Carbon Ink Research Articles

Effect of the physical adsorption of ionomer on Pt particles on the fluid characteristics of PEMFC catalyst ink

The physical adsorption between ionomer and Pt particles affects the fluid properties of a catalyst ink, which in turn affects the surface morphology of ink coating. In this study, catalysts with varying Pt loadings were used to produce catalyst ink with the same solid content, and carbon ink with different solid content was prepared as a comparative test. The rheological test revealed that in carbon ink without Pt, the interaction between ionomer and carbon was more stable, and ink showed a behavior similar to that of a Newtonian fluid. The viscosity and storage modulus of carbon ink have a linear relationship with the apparent volume fraction of carbon. In the catalyst ink, Pt particles and ionomer's action make the ink a pseudoplastic fluid. With the increase of carbon content of the catalyst ink, the structural strength of the ink increases rapidly. In the catalyst ink with carbon apparent volume fractions of 41.42, 38.59, 35.37, and 31.68 vol%, the storage modulus of ink is 31.20, 15.50, 5.10, and 1.10 Pa, respectively, and the solid-state physical properties of ink gradually disappear. When the Pt loading exceeds 40 wt%, the ink has an optimal thixotropy and improves the integrity of the surface morphology of the catalytic layer. The electrochemical test results show that the output voltage of 50 wt% Pt/C catalyst ink-MEA can achieve 0.711 V at 1000 mA cm−2, and the output power is 1121.1 mW cm−2 at 2000 mA cm−2.

Development of biobased polyol from epoxidized soybean oil for polyurethane anti‐smudge coatings

AbstractIn this work, a vegetable oil‐based polyol (ERD) with high hydroxyl value was obtained from ring‐opening reaction between the renewable epoxidized soybean oil and ricinoleic acid, and further esterified with 2,2‐bis(hydroxymethyl)propionic acid. To achieve anti‐smudge coating, the ERD polyol was utilized as the polyol component, hexamethylene diisocyanate trimer was employed as the curing agent, and mono‐hydroxy‐terminated polydimethylsiloxane (PDMS‐OH) was introduced as the low surface energy component. In consequence, the biobased polyurethane anti‐smudge coatings are highly smooth and transparent. With the incorporation of 1 wt% of PDMS‐OH, the obtained coating exhibited superb anti‐ink and self‐cleaning performance. Droplets of water, soy sauce, carbon ink, hexadecane, rice bran oil, and pump oil could slide off the coating surface without leaving any wetting footprints. More importantly, the coating was mechanically robust. Even after the coating was subjected to 2000 writing and erasing cycles with an oil‐based marker pen, it still displayed good ink shrinkage ability and the ink traces could be easily erased. Besides, this anti‐smudge coating retained its good hydrophobicity after being soaked in aqueous solutions with different pH values for 24 h. Therefore, the application of this biobased anti‐smudge coating would offer a lower carbon footprint than its petroleum‐based counterparts.

Electrochemical system designed on a paper platform as a label-free immunosensor for cancer derived exosomes based on a mesoporous carbon foam- ternary nanocomposite

• A cheap, disposable, biodegradable and fast electrochemical paper-based device (ePAD) for exosomes determination was designed. • Preparation of mesoporous carbon foam with a lot of pores without using a template. • An ePAD contains the synthetic carbon and silver ink screen printed on the paper modified with AuNPs@MCF/MWCNTs ternary nanocomposite. • The low detection limit, high sensitivity and selectivity were obtained. Mesoporous carbon as a new class of three-dimensional conductive carbon materials has attracted more attention due to its significant surface area, unique flexibility, and lots of porosity. In this paper, a cost-effective, biodegradable electrochemical sensor was fabricated based on a highly flexible chromatographic paper with a lab-made carbon ink. The electrochemical response was enhanced with mesoporous carbon functionalized with multi-carbon nanotubes and gold nanoparticles (AuNPs@MCF/MWCNTs). Then, the CD9 antibodies were immobilized on the porous surface of the nanocomposite to combine with proteins overexpressed on the exosomal membrane. This structure and electrostatic repulsion effectively protect the electron transfer of the redox probe and lead to quantitative detection of exosomes using changes in the current. This paper-based immunosensor revealed a high sensitivity (the very low detection limit of 70 exosomes/µL and a linear range of 1 × 10 2 to 1 × 10 7 exosomes/µL) and suitable selectivity for detection of exosomes in the plasma sample. This paper-based immunosensor can prepare a clear horizon for using this kind of biosensors in the early detection and screening of diseases such as cancers in miniaturization and accessible system, especially Point of Care Testing (POCT) devices.

High-performance paper-based biocathode fabricated by screen-printing an improved mesoporous carbon ink and by oriented immobilization of bilirubin oxidase

In this study, the performance of a paper-based, screen-printed biofuel cell with mesoporous MgO-templated carbon (MgOC) electrodes was improved in two steps. First, a small amount of carboxymethyl cellulose (CMC) was added to the MgOC ink. Next, the cathode was modified with bilirubin prior to immobilizing the bilirubin oxidase (BOD). The CMC increased the accessibility of the mesopores of the MgOC, and subsequently, the performance of both the bioanode and biocathode. CMC also likely increased the stability of the electrodes. The pre-modification with bilirubin improved the orientation of the BOD, which facilitated direct electron transfer. With these two steps, an open circuit potential of 0.65 V, a maximal current density of 1.94 mA cm−2, and a maximal power density of 465 μW cm−2 was achieved with lactate oxidase as bioanode enzyme and lactate as fuel. This is one of the highest reported performances for a biofuel cell.

High-resolution patterning of silica nanoparticle-based ionogels by reverse-offset printing and its characterization

In this study, nanoparticle-based, high-resolution patternable ionogels are presented to provide a route for realizing printed solid-state ionic devices. By incorporating an ionic liquid (IL) into a spherical silica nanoparticle suspension, a quasi-solid ionogel layer compatible with reverse-offset printing (ROP) with a spatial resolution of approximately 5 μm was realized. In situ near-infrared (NIR) spectroscopic analysis revealed the drying kinetics of the ionogel ink during printing, and a temporal margin for successful patterning in relation to its dry state was provided. In contrast to polymer-based gels, the present ionogel can be regarded as a porous medium of silica filled with ionic liquids with a certain degree of saturation. By optimizing the ink formulations, ROP patterning was successful for saturation up to 102%, indicating the nanoscale pores between silica nanoparticles can be fully used as an ion-conductive phase in the proposed patternable gel. The conductivity depends drastically on saturation, with a saturation exponent of approximately −7 according to Archie’s law. From a complementary scratch test, an ionogel at a saturated condition still exhibited fragile but solid-like characteristics. As a demonstration, planar micro-supercapacitors fully printed with reverse-offset printable ionogel and carbon inks were fabricated. A comparison with a drop-casted IL showing a similar capacitance indicates a limited ability of the carbon nanoparticle material used here, while a relatively high resistance of the silica-nanoparticle-based ionogel hinders a fast cyclic voltammetry response.

(Digital Presentation) Printed Wearable Electrochemical Sensor for Monitoring Human Performance Markers during Human Spaceflight

Additive manufacturing technologies are being explored by NASA for the in-space manufacturing of sensors and electronics. Additive manufacturing directly addresses the logistic challenge for long-duration human spaceflight missions while also offering a high degree of customization and tailorability. To ensure the health and safety of crew members during long duration missions, it can be advantageous to develop human health diagnostic tools that can be manufactured during those missions. Here we report the development of a wearable and fully printed electrochemical sensor for the detection of human performance markers in sweat.1 The sensor’s fabrication is complimentary with in-space manufacturing for an on-demand and hands-free fabrication and is comprised of commercial and custom carbon, gold and silver inks on a polyimide substrate to make a flexible, 3-electrode electrochemical sensor, shown in Figure 1. Sensor readout is performed using standard electrochemical procedures via a miniaturized, custom potentiostat. The initial prototyped printed electrochemical sensors demonstrate good electrochemical performance and high mechanical stability while also displaying low batch to batch variability. Our goal is to create a highly adaptable and versatile approach that utilizes fabrication processes consistent with in-space manufacturing, thus enabling the manufacture of point-of-care devices during flight.Reference Brasier, N. & Eckstein, J. Sweat as a Source of Next-Generation Digital Biomarkers. Digit. Biomarkers 3, 155–165 (2019). Figure 1

Performance improvements for the all-copper redox flow battery: Membranes, electrodes, and electrolytes

The ever-increasing demand for renewable energy storage has led to the development of many energy storage systems, such as redox flow batteries (RFBs), including vanadium, iron–chromium, and the copper redox flow battery (CuRFB). A multitude of materials and electrolytes have been investigated to improve the performance of the CuRFB using an in-house manufactured cell. Using carbon ink coatings for the negative electrode and modern ion exchange membranes (IEMs), this version of the CuRFB was improved to current efficiencies above 95% with high voltage efficiencies of up to 81%, thereby improving energy efficiency by nearly 9% over the previous state of the art at 20 mA cm−2. Additionally, the operating time of the CuRFB was significantly extended over 210 h of operation (50 cycles), 32% of the capacity remaining, without maintenance. Finally, stability of the new system with modern IEMs was proven by operation for over 1200 h operation, with over 300 charge and discharge cycles performed.

Screen-printed advanced all-solid-state symmetric supercapacitor using activated carbon on flexible nickel foam

There is an urgent demand to develop an all-solid-state flexible supercapacitor for portable digital products, screen printing technology is deemed a valid way. However, it still faces challenges including the use of printed substrate and low specific capacitance caused by printing. In this paper, a new route for the fabrication of advanced all-solid-state symmetric supercapacitors (SSC) via screen-printing is demonstrated. The mesoporous activated carbon (AC) inks are prepared to fabricate electrodes, while their performances as well as the printing parameter i.e. stencil meshes are investigated carefully. Surprisingly, the optimal screen-printed electrode shows an enhanced specific capacitance (159.0 F/g at a current density of 1 A/g with a retention rate of 98.2 % after 5000 cycles at 10 A/g) than that of electrodes made by the smearing method (139.8 F/g with a retention rate of 76.1 %). This improvement can be ascribed to the orderly aligned activated carbon after the shearing interaction in the process of screen-printing. Furthermore, flexible and porous nickel foam is served as a printed substrate and current collector, and the SSC with an interdigital pattern is assembled coating with KOH/PVA gel electrolyte, which can deliver a remarkable areal energy density of 64.8 μWh/cm2 at a power density of 0.2 mW/cm2. Notably, a red lamp (2.5 V) can be lightened up by SSC in series and sustained for more than 300 s. Therefore, this paper paves a new way for the facile fabrication of screen-printed energy storage devices.

Self-Powered Carbon Ink/Filter Paper Flexible Humidity Sensor Based on Moisture-Induced Voltage Generation.

Cellulose paper-based materials are highly flexible, hydrophilic, low-cost, and environmentally friendly and are good substrates for use as humidity sensors. Therefore, developing a paper-based humidity sensor with facile fabrication, low cost, and high sensitivity is important for expanding its practical applications. Herein, we propose a CI/FP self-powered humidity sensor based on everyday items such as writing and drawing carbon ink (CI), cellulose filter paper (FP), and polyester conductive adhesive tape, which is fabricated with the help of facile dip-coating and pasting methods. This sensor is self-powered, and the paper-based material itself can absorb water molecules in a humid environment to generate humidity-related voltage and current, which can indirectly reflect the ambient humidity level. They are characterized by a wide relative humidity (RH) sensing range (11-98%), good linearity (R2 = 0.97011), high response voltage (0.19 V), and excellent flexibility (over 1000 bends). This humidity sensor can be successfully applied to monitor human health (breathing, coughing), air humidity, and noncontact humidity sensing (skin, wet objects). This work not only proposes a low-cost and facile method for flexible humidity sensors but also provides a valuable strategy for the development of self-powered wearable electronics.

Bio-acceptability of wearable sensors: a mechanistic study towards evaluating ionic leaching induced cellular inflammation

The recent need for remote health wellness monitoring has led to the extensive use of wearable sensors. Owing to their increased use, these sensors are required to exhibit both functionality and safety to the user. A major component in the fabrication of these sensors and their associated circuitry is the use of metallic/organic conductive inks. However, very less is known about the interfacial and molecular interactions of these inks with biological matter as they can result in an inflammatory reaction to the user. Significant efforts are thus needed to explore and improve the bio-acceptability of such conductive ink-based wearable sensors. The present study investigates the biocompatibility of encapsulated and non-encapsulated wearable electrochemical sensors used for sensing uric acid as a biomarker for wound healing fabricated using screen-printing technique. Ionic release of metallic ions was investigated first to understand the susceptibility of the conductive inks towards ionic leaching when in contact with a fluid. Time-lapse investigation using ICPS (inductive couple plasma spectroscopy) shows a high concentration (607.31 ppb) of leached silver (Ag+) ions from the non-encapsulated sensors. The cell viability data suggests a 2.5-fold improvement in the sensor biocompatibility for an encapsulated sensor. While the carbon ink shows negligible effect on cell viability, the silver ink elicits significant decrease (< 50%) in cell viability at concentrations higher than 2 mg ml-1. The toxicity pathway of these sensors was further determined to be through the generation of reactive oxygen species resulting in over 20% apoptotic cell death. Our results show that the lower biocompatibility of the non-encapsulated sensor attributes to the higher leaching of Ag+ ions from the printed inks which elicits several different inflammatory pathways. This work highlights the importance biocompatibility evaluation of the material used in sensor fabrication to develop safe and sustainable sensors for long-term applications.

Fabrication of High-Density Vertical Closed Bipolar Electrode Arrays by Carbon Paste Filling Method for Two-Dimensional Chemical Imaging.

In this study, a carbon paste filling method was proposed as a simple strategy for fabricating high-density bipolar electrode (BPE) arrays for bipolar electrochemical microscopy (BEM). High spatiotemporal resolution imaging was achieved using the fabricated BPE array. BEM, which is an emerging microscopic system in recent years, achieves label-free and high spatiotemporal resolution imaging of molecular distributions using high-density BPE arrays and electrochemiluminescence (ECL) signals. We devised a simple method to fabricate a BPE array by filling a porous plate with carbon paste and succeeded in fabricating a high-density BPE array (15 μm pitch). After a detailed observation of the surface of the BPE array using a scanning electron microscope, the basic electrochemical and ECL emission characteristics were evaluated using potassium ferricyanide solution as a sample solution. Moreover, inflow imaging of the sample molecules was conducted to evaluate the imaging ability of the prepared BPE array. In addition, Prussian Blue containing carbon ink was applied to the sample solution side of the BPE array to provide catalytic activity to hydrogen peroxide, and the quantification and inflow imaging of hydrogen peroxide by ECL signals was achieved. This simple fabrication method of the BPE array can accelerate the research and development of BEM. Furthermore, hydrogen peroxide imaging by BEM is an important milestone for achieving bioimaging with high spatiotemporal resolution such as biomolecule imaging using enzymes.

Synthesis and characterization of ambient-processed FTO/ZnO/CsPbBr2Cl/C perovskite solar cell deposited by SILAR method

In the present study, for the very first time, an HTL-free perovskite solar cell (PSC) FTO/ZnO/CsPbBr2Cl/C was fabricated via successive ionic layer adsorption and reaction methods (SILAR) under an ambient atmosphere. Each layer of synthesized PSC was characterized by various sophisticated techniques like UV–Visible spectroscopy (UV–Vis), Photoluminescence spectroscopy (PL), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-Ray spectroscopy (EDX), and Field emission electron microscopy (FESEM). We explored the optical, morphological, and electrical behavior of the ZnO and CsPbBr2Cl layer of PSC. The p-type conductivity with charge carrier concentration of 1.1E+17 cm−3 and carrier mobility of 9.0 cm2V−1s−1 of CsPbBr2Cl has been observed. To reduce the cost of the device, the counter carbon electrode was prepared by an extremely cost-effective method by reusing the carbon from a used battery and converting it into a conducting carbon ink. The ambient processed cell-FTO/ZnO/CsPbBr2Cl/C achieved an average efficiency of 0.41%. Further, a theoretical study was performed to find a mechanism for enhancing the efficiency of fabricated PSC. It was observed that an optimized device can exhibit an enhanced efficiency of 4.53% by controlling the defect density and series resistance of the device. This study demonstrates a low-cost fabrication of HTL-free CsPbBr2Cl-based PSC processed under ambient air for their potential in the field of optoelectronic devices.

Evaluation of Activated Carbon and Platinum Black as High-Capacitance Materials for Platinum Electrodes

The application of direct current (DC) produces a rapid and reversible nerve conduction block. However, prolonged injection of charge through a smooth platinum electrode has been found to cause damage to nervous tissue. This damage can be mitigated by incorporating high-capacitance materials (HCM) (e.g., activated carbon or platinum black) into electrode designs. HCMs increase the storage charge capacity (i.e., “Q value”) of capacitive devices. However, consecutive use of these HCM electrodes degrades their surface. This paper evaluates activated carbon and platinum black (PtB) electrode designs in vitro to determine the design parameters which improve surface stability of the HCMs. Electrode designs with activated carbon and PtB concentrations were stressed using soak, bend and vibration testing to simulate destructive in vivo environments. A Q value decrease represented the decreased stability of the electrode–HCM interface. Soak test results supported the long-term Q value stabilization (mean = 44.3 days) of HCM electrodes, and both HCMs displayed unique Q value changes in response to soaking. HCM material choices, Carbon Ink volume, and application of Nafion™ affected an electrode’s ability to resist Q value degradation. These results will contribute to future developments of HCM electrodes designed for extended DC application for in vivo nerve conduction block.

120P AXSANA (AXillary Surgery After NeoAdjuvant Treatment) EUBREAST-3: An international prospective multicenter cohort study to evaluate different surgical methods of axillary staging in clinically node-positive breast cancer patients treated with neoadjuvant chemotherapy (NCT04373655)

The surgical staging procedure of the axilla in patients who convert from clinically positive (cN+) to clinically negative node status (ycN0) through neoadjuvant chemotherapy is still controversial. Different techniques such as Axillary Lymph Node Dissection (ALND), Targeted Axillary Dissection (TAD), Target Lymph Node Biopsy (TLNB) and Sentinel Lymph Node Biopsy (SLNB) are recommended by the national and international guidelines. In case of TAD and TLNB, the target lymph node can be marked using such markers as clip/coil, carbon ink, magnetic or radioactive seed, or a radar or radiofrequency marker.

Removal of Mist Particles by a Two-Stage Electrostatic Precipitator Featuring Plastic Plate Electrodes

To reduce corrosion, cost, and weight, we developed a nonmetallic, two-stage electrostatic precipitator (ESP) using electrodes fabricated from carbon ink and polyethylene terephthalate (a plastic), rather than expensive corrosion-resistant metals. Five collection modules were manufactured; we varied the materials used to fabricate the high-voltage and ground electrodes. The plate-type electrodes of the collection module were made of stainless steel, carbon-coated plastic (CPC), or plastic-coated carbon (PCP). Particle removal performance was investigated by the voltages of the precharger and collection modules, the particle diameter, the airflow rate, and the particle collection area. The particles were an oil mist. The electrode material had little effect on particle removal performance. The experimental performances of two-stage ESPs featuring plastic and carbon plate electrodes met the theoretical efficiencies predicted by the Deutsch equation and Cochet charging theory. Although fluttering developed when the flow velocity exceeded 2 m&#x002F;s over CPC electrodes, the use of PCP electrodes (the rigidity of which was reinforced by the plastic coatings) eliminated fluttering. Moreover, in an extremely humid condition where the water vapor continuously condensed into water droplets, the polyethylene terephthalate film of the PCP electrode ensured stable operation without spark regardless of humidity or water droplets on the surface. In summary, plastic electrodes were light and economical, while affording high removal efficiencies similar to the removal efficiencies of metals. Moreover, the PCP electrode plastic coating protected the carbon ink from abrasion and corrosion.

Different approaches for fabrication of low-cost electrochemical sensors

Electrochemistry combined with economical and sustainable platforms (such as paper) provides portable, affordable, robust, and user-friendly devices. In general, techniques, such as photolithography and sputtering, are excellent alternatives for producing these platforms. However, owing to the requirement of expensive and sophisticated instrumentation, as well as cleanroom facilities, these techniques have limited access. Thus, the search for easy to use and produce approaches have been reported, using consumables, including adhesives, carbon ink, graphite, pencil, office paper, paperboard, among others. In this sense, in this mini-review, we discuss various strategies explored to fabricate low-cost electrochemical sensors, including its main applications. Different manufacturing methods, such as screen and stencil printing, laser-scribing, and pencil drawing, will be discussed here, emphasizing the performance of the obtained devices, in addition to their advantages and disadvantages. • Low-cost materials can be used in the production of versatile disposable sensors. • Technical discussions focus on different parameters of electrode production that must take into account. • Three simple and practical techniques are discussed in detail, encouraging point-of-care approaches.

Impacts of plasmonic nanoparticles incorporation and interface energy alignment for highly efficient carbon-based perovskite solar cells

This work utilizes a realistic electro-optical coupled simulation to study the (i) impact of mesoporous TiO2 removal; (ii) the embedding of Ag@SiO2 and SiO2@Ag@SiO2 plasmonic nanoparticles; (iii) utilization of solution-processed inorganic p-type copper(I) thiocyanate (CuSCN) layer at the perovskite/carbon interface; and (iv) the increase of the work function of carbon electrodes (via incorporation of suitable additives/binders to the carbon ink) on the performance of carbon-based PSCs. Removal of mesoporous TiO2 increased the power conversion efficiency (PCE) of the device from 14.83 to 16.50% due to the increase in exciton generation rate and charge carriers’ mobility in the vicinity of the perovskite-compact TiO2 interface. Subsequently, variable mass ratios of Ag@SiO2 and SiO2@Ag@SiO2 plasmonic nanoparticles are embedded in the vicinity of the perovskite-compact TiO2 interface. In the optimum cases, the PCE of the devices increased to 19.72% and 18.92%, respectively, due to light trapping, scattering, and strong plasmonic fields produced by the plasmonic nanoparticles. Furthermore, adding the CuSCN layer remarkably increased the PCE of the device with a 0.93% mass ratio of Ag@SiO2 nanoparticles from 19.72 to 26.58% by a significant improvement of Voc and FF, due to the proper interfacial energy band alignment and the reduction of the recombination current density. Similar results were obtained by increasing the carbon work function, and the cell PCE was enhanced up to 26% in the optimal scenario. Our results pave the way to achieve high efficiencies in remarkably stable printable carbon-based PSCs.

Lab-on-cloth integrated with a photoelectrochemical cell and ion imprinting for point-of-care testing of Hg(Ⅱ)

In this work, we successfully developed a cloth-based device integrated with a photoelectrochemical (PEC) cell and ion imprinting for point-of-care testing (POCT) of divalent mercury ions (Hg(Ⅱ)). PEC cells have increasingly emerged as promising power supply units in recent years. The CdS/ZnS core-shell quantum dots (QDs) are used in the PEC cell, because they improve the spatial separation and transfer of charge and broaden the absorption of visible light. Ion imprinting can identify a specific metal ion selectively in the presence of other interfering ions. To achieve noninterference identification, the QDs-based PEC cell region is isolated from the ion imprinting-based detection area. In addition, wax screen-printing can be used in conjunction with carbon ink screen-printing for economical and facile fabrication of cloth-based devices. Under optimized conditions, Hg(Ⅱ) can be determined over the range of 0.0005–5 mg/L, with a detection limit of 0.090 µg/L (i.e., 0.45 nM). The proposed cloth-based devices are also applied successfully for the detection of Hg(Ⅱ) in sweat, complex water and food samples, with recoveries of 98.2–116.1% and relative standard deviations (RSDs) of 1.2–13.9%. Additionally, cloth-based devices have acceptable storage stability and selectivity. Therefore, the presented method offers a sensitive, low-cost, portable POCT device and has the potential to be applied for human body, environmental and food monitoring in remote areas and developing or industrialized countries.

A new disposable electrochemical sensor for the individual and simultaneous determination of carbamate pesticides using a nanocomposite modified screen-printed electrode

In this work, we developed a disposable electrochemical sensor with improved sensitivity for the individual and simultaneous detection of carbaryl (CBR), fenobucarb (FNB), and carbosulfan (CBS) pesticides. The device used a screen-printed carbon electrode (SPCE) modified with a nanocomposite comprising manganese dioxide nanoparticles (MnO2) and graphene nanoplatelets (GNPs). We prepared the MnO2-GNPs nanocomposite by an in-situ growth method. The product was characterized by X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The disposable sensor was fabricated by inhouse-printing using only carbon ink on inexpensive transparency paper. We investigated the electrochemical performance of the developed sensor by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The MnO2 and GNPs nanocomposite shows the highest electrocatalytic activity toward the oxidation of carbamate when in its phenol form. Under the optimized experimental conditions, the proposed strategy possess a good linear response of the disposable sensor for the individual determination of CBR, FNB and CBS in the concentration range of 1-40 μM, 5-150 μM and 50-600 μM with the low detection limit of 0.30 μM, 1.30 μM, 14.90 μM, respectively. Besides, the analytical performance of the proposed sensor for the simultaneous detection of CBR, FNB, and CBS exhibits a linear response in ranges of 1–30 µM, 5–80 µM, and 50–400 µM, with the limit of detection being 0.30, 1.40, and 15.15 µM, respectively. In addition, the sensor displays high reproducibility, repeatability, and good selectivity. The electrode simultaneously applied to determine the three carbamate residues in Jasmine rice and rice-field water samples. This developed electrochemical sensor is a promising high-sensitivity tool for fast, easy-to-use, low-cost electrochemical detection of multi-pesticide residues in agricultural samples.

Low-cost digital microfluidic approach on thin and pliable polymer films

A digital microfluidic device fabricated with a thin and pliable polyester film is reported with control by a custom-made battery-powered high voltage amplification circuit. Droplet movement on the tilt or curved surface was achieved. A low-cost approach for the fabrication of digital microfluidic device was used: the electrodes on the digital microfluidic device were fabricated with conductive carbon ink screen-printed on a polyester substrate, a layer of thin polyethylene film was used to seal and insulate the electrodes, and a layer of water repellent was coated on the surface of polyethylene film to enhance the hydrophobicity. The device is transparent and pliable, with a total thickness of approximately 70 μm. The controlled droplet movement on the curved polymer surface based on electrowetting was achieved with the compact voltage amplification circuit and the corresponding control algorithm. The fabrication for the proposed digital microfluidic device is low-cost and without sophisticated microfabrication instrumentation. Furthermore, the system is portable and may have widespread point-of-care in biological and medical applications.