Non-contact Electrodes Research Articles

Three-Terminal Single-Molecule Junctions Formed by Mechanically Controllable Break Junctions with Side Gating

Molecules are promising candidates for electronic device components because of their small size, chemical tunability, and ability to self-assemble. A major challenge when building molecule-based electronic devices is forming reliable molecular junctions and controlling the electrical current through the junctions. Here, we report a three-terminal junction that combines both the ability to form a stable single-molecule junction via the mechanically controllable break junction (MCBJ) technique and the ability to shift the energy levels of the molecule by gating. Using a noncontact side-gate electrode located a few nanometers away from the molecular junction, the conductance of the molecule could be dramatically modulated because the electrical field applied to the molecular junction from the side gate changed the molecular electronic structure, as confirmed by the ab initio calculations. Our study will provide a new design for mechanically stable single-molecule transistor junctions fabricated by the MCBJ method.

Evaluation of Micro Plasma Formed in the Narrow Gap in Electrolyte Solution

Microplasma was formed in a gap hole made in a quartz plate immersed in various kinds of electrolyte solutions at different concentrations. High-voltage AC was applied to the solution by using a pair of contact- or non-contact electrodes at both sides of the gap hole to ignite microplasma generation. Spectra of the light emitted from the microplasma showed elemental emission lines of the species contained in the solution, and their intensities depended on not only their concentration but also plasma conditions such as plasma temperature. A non-equilibrium plasma state was confirmed from estimated temperature of electrons and OH• radicals in the order of thousand and 10 thousand Kelvins. Deformation of the gap hole was observed depending on the polarization condition and species, probably due to high-temperature plasma and also dielectric loss in the gap hole.

Recent Patents on Non-Contact Electrodes for Measuring EEG and EKG

Recent Patents on Non-Contact Electrodes for Measuring EEG and EKG

Development of Novel Non-Contact Electrodes for Mobile Electrocardiogram Monitoring System.

Real-time monitoring of cardiac health is helpful for patients with cardiovascular disease. Many telemedicine systems based on ubiquitous computing and communication techniques have been proposed for monitoring the user's electrocardiogram (ECG) anywhere and anytime. Usually, wet electrodes are used in these telemedicine systems. However, wet electrodes require conduction gels and skin preparation that can be inconvenient and uncomfortable for users. In order to overcome this issue, a new non-contact electrode circuit was proposed and applied in developing a mobile electrocardiogram monitoring system. The proposed non-contact electrode can measure bio-potentials across thin clothing, allowing it to be embedded in a user's normal clothing to monitor ECG in daily life. We attempted to simplify the design of these non-contact electrodes to reduce power consumption while continuing to provide good signal quality. The electrical specifications and the performance of monitoring arrhythmia in clinical settings were also validated to investigate the reliability of the proposed design. Experimental results show that the proposed non-contact electrode provides good signal quality for measuring ECG across thin clothes.

Noncontact electrosurgical grounding – A useful and safe tool in the initial surgical management of thermal injuries

BackgroundElectrosurgical instruments – one of the useful and most-used instruments within the surgeon's armamentarium – are potentially dangerous by causing unanticipated direct burns; fire occurring as a result of electrosurgical instruments and electromagnetic interference with a pacemaker, defibrillator, or cardiac monitoring device. MethodsThe Mega 2000 Patient Return Electrode System produced by Megadyne Medical Products is a noncontact electrode designed to provide adequate electrical return to facilitate function of electrocautery devices. We used this noncontact device in 67 patients (28 women, 39 men) with large burns during their stay in our burn unit and in 11 of these patients (4 women, 7 men) for escharotomies during admission in our burn care. ResultsThe device functioned well in all cases, no additional cutaneous burns on the patients’ body were noticed. ConclusionThis paper is a review of our experience with this noncontact electrosurgical grounding in burn surgery highlighting its advantages comparing with the conventional electrosurgical instruments.

Dry and Noncontact EEG Sensors for Mobile Brain–Computer Interfaces

Dry and noncontact electroencephalographic (EEG) electrodes, which do not require gel or even direct scalp coupling, have been considered as an enabler of practical, real-world, brain-computer interface (BCI) platforms. This study compares wet electrodes to dry and through hair, noncontact electrodes within a steady state visual evoked potential (SSVEP) BCI paradigm. The construction of a dry contact electrode, featuring fingered contact posts and active buffering circuitry is presented. Additionally, the development of a new, noncontact, capacitive electrode that utilizes a custom integrated, high-impedance analog front-end is introduced. Offline tests on 10 subjects characterize the signal quality from the different electrodes and demonstrate that acquisition of small amplitude, SSVEP signals is possible, even through hair using the new integrated noncontact sensor. Online BCI experiments demonstrate that the information transfer rate (ITR) with the dry electrodes is comparable to that of wet electrodes, completely without the need for gel or other conductive media. In addition, data from the noncontact electrode, operating on the top of hair, show a maximum ITR in excess of 19 bits/min at 100% accuracy (versus 29.2 bits/min for wet electrodes and 34.4 bits/min for dry electrodes), a level that has never been demonstrated before. The results of these experiments show that both dry and noncontact electrodes, with further development, may become a viable tool for both future mobile BCI and general EEG applications.

A new technique for touch sensing based on measurement of current generated by electrostatic induction

In this paper, we propose a new concept for touch sensors that is based on measurement of the current generated by electrostatic induction. The proposed sensor can detect the timing of contact between two objects from a distance without contact with either object. When the human body comes in contact with an object, electrostatic charge is generated in the human body due to tribological interactions. We assume that the human body is a good conductor. As a result, an instantaneous change is observed in the electric potential of the human body. Therefore, contact can be detected via the change in the electric potential of the human body. We have developed an effective technique for measuring the change in the electric potential of the human body using a noncontact electrode. Such indirect measurement is made possible by the measurement of the instantaneous current flowing through the electrode, instead of measurement of the voltage of the electrode by the conventional capacitively coupled method. This new technique requires measurement of the electrostatic induction current generated due to changes in the electric potential of the human body.

Detection of human respiration based on measurement of current generated by electrostatic induction

In this study, we developed an effective technique for measuring human respiration using a noncontact and nonattached electrode. The technique requires the measurement of the current generated due to the difference in capacitance between a given electrode and the human body. The subpicoampere electrostatic induction current flowing through the electrode when placed a few centimeters from the subject is detected. We propose an occurrence model for the electrostatic induction current generated by the change in capacitance caused by the movement of the body surface while taking a breath. This model effectively describes the behavior of the current flowing through the measurement electrode.

Dry-Contact and Noncontact Biopotential Electrodes: Methodological Review

Recent demand and interest in wireless, mobile-based healthcare has driven significant interest towards developing alternative biopotential electrodes for patient physiological monitoring. The conventional wet adhesive Ag/AgCl electrodes used almost universally in clinical applications today provide an excellent signal but are cumbersome and irritating for mobile use. While electrodes that operate without gels, adhesives and even skin contact have been known for many decades, they have yet to achieve any acceptance for medical use. In addition, detailed knowledge and comparisons between different electrodes are not well known in the literature. In this paper, we explore the use of dry/noncontact electrodes for clinical use by first explaining the electrical models for dry, insulated and noncontact electrodes and show the performance limits, along with measured data. The theory and data show that the common practice of minimizing electrode resistance may not always be necessary and actually lead to increased noise depending on coupling capacitance. Theoretical analysis is followed by an extensive review of the latest dry electrode developments in the literature. The paper concludes with highlighting some of the novel systems that dry electrode technology has enabled for cardiac and neural monitoring followed by a discussion of the current challenges and a roadmap going forward.

On the presumed inductive behaviour of electrolyte solutes in low frequency conductance. Part I: Deficiency of the employed measurement technique

A measurement technique is examined that served to investigate the low frequency conductance of electrolyte solutes. The set-up, analyzed on the basis of its equivalent circuit, shows major deficiencies, which actually caused the observed frequency dispersion and the presumed inductive behaviour. The problem, basically, is due to the use of non-contacting electrodes for signal in/out coupling, in combination with a capillary flow cell as sample holder.

Ac electroosmotic pumping induced by noncontact external electrodes.

Electroosmotic (EO) pumps based on dc electroosmosis is plagued by bubble generation and other electrochemical reactions at the electrodes at voltages beyond 1 V for electrolytes. These disadvantages limit their throughput and offset their portability advantage over mechanical syringe or pneumatic pumps. ac electroosmotic pumps at high frequency (>100 kHz) circumvent the bubble problem by inducing polarization and slip velocity on embedded electrodes,1 but they require complex electrode designs to produce a net flow. We report a new high-throughput ac EO pump design based on induced-polarization on the entire channel surface instead of just on the electrodes. Like dc EO pumps, our pump electrodes are outside of the load section and form a cm-long pump unit consisting of three circular reservoirs (3 mm in diameter) connected by a 1x1 mm channel. The field-induced polarization can produce an effective Zeta potential exceeding 1 V and an ac slip velocity estimated as 1 mmsec or higher, both one order of magnitude higher than earlier dc and ac pumps, giving rise to a maximum throughput of 1 mulsec. Polarization over the entire channel surface, quadratic scaling with respect to the field and high voltage at high frequency without electrode bubble generation are the reasons why the current pump is superior to earlier dc and ac EO pumps.

AC electro-osmotic mixing induced by non-contact external electrodes

We demonstrate efficient mixing in a micro-fluidic reservoir smaller than 10 microL using ac electro-osmosis driven by field-induced polarization. Our mixing device, of that electrodes are outside of the mixing unit, consists of three circular reservoirs (3mm in diameter) connected by a 1 mm x 1 mm channel. Unlike dc electro-osmosis, whose polarization is from charged substrate functional groups, this new mechanism uses the external field to capacitively charge the surface and the surface capacitance becomes the key factor in the electrokinetic mobility. The charging and mixing are enhanced at tailor-designed channel corners by exploiting the high normal fields at geometric singularities. The induced surface dielectric polarization and the resulting electric counter-ion double layer produce an effective Zeta potential in excess of 1 V, over one order of magnitude larger than the channel Zeta potential. The resulting ac electro-osmotic slip velocity scales quadratically with respect to the applied field, in contrast to the linear scaling of dc electro-osmosis and at 1cm/s and larger, exceeds the classical dc values by two orders of magnitude. The polarization is non-uniform at the corners due to field leakage to the dielectric substrate and the inhomogeneous slip velocity produces intense mixing vortices that effectively homogenize solutes in 30s in a 3mm reservoir, in contrast to hour-long mixing by pure diffusion.

Precision and efficiency of laser assisted jet electrochemical machining

Laser assisted jet electrochemical machining (LAJECM) is a hybrid process, that combines a laser beam with an electrolyte jet thereby giving a non-contact tool electrode that removes metal by electrochemical dissolution. The laser beam effectively improves the precision of LAJECM as it is able to direct the dissolution to specifically targeted areas. This prevents the machining from unwanted areas due to stray current. This parallel application of a laser beam with the electrolyte jet enables an improvement of machining accuracy, also productivity. LAJECM has shown that machining with laser assistance can effectively facilitate material removal of 20, 25, 33, and 54% for Hasteloy, titanium alloy, stainless steel and aluminium alloy, respectively. There is also a noticeable improvement in the shape accuracy and slight decrease in surface roughness of the holes and cavities produced due to more focused machining (the order of 20%). The measured reduction in taper is of the order of 38, 40, 41, 65% for aluminium alloy, stainless steel, Hasteloy and titanium alloy, respectively.

A new intelligent bed care system for hospital and home patients.

An intelligent bed-care system has been developed for monitoring patient movements and behavior in the hospital and at home in order to prevent injuries from falls, a major problem in health care facilities. Falls, as well as patient activity immediately preceding falls (i.e. exiting the bed), are especially dangerous when infusion extubation also occurs. This new system detects in-bed infusion fluid leaks, bleeding due to infusion-tube pullout, and urine resulting from incontinence. It employs stainless steel tape and wire noncontacting electrodes, several linear integrated circuits, and a low-power, 8-bit single-chip microcomputer The electrodes are installed between the bed mattress and sheet to record changes in an always-present alternating current (AC) voltage, which is induced on the patient's body by electrostatic coupling from a 100-V, 60-Hz alternating current power line around the bed. The microcomputer uses changes in the induced alternating current voltage to detect the patient's movements before and after leaving the bed, as well as any fluid leakage. The microcomputer alerts the nursing station, via the nurse call system or personal handy phone (PHS), that the patient is in an active state; has a dangerous posture on the bed; is contaminating the sheet due to leaking, bleeding or incontinence; or is out of bed.

Radiofrequency catheter ablation with the split-tip electrode in the temperature-controlled mode.

The 7 Fr "split-tip electrode" (2.5-mm tip electrode divided longitudinally into four electrodes with an adjacent 2-mm ring electrode) improves mapping resolution due to its small recording electrodes and narrow interelectrode distances (0.1 mm). The purpose of this study was to examine the temperature-controlled ablation properties of this electrode. In seven anesthetized dogs, the thigh muscles were exposed and superfused with canine blood. A split-tip catheter electrode (with a thermocouple in each of the five electrodes) and a conventional 4-mm catheter electrode were positioned at constant pressure perpendicular or parallel to the surface of the thigh muscle. Impedance measured between each split electrode and a skin patch correlated with the degree of contact with blood and tissue. In the parallel catheter to tissue orientation, split electrodes not in contact with tissue had a low impedance (mean 210-224 ohms), and the split electrode almost entirely in contact with tissue had the highest impedance (380 +/- 56 ohms). In the perpendicular catheter to tissue orientation all split electrodes had a similar impedance (mean 279-286 ohms). A total of 75 radiofrequency (RF) lesions were produced in the temperature-controlled mode with the 4-mm electrode (target 60 degrees C) or the split-tip electrode (power limited by the hottest electrode reaching 70 degrees C) with current delivered to all five electrodes simultaneously, or only to electrodes in contact with tissue. Lesion depth was not significantly different between electrodes in the parallel orientation (5.2 +/- 0.9 vs 5.1 +/- 1.4 vs 5.3 +/- 1.1 mm), but significantly deeper with the conventional 4-mm tip electrode in the perpendicular orientation (6.7 +/- 1.2 vs 5.3 +/- 1.3 vs 5.6 +/- 0.9 mm, P < 0.05). This was due to higher power delivered to the conventional 4-mm electrode (27 +/- 9 vs 17 +/- 7 vs 15 +/- 7 W, P < 0.05) because convective cooling by the blood flow was less effective for the split-tip electrode due to a reduced heat conduction across the interelectrode space from the hottest electrode to cooler areas of the group of five electrodes (mean temperature difference between the hottest split electrodes and the ring electrode: 24 degrees C). Electrode cooling or heat conduction was not effected by the elimination of current delivery to non-contact electrodes. Steam pops occurred in 36% of applications with the conventional 4-mm electrode in the perpendicular orientation but never with the split-tip electrode in spite of the higher target temperature. Measurement of impedance from the split electrodes allow the determination of electrode tissue contact and RF lesions produced with the split-tip electrode in the temperature-controlled mode using a target of 70 degrees C were of reasonable size and not associated with steam pops.

Behavior of Stress-Induced Charges in Cement Containing Quartz Crystals

The recombination process of electric charges induced by stress release has been measured for cement samples embedded within quartz crystals to investigate the behavior of piezo-compensating charges in quartz-bearing rocks. The stress with a release constant τ of σ(t) = Δσ e -t/τ led to a theoretical pulse charge density q(t) = αΔσ{eρ/(τ - eρ)} (e -t/τ - e -t/eρ ), where α, e and ρ are the piezoelectric coefficient, permittivity and resistivity, respectively. The induced charges appeared on a sample measured with non-contacting electrodes depending on the number and orientation of synthetic quartz crystals, and two decay time constants of 0.25 and 2.5 s were obtained. The apparent piezoelectric coefficient for a sample with one piece of quartz was 1.0 × 10 -15 C/N. However, the coefficients for samples with two pieces of quartz, which were arranged in the same or alternate directions, were 4.1 × 10 -15 and 1.7 × 10 -15 C/N, respectively. The behavior of piezo-compensating charges around quartz crystals in conductive cement suggests ferroelectric charge migration through the measurements of depolarization current.

Electric Field Modulated Near-Field Photo-Luminescence of Organic Thin Films

The concentrated electric field (E-field) in the vicinity of a voltage-biased near-field optical probe is used to modulate the photoluminescence of organic thin films on the ∼100 nm scale. The samples are bilayers comprising a self-organized-thin-film (50−500 nm) layer of zinc-octakis (β-decoxyethyl) porphyrin (ZnODEP) on top of an indium tin oxide (ITO) coated glass electrode. The Al coated-optical-fiber-near-field probe functions simultaneously as a noncontacting moveable electrode and a local source of optical excitation (30−70 nm aperture). When the ITO electrode is charged positive relative to the probe (yielding a field on the order of 1MV/cm-1), the photoluminescence (fluorescence) intensity decreases ∼5% and the probe−sampleprobe−sample distance (under shear-force feedback control) increases ∼7 A. Opposite effects for both signals occur when the ITO is charged negative. The E-field effect on the near-field luminescence properties of thin films of ZnODEP is discussed in terms of the following physi...

Electrochemical studies on corrosion under a water film

The corrosion mechanism and corrosion rate were studied as a functionof the water film thickness using Kelvin probe (non-contacting reference electrode) and impedance methods. Cathodic polarization curves were measured at different film thicknesses on copper, platinum, iron and gold electrodes. The diffusion-limiting current of oxygen increased with decreasing thickness to around 20–30 μm, and then decreased with decreasing thickness. The corrosion rate of copper as a function of the water film thickness was measured by the impedance method. It was confirmed that the rate is constant for a thick film, increases with decreasing thickness to give a maximum and then decreases, as reported by Tomashov. The water film thickness was measured by the solution resistance of the water film. Using the impedance method, the corrosion rates of steels were monitored during wet and dry cycles. The importance of monitoring the corrosion rate, during evaluation or conventional corrosion tests, is illustrated by the results.

Electrochemical determination of microorganism populations by filtering samples to remove microorganisms and making an electrochemical measurement w.r.t. filtrate using non-contacting electrode : Infometrix Inc. WO-9209700; 11 June 1992

Electrochemical determination of microorganism populations by filtering samples to remove microorganisms and making an electrochemical measurement w.r.t. filtrate using non-contacting electrode : Infometrix Inc. WO-9209700; 11 June 1992

Proposal for precise manipulation of C60 molecules

Scanning tunneling microscope has previously been used to move single atoms. This article proposes a new method for performing accurate manipulations of C60 molecules. The new method may have potential advantages over previous approaches for molecular scale operations. One advantage comes from the noncontact electrode principle that allows longer distance manipulations and low-cost construction of the manipulating device. The unique properties of C60 may also facilitate precise manipulations of thin layers, in addition to single molecule operations. Construction of a device for testing the new principle is under work.