Optimization Of Devices Research Articles

Optimization of Microcapillary Flow Devices 3D Printed with Stereolithography Technology

Optimization of Microcapillary Flow Devices 3D Printed with Stereolithography Technology

Improved breakdown voltage and dynamic Ron characteristics in normally-off GaN-based HEMTs featuring fully-recessed and bilayer-dielectric gate structure

Abstract The degradation of dynamic on-resistance (Ron) is a major challenge in GaN-based high electron mobility transistors (HEMTs), which seriously affects their performance and reliability. The degradation area of dynamic Ron mainly comes from two aspects. One is the region below the gate that also affects the threshold voltage (Vth) of the devices. And the other one is the interface region of the gate to drain access. The optimal device exhibits a Vth of 0.97 V, a small Vth hysteresis of only 20 mV, a high current density of 723 mA/mm, and a breakdown voltage (BV) of 760 V which could be further boosted when additional field plate design is employed. It is found that when high voltage drain stress is applied, a positive Vth shift is induced, leading to the decrease of the effective gate driving voltage, and thus the dynamic Ron of the devices is increased. Of particular concern is the effects of dielectric layer and/or interface of the access region on the dynamic Ron degradation, which can be alleviated by removing the dielectric layer of the access region.

Pyrene‐Based Self‐Assembled Monolayer with Improved Surface Coverage and Energy Level Alignment for Perovskite Solar Cells

AbstractRecently, the efficiency of p‐i‐n perovskite solar cells drastically increased, a pivotal factor being the incorporation of self‐assembled monolayers (SAMs) as a hole‐transporting layer (HTL). SAMs offer many advantages over conventional HTLs, including minimal material requirements, low cost, and facile processing. Current research is mainly focused on the development of carbazole‐derived SAMs. However, the versatility of organic chemistry allows for the design of SAMs with alternative organic cores that may possess specific benefits. In this study, three novel SAMs are incorporated in p‐i‐n perovskite solar cells, each based on an aromatic core commonly used in organic semiconductors. The novel SAMs vary in their energy level alignment with the perovskite active layer. Optimal alignment is achieved with a pyrene‐based SAM (4PAPyr), resulting in solar cells that outperform the commercially available 2PACz. Moreover, due to improved surface coverage, the use of 4PAPyr leads to a significantly higher number of working solar cell devices when compared to 2PACz, which is of particular interest with regard to upscaling. After device optimization, a power conversion efficiency of 22.2% is achieved with 4PAPyr. This research underlines the importance of diversifying SAMs to unlock further advancements in perovskite solar cell efficiency and scalability.

Broadband Waveguide Chip Design with Phase Measurement Function for Enhancing Optical Interferometric Imaging

The waveguide chip with a phase measurement function has garnered significant attention in the field of imaging optics, emerging as a crucial component in optical interferometric imaging systems. Enhancing the working bandwidth of these waveguide chips is essential for improving the imaging quality of interferometric systems. However, most existing designs primarily focus on narrow bands, with no reported research on broadband designs. This paper introduces a novel broadband waveguide chip design that incorporates a phase measurement function. We explore the fundamental structure and working principle of this innovative design. Fabricated on a silicon substrate, the chip features a silicon dioxide cladding layer and a germanium-doped silicon dioxide core layer, strategically optimized for performance. Utilizing the Beam Propagation Method (BPM), we conduct detailed simulations to determine the optimal device parameters. The simulation results demonstrate the effectiveness of our design, showing a phase measurement deviation of approximately 5° at a center wavelength of 1550 nm across a 300 nm wavelength range. The loss of the device is approximately 0.8 dB. These findings provide a solid foundation for future experimental implementations and fabrications, offering both a theoretical framework and technical reference for advancing the practical use of broadband waveguide chips with phase measurement functions in optical interferometric imaging.

BLOOD PRESSURE MONITORING USING TELEMEDICINE TECHNOLOGIES IN PATIENTS WITH HEART FAILURE

An urgent task of modern cardiology is to ensure continuous monitoring of cardiovascular patients' condition indicators. Monitoring of patients with heart failure (HF) is especially important due to the instability of the condition, extremely high prevalence of pathology and life-threatening. Currently, active search and development of optimal devices and programs for medical telemonitoring continues. The review presents the results of Russian and foreign studies on the introduction of invasive and non-invasive technologies for blood pressure (BP) monitoring and demonstrates their clinical significance. The comparison of clinical data of several studies using wireless remote monitoring of pulmonary artery pressure with the help of CardioMEMS sensor was carried out. Mobile applications and telephone monitoring are also considered as an alternative to invasive devices, and information about their effectiveness and impact on the quality of life of patients is given. The article also compares the effectiveness of treatment of hypertension and HF using remote monitoring with standard practice and demonstrates the dependence of the risk of hospitalization for HF and the presence of monitoring of the condition.

Recent Advances in electrode optimization of electrochemical energy devices using Topology Optimization

Abstract Topology optimization (TO) has emerged as a prominent trend in recent years, driven by its ability to explore optimized material distributions from scratch. Recently, there has been a significant shift in the application of TO, in optimizing systems involving complex electrochemical reactions, particularly electrode porous structures. This paper aims to examine the utilization of TO in enhancing electrodes across various electrochemical devices. It encompasses a broad spectrum of applications, including the optimization of porous electrodes through the density-based method and interfaces between electrodes and electrolytes through the level-set method. The paper will delve into the challenges and opportunities associated with employing TO in electrode design for electrochemical devices. These challenges involve addressing computational complexity, the absence of theoretical foundations for optimized structures, and the fabrication of complex structures for practical real-world applications. Additionally, beyond TO, the paper will spotlight other notable techniques in the structural design of porous electrodes using mathematical optimization. By offering insights into state-of-the-art research and developments in TO's application to electrode design, this paper provides researchers with valuable resources to navigate the evolving landscape of electrode design for electrochemical energy devices.

A strategy for enhancing interfacial thermal transport in Ga2O3-diamond composite structure by introducing an AlN interlayer

Heat dissipation issues have emerged in power devices due to miniaturization and high power density, particularly for materials like low-thermal-conductivity gallium oxide (Ga2O3). Increasing interfacial heat transfer has been identified as a critical strategy for tackling these issues. This study first explored the thermal transport of Ga2O3-diamond interfaces in composite structures containing an AlN interlayer. First-principles calculations revealed that the AlN interlayer improved interfacial bonding between Ga2O3 and diamond. Subsequently, Ga2O3 membranes were deposited on diamond substrates with and without interlayers using pulsed laser deposition (PLD), and the structural and thermal characteristics were examined. The interlayer strategy was shown to be effective in improving the quality of Ga2O3 thin films, including improved crystallinity, a smoother surface, and fewer oxygen vacancies. The thermal characteristics were accordingly improved: the thermal conductivity of Ga2O3 increased from 5.5±0.3–6.0±0.3 W/m·K, and the thermal boundary conductance of Ga2O3-diamond interface (TBCGaO-dia) increased from 46.1±2.3–60.9±3.0 MW/m2·K. Molecular dynamics (MD) analysis further revealed that the enhancement in phonon transmission was due to the increase in the low-frequency phonon participation rate. Additionally, the electro-thermal simulation using COMSOL confirmed the effectiveness of the AlN interlayer in mitigating the self-heating effect. These findings offer a new route for improving interface heat transport and pave the way for the optimization and design of reliable Ga2O3-based devices.

Aeroelasticity of an aircraft wing with nonlinear energy sink

In this paper, the effectiveness of nonlinear energy sinks on enhancing aeroelastic stability and post-instability response of aircraft wings is investigated. The wing has two degrees of freedom in bending and torsion, and is modelled using an extended Euler-Bernoulli beam theory with hardening nonlinearity. A Nonlinear Energy Sink (NES) absorber is embedded inside the wing distributed along the wing span. The wing attached unsteady aerodynamic loads are simulated using the Wagner's indicial lift model. The structural dynamics of the wing are derived using Extended Hamilton's Principle and it is discretised using Galerkin's method. The NES mass is connected to the wing spar through a linear damper and nonlinear spring with a cubic stiffness nonlinearity. The coupled aeroelastic equations are then transformed to state space. Then, integrated numerically to resolve the bending and torsional response of the wing to study the impact of spanwise and chordwise positions of the embedded NES on flutter suppression and instability response enhancement. The results demonstrate that the NES is most efficient and is most sensitive to changes in the stiffness when placed at the wingtip. For a given chordwise location, it is found that there is a range of flow speeds over which the NES is most effective and reducing the chordwise offset lowers the speed of the peak efficiency range and moves it closer to the flutter speed. In addition, increasing the stiffness coefficient of the NES improves the efficiency of the device in the immediate post-flutter region. Two near optimum NES devices are proposed with a mass ratios of 1% (located at the wingtip) and 2.5% (located at 75% span). Both of these improve the flutter speed by 5%, and reduce the post-flutter response by 64.5% and 59.2%, respectively.

Multi-Objective Optimization of an Inertial Wave Energy Converter for Multi-Directional Wave Scatter

To advance wave energy devices towards commercialization, it is essential to optimize their design to enhance system performance. Additionally, a thorough economic evaluation is crucial for making these technologies competitive with other renewable energy sources. This study focuses on the techno-economic optimization of an innovative inertial system, the so-called SWINGO system, which is based on gyropendulum technology. SWINGO stands out due to its high energy efficiency in multi-directional installation sites, where wave directions vary significantly throughout the year. The study introduces the application of a multi-objective Evolutionary Algorithm (EA), specifically the Non-dominated Sorting Genetic Algorithm II (NSGA-II), to optimize the techno-economic performance of the SWINGO system. This approach aims to identify optimal design parameters that maximize energy extraction while considering economic viability. By deriving a Pareto frontier, a set of optimal devices is selected for further analysis. The performance of the SWINGO system is also compared to an alternative (mono-directional) inertial wave energy converter, the Inertial Sea Wave Energy Converter (ISWEC), to highlight the differences in techno-economic outcomes. Both systems are evaluated at two different installation sites: Pantelleria island and the North Sea in Denmark, with a focus on the directional wave scatter at each location.

Unlocking Nanoprecipitation: A Pathway to High Reversibility in Nanofluidic Memristors.

Solid-state nanochannels have emerged as a promising platform for the development of ionic circuit components with analog properties to their traditional electronic counterparts. In the last years, nanofluidic devices with memristive properties have attracted special interest due to their applicability in, for example, the construction of brain-like computing systems. In this work, an asymmetric track-etched nanofluidic channel with memory-enhanced ion transport is reported. The results illustrate that the formation of nanoprecipitates on the channel walls induces memory effects in ion transport, leading to characteristic hysteresis loops in the current-voltage curves, a hallmark of memristive behavior. Notably, these memristive properties are achievable with a straightforward experimental setup that combines an aqueous solvent and a relatively low-soluble inorganic salt. The various conductance states can be rapidly and reversibly tuned over prolonged time scales. Furthermore, under appropriate measurement conditions, the nanofluidic device can alternate between different iontronic regimes and states, encompassing ion current rectification, ON-OFF states, and memristor-like behavior. These findings provide insights into the design and optimization of nanofluidic devices for bioinspired ionic circuit components.

Decoding roughness perception in distributed haptic devices

Abstract The ability to render realistic texture perception using haptic devices has been consistently challenging. A key component of texture perception is roughness. When we touch surfaces, mechanoreceptors present under the skin are activated and the information is processed by the nervous system, enabling perception of roughness/smoothness. Several distributed haptic devices capable of producing localized skin stretch have been developed with the aim of rendering realistic roughness perception; however, current state-of-the-art devices rely on device fabrication and psychophysical experimentation to determine whether a device configuration will perform as desired. Predictive models can elucidate physical mechanisms, providing insight and a more effective design iteration process. Since existing models (1, 2) are derived from responses to normal stimuli only, they cannot predict the performance of laterally actuated devices which rely on frictional shear forces to produce localized skin stretch. They are also unable to predict the augmentation of roughness perception when the actuators are spatially dispersed across the contact patch or actuated with a relative phase difference (3). In this study, we have developed a model that can predict the perceived roughness for arbitrary external stimuli and validated it against psychophysical experimental results from different haptic devices reported in literature. The model elucidates two key mechanisms: 1) The variation in the change of strain across the contact patch can predict roughness perception with strong correlation 2) The inclusion of lateral shear forces is essential to correctly predict roughness perception. Using the model can accelerate device optimization by obviating the reliance on trial-and-error approaches.

Magneto-Dielectric Synergy and Multiscale Hierarchical Structure Design Enable Flexible Multipurpose Microwave Absorption and Infrared Stealth Compatibility

HighlightsA multiscale hierarchical structure design, integrating wrinkled MXene radar-infrared shielding layer and flexible Fe3O4@C/PDMS microwave absorption layerThe assembled stealth devices realize a near-perfect stealth capability in both X-band (8-12 GHz) and long-wave infrared (8-14 µm) wavelength ranges.The optimal device demonstrates exceptional curved surface conformability, self-cleaning capability (contact angle ≈ 129°), and abrasion resistance (recovery time ≈ 5 s).

Tunable interfacial properties of monolayer GeSb2Te4 on metal surfaces

Abstract Atomically thin monolayer (ML) GeSb 2 Te 4 (GST) holds promising prospects in non-volatile memory applications because of its high non-homogeneous crystallization rate. In GST-based devices, the interaction between GST and metals is crucial, as it affects the electronic properties. Herein, based on first-principles calculations, we investigate the interaction and Schottky barrier height of contacts formed by the combination of ML GST with various metals. It is found that the interfaces of GST with Pt, Pd, Ir and W exhibit strong interaction, characterized by large binding energies ranging from 1.394 to 1.015 eV , and the interfaces between GST and Cu, Ag and Au display weak interaction. For the seven contacts, Ag and W form Ohmic contacts with ML GST, while Cu, Au, Pd, Ir, and Pt form n-type Schottky contacts, with Schottky barrier heights ranging from 0.029 to 0.353 eV . The strong Fermi level pinning at GST-metal interface is observed with a pinning factor of 0.378. Additionally, altering the interfacial distance and optimizing the layers of GST enable a transition from Ohmic contact to Schottky contact. These findings provide crucial guidance for the design and optimization of electronic devices based on phase change materials like GST.

Efficient Triplet Harvesting via Hot Exciton Utilization in Solution Processed OLEDs Employing Tetraphenyl Buta‐1,3‐Diene Based AIE Emitters

AbstractHigh photoluminescence quantum yield (PLQY) especially in solid‐state together with harvesting radiative triplet excitons are essential to achieve efficient organic light‐emitting diodes (OLEDs). Herein, the aggregation induced emission (AIE) active tetraphenyl buta‐1,3‐diene (TPB) moiety has been employed and tactfully modified to obtain orthogonally oriented donor‐acceptor (D‐A‐π‐A‐D) type derivatives (namely, TPB‐CHO‐TPA and TPB‐CN‐TPA) which possess additionally the hybridized local and charge transfer (HLCT) type excited‐state. Moreover, computational studies have revealed the possibility of triplet harvesting through hot exciton mechanism in these designed emitters. These key features along with excellent solubility in most of the organic solvents have encouraged to utilize these as light emitting materials for solution processed non‐doped and doped OLED devices. The optimal OLED device using TPB‐CHO‐TPA exhibits yellow light emission (ELmax = 572 nm and CIEx,y = 0.48, 0.51) having maximum external quantum efficiency (EQEmax) of 7.6% with power and current efficiency of 6.1 lm W−1 and 8.9 cd A−1 where the calculated exciton utilization efficiency (EUE) approaches to 97%, indicating efficient triplet harvesting in electroluminescence process. This work signifies a novel design strategy for AIE‐based HLCT type emitters having efficient hot exciton utilization which can pave the way for future development of TPB based highly efficient OLED devices.

Electronic Barriers Behavioral Analysis of a Schottky Diode Structure Featuring Two-Dimensional MoS2

This research presents a comprehensive study of a Schottky diode fabricated using a gold wafer and a bilayer molybdenum disulfide (MoS2) film. Through detailed simulations, we investigated the electric field distribution, potential profile, carrier concentration, and current–voltage characteristics of the device. Our findings confirm the successful formation of a Schottky barrier at the Au/MoS2 interface, characterized by a distinct nonlinear I–V relationship. Comparative analysis revealed that the Au/MoS2 diode significantly outperforms a traditional W/Si structure in terms of rectification performance. The Au/MoS2 diode exhibited a current density of 1.84 × 10−9 A/cm2, substantially lower than the 3.62 × 10−5 A/cm2 in the W/Si diode. Furthermore, the simulated I–V curves of the Au/MoS2 diode closely resembled the ideal diode curve, with a Pearson correlation coefficient of approximately 0.9991, indicating an ideality factor near 1. A key factor contributing to the superior rectification performance of the Au/MoS2 diode is its higher Schottky barrier height of 0.9 eV compared to the 0.67 eV of W/Si. This increased barrier height is evident in the band diagram analysis, which further elucidates the underlying physics of Schottky barrier formation in the Au/MoS2 junction. This research provides insights into the electronic properties of Schottky contacts based on two-dimensional MoS2, particularly the relationship between electronic barriers, system dimensions, and current flow. The demonstration of high-ideality-factor Au/MoS2 diodes contributes to the design and optimization of future electronic and optoelectronic devices based on 2D materials. These findings have implications for advancements in semiconductor technology, potentially enabling the development of smaller, more efficient, and flexible devices.

Fabrication-related impurity study of thin superconducting Al films using x-ray absorption spectroscopy

Superconducting aluminum thin films are integral to many astrophysics detector applications. Using x-ray absorption spectroscopy (XAS), we have studied the residues and adsorbates created during various standard lithography and etch steps, which are commonly used to pattern thin aluminum films into device structures. We have observed the formation of aluminum oxide as α-Al2O3 and aluminum fluoride as β-AlF3. We have observed correlations between these XAS signatures and the Al film’s microwave loss due to two-level systems. This study, which guides the way for future device optimization, further explores the chemical impact of different process steps, including standard silicon substrate wafer cleaning processes, sulfur-hexa-fluoride plasma etching, passivation with a fluorocarbon, and exposure to photoresist adhesion promoters during the lithography process with the help of control samples.

Pacemaker Optimization Mechanisms in the Spectrum of Cardiac Disease Rationale to Protocol

Introduction: The problem can be stated as over three billion choices to improve 14 disease states with nine optimization goals (some of the optimization goals are diametrically opposed) to improve dyspnea, shortness of breath, fatigability, exercise intolerance, edema, swelling, fluid retention, and arrhythmias. The goal is to increase the Left Ventricular Outflow Integral, reduce mitral regurgitation, increase longitudinal conduction velocities, and restore synchrony of the septum to the ventricle that needs it the most. The paper is organized in the following sections: (I) Spectrum of Cardiac Disease and Desired Pacing Outcomes; (II) Echo Evaluation of Disease Processes; (III) Pacing Goals in the Spectrum of Disease; (IV) Remodeling—Mathematical Model; (V) Method of Optimization of the Pacing Devices. Conclusions: Pacing trials provided the basic justification for an additional pacing lead but fell short in optimizing individual patients. The physician needs to recognize the spectrum of disease and use the protocol to improve the quality of life of the individual patient. A method to accomplish this task for the spectrum of cardiac disease is presented.

Generation of a virtual cohort of TAVI patients for in silico trials: a statistical shape and machine learning analysis.

In silico trials using computational modeling and simulations can complement clinical trials to improve the time-to-market of complex cardiovascular devices in humans. This study aims to investigate the significance of synthetic data in developing in silico trials for assessing the safety and efficacy of cardiovascular devices, focusing on bioprostheses designed for transcatheter aortic valve implantation (TAVI). A statistical shape model (SSM) was employed to extract uncorrelated shape features from TAVI patients, enabling the augmentation of the original patient population into a clinically validated synthetic cohort. Machine learning techniques were utilized not only for risk stratification and classification but also for predicting the physiological variability within the original patient population. By randomly varying the statistical shape modes within a range of ± 2σ, a hundred virtual patients were generated, forming the synthetic cohort. Validation against the original patient population was conducted using morphological measurements. Support vector machine regression, based on selected shape modes (principal component scores), effectively predicted the peak pressure gradient across the stenosis (R-squared of 0.551 and RMSE of 11.67mmHg). Multilayer perceptron neural network accurately predicted the optimal device size for implantation with high sensitivity and specificity (AUC = 0.98). The study highlights the potential of integrating computational predictions, advanced machine learning techniques, and synthetic data generation to improve predictive accuracy and assess TAVI-related outcomes through in silico trials.

Microscopic Origin of Polarity-Dependent VTH Shift in Amorphous Chalcogenides for 3D Self-Selecting Memory.

Ovonic threshold switching (OTS) selectors based on amorphous chalcogenides can revolutionize 3D memory technology owing to their self-selecting memory (SSM) behavior. However, the complex mechanism governing the memory writing operation limits compositional and device optimization. This study investigates the mechanism behind the polarity-dependent threshold voltage shift (ΔVTH) through theoretical and experimental analyses. By examining the physical principles of threshold switching and conducting defect state analysis, the ΔVTH as a memory window is confirmed to be attributed to the dynamics of charged defects and their gradient near electrodes, influenced by the nonuniform electric field after threshold switching. This study provides critical insights into the operational mechanism of OTS-based SSM, known as selector-only memory, highlighting its advantages for developing high-density, low-cost, and energy-efficient memory technologies in the artificial intelligence era.

Don't Throw Away Your Notebook: Effects of Task Difficulty and Presentation Medium on Memory Performance.

People are increasingly reliant on various electrical devices for learning and memory, yet the implications and consequences of this dependence remain poorly understood. The present study aimed to investigate how learning through electrical media impacts recall under varying task difficulties. During this study, participants encoded information related to daily life situations (low difficulty), academic conceptual knowledge (middle difficulty), or associative word pairs (high difficulty), presented on smartphones, computers, or paper. At test, they recalled the omitted content based on the provided cue information. A significant screen-inferiority effect was observed for both computers and smartphones. However, the impairment related to computers disappeared in the retrieval of daily life situations and academic conceptual knowledge, whereas the impairment associated with smartphones was consistently present across all tasks. These results suggest that memory performance is modulated by the interaction between the presentation medium and the specific demands of the task, highlighting a more pronounced screen-inferiority memory effect when the media restrict the depth of processing or when the memory tasks pose greater external challenges. A deeper understanding of these factors can guide the optimization of electrical devices to enhance human memory abilities and functions.