Device Operating Conditions Research Articles

Thermal Characterization of Ultrawide Bandgap Semiconductor Devices: A Review

Abstract Ultrawide bandgap (UWBG) semiconductors—such as beta gallium oxide (β‐Ga₂O₃), aluminum nitride (AlN) and diamond—exhibit exceptional electrical and thermal properties, enabling next‐generation power electronics, RF systems, and quantum devices. However, the high power densities and extreme operating conditions of UWBG devices pose significant thermal management challenges. This review provides a comprehensive overview of thermal characterization techniques essential for understanding and mitigating self‐heating, thermal bottlenecks, and reliability concerns in UWBG systems. Optical methods such as thermoreflectance imaging, micro‐Raman thermometry, and IR thermography, alongside electrical approaches like gate resistance thermometry (GRT) and micro thin‐film thermocouples (micro‐TFTCs), are critically compared in terms of resolution, sensitivity, and application scope. The review also highlights recent advancements in hybrid techniques and material innovations to enhance heat dissipation. By evaluating the strengths and limitations of each method, this paper guides the selection of suitable thermal metrology tools for diverse UWBG device architectures and operating environments, facilitating their practical deployment in high‐performance electronics.

Hydrodynamic characteristics of a novel continuous countercurrent micro‐extractor

Abstract Despite the rapid development of micro‐extraction technology in recent years, achieving simple and robust countercurrent micro‐extraction remains a challenge. In this study, a novel rotating micro‐extractor was developed, and robust continuous countercurrent flow can be successfully achieved in it. The effect of device structure, operation condition, and system physical properties on the hydrodynamic characteristics was investigated. Mathematical models were also established to predict the operating region of different flow patterns, the liquid layer thickness, and the maximum throughput. The throughput is up to 18 mL/min in our experimental range and can be further improved by simply increasing the pitch of the spiral microchannel. The increase in channel length will not reduce the maximum throughput, which is quite different from the reported countercurrent micro‐extractors. The unique property enables the newly developed device to achieve both high throughput and large theoretical stages and provides a promising micro‐extraction technique.

A Blending Approach for Dual Surface and Bulk Functionality in Organic Transistors

Abstract Organic transistors are versatile electronic devices that offer diverse functionalities based on device structure and operation conditions. When utilizing an electrolyte, the transistor can operate either as an Electrolyte‐Gated Organic Field‐Effect Transistor (EGOFET), where charges accumulate at the semiconductor/electrolyte interface, offering fast response times but relatively low amplification, or as an Organic Electrochemical Transistor (OECT), where ions infiltrate the channel, offering high amplification but slower response times. In this study, we report combined characteristics of OECTs and EGOFETs, in a single device depending on operation conditions. The bifunctionality is achieved by blending an organic semiconducting p‐type polymer with an Organic Mixed Ionic Electronic Conductor (OMIEC), a n‐type fullerene derivative. The microstructure controlled through the composition and thermal treatments, directs the surface and volumetric processes in the corresponding transistor device. Polymer‐rich domains at the surface facilitate surface charge accumulation and effective p‐type EGOFET operation, while bulk fullerene‐rich domains enhance ionic transport for n‐type OECT behavior. Time response measurements reveal rapid surface charging in an EGOFET‐dominated regime and slower volumetric doping in an OECT‐dominated regime, highlighting the dual transport mechanisms. This research establishes guiding principles for tuning blend composition and microstructure for high‐performance, multifunctional transistors in sensing and bioelectronics.

Tracing Ion Migration in Halide Perovskites with Machine Learned Force Fields.

Halide perovskite optoelectronic devices suffer from chemical degradation and current-voltage hysteresis induced by migration of highly mobile charged defects. Atomic scale molecular dynamics simulations can capture the motion of these ionic defects, but classical force fields are too inflexible to describe their dynamical charge states. Using CsPbI3 as a case study, we train machine learned force fields from density functional theory calculations and study the diffusion of charged halide interstitial and vacancy defects in bulk CsPbI3. We find that negative iodide interstitials and positive iodide vacancies, the most stable charge states for their respective defect type, migrate at similar rates at room temperature. Neutral interstitials are faster, but neutral vacancies are 1 order of magnitude slower. Oppositely charged interstitials and vacancies, as they can occur in device operation or reverse bias conditions, are significantly slower and can be considered relatively immobile.

Electrical Generation of Color Centers in Hexagonal Boron Nitride.

Defects in wide band gap crystals have emerged as a promising platform for hosting color centers that enable quantum photonic applications. Among these, hexagonal boron nitride (hBN), a van der Waals material, stands out for its ability to be integrated into heterostructures, enabling unconventional charge injection mechanisms that bypass the need for p-n junctions. This advancement allows for the electrical excitation of hBN color centers deep inside the large hBN band gap, which has seen rapid progress in recent developments. Here, we fabricate hBN electroluminescence (EL) devices that generate narrowband color centers suitable for electrical excitation. The color centers are localized to tunneling current hotspots within the hBN flake, which are engineered during device fabrication. We outline the optimal conditions for device operation and color center stability, focusing on minimizing background emission and ensuring prolonged operation. Our findings follow up on the existing literature and mark a step forward toward the integration of hBN-based color centers into quantum photonic technologies.

Разработка алгоритма определения периодичности инспекции предохранительных устройств на основе качественного анализа риска

The most crucial aspect of the safe operation of a hazardous production facility is compliance with the industrial safety requirements established by the Federal Law № 116-FZ «On industrial safety of hazardous production facilities», federal norms and rules for industrial safety, and other documents that regulate ensuring industrial safety. Therefore, different types of devices, whose integrity and reliability must also be ensured, are used at hazardous production facilities. The matters of determination of inter-inspectional intervals are considered; Russian and international regulatory documents as to the inspection of safety devices are reviewed. The algorithm takes into account the following factors of safety device operation: working environment, corrosiveness, exposure of a safety device to vibration and pulsation, and the criticality of a safety device for personnel’s and production safety. The frequency of inspection of safety devices in accordance with the proposed algorithm does not contradict the maximum permissible intervals stipulated in API 510, API 576, and NBIC-2015; at the same time, conservatism and objectivity are preserved when determining the criticality. A direct-acting spring safety valve of direct action DN 25/50, PN20, used at hazardous production facilities of oil and gas refinery plants has been selected as an object of research. According to the calculations, the inter-inspectional interval under IPKM—2005 is 36 months (3 years), under API 510/576 is 120 months (10 years), and under the proposed algorithm is 48 months (4 years). Therefore, the proposed algorithm implies qualitative risk analysis that considers operating conditions of safety devices, which requires a high level of expertise and skills from inspecting persons. It is based on the risk assessment, which does not contradict the effective regulatory documents of the Russian Federation and therefore can be applied at hazardous production facilities. Determining frequency in accordance with the proposed algorithm will help improve the economic efficiency of operating companies and ensure an acceptable level of industrial safety.

Topological insulators for thermoelectrics: A perspective from beneath the surface.

Thermoelectric properties of topological insulators have traditionally been examined in the context of their metallic surface states. However, recent studies have begun to unveil intriguing thermoelectric effects emerging from the bulk electronic states of topological insulators, which have largely been overlooked in the past. Charge transport phenomena through the bulk are especially important under typical operating conditions of thermoelectric devices, necessitating a comprehensive review of both surface and bulk transport in topological insulators. Here, we review thermoelectric properties that are uniquely observed in topological insulators, placing special emphasis on unconventional phenomena emerging from bulk states. We demonstrate that unusual thermoelectric effects arising from bulk states, such as band inversion-driven warping, can be discerned in experiments through a simple analysis of the weighted mobility. We believe that there is still plenty to uncover within the bulk of topological insulators, yet our current understanding can already inspire new strategies for designing and discovering new materials for next-generation thermoelectrics.

Prototype Alat Pegering Kaos Kaki Prototype Of Sock Drying Machine

Socks are essential daily wear that require special care, including an effective drying process to prevent unpleasant odors and the growth of bacteria and fungi. Conventional drying methods often face challenges, especially in high-humidity environments or during unfavorable weather conditions. This study aims to design and develop a prototype sock dryer that is more efficient and hygienic. The prototype utilizes a combination of a heater, UV lamp, and humidity and temperature sensors to ensure optimal drying without damaging fabric fibers. A microcontroller-based control system using Arduino Uno is implemented to regulate device operation and monitor sock conditions during drying. Testing results indicate that the device effectively dries cotton socks in damp conditions faster than conventional methods. Additionally, the sterilization feature with a UV lamp helps reduce the risk of microbial growth. This innovation is expected to provide users with a practical, hygienic, and efficient way to dry socks without depending on weather conditions. Further development can be carried out to enhance drying capacity and energy efficiency.

In-device Battery Failure Analysis.

Lithium-ion batteries are indispensable power sources for a wide range of modern electronic devices. However, battery lifespan remains a critical limitation, directly affecting the sustainability and user experience. Conventional battery failure analysis in controlled lab settings may not capture the complex interactions and environmental factors encountered in real-world, in-device operating conditions. This study analyzes the failure of commercial wireless earbud batteries as a model system within their intended usage context. Through multiscale and multimodal characterizations, the degradations from the material level to the device level are correlated, elucidating a failure pattern that is closely tied to the specific device configuration and operating conditions. The findings indicate that the ultimate failure mode is determined by the interplay of battery materials, cell structural design, and the in-device microenvironment, such as temperature gradients and their fluctuations. This holistic, in-device perspective on environmental influences provides critical insights for battery integration design, enhancing the reliability of modernelectronics.

Melting conditions for porous heat-generating device with active cooling: approximate analytical solution

In thermal engineering applications (for example, when studying the operating conditions of thermal storage and electrochemical devices), problems often arise related to the phase transition front propagation in thermally stressed elements. This paper considers the solution of a simplified problem of heating element flow cooling. To this end, analytical estimates were obtained for the critical values of heat release intensity corresponding to the onset of melting and complete melting of the porous sample. The results are compared with numerical calculations.

On the increase of the melting temperature of water confined in one-dimensional nano-cavities.

Water confined in nanoscale cavities plays a crucial role in everyday phenomena in geology and biology, as well as technological applications at the water-energy nexus. However, even understanding the basic properties of nano-confined water is extremely challenging for theory, simulations, and experiments. In particular, determining the melting temperature of quasi-one-dimensional ice polymorphs confined in carbon nanotubes has proven to be an exceptionally difficult task, with previous experimental and classical simulation approaches reporting values ranging from ∼180K up to ∼450K at ambient pressure. In this work, we use a machine learning potential that delivers first principles accuracy (trained to the density functional theory approximation revPBE0-D3) to study the phase diagram of water for confinement diameters 9.5 < d < 12.5 Å. We find that several distinct ice polymorphs melt in a surprisingly narrow range between ∼280 and ∼310K, with a melting mechanism that depends on the nanotube diameter. These results shed new light on the melting of ice in one-dimension and have implications for the operating conditions of carbon-based filtration and desalination devices.

Drop-by-Drop Addition of Reagents to a Double Emulsion.

Developments in droplet microfluidics have facilitated an era of high-throughput, sensitive single-cell, or single-molecule measurements capable of tackling the heterogeneity present in biological systems. Relying on single emulsion (SE) compartments, droplet assays achieve absolute quantification of nucleic acids, massively parallel single-cell profiling, and more. Double emulsions (DEs) have seen recent interest for their potential to build upon SE techniques. DEs are compatible with flow cytometry enabling high-throughput multi-parameter drop screening and eliminate content mixing due to coalescence during lengthy workflows. Despite these strengths, DEs lack important technical functions that exist in SEs such as methods for adding reagents to droplets on demand. Consequently, DEs cannot be used for multistep workflows which has limited their adoption in assay development. Here, strategies to enable reagent addition and other active manipulations on DEs are reported by converting DE inputs to SEs on chip. After conversion, drops are manipulated using existing SE techniques, including reagent addition, before reforming a DE at the outlet. Device designs and operation conditions achieving drop-by-drop reagent addition to DEs are identified and used as part of a multi-step aptamer screening assay performed entirely in DE drops. This work enables the further development of multistep DE droplet assays.

An Approach for Predicting the Lifetime of Lead-Free Soldered Electronic Components: Hitachi Rail STS Case Study

Throughout much of the 20th century, Sn–Pb solder dominated electronics. However, environmental and health concerns have driven the adoption of lead-free alternatives. Since 2006, legislation such as the European Union’s RoHS Directive has mandated lead-free solder in most electronic devices, prompting extensive research into high-performance substitutes. Lead-free solders offer advantages such as reduced environmental impact and improved reliability but replacing Sn–Pb presents challenges in areas like melting point and wetting ability. This transition is primarily motivated by a focus on protecting environmental and human health, while ensuring equal or even improved reliability. Research has explored lead-free solder’s mechanical properties, microstructure, wettability, and reliability. However, there is a notable lack of studies on its long-term performance and lifetime influence. To address this gap, mathematical models are used to predict intermetallic bond evolution from process conditions, validated with experimental tests. This study contributes by extending these models to predict bond evolution under typical operating conditions of devices and comparing the predictions with actual intermetallic thickness values found through metallographic sections.

Stability of the properties of an acousto-optical converter based on polyvinylidene fluoride films under external influence

Subject of study. The study focuses on an acousto-optical modulator composed of a polyvinylidene fluoride film with transparent indium–tin oxide electrodes deposited on both surfaces. Aim of study. The aim is to analyze the stability of the mechanical, piezoelectric, and optical properties of the polyvinylidene fluoride film-based acousto-optical modulators with indium–tin oxide electrodes during manufacturing and operation at different temperatures. Method. In this method, the mechanical characteristics of samples under tension are measured along two directions (parallel and perpendicular to the drawing direction of the polyvinylidene fluoride film) at room temperature to perform a dynamic mechanical analysis under isothermal conditions and within a temperature range of 30°C–180°C. The piezoelectric coefficient d33 is measured, under temperature variation from −40∘C to +80∘C, using a charge-based method with pulsed force impact, and the transmittance is determined within the visible wavelength range from 380 nm to 780 nm to calculate the light transmission coefficient. Main results. An experimental measurement cell was created to measure the piezoelectric coefficient d33 across a wide temperature range. Mechanical test results for static and dynamic loading of the polyvinylidene fluoride film, both before and after the deposition of the indium–tin oxide electrodes, were obtained. Temperature dependencies of d33 for this structure were established from −40∘C to +80∘C, and the optical properties of the samples exposed to low and high temperatures were documented. Practical significance. Based on these findings, recommendations for the operating and storage conditions of acousto-optic devices incorporating the studied structures, along with guidelines for manufacturing, are presented.

Solution-Processable and Eco-Friendly Functionalization of Conductive Silver Nanoparticles Inks for Printable Electronics

The functionalization of conductive inks has been carried out through the decomposition of hydrogen peroxide (H2O2) onto the surface of silver nanoparticles (AgNPs). The ink prepared using this eco-friendly chemical reagent has been characterized structurally, chemically, and morphologically, showing the presence of stable AgNPs with suitable properties as well as the absence of residual contamination. The electrical conductivity of such a solution-processable ink is evidenced for patterns designed on flexible photographic paper substrates, using a refillable fountain pen that is implemented as a printing mechanism for the fabrication of simple printed circuit boards (PCBs). The functionality and durability of the tested systems are demonstrated under various mechanical constraints, aiming to basically reproduce the normal operation conditions of flexible electronic devices. The obtained results indicate that the implementation of these AgNP-based inks is relevant for direct applications in inkjet printing technology, thus paving the way for the use of greener chemicals in ink preparation.

Highly thermal conductive Graphene/Paraffin composite for efficient thermal management of electronics

Highly thermal conductive Graphene/Paraffin composite for efficient thermal management of electronics

Monitoring internal heat fluxes on Pulsating Heat Pipes using Kalman filter – Numerical and experimental results

The present study proposes an approach to monitor the wall-to-fluid internal heat flux on Pulsating Heat Pipes (PHP), which provides meaningful information about the efficiency and limiting operation conditions of such devices. In this sense, the current work adopts the Kalman Filter (KF) to estimate the heat flux between the working fluid and the internal tube wall along the adiabatic section of a PHP device by solving an inverse heat conduction problem. The KF is a well-known tracking technique, and therefore the current study is attractive due to the possibility of real-time evaluation of internal heat fluxes, a prospect that is extremely difficult to realize by standard whole domain inverse problem techniques. A high-speed and high-resolution infrared camera performs the temperature acquisition on the external wall of the PHP device. Two mathematical heat conduction models are considered: complete and thin-wall models. The complete model determines the temperature and heat flux evolution over time, and the thin-wall model is used to correct the random walk parameter on the KF formulation. Since the time step needed to the KF evolution model is smaller than the measurements acquisition interval, a matrix manipulation is used during the prediction step, reducing the number of mathematical operations. Hence, instead of predicting the states until reaching the measurement times, a proper mathematical manipulation reduces several mathematical operations to a single one. Then, the KF estimation capability is evaluated by considering synthetic data with different noise levels and different heat flux values. Subsequently, real experimental data are employed, and the results are compared with the ones obtained via a standard whole domain technique. The results obtained with the KF presented good visual agreement with the exact solution. Once the KF presents a delayed response, which is a characteristic of some filtering techniques, the errors with synthetic data were calculated offsetting the delay of the estimation in time in order to make a fair comparison, showing a maximum estimation error lower than 36 % considering the highest noise level. The synthetic data considered 20 s of time experiment, and the KF was able to estimate the PHP internal heat flux in less than 12 s, including the smoothing temperature step, showing fast and accurate results. For the real experimental data, the agreement between the KF and a whole domain technique is highly commendable, demonstrating a deviation of 25.5 % between both techniques. Moreover, the KF required significantly less computational time. The proposed methodology for heat flux estimation on PHPs is promising to evaluate their thermal behavior in real-time due to a low CPU time and computational memory required, as well as its simplicity to be implemented, possibly on embarked devices. Such information may therefore provide a thermal indicator of the correct functioning of PHPs in real time applications.

Limitations in the electrochemical analysis of voltage transients.

Objective. Chronopotentiometric voltage transients (VTs) are used to assess the performance of bionic electrodes. The data obtained from VTs are used to define the safe operating conditions of clinical devices. Various approaches to analysing VTs have been reported, and a number of limitations in the accuracy of the measurements in relation to electrode size have been noted previously.Approach. The impact of electronic hardware and electrode configuration on VTs is discussed.Main results. The slew rate, rise time, sample time, minimum pulse length and waveform averaging characteristics of the electronic hardware, and electrode configuration will impact on VT measurement accuracy. Subsequently, activation and polarisation voltage measurements, and the definition of safe stimulation levels can be affected by the electronic hardware and electrode configuration.Significance. This article has identified some limitations in the previous literature related to the measurement and reporting of VTs and subsequent analysis of access and polarisation voltages. Furthermore, the commonly used Shannon plot used to define safe stimulation protocols does not correct for uncompensated resistance, account for electrode roughness or changes in electrode configuration. The creation of a safe stimulation plot which has been corrected for uncompensated resistance would generate more widely applicable stimulation guidelines for clinical devices used in different anatomical locations such as endovascular neural interfaces.

Ag(IPr)(bpy)][PF6]: brightness and darkness playing with aggregation induced phosphorescence for light-emitting electrochemical cells.

Heteroleptic silver(I) complexes have recently started to attract attention in thin-film lighting technologies as an alternative to copper(I) analogues due to the lack of flattening distortion upon excitation. However, the interpretation of their photophysical behavior is challenging going from traditional fluorescence/phosphorescence to a temperature-dependent dual emission mechanism and ligand-lock assisted thermally activated delayed fluorescence. Herein, we unveil the photoluminescence behavior of a three-coordinated Ag(I) complex with the N-heterocyclic carbene (NHC) ligand and 2,2'-bipyridine (bpy) as the N^N ligand. In contrast to its low-emissive Cu(I) complex structural analogues, a strong greenish emission was attributed to the presence of aggregates formed by π-π intermolecular interactions as revealed by the X-ray structure and aggregation induced emission (AIE) studies in solution. In addition, the temperature-dependent time-resolved spectroscopic and computational studies demonstrated that the emission mechanism is related to a phosphorescence emission mechanism of two very close lying (ΔE = 0.08 eV) excited triplet states, exhibiting a similar delocalized nature over the bipyridine ligands. Unfortunately, this favourable AIE is lost upon forming homogeneous thin films suitable for lighting devices. Though the films showed very poor emission, the electrochemical stability under device operation conditions is remarkable compared to the prior-art, highlighting the potential of [Ag(NHC)(N^N)][X] complexes in thin-film lighting.

Are topological insulators promising thermoelectrics?

Some of the best thermoelectric (TE) materials to date are also topological insulators (TIs). While many studies have investigated the effects of topologically-protected TI surface states on TE properties, the conditions needed to realize such effects are quite different from typical operating conditions of TE devices for, e.g., power generation and room-temperature Peltier cooling. As a result, it is still unclear what properties of TIs, especially those related to the bulk band structure, are beneficial for TE performance, if any. Here, we perform high-throughput transport calculations using density functional theory to reveal that, within the same structure type, TIs tend to outperform normal insulators as TEs when properly optimized. The calculations also indicate that the TE performance is higher for TIs with strongly inverted bands. To explain these observations, we develop models based on Boltzmann transport theory which show that warping driven by band inversion, a key characteristic of TIs, is responsible for the high TE performance of TIs. We find that warping benefits the TE performance because of reduced transport mass and effectively higher valley degeneracy. Our results show that the band inversion strength is a critical property of a TI dictating the TE performance, and we suggest potential strategies to tune the inversion strength and enhance the TE performance in TIs, such as alloying and strain engineering. The study marks TIs as serious candidates for TE applications owing to band inversion-driven warping.