Electrode Chip Research Articles

Robust Bioengineered Apoferritin Nanoprobes for Ultrasensitive Detection of Infectious Pancreatic Necrosis Virus.

Infectious pancreatic necrosis virus (IPNV) has been identified as a viral pathogen for many fish diseases that have become a huge hurdle for the growing fishing industry. Thus, in this work, we report a label-free impedance biosensor to quantify IPNV in real fish samples at point-of-care (POC) level. High specificity IPNV sensor with a detection limit of 2.69 TCID50/mL was achieved by conjugating IPNV antibodies to portable Au disk electrode chips using human heavy chain apoferritin (H-AFN) nanoprobes as a binding agent. H-AFN probes were bioengineered through PCR by incorporating pET-28b(+) resulting in 24 subunits of 6 × his-tag and protein-G units on its outer surface to increase the sensitivity of the IPNV detection. The biosensor surface modifications were characterized by differential pulse voltammetry (DPV) and EIS methods for each modification step. The proposed nanoprobe based sensor showed three-fold enhancement in charge transfer resistance toward IPNV detection in comparison with the traditional linker approach when measured in a group of similar virus molecules. The portable sensor exhibited a linear range of 100-10000 TCID50/mL and sensitivity of 5.40 × 10-4 TCID50/mL in real-fish samples. The performance of the proposed IPNV sensor was fully validated using an enzyme-linked immunosorbent assay (ELISA) technique with a sensitivity of 3.02 × 10-4 TCID50/mL. Results from H-AFN nanoprobe based IPNV sensor indicated high selectivity, sensitivity, and stability could be a promising platform for the detection of similar fish viruses and other biological molecules of interest.

Tantalum/ Nitrogen and n-type WO3 semiconductor/FTO structures as a cathode for the future of nano devices

In the last decades an important number of research papers published on nano chip electrode and cathode electrochromic materials. Tantalum (Ta) with so high melting point can be as a good candidate for the future of nano chip devices. However, its surface has not enough trap centers and/or occupation states, so nitrogen ions exposed on Ta surafce, may solve this problem. For this purpose, in the present work, samples of tantalum with purities of 99.99% (0.58 mm thickness) were implanted by nitrogen ions. The ions’ implantation process was performed at 30 keV and also at different doses which were in the range between 1017- 1018 ions/cm2. The electrical, nano structural characteristics, sample surface topography characteristic were investigated on Tantalum nitrides (Ta/N) structures by looking at current–voltage (I–V) curves.In addition to Ta/N, WO3powders as a famous EC metal oxide, a silver metal deposited on fluorine doped tin oxide (FTO)-coated glass andmultilayer structure with using the physical vapor deposition (PVD) apparatus are formed. Some techniques such as uv- visible, Atomic Force Microscopy (AFM) and X Ray Diffraction (XRD) have been used. The obtained results show the formation of hexagonal tantalum nitride (TaN0.43), and more trap centers of sample surface (in comparison to current cathode material of EC device). The electrical resistivity of the tantalum after nitrogen implantation is also found to increase with ion doses.Therefore, Ta/N with more trap centers (rough surface) can be suggested as a good element of the future of EC and nano devices.

Palladium-Gold Modified Ultramicro Interdigital Array Electrode Chip for Nitrate Detection in Neutral Water.

An ultramicro interdigital array electrode modified by palladium-gold was developed for nitrate detection in neutral water. The ultramicro interdigital array electrode was fabricated based on silicon substrate by Micro Electro-Mechanical System (MEMS) technique. The nanostructured palladium-gold (Pd-AuNPs) composite sensing film was electrodeposited on the surface of a working electrode by electrochemical method. The synergistic effect of Pd-AuNPs composite was investigated and its enhancement of the catalytic activity and stability was revealed. The Pd-AuNPs modified electrode showed good linearity (R2 = 0.99) from 1 mg/L to 15 mg/L (as N) for nitrate determination in a neutral water environment (pH = 7.2), with a sensitivity of 4.7 μA·mg−1·L. The results showed that the developed Pd-AuNPs-modified ultramicro interdigital array electrode chip can achieve sensitive and environmentally-friendly detection for nitrate in neutral water.

Bipolar electrode-electrochemiluminescence (ECL) biosensor based on a hybridization chain reaction.

A novel electrochemiluminescence (ECL) closed bipolar electrode (BPE) chip was designed based on a hybridization chain reaction (HCR)-induced ECL amplification strategy for the detection of both DNA and H2O2. Without the utilization of a patterned ITO bipolar electrode (BPE), this chip platform consisted of an ITO glass coated with two layers of PDMS slices. The ITO cathode was modified with Au nanoparticles for further functionalization of biomolecules, which could also amplify the ECL signal at the anode of the BPE. Based on the specific hybridization and hybridization chain reaction (HCR), DNA sequences were greatly extended, leading to a significant increase in the resistance of the cathode. The reduction of H2O2 was inhibited on the cathode of the BPE, resulting in a quenching effect on the ECL intensity on the anode of the BPE. The designed biosensor displayed a satisfactory linear relationship for the detection of both DNA and H2O2. Therefore, the biosensor could not only be employed for DNA assays but also used in enzyme reactions based on the generation of H2O2.

Robustness Improvement of Thermosonic Flip Chip Bonding to Device Chip Tilt

In this paper, we describe the robustness of thermosonic flip chip bonding when the bottom chip is tilted in the chip-on-chip assembly. Experiments were carried out using a bottom chip with 12 Au ball bumps and a top chip with Al pads. A bonding condition that causes gross sliding at the bonding interface was chosen to improve the robustness to chip tilt. The bottom chip was tilted around the axis perpendicular to the direction of the ultrasonic vibration. We found that die-shear force and the sum of the contact area between bumps and the top chip electrodes were constant in spite of tilting of the bottom chip. Although the contact area between each bump and top chip electrode depended on different bonding forces generated by bottom chip tilting, the fractional area of Au-Al alloy of each bonding area became nearly equal. These were caused by the deformation stress of the gold ball bump under the application ofultrasonic vibration being constant in the deformation range in this study.

Picomolar detection of retinol binding protein 4 for early management of type II diabetes

Type (II) diabetes is one of the major threats to mankind as it causes insulin resistance in human body and Retinol Binding Protein 4 (RBP4) is currently considered as a potential biomarker for early management of this disease. Hence a low-level detection of RBP4 is a very important task and for this purpose, a novel RBP4 biosensor has been developed using homemade plastic chip electrodes (PCEs) as a platform for self-assembled monolayer (SAM) of 4-ATP and further functionalization with glutaraldehyde. Anti RBP4 is used as biorecognition species and electrochemical impedance spectroscopy has been performed to detect different RBP4 concentrations plotted against charge transfer resistance. A wide concentration range from 100 fg/mL to 1 ng/mL has been tested and a low limit of detection (LOD) of 100 fg/mL has been achieved. This is the first report for fabrication of electrochemical biosensor of RBP4 using Ag-Ab interaction having such low LOD. The sensor is characterized by various physico-chemical techniques. Excellent reproducibility and quick measurement make this biosensor extremely useful for the biomedical industry.

Microfluidic electrochemical immunosensor for the trace analysis of cocaine in water and body fluids.

Quick but accurate testing and on-the-spot monitoring of cocaine in oral fluids and urine continues to be an important toxicological issue. In terms of drug testing, a number of devices have been introduced into the market in recent decades, notably for workplace inspection or roadside testing. However, these systems do not always fulfill the requirements in terms of reliability, especially when low cut-off levels are required. With respect to surface water, the presence of anthropogenic small organic molecules such as prescription and over-the-counter pharmaceuticals as well as illicit drugs like cannabinoids, heroin, or cocaine, has become a challenge for scientists to develop new analytical tools for screening and on-site analysis because many of them serve as markers for anthropogenic input and consumer behavior. Here, a modular approach for the detection of cocaine is presented, integrating an electrochemical enzyme-linked immunosorbent assay (ELISA) performed on antibody-grafted magnetic beads in a hybrid microfluidic sensor utilizing flexible tubing, static chip and screen-printed electrode (SPE) elements for incubation, recognition, and cyclic voltammetry measurements. A linear response of the sensor vs. the logarithm of cocaine concentration was obtained with a limit of detection of 0.15ng/L. Within an overall assay time of 25minutes, concentrations down to 1ng/L could be reliably determined in water, oral fluids, and urine, the system possessing a dynamic working range up to 1mg/L.

Fabrication and H2-Sensing Properties of SnO2 Nanosheet Gas Sensors.

Vertically formed and well-defined SnO2 nanosheets are easy to fabricate, involving only a single process that is performed under moderate conditions. In this study, two different sizes of a SnO2 nanosheet were concurrently formed on a Pt interdigitated electrode chip, with interconnections between the two. As the SnO2 nanosheets were grown over time, the interconnections became stronger. The ability of the fabricated SnO2 nanosheets to sense H2 gas was evaluated in terms of the variation in their resistance. The resistance of a SnO2 nanosheet decreased with the introduction of H2 gas and returned to its initial level after the H2 gas was replaced with air. Also, the response–recovery behaviors were improved as a result of the growth of the SnO2 nanosheets owing to the presence of many reaction sites and strong interconnections, which may provide multipassages for the electron transfer channel, leading to the acceleration of the reaction between the H2 gas and SnO2 nanosheets.

Evaluating Nonlinear Impedance Excitation as Detection Method for Biosensors

Chemical and microbial contamination of natural water supplies is one of the biggest challenges faced by developing nations, especially communities in rural areas. An estimated 1.6 million children die each year due to water-related deaths. Low-cost, portable, and point-of-use biosensors are required to monitor water quality and improve living standards. This paper investigates the possibility of developing a biosensor using a nonlinear impedance spectroscope (NLIS) and low-cost patterned platinum and titanium electrode chips. Divalent (Mg $^{2+}$ ) and monovalent (Cl $^-$ , Na $^+$ , and K $^+$ ) ions, and Escherichia coli strain B44 served as targets. The NLIS was set at a high excitation voltage and a fixed frequency. The spectra were imaged using a low-cost desktop audio interface and a computer. Electrical characteristics were optimized for the sensor, and the detection setup carefully defined. As little as 0.1 mg/ml NaCl and as few as $10^{11}$ cells of E. coli per milliliter were detected in less than 4 min. The sensitivity of the method was demonstrated by recording different electrochemical patterns for cells of E. coli treated with ethanol and for cells killed by heat. These findings form the basis of developing a cost-effective biosensor to detect changes in ion levels and bacterial cell numbers, and record the electrical activity (metabolic state) of bacterial cells. Apart from testing water quality, the biosensor may also be used to determine the microbial load in food and beverages.

Genomagnetic LAMP-based electrochemical test for determination of high-risk HPV16 and HPV18 in clinical samples

Major cause of cervical cancer is a persistent infection with high-risk types of human papillomaviruses (HPV). For that reason, HPV testing is now becoming an important addition to standard cytological screening of cervical malignancies in women (known as Pap test). New methods are sought which could offer rapid and inexpensive detection schemes, such as those based on electrochemical (EC) readout. Here, we developed an assay for parallel detection of two most oncogenic high-risk HPV types, HPV16 and HPV18, by combining loop-mediated amplification (LAMP) of template DNA, its separation using magnetic beads and detection with amperometry at carbon-based electrode chips. Our EC-LAMP test enabled us to successfully discriminate both HPV types not only in cancer cell lines, but also using clinical material obtained from HPV-positive patient samples.

Particle precipitation by bipolar corona discharge ion winds

The paper reports the development of a particle precipitation based aerosol sampler using bipolar corona discharge ion winds with collected particles of minimized net charge. For the new approach, neutralized particles move towards a sampler under the effect of electric field and dual ion winds. Since there is no electrode or sampling chip installed inside the air-flow channel, impediments to airborne particle flow or ion winds are removed along the flow direction. In addition, the isolation of ion winds, which generate circuit, allows using various materials for the sampling chip including non-conductors and also protecting collected particles from any discharge ignition on the chip. The device mechanism is numerically simulated in OpenFOAM to study the electrofluidodynamic interaction of charged particles and bipolar ion winds. The efficiency of the new approach has been investigated by experiment with a maximum efficiency of 94%. The effects of flow rate, discharge voltage and electrode distances on the method are also evaluated.

NiO hollow microspheres as efficient bifunctional electrocatalysts for Overall Water-Splitting

Development of efficient, earth-abundant and low-cost electrocatalyst for effective water electrolysis is highly demanding for production of sustainable hydrogen energy. In this paper, we report the cost-effective synthetic protocol for porous NiO hollow spheres in large scale through a simple spray drying strategy, using aqueous nickel ammonium carbonate complex solution, followed by calcination. The synthesized NiO hollow spheres calcined at 300 °C (NiO-300) are porous, made of nanoparticles in size range of 10–16 nm with a size range of 2.5–4 μm and total surface area of 120 m2/g. The NiO-300 exhibited excellent bifunctional electrocatalytic water splitting characteristic, both OER, and HER, in basic solution. NiO-300 modified glassy carbon electrode showed superior water electrolysis kinetics and to achieve 10 mA cm−2 current density, it required 370 mV overpotential for OER and 424 mV overpotential for HER in 1 M KOH. It is also worked well with cost-effective plastic chip electrode. An assembled two-electrode system by pairing NiO modified plastic chip electrode as both anode and cathode in a 1.0 M KOH electrolyte for overall water splitting exhibit clear bubble formation at 1.6 V potential.

Micropatterned Carbon-on-Quartz Electrode Chips for Photocurrent Generation from Thylakoid Membranes

Harvesting the energy generated by photosynthetic organisms through light-dependent reactions is a significant step toward a sustainable future energy supply. Thylakoid membranes are the site of photosynthesis, and thus particularly suited for developing photo-bioelectrochemical cells. Novel electrode materials and geometries could potentially improve the efficiency of energy harvesting using thylakoid membranes. For commercial applications, electrodes with large surface areas are needed. Photolithographic patterning of a photoresist, followed by pyrolysis, is a flexible and fast approach for the fabrication of carbon electrodes with tailored properties. In this work, electrode chips consisting of patterned carbon supported on quartz were designed and fabricated. The patterned electrode area is 1 cm2, and the measurement chamber footprint is 0.5 cm2, 1 order of magnitude larger than previously tested electrodes for thylakoid membrane immobilization. The use of a transparent substrate allows back-side illu...

Design, fabrication and performance evaluation of a printed-circuit-board microfluidic electrolytic pump for lab-on-a-chip devices

We report for the first time an electrolytic micropump based on an electrode chip fabricated on a printed circuit board (PCB), and compare its performance with that of a micropump based on an electrode chip fabricated using conventional microfabrication. Gold interdigitated (IDT) electrodes are patterned on a PCB to minimize ohmic loss during electrolysis. Custom-built acrylic fixtures are used to characterize pumping performance of various electrode chips with different electrode shapes and materials. Hydrogen and oxygen gas bubbles produced by electrolysis generate liquid flow inside a microchannel. As predicted by the theory of water electrolysis, the micropump produces flow rate increasing linearly with current at a wide range (1 mA–2 A). Our micropump yields the maximum flow rate of 31.6 ml/min and maximum backpressure of 547 kPa (at 34 μl/min), significantly high compared with the previous micropumps based on various actuation mechanisms including piezoelectric actuation, electroosmosis and phase change. The PCB-based micropump with a thick electroplated-gold electrode (0.43 μm) chip shows the overall best performance in terms of flow generation, power consumption and cost, compared with the PCB-based pump using an thin electroless-gold electrode (0.04 μm) and the pump using a microfabricated chip with a sputtered gold electrode (0.2 μm). We anticipate the PCB-based electrolysis pump will be used in portable lab-on-a-chip devices where an integrated microscale pressure source with low power consumption and simple fabrication is crucial.

Electrochemical immunosensor for highly sensitive and quantitative detection of tumor necrosis factor-α in human serum

Highly sensitive and selective biosensors for accurate determination of specific protein biomarkers at low levels in serum are a prerequisite for the present healthcare systems. Therefore, here we developed a label-free impedimetric method for tumor necrosis factor-alpha (TNF-α) detection using reduced graphene oxide (RGO) with gold nanoparticles (AuNP) on an indium tin oxide (ITO) microdisk electrodes. The detection mechanism relies on resistance change occurs due to [Fe(CN)6]3−/4− redox probe movement towards the conductive channels of the AuNP-RGO films gated by the recognition of the target biomarker by its anti-TNF-α antibody. The conductivity of the AuNP-RGO structures enhanced by 10-fold in comparison with bare electrode chips. The observed resistance changes at 2Hz (ΔR at 2Hz) enabled the quantification of various concentrations of TNF-α in human serum (CHS-TNF-α). The antibody-adsorbed electrode showed a good increment of resistance change (ΔR) with additions of antigen concentration. The sensor possesses a linear range of 1–1000pg/ml had a detection limit of 0.67pg/ml (38.51fM) and 0.78pg/ml (44.83fM) in PBS and human serum, respectively.

Dielectrophoretic Microfluidic Device for in Vitro Fertilization.

The aim of this work was to create a microfluidic platform that uses in vitro fertilization (IVF) and avoids unnecessary damage to oocytes due to the dielectrophoretic force manipulation of the sperms and oocytes that occurs in a traditional IVF operation. The device from this research can serve also to decrease medium volumes, as well as the cost of cell culture under evaporation, and to prevent unnecessary risk in intracytoplasmic sperm injection (ICSI). To decrease the impact and destruction of the oocyte and the sperm, we adopted a positive dielectrophoretic force to manipulate both the sperms and the oocyte. The mouse oocytes were trapped with a positive dielectrophoretic (p-DEP) force by using Indium Tin Oxide (ITO)-glass electrodes; the ITO-glass electrode chip was fabricated by wet etching the ITO-glass. The polydimethylsiloxane (PDMS) flow-focusing microfluidic device was used to generate microdroplets of micrometer size to contain the zygotes. The volume of the microdroplets was controlled by adjusting the flow rates of both inlets for oil and the DEP buffer. As a result, the rate of fertilization was increased by about 5% beyond that of the DEP treatment in traditional IVF, and more than 20% developed to the blastocyst stage with a low sperm-oocyte ratio.

A novel 3D-microstructured multielectrode array configuration for high-yield and high-fidelity electrophysiological recordings

A novel 3D-microstructured multielectrode array configuration for high-yield and high-fidelity electrophysiological recordings

Electrochemical sensor chips for multiple measurements of dissolved oxygen, pH and oxidation-reduction potential in aquacultural farming

Dissolved oxygen (DO), pH and oxidation-reduction potential (ORP) are important parameters of water quality in aquacultural farming and these parameters need to be monitored continuously. In this paper we report fabrication and characterisation of electrochemical sensor chips with pairs of platinum (Pt) electrodes and Ag/AgCl electrodes to measure multiple parameters including DO, pH and ORP with low cost and simple operation. The platinum electrodes were fabricated by lithography, sputtering and lift-off techniques. The fabricated platinum electrodes were used as working and counter electrodes and a silver/silver chloride (Ag/AgCl) was used as a reference electrode. To measure DO, cyclic voltammetry (CV) measurements were performed when the platinum electrodes were dipped in pH buffer solutions as DO levels ranged from 1.5 to 26 ppm. The CV results showed the increase in current related to the reduction peak of oxygen when DO concentration increased. The correlation of the current and DO levels was also determined. The ORP of various electrolyte solutions which have different pH and ORP values was determined by open circuit potential (OCP) measurements. The correlation of OCP values, pH and ORP values was investigated. The stability of ORP values and durability of the fabricated electrodes were also studied. The results exhibited the possibility of using the fabricated electrode chips for multiple measurements of DO, pH and ORP in aquacultural farming.

Regenerable bipolar electrochemiluminescence device using glassy carbon bipolar electrode, stainless steel driving electrode and cold patch

A regenerable bipolar electrochemiluminescence (ECL) device was designed using glassy carbon rod as bipolar electrode (BPE), stainless steel rod as driving electrode, and cold patch for the construction of ECL cell. Two glassy carbon rods linked with a copper wire and two stainless steel rods were embedded perpendicularly into polypropylene slide to make electrode chip. The cheap and commercially available cold patch with a hole can be repeatedly removed and attached to flat electrode chip to form a ECL cell free from solution leakage. The combination of polishable electrode and repeatedly attachable cold patch enables the facile regeneration of bipolar ECL device. Interestingly, the use of stainless steel as driving electrode remarkably reduce background ECL from driving electrode at appropriate voltage probably because of the formation of thick passivation layer. This newly developed bipolar ECL device is simple, cost-effective and its BPE has high conductivity. Based on the advantages above, it is used to detect hydrogen peroxide by luminol ECL using a smart phone as a portable detector. The obtained calibration curve of the proposed method demonstrates a good linearity in the range from 5.0 μmol L−1 to 300 μmol L−1 with a limit of detection of 3.67 μmol L−1 (S/N = 3:1). This device has been successfully employed for the detection of medical hydrogen peroxide solution and displayed excellent recovery.

Investigating the Enhancement of Microfluidics-Based Electrochemical Biosensor Response with Different Microchannel Dimensions

The microfluidics-based electrochemical biosensor (MBEB) is a new approach to laboratory diagnostics that offers many advantages over the conventional bulky and expensive laboratory instruments. Despite its small size and portability, the biosensor requires a specific sample volume to completely cover the detection zone and be analyzed. However, the sample volume for a particular microchannel size is of crucial importance, and the use of an inadequate sample volume results in less accurate measurements, lower sensitivity and increased detection limits. Therefore, this paper investigated the effects of microchannel size on sensor performance. First, microchannels ranging in size from 100- 1000 μm were fabricated, integrated and bonded to an electrode chip. Cyclic voltammetry scans for four different microchannel sizes fabricated for an electrode size of 100 μm were then conducted. The response and sensitivity of the fabricated biosensor increased with increasing microchannel size. The highest sensor sensitivity was observed using a microchannel size of 400 μm, and the response was maximized when a sufficient amount of the target was loaded in the microchannel. However, further increasing the microchannel size decreased the response current of the sensor due to the uncompensated solution resistance, which was considered a minor factor affecting the sensitivity of the sensor. Thus, optimizing the size of the channel is critical for maximizing the sensor performance. Keywords: Microfluidics, electrochemical biosensor, SEM, microchannel, electrodes, cyclic voltammetry.