Electrode Contact Research Articles

Intracerebral electrical stimulation of the face-selective right lateral fusiform gyrus transiently impairs face identity recognition

Neuroimaging and intracranial electrophysiological studies have consistently shown the largest and most consistent face-selective neural activity in the middle portion of the human right lateral fusiform gyrus (‘fusiform face area(s)’, FFA). Yet, direct evidence for the critical role of this region in face identity recognition (FIR) is still lacking. Here we report the first evidence of transient behavioral impairment of FIR during focal electrical stimulation of the right FFA. Upon stimulation of an electrode contact within this region, subject CJ, who shows typical FIR ability outside of stimulation, was transiently unable to point to pictures of famous faces among strangers and to match pictures of famous or unfamiliar faces presented simultaneously for their identity. Her performance at comparable tasks with other visual materials (written names, pictures of buildings) remained unaffected by stimulation at the same location. During right FFA stimulation, CJ consistently reported that simultaneously presented faces appeared as being the same identity, with little or no distortion of the spatial face configuration. Independent electrophysiological recordings showed the largest neural face-selective and face identity activity at the critical electrode contacts. Altogether, this extensive multimodal case report supports the causal role of the right FFA in FIR.

A retrospective review of elevated lead impedances in impedance-dependent magnetic resonance-conditional spinal cord stimulation devices.

Advances in Spinal cord stimulation (SCS) device technology in recent years have led to the development of SCS systems that are magnetic resonance imaging (MRI)-conditional, most of which are dependent on normal lead impedances. The objective of this study was to retrospectively analyze the rate of elevated lead impedance in these devices to determine the rate of failure of MR-conditional modes. This was a single-center, retrospective, chart-based review conducted during a five-year period. Patients were included if they had been implanted with an impedance-dependent MR-conditional SCS and had a documented impedance check at least 6 months after implantation. A Kaplan-Meier survival analysis was performed to map the survival of MR-conditionality over time. There were 363 cases included between 2015 and 2020, which corresponded to a total of 602 SCS leads. Nevro was the most common manufacturer (67.8%), followed by Boston Scientific (22.3%) and Abbott (9.9%). The average overall follow-up time was 2.25 years. Overall, 67 (18.5%) of patients had lead impedances over 10,000 Ω at follow-up with a total of 186 electrode contacts (3.9%). Leads most commonly had either one (40%), two (22%) or three (12%) electrode contacts out of range. Risk of failure of lead impedances increased by 35.4% with each successive year to a peak of 43% of all leads by year 5. Mean overall survival time of normal lead impedances was 4.77 years (CI 4.40-5.13). There was no statistically significant difference in mean overall survival time between Abbott (M = 4.0 years, SD = 1.25), Boston Scientific (M = 4.64 years, SD = 1.75) and Nevro (M = 4.80 years, SD = 3.28), χ2 (2, N = 358) = 1.511, p = 0.47; however, Abbott leads had a greater total number of failed impedance contacts (50/568, 8.8%), in comparison to Nevro (124/3064, 4.0%), χ2 (1, N = 3630) = 23.76, p < 0.00001, at a similar follow-up time. This retrospective study identified elevated impedances in 18.5% of MR-conditional SCS devices at an average of 2.25 years follow-up resulting in loss of MR-conditionality and a mean overall lead survival time of 4.77 years for normal lead impedance.

The guiding effect of local field potential during deep brain stimulation surgery for programming in Parkinson's disease patients.

Parkinson's disease (PD) patients undergoing deep brain stimulation (DBS) surgery require subsequent programming, which is complex and cumbersome. The local field potential (LFP) in the deep brain is associated with motor symptom improvement. The current study aimed to identify LFP biomarkers correlated with improved motor symptoms in PD patients after DBS and verify their guiding role in postoperative programming. Initially, the study included 36 PD patients undergoing DBS surgery. Temporary external electrical stimulation was performed during electrode implantation, and LFP signals around the electrode contacts were collected before and after stimulation. The stimulating contact at 6 months of programming was regarded as the optimal and effective stimulating contact. The LFP signal of this contact during surgery was analyzed to identify potential LFP biomarkers. Next, we randomly assigned another 30 PD patients who had undergone DBS to physician empirical programming and LFP biomarker-guided programming groups and compared the outcomes. In the first part of the study, LFP signals of electrode contacts changed after electrical stimulation. Electrical stimulation reduced gamma energy and the beta/alpha oscillation ratio. The different programming method groups were compared, indicating the superiority of beta/alpha oscillations ratio-guided programming over physician experience programming for patients' improvement rate (IR) of UPDRS-III. There were no significant differences in the IR of UPDRS-III, post-LED, IR-PDQ39, number of programmings, and the contact change rate between the gamma oscillations-guided programming and empirical programming groups. Overall, the findings reveal that gamma oscillations and the beta/alpha oscillations ratio are potential biomarkers for programming in PD patients after DBS. Instead of relying solely on spike action potential signals from single neurons, LFP biomarkers can provide the appropriate depth for electrode placement.

Engineering the contact resistance of copper/copper oxide via inserting a mediated molybdenum trioxide layer

The interface of metal/semiconductor contact electrode is a crucial key that affects the charge carrier injection and, hence, influences the whole device performance. A sufficient effort should be devoted to engineer the contact resistance in any semiconductor devices principally those based on p-type semiconductors. In this study we aimed to achieve a proper electrode for nitrogeN-treated copper oxide films by introducing molybdenum trioxide (MoO3) as a mediated hole-injection layer between the metal and the semiconductor. Copper oxide (CuxO) films were sputtered under three different conditions of nitrogen flow (0 %, 3 % and 5 %). According to XRD, XPS and optical transmission measurements, CuxO-5 % N revealed improved characterizations, including pure Cu2O phase, less compressive strain and high optical transparency. Copper (Cu) electrodes were examined on all three films with/(without) inserting a thin MoO3 layer between Cu and the CuxO layer. Based on transmission line model (TLM), our results showed that the insertion of a 5 nm of MoO3-mediated layer had a significant impact on reducing the contact resistance of the Cu/MoO3/CuxO-5 %N2 stacked electrodes to an adequate contact resistance of 371 KΩ. This value is smaller than that which resulted when gold (Au) electrodes were employed by two orders of magnitude. These results provide new insights to the Cu/CuxO electrodes and the ability of tuning their resistance to an ohmic contact by incorporating a thin MoO3-mediated hole injection layer.

Flexible dye solar cells with TiO2 nanopaper and Ti back contact electrodes

Flexible dye solar cells (F-DSCs) have attracted great attention because of their low cost, flexibility and lightweight, and their advantages for wearable electronic devices and other applications. We propose here a novel structure of F-DSCs using flexible TiO2 nanopapers as substrates and Ti back contact electrodes(Ti BCE) as electron collection electrodes. By combining the high-temperature hydrothermal nanowire synthesis with conventional paper preparation, TiO2 nanopapers (long nanowire TiO2 free-standing membranes) with good mechanical strength and flexibility were prepared. This TiO2 nanopapers from pure long inorganic nanowires, can be used as an ideal flexible substrate for Ti BCE and nanocrystalline TiO2 films, because they retain their excellent mechanical strength and flexibility at high temperatures. The PCE of F-DSCs with TiO2 nanopaper substrate and the porous Ti BCE reached 4.38% under AM 1.5G and 100 mW cm−2 simulated solar irradiation. The F-DSCs remained stable after 100 bending tests at 16 mm bending radius.

Post-operative evaluation of computed tomography imaging following cochlear implantation

PurposeThis study utilized an automated segmentation algorithm to assess the cochlear implant electrode array within the cochlea and investigate its impact on audiologic outcomes as measured by post-operative speech perception scores. Furthermore, manual evaluations of electrode placement were compared to automatic segmentation methods to determine their accuracy in predicting post-operative audiologic outcomes. Materials and methodsThis retrospective chart review was conducted at a tertiary care referral center involving adult post-lingually deafened cochlear implant recipients implanted from 2015 to 2019. Patients with appropriate postoperative imaging and speech testing were included. Patients were excluded if non-English speaking, had a cognitive deficit, or a labyrinthine malformation. Automated and manual methods were used to analyze computed tomography (CT) scans and correlate the findings with post-operative speech perception scores and detection of electrode translocation. ResultsAmong the 47 patients who met inclusion criteria, 15 had electrode translocations confirmed by automatic segmentation methods. Controlling for CI usage and pre-operative AzBio scores, patients with translocation exhibited significantly lower consonant-nucleus consonant (CNC) and AzBio scores at 6-months post-implantation compared to patients with ST insertions. Moreover, the number of translocated electrode contacts was significantly associated with post-operative CNC scores. Manual evaluations of electrode location were predictive but less sensitive to electrode translocations when compared with automated 3D segmentation. ConclusionsPlacement of CI electrode contacts within ST without translocation into SV, leads to improved audiologic outcomes. Manual assessment of electrode placement via temporal bone CT, without 3D reconstruction, provides a less sensitive method to determine electrode placement than automated methods. Level of evidenceLevel 4. Lay summaryThis study investigated the impact of electrode placement on speech outcomes for cochlear implant recipients. Using advanced imaging techniques, the researchers compared automated and manual methods for evaluating electrode position and examined the relationship between electrode translocation and audiologic outcomes. The findings revealed that proper placement within the cochlea without translocation into inappropriate compartments inside the cochlea improves speech understanding. Manual evaluations were somewhat accurate but less sensitive in detecting translocations compared to automated methods, which offer more precise predictions of patient outcomes. These results contribute to our understanding of factors influencing cochlear implant success and highlight the importance of optimizing electrode placement for improved speech outcomes.

Electrically evoked compound action potentials in cochlear implant users with preoperative residual hearing.

Residual hearing in cochlear implant (CI) candidates requires the functional integrity of the nerve in particular regions of the cochlea. Nerve activity can be elicited as electrically evoked compound action potentials (ECAP) after cochlear implantation. We hypothesize that ECAP thresholds depend on preoperative residual hearing ability. In a retrospective study, we analyzed 84 adult cochlear implant users who had received a Nucleus® CI632 Slim Modiolar Electrode and who preoperatively had had residual hearing. Inclusion criteria were severe to profound hearing loss with preoperative measurable hearing in the ear to receive the implant, postlingual hearing loss, German as native language and correct placement of the electrode, inserted completely into the scala tympani. Electrically evoked compound action potential (ECAP) was recorded intraoperatively. The angular insertion was measured for each electrode contact from postoperative computed tomography to estimate the corresponding spiral ganglion frequency. Pure-tone audiometry and allocated ECAP thresholds were tested to investigate possible correlation. The average of hearing thresholds, tested at 0.5, 1, 2, and 4 kHz (4FPTA) was 82 ± 18 (range 47-129) dB HL. The success rate for recording ECAP thresholds was 96.9%. For all comparable pure-tone frequencies (1, 2, 4, and 8 kHz), there was significant correlation between preoperative hearing levels and intraoperative ECAP thresholds (p < 0.001). Higher hearing thresholds are associated with increased ECAP thresholds. In CI candidates with adequate residual hearing, intraoperative electrophysiological measurement records lower thresholds. This outcome may be explained by the neural survival density of the peripheral system, with less neural degeneration.

Численное исследование влияния изменения электрической проводимости на решение прямой задачи электроимпедансной томографии

Electrical Impedance Tomography (EIT) uses electrical stimulation and measurement at the body surface to image the electrical properties of internal tissues. It has the advantage of non-invasiveness and high temporal resolution but suffers from poor spatial resolution and sensitivity to electrode movement and contact quality. EIT can be useful to applications where there are conductive contrasts between tissues, fluids or gases, such as imaging of cancerous or ischemic tissue or functional monitoring of breathing, blood flow, gastric motility and neural activity. The work uses a complete electrode model (CEM), which is a practical model in EIT, which most realistically models electrodes. This model can simulate EIT measurements with much greater accuracy than continuum models. The mathematical formulation of the problem is written as follows: In the article [15] shows that in order for the problem to have a unique solution, the following condition must be met: Numerical studies are consistent with the conclusions from the article [14]. Useful information in the EIT is contained mainly on a small part of the boundary, i.e., on the electrodes close to the perturbations of the electrical conductivity. Boundary measurements, which are the input to the inverse conductivity problem, are more sensitive to anomalies near the boundary and to larger anomalies. This study is useful in order to know the critical values of the parameters (size, location) of a low-amplitude perturbation of conductivity, at which the measurements are insensitive and, therefore, inhomogeneities cannot be detected.

Differential spatiotemporal gait effects with frequency and dopaminergic modulation in STN-DBS.

The spatiotemporal gait changes in advanced Parkinson's disease (PD) remain a treatment challenge and have variable responses to L-dopa and subthalamic deep brain stimulation (STN-DBS). The purpose of this study was to determine whether low-frequency STN-DBS (LFS; 60 Hz) elicits a differential response to high-frequency STN-DBS (HFS; 180 Hz) in spatiotemporal gait kinematics. Advanced PD subjects with chronic STN-DBS were evaluated in both the OFF and ON medication states with LFS and HFS stimulation. Randomization of electrode contact pairs and frequency conditions was conducted. Instrumented Stand and Walk assessments were carried out for every stimulation/medication condition. LM-ANOVA was employed for analysis. Twenty-two PD subjects participated in the study, with a mean age (SD) of 63.9 years. Significant interactions between frequency (both LFS and HFS) and electrode contact pairs (particularly ventrally located contacts) were observed for both spatial (foot elevation, toe-off angle, stride length) and temporal (foot speed, stance, single limb support (SLS) and foot swing) gait parameters. A synergistic effect was also demonstrated with L-dopa and both HFS and LFS for right SLS, left stance, left foot swing, right toe-off angle, and left arm range of motion. HFS produced significant improvement in trunk and lumbar range of motion compared to LFS. The study provides evidence of synergism of L-dopa and STN-DBS on lower limb spatial and temporal measures in advanced PD. HFS and LFS STN-DBS produced equivalent effects among all other tested lower limb gait features. HFS produced significant trunk and lumbar kinematic improvements.

Incidence of Cochlear Implant Electrode Contacts in the Functional Acoustic Hearing Region and the Influence on Speech Recognition with Electric-Acoustic Stimulation.

To investigate the incidence of electrode contacts within the functional acoustic hearing region in cochlear implant (CI) recipients and to assess its influence on speech recognition for electric-acoustic stimulation (EAS) users. Retrospective review. Tertiary referral center. One hundred five CI recipients with functional acoustic hearing preservation (≤80 dB HL at 250 Hz). Cochlear implantation with a 24-, 28-, or 31.5-mm lateral wall electrode array. Angular insertion depth (AID) of individual contacts was determined from imaging. Unaided acoustic thresholds and AID were used to calculate the proximity of contacts to the functional acoustic hearing region. The association between proximity values and speech recognition in quiet and noise for EAS users at 6 months postactivation was reviewed. Sixty percent of cases had one or more contacts within the functional acoustic hearing region. Proximity was not significantly associated with speech recognition in quiet. Better performance in noise was observed for cases with close correspondence between the most apical contact and the upper edge of residual hearing, with poorer results for increasing proximity values in either the basal or apical direction ( r14 = 0.48, p = 0.043; r18 = -0.41, p = 0.045, respectively). There was a high incidence of electrode contacts within the functional acoustic hearing region, which is not accounted for with default mapping procedures. The variability in outcomes across EAS users with default maps may be due in part to electric-on-acoustic interference, electric frequency-to-place mismatch, and/or failure to stimulate regions intermediate between the most apical electrode contact and the functional acoustic hearing region.

Cobalt oxide nanoparticles modified coated graphite potentiometric sensor for quantification of sulfacetamide sodium in its pharmaceutical dosage form and spiked rabbit aqueous humor samples with greenness assessment

This study presents the fabrication of an innovative coated graphite electrode modified with cobalt oxide nanoparticles, for potentiometric determination of Sulfacetamide sodium. The functionalized nano-electrode was compared to a classical one; to study the advantages of addition of nanoparticles which was found to improve the performance characteristics of the electrode including improved sensitivity and selectivity, as well as, extended operational lifespan. The functionalized nano-electrode was more sensitive than the classical one with linearity range (1 × 10−7–1 × 10−2 M) and a limit of detection down to 2.24 × 10−8 M. This small modification increased the electrode’s potential stability by preventing the formation of a water layer on the surface of the solid contact electrode. The electrochemical performance of the proposed sensors was evaluated according to the IUPAC recommendation data and was found to be within the acceptable ranges. These developed potentiometric platforms were applied to quantitatively analyze Sulfacetamide sodium in its pure solutions, pharmaceutical dosage form and spiked rabbit aqueous humor with satisfactory recovery percentages without pre-extraction procedure nor interference of the co-formulated drug; Prednisolone acetate and excipients. The proposed method was statistically compared with the reported method in literature and no statistically significant difference was found. The proposed method was evaluated for its environmental sustainability utilizing the Green Analytical Procedure index (GAPI) as a greenness assessment tool.

Intracranial EEG Structure-Function Coupling and Seizure Outcomes After Epilepsy Surgery.

Surgery is an effective treatment for drug-resistant epilepsy, which modifies the brain's structure and networks to regulate seizure activity. Our objective was to examine the relationship between brain structure and function to determine the extent to which this relationship affects the success of the surgery in controlling seizures. We hypothesized that a stronger association between brain structure and function would lead to improved seizure control after surgery. We constructed functional and structural brain networks in patients with drug-resistant focal epilepsy by using presurgery functional data from intracranial EEG (iEEG) recordings, presurgery and postsurgery structural data from T1-weighted MRI, and presurgery diffusion-weighted MRI. We quantified the relationship (coupling) between structural and functional connectivity by using the Spearman rank correlation and analyzed this structure-function coupling at 2 spatial scales: (1) global iEEG network level and (2) individual iEEG electrode contacts using virtual surgeries. We retrospectively predicted postoperative seizure freedom by incorporating the structure-function connectivity coupling metrics and routine clinical variables into a cross-validated predictive model. We conducted a retrospective analysis on data from 39 patients who met our inclusion criteria. Brain areas implanted with iEEG electrodes had stronger structure-function coupling in seizure-free patients compared with those with seizure recurrence (p = 0.002, d = 0.76, area under the receiver operating characteristic curve [AUC] = 0.78 [95% CI 0.62-0.93]). Virtual surgeries on brain areas that resulted in stronger structure-function coupling of the remaining network were associated with seizure-free outcomes (p = 0.007, d = 0.96, AUC = 0.73 [95% CI 0.58-0.89]). The combination of global and local structure-function coupling measures accurately predicted seizure outcomes with a cross-validated AUC of 0.81 (95% CI 0.67-0.94). These measures were complementary to other clinical variables and, when included for prediction, resulted in a cross-validated AUC of 0.91 (95% CI 0.82-1.0), accuracy of 92%, sensitivity of 93%, and specificity of 91%. Our study showed that the strength of structure-function connectivity coupling may play a crucial role in determining the success of epilepsy surgery. By quantitatively incorporating structure-function coupling measures and standard-of-care clinical variables into presurgical evaluations, we may be able to better localize epileptogenic tissue and select patients for epilepsy surgery. This is a Class IV retrospective case series showing that structure-function mapping may help determine the outcome from surgical resection for treatment-resistant focal epilepsy.

Two-step electrodeposition synthesis of lamellar Ni@NiCo phosphate heterostructures as cathodes for high-performance hybrid supercapacitors

Porous structures grown in situ increase the electrode contact area with the electrolyte, reduce ion diffusion distance, and enhance electrode material electrochemical properties. In this paper, we have adopted a dual-channel electrodeposition strategy with simultaneous electrodeposition and phosphorylation to construct metal-semiconductor contact heterostructures by depositing Ni@NiCo phosphate microspherical nanostructures directly on a copper foam (CF) (Ni@NiCoP/CF) framework at room temperature. The results show that Ni@NiCoP/CF has excellent electrochemical performance with a high specific capacity of 200 mAh g–1 at 1 A g–1, 147.2 mAh g–1 at 20 A g–1 and 93.6 % after 5000 cycles, showing excellent ration performances and cycling stability. In addition, the hybrid supercapacitor composed of Ni@NiCoP/CF as the positive electrode and activated carbon as the negative electrode achieves a high energy density of 48.7 Wh kg−1 at 874 W kg−1 and has excellent cycling stability with 113.23 % capacity retention after 30,000 charge/discharge cycles at a high current density of 10 A g–1. This study serves as a guide for the development of high-performance capacitor cathode materials with high electrochemical activity and capacity.

Electrical Activity and Extremes of Individual Suspended ZnO Nanowires for 3D Nanoelectronic Applications.

We explored the electrical activity and extremes inside individual suspended zinc oxide (ZnO) nanowires (NWs) (diameter: 50-550 nm, length: 5-50 μm) subjected to high forward bias-induced Joule heating using two-terminal current-voltage measurements. NWs were isolated using a reproducible nanometrology technique, employing a nanomanipulator inside a scanning electron microscope. Schottky behavior is observed between installed tips and ZnO NW. The suspended ZnO NWs exhibited an average electrical resistivity ρ (approximately 2.3 × 10-2 Ω cm) and a high electron density n (exceeding 1.89 × 1018 cm-3), comparable to that of InP NWs, GaN NWs, and InAs NWs (1018∼1019 cm-3), suggesting the potential to drive advancements in high-performance NW devices. A maximum breakdown current density (JBD) of ∼0.14 MA/cm2 and a maximum breakdown power density (PBD) of 6.93 mW/μm3 were obtained, both of which are higher than substrate-bound ZnO NWs and consistent with previously reported results obtained from probed ZnO NWs grown vertically on the substrate. Moreover, we discovered that NWs experienced thermal breakdown due to Joule heating and exploited this breakdown mechanism to further investigate the temperature distribution along the ZnO NWs, as well as its dependence on the electrical properties and thermal conductance of contact electrodes. Thermal conductance was determined to be ∼0.4 nW K-1 and ∼1.66 pW K-1 at the tungsten(W)-ZnO NW and platinum(Pt)-ZnO NW contacts, respectively. In addition, we measured the elastic modulus (130-171 GPa), which closely approximated bulk values. We also estimated the nanoindentation hardness to be between 5 and 10 GPa. This work provides valuable insights into the electrical activity and extreme mechanisms, thus providing a better understanding of the potentials and limitations associated with utilizing suspended NWs in 3D nanodevices.

Influence of Lattice Mismatch on Structural and Functional Properties of Epitaxial Ba0.7Sr0.3TiO3 Thin Films.

Substrate-induced strains can significantly influence the structural properties of epitaxial thin films. In ferroelectrics, this might lead to significant changes in the functional properties due to the strong electromechanical coupling in those materials. To study this in more detail, epitaxial Ba0.7Sr0.3TiO3 films, which have a perovskite structure and a structural phase transition close to room temperature, were grown with different thicknesses on REScO3 (RE-rare earth element) substrates having a smaller lattice mismatch compared to SrTiO3. A fully strained SrRuO3 bottom electrode and Pt top contacts were used to achieve a capacitor-like architecture. Different X-ray diffraction techniques were applied to study the microstructure of the films. Epitaxial films with a higher crystalline quality were obtained on scandates in comparison to SrTiO3, whereas the strain state of the functional layer was strongly dependent on the chosen substrate and the thickness. Differences in permittivity and a non-linear polarization behavior were observed at higher temperatures, suggesting that ferroelectricity is supressed under tensile strain conditions in contrast to compressive strain for our measurement configuration, while a similar reentrant relaxor-like behavior was found in all studied layers below 0°C.

Optimization Techniques for Semi-Automated 3D Rigid Registration in Multimodal Image-Guided Deep Brain Stimulation

Abstract Multimodal image registration is vital in Deep Brain Stimulation (DBS) surgery. DBS treats movement disorders by implanting a neurostimulator device in the brain to deliver electrical impulses. Image registration between computed tomography (CT) and cone beam computed tomography (CBCT) involves fusing images with a specific field of view (FOV) to visualize individual electrode contacts. This contains important information about the location of segmented contacts that can reduce the time required for electrode programming. We performed a semi-automated multimodal image registration with different FOV between CT and CBCT images due to the tiny structures of segmented electrode contacts that necessitate high accuracy in the registration. In this work, we present an optimization workflow for multi-modal image registration using a combination of different similarity metrics, interpolators, and optimizers. Optimization-based rigid image registration (RIR) is a common method for registering images. The selection of appropriate interpolators and similarity metrics is crucial for the success of this optimization-based image registration process.We rely on quantitative measures to compare their performance. Registration was performed on CT and CBCT images for DBS datasets with an image registration algorithm written in Python using the Insight Segmentation and Registration Toolkit (ITK). Several combinations of similarity metrics and interpolators were used, including mean square difference (MSD), mutual information (MI), correlation and nearest neighbors (NN), linear (LI), and B-Spline (SPI), respectively. The combination of a correlation as similarity metric, B-Spline interpolation, and GD optimizer performs the best in optimizing the 3D RIR algorithm, enhancing the visualization of segmented electrode contacts. Patients undergoing DBS therapy may ultimately benefit from this.

Fabrication of a Field-Effect Transistor Based on 2D Novel Ternary Chalcogenide PdPS.

Two-dimensional (2D) palladium phosphide sulfide (PdPS) has garnered significant attention, owing to its exotic physical properties originating from the distinct Cairo pentagonal tiling topology. Nevertheless, the properties of PdPS remain unexplored, especially for electronic devices. In this study, we introduce the thickness-dependent electrical characteristics of PdPS flakes into fabricated field-effect transistors (FETs). The broad thickness variation of the PdPS flakes, ranging from 0.7-306 nm, is prepared by mechanical exfoliation, utilizing large bulk crystals synthesized via chemical vapor transport. We evaluate this variation and confirm a high electron mobility of 14.4 cm2 V-1 s-1 and Ion/Ioff > 107. Furthermore, the 6.8 nm-thick PdPS FET demonstrates a negligible Schottky barrier height at the gold electrode contact, as evidenced by the measurement of the temperature-dependent transfer characteristics. Consequently, we adjusted the Fowler-Nordheim tunneling mechanism to elucidate the charge-transport mechanism, revealing a modulated mobility variation from 14.4 to 41.2 cm2 V-1 s-1 with an increase in the drain voltage from 1 to 5 V. The present findings can broaden the understanding of the unique properties of PdPS, highlighting its potential as a 2D ternary chalcogenide in future electronic device applications.

Optimization design of electrode structure of GaAs photoconductive semiconductor switch

Previous studies revealed that changing the electrode structures of a gallium arsenide photoconductive semiconductor switch (GaAs PCSS) can significantly affect the local electric field and current density at the electrodes. Knowing the optimization of the electrode structures of GaAs PCSS can improve the withstand voltage performance and current carrying capability. In this work, we optimize the surface contact electrode structure of GaAs PCSS, and numerical simulations are performed to systematically study the electric field and current density distribution in the bulk of the device. The result shows that the maximum transverse current density and maximum longitudinal current density of the embedded 172° isosceles trapezoid electrode structure are smaller than other kinds of electrode structures, which is the most favorable for improving the withstand voltage and current carrying capability of GaAs PCSS.

Improving Wettability at Positive Electrodes to Enhance the Cycling Stability of Bi-Based Liquid Metal Batteries.

Liquid metal batteries (LMBs) are promising candidates for grid-scale energy storage due to their exceptional kinetics, scalability, and long lifespan derived from the distinctive three-liquid-layer structure. However, the positive electrode (such as Bi) suffers from insufficient wettability on the current collector, resulting in excess electrical resistance and uneven current distribution, thus deteriorating the cycling stability. Here the incorporation of 4 mol% Se into Bi-based metal is proposed producing an interface layer with highly surface-active property that decreases the electrode's contact angle with the 304 stainless-steel (SUS304) from 144.7° to 74.3°, so as to improve the wettability. The as-prepared 20 Ah Li || Bi-Se4 (the content of Se is 4 mol% of Bi) cell cycled 1200 times with capacity fade rate of merely 0.00174% per cycle. This facile and effective approach provides a pathway toward the production of stable cells with an extended lifespan and boosts the practical implementation of LMBs.

RESEARCH ON WIDE SPECTRUM FULL-COLOR NIGHT VISION ELDERLY FACIAL VIDEO HEART RATE AUTOMATIC MEASUREMENT AND WARNING SYSTEM

In recent years, the prevalence of cardiovascular diseases has been growing geometrically, especially among the elderly. Real-time heart rate monitoring becomes an effective measure for preventing cardiovascular diseases. Traditional contact-based real-time heart rate measurement methods require long-term wearing of contact electrodes, which can cause inconvenience to the elderly population. In this study, a wide spectrum full color night vision elderly face video heart rate automatic measurement and early warning system was designed and developed by combining imaging photoplethysmography (IPPG), video acquisition equipment based on starlight wide spectrum camera and high-speed face recognition signal processing algorithm based on deep learning. By constructing a software and hardware platform, a comprehensive evaluation of the system’s application in elderly facial video heart rate measurement experiments was conducted.