic method has been achieved. The specific capacitance of PANI demonstrates comparability to previous studies utilizing conventional current collectors. Notably, the electrode exhibits exceptional stability in highly acidic environments. Comprehensive characterization utilizing bulk conductivity measurements, XRD, TGA, DSC, SEM, and stress-strain analyses shows advanced properties of the electrode. It complements the evaluation of PANI's supercapacitive performance through cyclic voltammetry, charge-discharge measurements, and impedance spectroscopy. We achieved a specific capacitance of ≈162 F g-1 at 0.5 A g-1. This innovative electrode presents a promising alternative to conventional counterparts across various electrochemical applications.

Smart Home Sleep Respiratory Monitoring System Based on a Breath-Responsive Covalent Organic Framework.

A smart home sleep respiratory monitoring system based on a breath-responsive covalent organic framework (COF) was developed and utilized to monitor the sleep respiratory behavior of real sleep apnea patients in this work. The capacitance of the interdigital electrode chip coated with COFTPDA-TFPy exhibits thousands-level reversible responses to breath humidity gases, with subsecond response time and robustness against environmental humidity. A miniaturized printed circuit board, an open-face-mask-based respiratory sensor, and a smartphone app were constructed for the wearable wireless smart home sleep respiratory monitoring system. Leveraging the sensitive and rapid reversible response of COFs, the COF-based respiratory monitoring system can effectively record normal breath, rapid breath, and breath apnea, enabling over a thousand cycles of hour-level continuous monitoring during daily wear. Next, we took the groundbreaking step of advancing the humidity sensor to the clinical trial stage. In clinical experiments on real sleep apnea patients, the COF-based respiratory monitoring system successfully recorded hour-level sleep respiratory data and differentiated the breathing behavior characteristics and severity of sleep apnea patients and subjects with normal sleep function and primary snoring patients. This work successfully advanced humidity sensors into clinical research for real patients and demonstrated the enormous application potential of COF materials in clinical diagnosis.

Front Cover: Plastic Chip Electrode: An Emerging Multipurpose Electrode Platform (Chem. Asian J. 22/2023)

Front Cover: Plastic Chip Electrode: An Emerging Multipurpose Electrode Platform (Chem. Asian J. 22/2023)

Modification-free pumpless laser-induced graphene multichannel open microfluidic electrode chip for simultaneous quantification of dual targets

Pumpless surface fluid transport technology has attracted concerns in the field of electroanalysis. However, the combination of surface wettability-controlled multichannel fluid transport and flexible three-electrode systems has been rarely reported for electrochemical detection. Here, we have developed a modification-free pumpless laser-induced graphene multichannel open microfluidic electrode chip (LIG-MOMEC) for simultaneous quantification of dual targets. The LIG-MOMEC enables rapid sample distribution to four addressable locations for multiple parallel tests on a single chip and simultaneous detection of dopamine (DA) and uric acid (UA) using differential pulsed voltammetry. The flexible polyimide templated by laser parameters supports a programmable electrochemical sensing surface with desired conductivity and optimal surface wettability without post-chemical modification, effectively avoiding the tedious multi-step processing and time-consuming surface modification of conventional modified electrodes. The LIG-MOMEC has a linear detection range of 0.91 ∼ 171.15 μM for DA and 0.83 ∼ 250.04 μM for UA with the LODs of 72 nM and 48 nM. Due to the advantages of superior selectivity, anti-interference and reliable stability, the LIG-MOMEC could be reversibly used 30 times with high reproducibility and attain satisfactory recovery in human serum samples. The LIG-MOMEC provides great potential for the rapid detection of biomolecules in clinical diagnostics and biochemical analysis.

Interference-free multimodal biosensing of adrenaline over other neurotransmitters: Role of 2-iminomethylenephenylboronic acid as the signal transduction unit of fluorescence and impedance

Aberrant levels of the neurotransmitters adrenaline (AD), noradrenaline (NA), and dopamine (DA) are linked to various diseases. Therefore, interference-free biosensing of neurotransmitters has become an important area of research. However, structural similarity (presence of diol/amine functionalities), small size, and neutral charge of the catecholamines add complexity to designing recognition systems and make the detection non-specific. Herein, we report a recognition unit 2-iminomethylenephenylboronic acid (2-IMPBA), which appears to be a remarkable transduction unit for the tailor-made development of biosensors for interference-free detection of the neurotransmitter AD via multiple techniques. Integrating a signaling unit 4-methylbenzothiazole-2-amine to 2- formylphenylboronic acid (2-FPBA), yielded a novel fluorosensor, which showed 38- fold fluorescence enhancement selectively with AD without any competition from other bioanalytes, including NA and DA. The attachment of 2-FPBA on the homemade plastic chip electrode surface afforded an impedimetric sensor that detects AD in the picomolar range without any challenge from its competitors. Both optical and electrochemical sensors have been tested for AD measurement in human plasma samples. We are not aware of any report describing the selective discrimination of AD from NA or other biomolecules commonly found in humanbiofluids.

Plastic Chip Electrode: An Emerging Multipurpose Electrode Platform.

The properties of electrodes play a crucial role in the processes occurring on them. Therefore, a variety of materials have been tried as electrodes. Carbon composite materials are among the most admired ones. Use of composites as electrode material dates back to the mid of the last century when polymer-carbon composites were tried as general-purpose electrode platforms and epoxy impregnated graphite paste/ solid electrodes were tried in polarography. Later the composite electrodes have seen several phases of development. Plastic Chip Electrode (PCE) is a class of polymer composite electrode developed by our group. This monographic review gives a bird's eye account of polymer composite electrodes and appurtenant work, followed by elaborating on various aspects and state-of-the-art plastic chip electrodes.

A microfluidic chip integrating electrochemical impedimetric immunosensors constructed by top-bottom opposite electrodes for rapid detection of peanut allergen-Ara h 1

Developing a rapid and ultrasensitive immunosensor is significant for detecting allergenic contamination in food safety fields. This study reports a microfluidic biosensing device consisting of two top-bottom opposite electrode chips and a channel slab for constructing peanut allergen-Ara h 1 immunosensors. Under optimal fluidic manipulation (OFM), transporting an 80 μL aliquot of Ara h 1-containing phosphate buffer solution spiked by 2.5 mM Fe(CN)63−/4− mediator with a 50 μL/min flow rate for 2.5 min, the device can obtain better immunoreaction. The electron transfer resistance (Ret) of the label-free immunosensors was analyzed by electrochemical impedance spectroscopy (EIS) to quantify Ara h 1 immunoreaction. After performing OFM once, the linear range and the limit of detection were 1 pg/mL− 10 ng/mL and 3.9 fg/mL, respectively. Furthermore, the Ret response of the immunosensors increased with OFM times. The sensing device can detect the Ara h 1 concentration with good recovery (95 −103%) for the diluted supernatant extracted from standard peanut butter. The microfluidic device integrating EIS-based immunosensors exhibits rapid and ultrasensitive sensing properties with promising potential for label-free detection of allergens in food products.

Simultaneous detection of Alzheimer's biomarkers using a visual electrochemiluminescence bipolar array

Alzheimer's disease (AD), a progressive neurological disorder, presents challenges in early detection due to the limitations and costs of neuropsychological tests and neuroimaging. This study introduces a visual electrochemiluminescence (ECL) sensing device employing red and green signal lights on dual-channel closed bipolar electrodes (BPEs) for simultaneous Aβ oligomers and Tau proteins detection. To mitigate cross-chemical reactions, we physically separated target detection and ECL production within different chambers connected by BPEs. Utilizing efficient gold clusters (Au NCs) and Ru(bpy)32+ as green and red emitters, respectively, along with methylene blue (MB) as the recognition probe on the cathode sensing platform, we achieved a detection limit of 2.6 pM for Aβ oligomers and 0.3 pM for Tau proteins by measuring visual ECL intensity at two anodic poles of BPEs. This approach minimizes cross-chemical reactions, ensures robust ECL signal sensors, and allows integration of multiple sensors on a single chip. The proposed portable bipolar electrode chips employing ECL technology show promise for early and precise Alzheimer's disease diagnosis and personal healthcare.

A self-enhanced electrochemiluminescence array chip for portable label-free detection of SARS-CoV-2 nucleocapsid protein with smartphone

SARS-CoV-2 antigen detection plays a key role in the rapid diagnosis of COVID-19. However, current clinically used immunoassays are often limited by assay throughput, sensitivity, accuracy, and field operating conditions. To address these challenges, we constructed a self-enhanced electrochemiluminescence (ECL) array chip (SE2AC) for highly sensitive and label-free detection of SARS-CoV-2 nucleocapsid protein (N protein) with a facile and portable assay setup. Firstly, the self-enhanced ECL nanomaterials with inherent film-forming properties were synthesized by co-doping Ru(bpy)32+ and polyethyleneimine (PEI) in silica nanoparticles (Ru/PEI@SiO2). Secondly, a resistance-induced potential difference-based single-electrode electrochemical system (SEES) was adapted to serve as the electrode array to facilitate one-step assembly without the need for chip alignment. Thirdly, the chip electrode array was functionalized with the synthesized self-enhanced ECL emitters and captured antibodies. In addition, a portable detection box equipped with a smartphone was 3D-printed to serve as the chip holder and “dark room” for imaging acquisition. The SE2AC performance was validated with N protein with a limit of detection (LOD) of 0.47 pg/mL in the range of 1–10,000 pg/mL. Furthermore, the chip successfully detected the viral antigen residue as low as 1.92 pg/mL from diluted rehabilitation patients’ serum samples. This is the first study reporting label-free detection of SARS-Cov-2 N protein based on a self-enhanced ECL immunosensor, which provides a novel facile method for highly sensitive diagnosis of COVID-19 with high throughput, portability, and low cost.

Rolling Circle Amplification/G‐Quadruplex‐Based Dual‐Signal Ratiometric Electrochemical Aptasensor for Ultrasensitive Detection of Pathogenic Bacteria

AbstractAccurate and efficient detection of pathogenic bacteria plays a crucial role in the diagnosis of infectious diseases. However, rapid and highly sensitive detection of specific bacteria in clinical samples remains challenging. In this study, we developed a ratiometric dual‐signal electrochemical biosensor for ultrasensitive detection of pathogenic bacteria, based on an aptamer recognition‐induced rolling circle amplification (RCA)/G‐quadruplex strategy. On the surface of a gold electrode chip, we used an aptamer sequence (P1) conjugated to ferrocene (Fc) to capture the target bacterium. This capture released a different, previously bound sequence (P2) sequence that initiated the RCA/G‐quadruplex cascade, which, in the presence of potassium ions, was able to bind the electrochemical indicator methylene blue (MB). We integrated the signals from the loss of Fc and the appearance of MB (IMB/IFC ratio) to quantify the target bacteria concentration. This biosensor showed excellent detection performance and specificity, with a detection limit of 10 CFU/mL. Notably, it showed great diagnostic potential for clinical infectious diseases caused by pathogenic bacteria in precise/personalized medicine applications.