Bulky Electrode Research Articles

Morphological Evolution of Sn-Metal-Based Anodes for Lithium-Ion Batteries Using Operando X-Ray Imaging.

Sn-based electrodes are promising candidates for next-generation lithium-ion batteries. However, it suffers from deleterious micro-structural deformation as it undergoes drastic volume changes upon lithium insertion and extraction. Progress in designing these materials is limited to complex structures. There is a significant need to develop an alloy-based anode that can be industrially manufactured and offers high reversible capacity. This necessitates a profound understanding of the interplay between structural changes and electrochemical performance. Here, operando X-ray imaging is used to correlate the morphological evolution to electrochemical performance in foil and foam systems. The 3D Sn-foam-like structure electrode is fabricated in-house as a practical approach to accommodate the volume expansion and alleviate the mechanical stress experienced upon alloying/dealloying. Results show that generating pores in Sn electrodes can help manage the volume expansion and mitigate the severe mechanical stress in thick electrodes during alloying/dealloying processes. The foam electrode demonstrates superior electrochemical performance compared to non-porous Sn foil with an equivalent absolute capacity. This work advances the understanding of the real-time morphological evolution of Sn bulky electrodes.

Evaluation of a same-metal PCB-based three-electrode system via impedance studies using potassium ferricyanide.

We report for the first time the successful acquisition of electrochemical impedance spectroscopy data using an unconventional same-metal PCB-based three-electrode system. Conventional three-electrode systems primarily require expensive and bulky electrodes, and a high volume of analytes to conduct electrochemical impedance spectroscopy studies. The miniaturized PCB-based three-electrode system used in this work requires only trace amounts of analytes in the order of 10-20 μL owing to the design of the electrode sensor. Prominent standard redox probe potassium ferricyanide was used for impedance spectroscopic characterization studies. The results obtained were in congruence with existing literature; additionally the PCB-based three-electrode system demonstrated significantly higher repeatability, reproducibility, and consistency across different models of electrochemical instrumentations. Interestingly, the electrochemical impedance spectroscopy data of the PCB-3T sensor exhibited a consistent semi-circular impedance curve on a Nyquist plot and two distinct phase change regions on a Bode plot indicative of a simplified Randles cell model with an excellent circuit fit. Additionally this model provides an accurate impedance model for analysing trace analytes of potassium ferricyanide. Based on the circuit fitting model, potassium ferricyanide samples of varying concentrations at 1 mM, 5 mM, 10 mM, 15 mM and 20 mM demonstrated characteristic EIS charge transfer resistance corresponding to 435, 300, 233, 72 and 55 kΩ, respectively, and solution resistance of 260, 254, 218, 169 and 157 Ω, respectively. Therefore, the proposed novel same-metal three-electrode sensor can be employed in effective analysis and detection of samples with high accuracy and high sensitivity for trace amounts of analytes.

Adhesive free, conformable and washable carbon nanotube fabric electrodes for biosensing

AbstractSkin-mounted wearable electronics are attractive for continuous health monitoring and human-machine interfacing. The commonly used pre-gelled rigid and bulky electrodes cause discomfort and are unsuitable for continuous long-term monitoring applications. Here, we design carbon nanotubes (CNTs)-based electrodes that can be fabricated using different textile manufacturing processes. We propose woven and braided electrode design using CNTs wrapped textile yarns which are highly conformable to skin and measure a high-fidelity electrocardiography (ECG) signal. The skin-electrode impedance analysis revealed size-dependent behavior. To demonstrate outstanding wearability, we designed a seamless knit electrode that can be worn as a bracelet. The designed CNT-based dry electrodes demonstrated record high signal-to-noise ratios and were very stable against motion artifacts. The durability test of the electrodes exhibited robustness to laundering and practicality for reusable and sustainable applications.

Electronic Sensing Platform (ESP) Based on Open-Gate Junction Field-Effect Transistor (OG-JFET) for Life Science Applications: Design, Modeling and Experimental Results.

This paper presents a new field-effect sensor called open-gate junction gate field-effect transistor (OG-JFET) for biosensing applications. The OG-JFET consists of a p-type channel on top of an n-type layer in which the p-type serves as the sensing conductive layer between two ohmic contacted sources and drain electrodes. The structure is novel as it is based on a junction field-effect transistor with a subtle difference in that the top gate (n-type contact) has been removed to open the space for introducing the biomaterial and solution. The channel can be controlled through a back gate, enabling the sensor’s operation without a bulky electrode inside the solution. In this research, in order to demonstrate the sensor’s functionality for chemical and biosensing, we tested OG-JFET with varying pH solutions, cell adhesion (human oral neutrophils), human exhalation, and DNA molecules. Moreover, the sensor was simulated with COMSOL Multiphysics to gain insight into the sensor operation and its ion-sensitive capability. The complete simulation procedures and the physics of pH modeling is presented here, being numerically solved in COMSOL Multiphysics software. The outcome of the current study puts forward OG-JFET as a new platform for biosensing applications.

On the feasibility of wireless radio frequency ablation using nanowire antennas.

Radio frequency ablation (RFA) is a proven technique for eliminating cancerous or dysfunctional tissues in the body. However, the delivery of RFA electrodes to deep tissues causes damage to overlying healthy tissues, while a minimally invasive RFA technique would limit damage to targeted tissues alone. In this manuscript, we propose a wireless RFA technique relying on the absorption of radio frequencies (RFs) by gold nanowires in vivo and the deep penetration of RF into biological tissues. Upon optimizing the dimensions of the gold nanowires and the frequency of the applied RF for breast cancer and myocardium tissues, we find that heating rates in excess of 2000 K/s can be achieved with high spatial resolution in vivo, enabling short heating durations for ablation and minimizing heat diffusion to surrounding tissues. The results suggest that gold nanowires can act as “radiothermal” agents to concentrate heating within targeted tissues, negating the need to implant bulky electrodes for tissue ablation.

Two-Ply Carbon Nanotube Fiber-Typed Enzymatic Biofuel Cell Implanted in Mice.

Implantable devices have emerged as a promising industry. It is inevitable that these devices will require a power source to operate in vivo. Thus, to power implantable medical devices, biofuel cells (BFCs) that generate electricity using glucose without an external power supply have been considered. Although implantable BFCs have been developed for application in vivo, they are limited by their bulky electrodes and low power density. In the present study, we attempted to apply to living mice an implantable enzymatic BFC (EBFC) that was previously reported to be a high-power EBFC comprising carbon nanotube yarn electrodes. To improve their mechanical properties and for convenient implantation, the electrodes were coated with Nafion and twisted into a micro-sized, two-ply, one-body system. When the two-ply EBFC system was implanted in the abdominal cavity of mice, it provided a high-power density of 0.3 mW/cm2. The two-ply EBFC system was injected through a needle using a syringe without surgery and the inflammatory response in vivo initially induced by the injection of the EBFC system was attenuated after 7 days, indicating the biocompatibility of the system in vivo.

Elastic kirigami patch for electromyographic analysis of the palm muscle during baseball pitching

Surface electromyography (sEMG) is widely used to analyze human movements, including athletic performance. For baseball pitchers, a very precise movement is required to pitch the ball into the strike zone. The palm muscles appear to play a key role in this movement, and a real-time recording of sEMG from the palm muscle is useful in the analysis of motion during baseball pitching. However, the currently available devices with rigid and bulky electrodes (including connective wires) impede natural movements of the wearer and recording of sEMG from the palm muscles during vigorous action. Here, we describe a skin-contact patch consisting of kirigami-based stretchable wirings and conductive polymer nanosheet-based ultraconformable bioelectrodes, which address the challenge of mechanical mismatch between human skin and electrical devices. The key strategy is a kirigami-inspired wiring design and a mechanical gradient structure from nanosheet-based flexible bioelectrodes to a bulk wearable device. This approach would buffer the mechanical stress applied to the skin-contact bioelectrodes during an arm swing movement. With this patch, we precisely measure sEMG at the abductor pollicis brevis muscle (APBM) in a baseball player during ball pitching. We observe differences in the activity of the APBM between different types of pitches—fastball and curveball. This sEMG measurement system will enable the analysis of motion in unexplored muscle areas, such as on the palm and the sole, leading to a deeper understanding of muscular activity during performance in a wide range of sports and other movements.

Universal Brain-Machine Interfaces Enabled By Flexible Scalp Electronics and Deep Convolutional Neural Networks

Electroencephalography (EEG) allows non-invasive monitoring of brain electrical activity at a fine temporal resolution. However, it is difficult to consistently capture high-quality biopotential signals due to natural variations in scalp and skin conditions. Conventional EEG systems suffer from inconsistent signal quality extensive preparation time, and uncomfortable and bulky electrode setups from long, inflexible wires and rigid electrodes. Improvements in analysis and machine learning techniques have allowed researchers to extract more information from EEG with fewer electrodes on the scalp with certain EEG paradigms. However, further hardware improvements would be required before these systems could be comfortably used daily. Here, we introduce skin-like hybrid electronics (SKINTRONICS), a fully portable, wireless, flexible biomonitoring electronics platform incorporating a soft elastomeric membrane for maximum conformability and wearability on the skin. This concept allows for a comfortable and ergonomic wearable BMI concept that can be used long-term without discomfort and is optimized for use in a rehabilitation setting for patients with brainstem injury or other motor impairment. Analytical and computational studies establish the fundamental design criteria of the SKINTRONICS, enabling seamless portable EEG recording with significantly enhanced signal quality over commercial systems. Analysis in the time domain and frequency domain are completed, with deep convolutional neural networks providing appreciable improvements over conventional techniques such as SVM. The real-time time-domain analysis with deep convolutional neural networks allows for highly accurate classification and fine machine control with high information transfer rates from only two channels. With six human subjects this wireless interface achieves a high accuracy (94.54% ± 0.90%) for a corresponding information transfer rate of 122.1 ± 3.53 bits per minute, demonstrated using a wireless wheelchair, motorized vehicle, and keyboard-less presentation using a two-channel EEG. This demonstrates great potential for this platform, which can accommodate a wide range of assistive technologies as well as different EEG paradigms like motor imagery (MI).

Electrophysiology Meets Printed Electronics: The Beginning of a Beautiful Friendship

Electroencephalography (EEG) and surface electromyography (sEMG) are notoriously cumbersome technologies. A typical setup may involve bulky electrodes, dangling wires, and a large amplifier unit. Adapting these technologies to numerous applications has been accordingly fairly limited. Thanks to the availability of printed electronics, it is now possible to effectively simplify these techniques. Elegant electrode arrays with unprecedented performances can be readily produced, eliminating the need to handle multiple electrodes and wires. Specifically, in this Perspective paper, we focus on the advantages of electrodes printed on soft films as manifested in signal transmission at the electrode-skin interface, electrode-skin stability, and user convenience during electrode placement while achieving prolonged use. Customizing electrode array designs and implementing blind source separation methods can also improve recording resolution, reduce variability between individuals and minimize signal cross-talk between nearby electrodes. Finally, we outline several important applications in the field of neuroscience and how each can benefit from the convergence of electrophysiology and printed electronics.

Filter paper derived three-dimensional mesoporous carbon with Co3O4 loaded on surface: An excellent binder-free air-cathode for rechargeable Zinc-air battery

As promising energy storage equipment, Zn-air battery exhibits the advantage of high energy density, lightweight and compact structure over other rechargeable batteries, which is an ideal choice for electric vehicles. For Zn-air battery, the activity of air cathode plays an important role in its performance. Here, we report the fabrication of Co3O4 based bulky electrode with three-dimensional mesoporous carbon as matrix, which originates from cheap filter paper precursor. This electrode exhibits excellent activity and durability in oxygen reduction (ORR) and oxygen evolution reaction (OER) process, which possesses small half-wave potential (ORR1/2 = 0.811 V) and low overpotential (OER10 = 1.518 V) for ORR and OER, respectively. With this electrode as air cathode directly, a rechargeable Zn-air battery is assembled successfully. During discharge process, the maximum power density of this Zn-air battery achieves 71 mW cm−2. Furthermore, it also exhibits high specific capacity (828 mAh g−1 at 20 mA cm−2, 544 mAh g−1 at 50 mA cm−2) and small voltage gap (0.91 V at 10 mA cm−2) in charge and discharge process. As a rechargeable battery, it also shows promising stability after long time charge-discharge experiments. Thus, we find out a simple and convenient method to fabricate cheap and effective bi-functional air cathode for rechargeable Zn-air battery.

High temperature performance of La0.6Ce0.4Ni3.45Co0.75Mn0.7Al0.1 hydrogen storage alloy for nickel/metal hydride batteries

La0.6Ce0.4Ni3.45Co0.75Mn0.7Al0.1 hydrogen storage alloy has been prepared and its electrochemical characteristics and gas hydrogen absorption/desorption properties have been investigated at different temperatures. X-ray diffraction results indicated that the alloy consists of a single phase with CaCu5-type structure. It is found that the investigated alloy shows good cycle performance and high-rate discharge ability, which display its promising use in the high-power type Ni-MH battery. The exchange current density and the diffusion coefficient of hydrogen in the bulky electrode increase with increasing temperature, indicating that increasing temperature is beneficial to charge-transfer reaction and hydrogen diffusion. However, the maximum discharge capacity, the charge retention and the cycling stability degrade with the increase of the temperature.

A Fully Microfabricated Electrochemical Sensor and its Implementation for Detection of Methicillin Resistance in <italic>Staphylococcus Aureus</italic>

On-chip detection of biological analytes can enable diagnosis at the point of care. Combining the advantages of microelectromechanical system (MEMS) technology and molecular methods, we present the design of an integrated microfluidic platform, a microelectrochemical sensor (μECS), and its implementation for the detection of methicillin resistance in Staphylococcus aureus. This platform is capable of electrochemically sensing the target analyte in a microfluidic reactor without the usage of bulky electrodes, rendering it useful for in vitro diagnostics. In our experiments, the functionality of the sensor was tested for detecting specific DNA sequences of mecA gene (an indicator of methicillin resistance) over a range of concentrations of DNA (down to 10 pM). Synthetic oligonucleotides and bacterial PCR product were used as a target analyte in Hoechst 33258 marker-based detection and horseradish peroxidase-based detection, respectively. The results revealed that this platform has high sensitivity and selectivity. Also, its compatibility to MEMS processes enables its use with different applications ranging from detecting various types of cancers to endemics. The designed μECS can enable the detection of biological analytes of interest at low cost and high throughput.

'Electronic skin' could replace bulky electrodes

'Electronic skin' could replace bulky electrodes

A nanoscale meshed electrode of single-crystalline SnO for lithium-ion rechargeable batteries

A high specific capacity with good cycle performance for lithium-ion rechargeable batteries was achieved by using a nanoscopically meshed electrode of single-crystalline SnO produced through Sn 6O 4(OH) 4 as the intermediate state, whereas conventional bulky electrodes of SnO readily degraded due to a large volume change during lithium-ion insertion/extraction processes. The skeletal framework of the meshed architecture would be suitable to prevent damage to the electrode through the relaxation of the mechanical strain originating from the expansion.

A micro amperometric immunosensor for detection of human immunoglobulin

A novel amperometric immunosensor based on the micro electromechanical systems (MEMS) technology, using protein A and self-assembled monolayers (SAMs) for the orientation-controlled immobilization of antibodies, has been developed. Using MEMS technology, an “Au, Pt, Pt” three-microelectrode system enclosed in a SU-8 micro pool was fabricated. Employing SAMs, a monolayer of protein A was immobilized on the cysteamine modified Au electrode to achieve the orientation-controlled immobilization of the human immunoglobulin (HIgG) antibody. The immunosensor aimed at low unit cost, small dimension, high level of integration and the prospect of a biosensor system-on-a-chip. Cyclic voltammetry and chronoamperometry were conducted to characterize the immunosensor. Compared with the traditional immunosensor using bulky gold electrode or screen-printed electrode and the procedure directly binding protein A to electrode for immobilization of antibodies, it had attractive advantages, such as miniaturization, compatibility with CMOS technology, fast response (30 s), broad linear range (50―400 μg/L) and low detection limit (10 μg/L) for HIgG. In addition, this immunosensor was easy to be designed into micro array and to realize the simultaneously multi-parameter detection.

Electrodeposited Nickel-Boron Thin-Film Ethanol Sensor

Electrodeposited nickel-boron-based ethanol sensor was constructed by thin-film technique. The sensing layers of nickel-boron films were prepared at constant cathodic current density of in , , and aqueous solution. Amperometric response of this miniaturized sensor was higher than that of the traditional bulky electrodes. The microfabricated electrodeposited nickel-boron electrode exhibits good electrochemical performance in terms of response time , linearity (, ), and sensitivity . This sensor also shows a high selectivity to ethanol over malic, citric, ascorbic, and acetic acids. The optimal operating conditions of these ethanol sensors were of electrodeposition temperature and of electrodeposition time.

Determination of trace tin by stripping potentiostatic coulometry

On the basis of voltammetric and coulometric studies of the behavior of tin(II) in a 2 M HCl solution at a carbon-graphite bulky electrode made of fibrous porous felt (FPF), we have found the optimum conditions for the stripping potentiostatic coulometric determination of 10–1000 μg tin(II) by the reaction Sn(0)-ē ⇌ Sn(I) after preconcentrating Sn(0) at the electrode surface. The relative standard deviation varied from 0.5 to 4%. The results of the coulometric determination of the number of electrons involved in the oxidation of Sn(0) suggest that the stripping Sn(0) from the surface of the FPF electrode proceeds in two stages. The first stage Sn(0) → Sn(I) was electrochemical, and the second stage Sn(I) → Sn(II) was chemical. The procedure was applied to the determination of ∼1% tin in a jewelry alloy based on gold, silver, platinum, and copper.

Kinetic and electrochemical properties of icosahedral quasicrystalline [formula omitted] powder

Kinetic and electrochemical properties of icosahedral quasicrystalline Ti 45 Zr 35 Ni 17 Cu 3 alloy powder as negative electrode material of Ni–MH battery have been investigated at different temperatures. The calculated results show that the apparent activation enthalpy of the charge-transfer reaction is 43.89 kJ mol - 1 , and the activation energy of hydrogen diffusion is 21.03 kJ mol - 1 . The exchange current density and the diffusion coefficient of hydrogen in the bulky electrode increase with increasing temperature, indicating that increasing temperature is beneficial to charge-transfer reaction and hydrogen diffusion. As a result, the maximum discharge capacity, activation property and high-rate dischargeability are greatly improved with increasing temperature. However, the charge retention and the cycling stability degrade with the increase of the temperature.

Fingerprints of mesoscopic leads in the conductance of a molecular wire

The influence of contacts on linear transport through a molecular wire attached to mesoscopic tubule leads is studied. It is shown that low dimensional leads, such as carbon nanotubes, in contrast to bulky electrodes, strongly affect transport properties. By focusing on the specificity of the lead-wire contact, we show, in a fully analytical treatment, that the geometry of this hybrid system supports a mechanism of channel selection and a sum rule, which is a distinctive hallmark of the mesoscopic nature of the electrodes.

Modulation resistometry of a gold electrode

Electronic properties of metals are very important for electrochemical processes occurring at the metal/electrolyte interface [1]. One of the main parameters of solid metals reflecting their electronic structures is the conductivity or the electric resistance. However, when working with bulky electrodes, it is practically impossible to detect variations in the conductivity caused by processes on their surfaces. Quite different conditions take place in the case of thin metal films (<1 ~tm). Shimizu [2] was among the first to suggest measuring the resistance of thin films in electrochemical systems. The conductivity of a thin-film electrode (TFE) is usually measured using ac or dc passed along the electrode [3]. In [4], the method of modulation resistometry was described for the first time, but the experimental data were not interpreted.