A potentiometric cobalt-based phosphate sensor based on screen-printing technology

A potentiometric cobalt-based screen-pritning sensor was fabricated by electroplating cobalt on the surface of a screen-printing electrode as the sensitive layer for the determination of dihydrogenphosphate （H2PO4） in wastewater samples. The electrochemical performance of this sensor was fully examined to determine its detection calibration, detection limit, response time, selectivity, and interference with pH, various ions, and dissolved oxygen （DO）. The cobalt-based phosphate sensor showed a phosphate-selective potential response in the range of 10 5mol·L^-1 to 10^-1 mol^-1, yielding a detection limit of 3.16 × 10μmol·L^l and a slope of -37.51 mV·decade＇ in an acidic solution （pH 4.0） of H2PO4-. DO and pH were found to interfere with sensor responses to phosphate. Ultimately, the performance of the sensor was validated for detecting wastewater samples from the Xiaojiahe Waste- water Treatment Plant against the standard speetrophotometric methods for HzPO4 analysis. The discrepancy between the two methods was generally ＋5% （relative standard deviation）. Aside from its high selectivity, sensitivity, and stability, which are comparable with conventional bulk Co-wire sensors, the proposed phosphate sensor presents many other advantages, such as low price, compactness, ease of use, and the possibility of integration with other analytical devices, such as flow injectors.

Screen-Printable Functional Nanomaterials for Flexible and Wearable Single-Enzyme-Based Energy-Harvesting and Self-Powered Biosensing Devices

Developing flexible bioelectronics is essential to the realization of artificial intelligence devices and biomedical applications, such as wearables, but their potential is limited by sustainable energy supply. An enzymatic biofuel cell(BFC) is promising for power supply, but its use is limited by the challenges of incorporating multiple enzymes and rigid platforms. This paper shows the first example of screen-printable nanocomposite inks engineered for a single-enzyme-based energy-harvesting device and a self-powered biosensor driven by glucose on bioanode and biocathode. The anode ink is modified with naphthoquinone and multiwalled carbon nanotubes(MWCNTs), whereas the cathode ink is modified with Prussian blue/MWCNT hybrid before immobilizing with glucose oxidase. The flexible bioanode and the biocathode consume glucose. This BFC yields an open circuit voltage of 0.45 V and a maximum power density of 266 μW cm-2. The wearable device coupled with a wireless portable system can convert chemical energy into electric energy and detect glucose in artificial sweat. The self-powered sensor can detect glucose concentrations up to 10 mM. Common interfering substances,including lactate, uric acid, ascorbic acid, and creatinine, have no effect on this self-powered biosensor. Additionally, the device can endure multiple mechanical deformations. New advances in ink development and flexible platforms enable a wide range of applications, including on-body electronics, self-sustainable applications, and smart fabrics.

Flexible planar micro supercapacitor diode

Supercapacitor diode is a novel ion device that performs both supercapacitor energy storage and ion diode rectification functions.However,previously reported devices are limited by their large size and complex processes.In this work,we demonstrate a screen-printed micro supercapacitor diode(MCAPode)that based on the insertion of a finger mode with spinel ZnCo_(2)O_(4) as cathode and activated carbon as anode for the first time,and featuring an excellent area specific capacitance(1.21 mF cm^(-2)at 10 mV s^(-1))and high rectification characteristics(rectification ratioⅠof 11.99 at 40 mV s^(-1)).Taking advantage of the ionic gel electrolyte,which provides excellent stability during repeated flexing and at high temperatures.In addition,MCAPode exhibits excellent electrochemical performance and rectification capability in"AND"and"OR"logic gates.These findings provide practical solutions for future expansion of micro supercapacitor diode applications.

Noninvasive Label-Free Detection of Cortisol and Lactate Using Graphene Embedded Screen-Printed Electrode

A sensitive and specific immunosensor for the detection of the hormones cortisol and lactate in human or animal biological fluids, such as sweat and saliva, was devised using the label-free electrochemical chronoamperometric technique. By using these fluids instead of blood,the biosensor becomes noninvasive and is less stressful to the end user, who may be a small child or a farm animal.Electroreduced graphene oxide(e-RGO) was used as a synergistic platform for signal amplification and template for bioconjugation for the sensing mechanism on a screenprinted electrode. The cortisol and lactate antibodies were bioconjugated to the e-RGO using covalent carbodiimide chemistry. Label-free electrochemical chronoamperometric detection was used to analyze the response to the desired biomolecules over the wide detection range. A detection limit of 0.1 ng mL^(-1) for cortisol and 0.1 mM for lactate was established and a correlation between concentration and current was observed. A portable, handheld potentiostat assembled with Bluetooth communication and battery operation enables the developed system for point-of-care applications. A sandwich-like structure containing the sensing mechanisms as a prototype was designed to secure the biosensor to skin and use capillary action to draw sweat or other fluids toward the sensing mechanism. Overall, the immunosensor shows remarkable specificity, sensitivity as well as the noninvasive and point-of-care capabilities and allows the biosensor to be used as a versatile sensing platform in both developed and developing countries.

A sensitive electrochemical detection of metronidazole in synthetic serum and urine samples using low-cost screen-printed electrodes modified with reduced graphene oxide and C60

Monitoring the concentration of antibiotics in body fluids is essential to optimizing the therapy and minimizing the risk of bacteria resistance,which can be made with electrochemical sensors tailored with appropriate materials.In this paper,we report on sensors made with screen-printed electrodes(SPE)coated with fullerene(C60),reduced graphene oxide(rGO)and Nafion(NF)(C60-rGO-NF/SPE)to determine the antibiotic metronidazole(MTZ).Under optimized conditions,the C60-rGO-NF/SPE sensor exhibited a linear response in square wave voltammetry for MTZ concentrations from 2.5×10^(-7) to 34×10^(-6) mol/L,with a detection limit of 2.1×10^(-7) mol/L.This sensor was also capable of detecting MTZ in serum and urine,with recovery between 94%and 100%,which are similar to those of the standard chromatographic method(HPLC-UV).Because the C60-rGO-NF/SPE sensor is amenable to mass production and allows for MTZ determination with simple principles of detection,it fulfills the requirements of therapeutic drug monitoring programs.

Anodic voltammetric determination of gemifloxacin using screen-printed carbon electrode

The electrochemical oxidation behavior and voltammetric assay of gemifloxacin were investigated using differential-pulse and cyclic voltammetry on a screen-printed carbon electrode.The effects of pH,scan rates,and concentration of the drug on the anodic peak current were studied.Voltammograms of gemifloxacin in Tris-HCl buffer（pH 7.0） exhibited a well-defined single oxidation peak.A differential-pulse voltammetric procedure for the quantitation of gemifloxacin has been developed and suitably validated with respect to linearity,limits of detection and quantification,accuracy,precision,specificity,and robustness.The calibration was linear from 0.5 to 10.0 μM,and the limits of detection and quantification were 0.15 and 5.0 μM.Recoveries ranging from 96.26% to 103.64% were obtained.The method was successfully applied to the determination of gemifloxacin in pharmaceutical tablets without any pre-treatment.Excipients present in the tablets did not interfere in the assay.

Dye-sensitized solid-state solar cells fabricated by screen-printed TiO_2 thin film with addition of polystyrene balls

The screen-printed nanoporous TiO2 thin film was employed to fabricate dye-sensitized solid-state solar cells using CuI as hole-transport materials. The solar cell based on nanoporous TiO2 thin film with large pores formed by the addition of polystyrene balls with diameter of 200 nm to the TiO2 paste exhibits photovoltaic performance enhancement, which is attributed to the good contact of CuI with surface of dye-sensitized thin film due to easy penetration of CuI in the film with large pores.

Amperometric Hydrogen Peroxide Biosensor Based on Horseradish Peroxidase Entrapped in Titania Sol-Gel Film on Screen-Printed Electrode

We report the fabrication of disposable and flexible Screen-Printed Electrodes (SPEs). This new type of screen-printed electrochemical platform consists of Ag nanoparticles (AgNPs) and graphite composite. For this purpose, silver nanoparticles were first synthesized by a chemical reduction method. The morphology and structure of the AgNPs were analyzed using a Scanning Electron Microscope (SEM) and UV-Visible spectroscopy. Graphite was chosen as the working electrode material for the fabrication of a thick-film. The fabrication of a screen-printed hydrogen peroxide biosensor consisting of three electrodes on a polyethylene terephthalate (PET) substrate was performed with a spraying approach (working, counter and reference: enzyme electrode, graphite, pseudo reference: Ag/AgCl). This biosensor was fabricated by immobilizing the peroxidase enzyme (HRP) in a Titania sol-gel membrane which was obtained through a vapor deposition method. The biosensor had electrocatalytic activity in the reduction of H2O2 with linear dependence on H2O2 concentration in the range of 10-5 to 10-3 M;the detection limit was 4.5 × 10-6 M.

Gold Nanoparticles/Thermochromic Composite Film on Screen-Printed Electrodes for Simultaneous Detection of Protein and Temperature

In this study, gold nanoparticles and thermochromic composite films modified screen-printed carbon electrodes (TM-AuNPsSPCEs) were developed as a platform for the simultaneous detection of protein and temperature. The TM-AuNPs composited film had better sensitivity resulting from the gold nanoparticles amplification effect. A phase transition model analysis of TM-AuNPs films found that the TM-AuNPs films had three-phase transition intervals (<45℃, 45℃ to 80℃ and >80℃) which accommodated the temperature requirements for protein denaturation. When used to detect different concentrations of haemoglobin (Hb) solution, the TM-AuNPs modified SPCEs had a better sensitivity in detecting the different concentrations in comparison to TM and AuNP modified SPCEs which showed no clear sensitivity towards the different Hb concentrations. The dual detection and excellent sensitivity show a good application prospect for the study of the TM-AuNPs composite film.

Screen-printed graphite electrode on polyvinyl chloride and parchment strips integrated with genetic programming for in situ nitrate sensing of aquaponic pond water

Nitrate is the primary water-soluble macronutrient essential for plant growth that is converted from excess fish feeds,fish effluents,and degrading biomaterials on the aquaponic pond floor,and when aquacultural malpractices occur,large amounts of it retain in the water system causing increase rate in eutrophication and toxifies fish and aquaculture plants.Recent nitrate sensor prototypes still require performing the additional steps of water sample deionization and dilution and were constructed with expensive materials.In response to the challenge of sensor enhancement and aquaponic water quality monitoring,this study developed sensitive,repeatable,and reproducible screen-printed graphite electrodes on polyvinyl chloride and parchment paper substrates with silver as electrode material and 60:40 graphite powder:nail polish formulated conductive ink for electrical traces,integrated with 9-gene genetic expression model as a function of peak anodic current and electrochemical test time for nitrate concentration prediction that is embedded into low-power Arduino ESP32 for in situ nitrate sensing in aquaponic pond water.Five SPE electrical traces were designed on the two types of substrates.Scanning electron microscopy with energy dispersive X-ray confirmed the electrode surface morphology.Electrochemical cyclic voltammetry using 10 to 100 mg/L KNO3 and water from three-depth regions of the actual pond established the electrochemical test time(10.5 s)and electrode potential(0.135 V)protocol necessary to produce peak current that corresponds to the strength of nitrate ions during redox.The findings from in situ testing revealed that the proposed sensors have strong linear predictions(R2=0.968 MSE=1.659 for nSPEv and R2=0.966 MSE=4.697 for nSPEp)in the range of 10 to 100 mg/L and best detection limit of 3.15μg/L,which are comparable to other sensors of more complex construction.The developed three-electrode electrochemical nitrate sensor confirms that it is reliable for both biosensing in controlled solutions and in situ aquaponic pond water systems.

A flow chemiluminescence paper-based microfuidic device for detection of chromium(Ⅲ)in water

In this work,a solely gravity and capillary force-driven flow chemiluminescence(GCF-CL)paper-based microfuidic device has been proved for the first time as a new platforn for inex-pensive,usable,mini mally instrumented dynamic chemiluninescence(CL)detection of chromium(Ⅲ)[Cr(Ⅲ)],where an appropriate angle of inclination between the loading and detection zones on the paper produces a rapid flow of CL prompt solution through the paper charnel.For this study,we use a cost-effective paper device that is manufactured by a simple wax screen-printing method,while the signal generated from the Cr(Ⅲ)-catalyzed oxidation of luminol by H_(2)O_(2) is recorded by a low-cost and luggable CCD camera.A series of GCF-CL affecting factors have been evaluated carefully.At optimal conditions,two linear relationships between GCF-CL intensities and the logarithms of Cr(Ⅲ)concentrations are obtained in the concentration mnges of 0.025-35 mg/L and 50-500 mg/L separately,with the detection limit of 0.0245mg/L for a les than 30s assay,and relative standard deviations(RSDs)of 38%,4.5%and 2.3%for 0.75,5 and 50 mg/L of Cr(Ⅲ)(n=8).The above results indicate that the GCF-CL paper-based microfluidic device possesses a receivable sensitivity,dynamic range,storage stability and reproducibility.Finally,the developed GCF-CL is utilized for Cr(Ⅲ)detection in real water samples.

Bilayered Glass-Ceramics as Sealants for SOFCs

Glass-ceramics are often used as sealants in solid oxide fuel cells (SOFC). But interfacing components, such as ferritic stainless steel and YSZ electrolyte, may vary in their requirements regarding sealing properties, especially in terms of thermal expansion. A bilayered glass-ceramic system was developed to overcome the mismatch in coefficients of thermal expansion (CTE) between ferritic steel and YSZ. Therefore, two different glass-ceramics with slightly different CTEs were developed, one with good bonding characteristics to the ferritic steel and the other to the YSZ electrolyte. Steel and electrolyte components were coated with a layer of their corresponding glass sealant paste and heated up to form a sandwich sample. During the heat treatment of the sealing process, the glasses are crystallized into glass-ceramics. The resulting interface between the two glass-ceramics is of special interest. Cross-sections of the sandwich samples were cut, polished and investigated using SEM. The glass-ceramics show continuous, gap-free layers and excellent bonding to both steel and YSZ. Energy release rates are measured for single and bilayered glass sealants by mechanical testing. The designed bilayered glass-ceramics fulfill the special requirements of ferritic steel and YSZ. They show excellent potential to become a new outstanding sealant for SOFCs.

Model of Pollution Management Control in Badung River： Enhancing Role of Traditional Law on Common Resource

Badung River in the Denpasar city of Bali Province, Indonesia, faces many challenging issues recently. As a common pool resource, the river has been under pressure from many activities including household activities which dump household wastes, and pollution externalities arising from dyeing and screen-printing of fabric industries. Conventional approach to control the pollution might not be effective since it will end up in zero sum game. This paper attempts to explore the role of traditional institituion in managing common pool resource such as controlling river pollution. This research is aimed to know the effectiveness of traditional law on managing pollution of printing and dyeing industries on this big river. Survey method was used for collecting primary data and then the data was analyzed by ordinal regression to determine the effect of internal and external factors which influence the intensity of pollution. The result indicates that even though traditional might help to influence household and industry＇s decision making, it might not sufficient enough to reduce the pollution of the river. Other factors are influencing the waste management, such as level of waste management knowledge of the entrepreneur, the attitude of the entrepreneur toward public program especially on waste and pollution management, the financial support, and the education level of government supervision. Furthermore, Government of Denpasar City need to arrange policy that giving incentive to businessman who handling waste properly and also giving reward to traditional organization who implementing local wisdom and norm to control river pollution strictly.

Use of a Simple Fabrication Process to Produce a Biosensor： The 3-Hydroxybutyrate Dehydrogenase Case

This study was aimed to construct a biodegradable but reliable 3-β-hydroxybutymte biosensor. In this context a versatile paper based biosensor, quickly, easily and cheaply fabricated is reported. The procedure of fabrication is based on the assumption that the introduction of the enzyme in the carbon ink will allow enzyme stabilization and facilitate the study of the catalysis of enzymes and the detection of substrates. To prove this concept we use the enzyme 3-hydroxybutyrate dehydrogenase, in aqueous solution. This enzyme was chosen because it catalyzes the 3-β-hydroxybutyrate, which results from ketoacidosis. The quantification this substance in the diabetics＇ blood is very important as it can increase the reliability of the diagnosis of glycaemia. To prove the multi-use of this biosensor we not only study the redox process in steady state and during the catalytic process, but also detected and quantify the 3-β-hydroxybutyrate. Our results showed that it was possible to study the redox process that occurred during the catalysis and to confirm the amino acid residues that participate in it. It was also observed that glucose and ascorbic acid can interfere in the detection and quantification of the 3-β-hydroxybutyrate, what should be in mind when the quantification of the 3-β-hydroxybutyrate is made in blood samples.

A Simple Procedure to Fabricate Paper Biosensor and Its Applicability-NADH/NAD＊ Redox System

A simple device which incorporates three electrodes （working electrode, counter electrode and reference electrode） was constructed to be used currently in laboratories without elevated cost. It does not need more than 2 μL of electrolyte, sample or working solution, his support material is paper, and the working electrode which is based on carbon ink can incorporate enzymes and cofactors. To test this concept we started this investigation using the NADH/NAD＋ redox couple which is an onmipresent coenzyme in living systems but is also a challenge to electrochemistry. The paper sensor fabrication was simple, rapid and cheaper. NADH was incorporated in the carbon ink by mixing both and, this mixture was used to print the working electrode. The direct electrochemical system NADH/NAD＋ signal obtained, using this device, appeared at low potentials. A quasi-reversible diffusional redox process was achieved and regeneration of the NADH after oxidation was reached. This small paper device was not only used to study the redox process of NAD＋/NADH, but also its behavior in the presence of electroactive （ascorbic acid） and non-eletroactive species （glucose）.

Aptasensor Based on Screen-Printed Carbon Electrodes Modified with CS/AuNPs for Sensitive Detection of Okadaic Acid in Shellfish

Okadaic acid(OA),a small molecule substance derived from shellfish,is one of the most widely distributed marine toxins with acute symptoms of vomiting and diarrhea after accidental ingestion.For this,there is an urgently need for sensitive and reliable methods to detect OA in real shellfish samples.In this study,a simple aptasensor based on screen-printed carbon electrode(SPCE)with modification of chitosan(CS)and gold nanoparticles(Au NPs)was designed for electrochemical determination of OA,and the electrode surface was modified with Au NPs by potential-sweeping electrodeposition,which greatly improved the electrochemical response.The entire detection and characterization process were carried out by cyclic voltammetry(CV)with a linear correlation in the range of 0.01-100 ng/m L and a limit of detection(LOD)of 6.7 pg/m L.Furthermore,recovery rates of 92.3-116%were obtained demonstrating excellent accuracy through the recovery trial of mussel and scallop samples.

The Influencing Factors of Disposable Acetylcholinesterase Biosensor for in Situ Detection of Organophosphorus Pesticide

An amperometric biosensor based on acetylcholinesterase (ACHE) is assembled by simple adsorption of the AChE on 7,7,8,8-tetracyanoquinodimethane (TCNQ) modified screen-printed electrodes.This biosensor is used to detect the inhibitory effect of organophosphorus pesticides on AChE activity.The detection of organophosphorus pesticides is done with acetylthiocboline chloride (ATCh) as substrate.In order to obtain the optimized response to substrate,the influencing factors of the biosensor are investigated,including temperature,pH,incubation time,substrate concentration and AChE concentration. The measurements were performed after inhibition by immersing the enzyme electrode into the parathion methyl solution. Under the optimized conditions,that is,500 U/ml AChE concentration,pH 7.2,10 min incubation time,2 mmol/L substrate concentration and temperature of 37℃,from 5×10^(-8) mol/L to 5×10^(-5) mol/L is close to linear (regression equation: y(%)=124.055+15.7991gx,R^2=0.99644),which corresponds to 8.7%～56.1% AChE inhibition.With the optimized conditions, the lowest detectable amount of parathion methyl is 13×10^(-9).

Disposable Amperometric Acetylcholinesterase Biosensor for the Detection of Organophosphorus Pesticides

A rapid,simple,disposable and inexpensive acetylcholinesterase (ACHE) amperometric biosensor for the detection of organophosphorus pesticides was developed by simple adsorption of the enzyme on screen-printed electrodes.The biosensor consisted of an Ag/AgCl reference electrode and a graphite working electrode.The mixture of graphite and the 7,7,8,8-tetracyanoquinodimethane (TCNQ) was printed on electrodes.The detection of organophosphorus pesticides was done with acetylthiocholine chloride (ATCh) as substrate.The biosensor was used to detect the inhibitory effect of organophosphorus pesticides on AChE activity.The 1μl of enzyme solution containing 0.1 U AChE and 1% bovine serum albumin (BSA) were simply dropped on the working electrode surface.The biosensor operated at a potential of 300 mV vs. Ag/AgCl in a pH 7.2 0.1 mol/L phosphate buffer and 0.1 mol/L KCl.We obtained a calibration plot of the percentage inhibition versus the logarithm of parathion methyl concentration following an incubation time of 10 mix in parathion methyl solution. The lowest detectable amount of parathion methyl was 0.026 ppm.The amperometric biosensor based on acetylcholinesterase was disposable and low cost (about 1 yuan RMB).

Deep learning-based prediction of 3-dimensional silver contact shapes enabling improved quality control in solar cell metallization

The industrial metallization of Si solar cells predominantly relies on screen printing,with silver as the preferred electrode material.However,the design of commercial screens often leads to suboptimal silver usage and increased electrical resistance due to print-related inhomogeneities like mesh marks,constrictions and spreading.Real-time monitoring of quality parameters during production has thus become increasingly critical.Current inline optical quality control systems usually only include 2D visualizations of the printed layout,which limits their effectiveness in quality control.Options that allow 3D measurements are usually slow,expensive,and therefore not worth considering in most cases.This research focuses on the development of a model that can estimate the three-dimensional shape of printed contact fingers from a single 2D image without the need of additional hardware using deep learning.Furthermore,a workflow for the generation of training data,which involves the creation of image pairs from a 2D microscope and a 3D confocal laser scanning microscope(CLSM)to accurately represent solar cell fingers,is presented.After model training,the predicted height maps are compared with the ground truth height maps,and the robustness of the model with respect to a paste variation and screen parameter variation is examined.The results confirm the feasibility and reliability of deep learning-based 3D shape estimation,extending its applicability to new,previously unseen data from screen-printed contact fingers.With a structural similarity index(SSIM)score of 0.76,a strong correlation between the estimated and ground truth height maps is established.In summary,our deep learning-based approach for height map estimation offers an effective and reliable solution for fast inline detection and analysis of the cross-sectional area of the printed contact fingers.

Self-powered nanofiber-based screen-print triboelectric sensors for respiratory monitoring

Scientific and commercial advances have set high requirements for wearable electronics. However, the power supply, breathability, and mass production of wearable electronics still have many challenges that need to be overcome. In this study, a self-powered nanofiber-based triboelectric sensor （SNTS） was fabricated by batch-scale fabrication technologies using electrospinning and screen-printing for health monitoring via respiratory monitoring. Typically, an arch structural SNTS is assembled by a nanofiber membrane and a Ag nanoparticle electrode. The pile of nanofibers and the conductive network of Ag nanoparticles ensure a gas channel across the whole device. The gas permeability of the SNTS was as high as 6.16 mm/s, which has overwhelming advantages when compared with commonly used wearable devices composed of air-tight cast films. Due to the softness of the nanofiber membrane, the SNTS showed excellent electronic output performance irrespective of whether it was bent, twisted, or folded. The superior properties, such as breathability, skin-friendliness, self-power, and batch fabrication of SNTS offer huge potential for their application in healthcare monitoring and multifunctional intelligent systems.