Active Devices Research Articles

Applications, Design Methods, and Challenges for Additive Manufacturing of Thermal Solutions for Heterogeneous Integration of Electronics

Abstract Heterogeneous integration of electronics is critical to the next wave of electronics applications ranging from extremely power dense energy conversion systems to advanced chiplet and co-packaged optics architectures for next-generation computing. Enhanced functionality and operation are essential goals in heterogeneous integration. In all applications, effective thermal management of both active and passive electronic devices is required to support these goals. Additive manufacturing opens new avenues for heterogeneous integration of electronics. This article thus provides a review of additive manufacturing methods and applications in the specific context of thermal solutions for heterogeneous integration of electronics. Three-dimensional printing methods, associated materials (e.g., metal, polymer, ceramic, and composite), and electronics package integration approaches, or conceptual fabrication workflows, are outlined for cold plates, heat sinks, fluid flow manifolds, and thermal interface materials plus composites for electronics. The current status of design optimization methods for additive manufacturing of thermal solutions for electronics is also covered. Future challenges and research directions are outlined to further stimulate the development of advanced manufacturing methods, novel design techniques, and unique electronics package integration capabilities for thermal solutions.

All-optical perception based on partially coherent optical neural networks

In the field of image processing, optical neural networks offer advantages such as high speed, high throughput, and low energy consumption. However, most existing coherent optical neural networks (CONN) rely on coherent light sources to establish transmission models. The use of laser inputs and electro-optic modulation devices at the front end of these neural networks diminishes their computational capability and energy efficiency, thereby limiting their practical applications in object detection tasks. This paper proposes a partially coherent optical neural network (PCONN) transmission model based on mutual intensity modulation. This model does not depend on coherent light source inputs or active electro-optic modulation devices, allowing it to directly compute and infer using natural light after simple filtering, thus achieving full optical perception from light signal acquisition to computation and inference. Simulation results indicate that the model achieves a highest classification accuracy of 96.80% and 86.77% on the MNIST and Fashion-MNIST datasets, respectively. In a binary classification simulation test based on the ISDD segmentation dataset, the model attained an accuracy of 94.69%. It is estimated that this system’s computational inference speed for object detection tasks is 100 times faster than that of traditional CONN, with energy efficiency approximately 50 times greater. In summary, our proposed PCONN model addresses the limitations of conventional optical neural networks in coherent light environments and is anticipated to find applications in practical object detection scenarios.

Characterization of Spray-Dried Powders Using a Coated Alberta Idealized Nasal Inlet.

Background: Dry powders offer the potential to increase stability and reduce cold-chain requirements associated with the distribution of vaccines and other thermally sensitive products. The Alberta Idealized Nasal Inlet (AINI) is a representative geometry for in vitro characterization of nasal products that may prove useful in examining intranasal delivery of powders. Methods: Spray-dried trehalose powders were loaded at 10, 20, and 40 mg doses into active single-dose devices. Primary particle sizes (∼Dv50 = 10 µm for powder A and 25 µm for powder B), and sizes dispersed by devices, were evaluated using laser diffraction. The interior of the AINI was coated with a glycerol-surfactant mixture to mitigate particle bounce, and flow rates of 7.5 or 15 L/min were drawn through the AINI. Deposition of trehalose powder was determined in the four regions of the AINI (vestibule, turbinates, olfactory, and nasopharynx), a downstream preseparator, and an absolute filter (representing in vitro lung deposition) using liquid chromatography coupled with mass spectrometry. Results: Coating the AINI was effective in mitigating particle bounce for both trehalose powders. No difference in regional nasal deposition was observed when testing at a flow rate of 7.5 versus 15 L/min. A high fraction of both powders penetrated past the vestibule and deposited in the turbinates and nasopharynx for all loaded doses. For powder A, a non-negligible fraction of the recovered dose (up to 7%) is deposited on the filter, representing potential lung exposure. Conversely, a negligible fraction of the total recovered dose was deposited on the filter for powder B. Conclusion: Powders with a larger primary particle size showed reduced penetration through the nasal airways while maintaining high turbinate deposition. Optimized spray-dried powders offer the potential to target delivery to the peripheral nasal airways based on powder particle size while reducing lung exposure.

Reusable EWOD-based microfluidic system for active droplet generation.

Droplets are essential in a wide range of microfluidic applications, but traditional passive droplet generation methods suffer from slow response speed and the need for precise flow rate adjustment. Here, we present an active droplet generation method through electrowetting-on-dielectric (EWOD). Electrowetting is a technique that uses an electric field to change the wettability of a surface. In our method, we apply an electric field to the laminar flow of the dispersed and continuous phases in a microchannel, which induces the discretization of the dispersed thread and leads to droplet formation. A key feature of the proposed active droplet-generating microfluidic device is the reusability of the EWOD actuation substrate, dramatically reducing operational costs. In addition, this approach offers significant advantages over passive methods, including fast response speeds, a wider range of droplet sizes, and greater control over droplet size. In addition, the ultrathin polymer film used in this device allows for a low electrowetting voltage, which helps to prevent damage to encapsulated cells. We believe that our active droplet generation method is a promising new method for generating droplets in microfluidic applications. It is faster, more versatile, and more precise than passive methods, making it ideal for a wide range of applications, including single-cell genomics and drug discovery.

Effectiveness of Hypothermia Prevention Protocol Among Patients Subjected to Major Surgeries at KMCH, Coimbatore.

Hypothermia is a significant risk factor for peri-operative complications. Whatever method is used for maintaining normothermia, first and foremost, it should be remembered that careful and thoughtful actions directed at maintaining normothermia can significantly affect the course of the patient’s peri-operative experience. Objective of the study is to assess the incidence and extent of hypothermia among patients subjected to major surgeries, to determine the effectiveness of hypothermia prevention protocol among patients subjected to major surgeries and to associate the demographic, clinical variables and risk factors of hypothermia with core body temperature among patients subjected to major surgeries. The methodology adopted for this study was a Quasi-experimental one group pre test and post test design. Hypothermia prevention management strategies (active and passive warming as per core body temperature) were implemented and were observed by using Hypothermia prevention protocol checklist by the investigator. Descriptive and inferential statistics were used to analyze the data. Repeated measures ANOVA of core body temperature, heart rate, respiratory rate, blood pressure and SPO2 over a period of time revealed that there is a statistically significant difference in the mean scores of vitals parameters were measured at various time periods in peri-operative period at the level of p<.05. Keywords: hypothermia, peri-operative period, active warming device, passive warming device.

Prospects of Band Structure Engineering in MXenes for Active Switching MXetronics: Computational Insights and Experimental Approaches.

MXenes, two-dimensional (2D) transition metal carbides and nitrides, have shown promise in a variety of applications. The use of MXenes in active electronic devices is restricted to electrode materials due to their metallic nature. However, MXenes can be modified to be semiconducting and can be used for next-generation channel materials. The inherent metallic characteristics of pristine Mn+1Xn-structured MXene can be tuned to semiconducting by (i) functionalizing MXenes with different moieties, (ii) applying external strain, and (iii) varying the composition. These strategies effectively modify the metallic electronic structure of MXene into a semiconducting one. This review focuses on the potential of tuning the electronic band structure of MXenes by surface functionalization, strain engineering, and compositional variation. The computational and experimental approaches to tuning the electronic band structure using these strategies are discussed in detail. In addition, the experimental methods which can be used to prepare semiconducting MXenes are described.

Multi-Layer Absorber based on Plasmonic Resonances for Photovoltaic Applications at Visible Spectra

This paper introduces a broadband absorber based on a multilayered, double-cylindrical-shaped metamaterial, numerically characterized for its performance. The structure comprises four interacting layers that generate plasmonic resonances. CST microwave simulations were conducted to analyze its absorption characteristics. The results demonstrate that the proposed metamaterial absorber achieves 99% absorption at 847 nm frequency region and 98% absorption in the 500-1200 nm frequency region. Additionally, polarization dependency analysis confirms that the absorber performs as a perfect, polarization-independent absorber across the studied frequency range. It exhibits high absorption in both TE and TM modes and remains unaffected by polarization or variations in the incident angle. Numerical simulations reveal that the absorption performance is driven by a combination of Fabry–Perot resonance effects, localized surface plasmons, and propagating surface plasmons. In summary, the proposed metastructure demonstrates omnidirectional absorption, polarization independence, and wide-angle incident absorption. This design shows significant potential for applications in photodetectors, active optoelectronic devices, and sensors.

Doped‐NiOx Seed Layer on Textured Substrates for Low‐Loss Contacts in Perovskite Solar Cells

AbstractFurther improvements in photocurrent are essential to unlock higher efficiencies in inverted (p‐i‐n) perovskite solar cells (PSCs). While the use of textured substrates has proven successful in normal structure (n‐i‐p) devices to improve photocurrent, applying the same approach to p‐i‐n architecture is challenging due to difficulties in depositing ultra‐thin self‐assembled monolayers (SAMs) on uneven surfaces. To overcome this limitation, a rubidium‐based ammonia treatment for nickel oxide seed layers is proposed. This strategy enhances the surface homogeneity of hole‐transporting layers on textured substrates, facilitates perovskite defect passivation, and improves SAM anchoring, collectively enhancing hole extraction and suppressing non‐radiative recombination. As a result, the optimized PSCs achieves a champion power conversion efficiency (PCE) of 25.66% with a fill factor of 86.35% and demonstrates excellent long‐term stability, retaining 95% of their initial PCE after 1,000 hours following ISOS‐L‐2I protocol. Moreover, the scalability of this approach is validated with a 1 cm2 active area device, achieving a PCE of 23.90%. These findings highlight the potential of the strategy to address key challenges in PSC interfaces and advance the commercial viability of high‐performance perovskite photovoltaics.

A Review: Developments in Hardware Systems of Active Ankle Orthoses.

Active ankle orthoses which have been designed over the past few years by diverse sources were critically reviewed in this paper. It begins by providing an overview of the anatomy of the ankle joint complex, establishing a basis for understanding the subsequent discussion on the research challenges and design difficulties associated with developing active ankle orthosis devices. The review systematically examined the mechanisms, actuation methods, and control strategies utilized in these orthosis devices. This covers various control strategies, including Electromyography (EMG)-based, adaptive, and modular control systems, emphasizing their importance in achieving precise and user-intended movements. By integrating insights from recent studies and technological innovations, this paper provides a holistic view of the progress in active ankle orthoses. The paper concludes with design recommendations aimed at overcoming existing limitations and promoting further development of advanced active ankle orthosis devices for future research.

Orthogonal‐Based Reconfigurable Light‐Controlled Metasurface for Multichannel Amplitude‐Modulation Communication

AbstractOptical‐control reconfigurable metasurfaces can avoid crosstalk between microwave signal and direct current (DC) signal caused by physical wire connection, which paves a paradigm for dynamically and remotely controlling electromagnetic (EM) wave. However, the traditional light‐controlled reconfigurable metasurfaces mainly focus on the modulation of single polarized EM wave, which is difficult to adapt to the modulation of various signals in communication. In this work, a photoresistor is fully embedded into the meta‐atom as an active device, and a light‐controlled reconfigurable metasurface (LCRM) with multi‐polarization amplitude modulations is proposed. The designed metasurface controls the luminous intensity of light emitting diode (LED) array through computer, and then adjusts the photoresistor value, which can achieve amplitude modulations. In order to verify the feasibility and effectiveness of the proposed framework, the metasurface is simulated, fabricated, and measured, and the measurement results are basically consistent with the theoretical simulation results. Based on the EM characteristics of the designed metasurface, linear polarized (LP) wave synthesis and information transmission are carried out to demonstrate the design. This work designs an amplitude modulation metasurface under orthogonal‐polarization wave incidence to expand the LCRM application, which has broad development prospects in many fields such as information transmission, communication systems, and holographic imaging.

Clinical Safety and Efficacy of Dual Wavelength Low-Level Light Therapy in Androgenetic Alopecia: A Double-Blind Randomized Controlled Study.

The light-emitting diode cap being investigated is FDA cleared for the treatment of androgenetic alopecia (AGA). Evaluating 3 versions of a red and blue light LED cap: (1) 625- and 660-nm red light, (2) 425-nm blue light, and (3) both 425-nm blue light and 625- and 660-nm red light against sham. Twenty-six-week, multicenter, randomized, controlled, double-blinded study. Adults aged 18 to 65 years with AGA were randomized to an active device or sham and underwent 10-minute treatments daily. One hundred sixty subjects were randomized. Ninety-one subjects were excluded for the per-protocol analysis. The per-protocol population included participants who completed 16 weeks of treatment, had no major protocol violations, and were at least 80% treatment compliant. Although the primary endpoint (mean change in non-vellus hair count from baseline to week 16) did not reach statistical significance in the individual study arms, in the pooled analysis (combining the 3 active study arms), there was a statistically significant (p = .033) difference versus sham. The pooled study cap group achieved 28.5 more hairs per cm2 when compared with sham. The LED caps were well tolerated and increased hair density in patients with AGA.

Programmable anisotropic soft matrix enabling robust active waveguide film

In soft matrix, liquid crystals (LCs) enable low-temperature integration of multiple optical modules, owing to their remarkable programmability and anisotropicity. However, achieving efficient coupling of light source to waveguide remains challenging, primarily due to their refractive index mismatches and alignment deviations. Herein, we developed a robust waveguide film with an integrated active light source, utilizing a laser-dye-doped LC soft matrix, where efficient coupling is achieved by precisely controlling the LC alignment and careful positioning of the external pump spot to induce amplified spontaneous emission within the waveguide. This active waveguide film provides efficient light conduction with optical loss coefficients as low as 0.08 dB/mm. The special design LC arrangement in waveguide enables the manipulation of light propagation direction such as linear propagation and 180° turns. Furthermore, a four-channel equal-power splitter is established for multi-channel light output. This robust active waveguide film device demonstrates remarkable stability under high temperatures, humidity, and harsh chemical environments, along with excellent fatigue resistance. This study lays a solid foundation for the development of optical chips optimized for programmable integrated photonic systems.

Original Research: Exploring the Use of Passive vs. Active Insulin Safety Pen Needle Devices in a Pediatric Population: A Feasibility Study.

Insulin pens are the mainstay of insulin delivery in the pediatric population, especially among patients unable to use an insulin pump. Safety pen needle (SPN) devices have been embraced by both nurses and patients because they limit the risks of needlestick injury and exposure to blood-borne pathogens. With the commonly used traditional passive SPN device, however, it can be difficult to observe that the dose has been accurately or fully administered. The purpose of this study was to determine nurses' perceptions about the feasibility of using an active SPN device (specifically the Unifine SafeControl insulin pen needle), compared with the currently used passive SPN device, in pediatric patients ages 21 years or younger who require subcutaneous insulin injections. This feasibility study was conducted on a pediatric inpatient unit at 1 pediatric hospital in the southeastern United States. A total of 49 RNs completed both a pre-device change survey regarding the currently used passive SPN device and a post-device change survey regarding the active SPN device. The RNs also completed daily evaluations assessing the ease of teaching patients and their caregivers how to use the active SPN device. Participation consent was also obtained for 132 pediatric patients with diabetes who were admitted to the unit. The majority of the RNs (87.8%) reported overall satisfaction with the active SPN device, compared to about half (52.7%) who reported overall satisfaction with the passive SPN device. Almost all the RNs (98.6%) reported that the active SPN device was easy or very easy to use. Nearly all the nurses (93.9%) reported feeling completely or very confident that the active SPN device allowed them to deliver the full intended dose; and nearly all reported that it was easy or very easy to teach patients (98.2%) and their caregivers (96.4%) how to use the active device. As frontline workers in patient care, nurses can lead the innovation and development of new treatment approaches, protocols, and equipment. This nurse-led study explored the nurses' perceptions about the feasibility of a new active SPN device versus the passive SPN device in terms of safety, ease of use, ease of and confidence in dose administration, and ease of teaching device use to pediatric patients and their caregivers. The RNs' clear preference for the active over the passive SPN device suggests that the newer, active devices warrant more widespread use in hospital settings, with further research also recommended.

Siloxane as Humidity‐Resistant and Stabilizing Additive for Ambient‐Processed Organic Solar Cells

AbstractHigh‐performing organic solar cells (OSCs) being processed in ambient conditions and possessing long‐term stability are desired toward commercialization. Here, resultantly bifunctional additive is proposed for organic active layer, which can greatly enhance humidity endurance during the air‐processing of the active layer and device stability in the meantime. Intriguingly, with 1% octamethyltrisiloxane (3Si) as the additive, casting PM6:L8‐BO active layer even in 90% relative humidity (RH) air could show comparable efficiency to that in N2 condition. Furthermore, the 3Si‐processed active layers also display remarkably enhanced thermal and light stabilities in conventional OSCs. After thermal aging at 85 °C for 1000 h and simulated solar light aging with UV band at 100 mW cm−2 and 55°C for 1000 h, the 3Si‐processed PM6:L8‐BO binary OSCs maintain 91.6% and 86.1% of the initial efficiency, leading to final averaged efficiencies of 16.17% and 15.42%, respectively. The results represent the most stable OSCs based on additive strategy. The universality of siloxane as a humidity‐resistant and stabilizing agent is also confirmed with other active layer systems, paving a way for broader application of the bifunctional additive.

Current Collectors for Supercapacitors: Objectives, Modification Methods and Challenges

AbstractSupercapacitors (SCs) have emerged as promising candidates for efficient and sustainable energy storage devices due to their unique merits, including high power density and long lifespan. However, despite these advantages, SCs face significant challenges related to their relatively low energy density. Current collectors are critical components of SCs, which significantly impacts the efficiency and overall performance by connecting active materials and external devices. However, the reviews on SCs are predominantly focused on electrode active materials or electrolyte materials, with insufficient comprehensive summaries regarding current collectors. This review focuses on the research progress related to current collectors in SCs. Firstly, the article outlines the modification objectives mechanism and inherent nature of SC current collectors. Building on this foundation, the authors further classify the current collector materials towards metallic, carbon‐based, polymers and other ones and highlights their modification strategies. Finally, the future development trends and challenges of SCs current collectors are comprehensively discussed.

Observation of perovskite topological valley exciton-polaritons at room temperature

Topological exciton-polaritons are a burgeoning class of topological photonic systems distinguished by their hybrid nature as part-light, part-matter quasiparticles. Their further control over novel valley degree of freedom (DOF) has offered considerable potential for developing active topological optical devices towards information processing. Here, employing a two-dimensional (2D) valley-Hall perovskite lattice, we report the experimental observation of valley-polarized topological exciton-polaritons and their valley-dependent propagations at room temperature. The 2D valley-Hall perovskite lattice consists of two mutually inverted honeycomb lattices with broken inversion symmetry. By measuring their band structure with angle-resolved photoluminescence spectra, we experimentally verify the existence of valley-polarized polaritonic topological kink states with a large gap opening of ~ 9 meV in the bearded interface at room temperature. Moreover, these valley-polarized states exhibit counter-propagating behaviors under a resonant excitation at room temperature. Our results not only expand the landscape of realizing topological exciton-polaritons, but also pave the way for the development of topological valleytronic devices employing exciton-polaritons with valley DOF at room temperature.

Control Strategy for Power Fluctuation Smoothing at Distribution Network Substations Considering Multiple Types of Adjustment Resources

With the proposal of the dual carbon target, the distributed photovoltaic (PV) industry has rapidly developed in recent years. However, the randomness and volatility of photovoltaic energy can be transmitted to the main grid through distribution network substations, posing challenges to the stable operation of the power system. Therefore, this paper considers tapping into the regulation potential of feeder loads on the distribution network side, as well as distributed energy storage and distributed PV resources, to enhance the grid’s control methods. A power fluctuation smoothing control strategy for substations in distribution networks, accounting for multiple types of regulation resources, is proposed. In the day-ahead stage, traditional voltage regulation devices such as the OLTC (on-load tap changer) and CB (circuit breaker) are pre-dispatched based on source–load forecasts, optimizing the fluctuation range of substation power and the number of device operations. This provides optimal substation power values for day-to-day optimization. During the intraday phase, fast regulation devices such as PV (photovoltaic), SVC (static var compensator), and energy storage systems are coordinated, and an optimization model is established with the goal of reducing power curtailment while closely tracking substation trends. This model quickly calculates the active power regulation and device operations of various adjustable resources, improving the economic efficiency of the distribution network system while achieving power fluctuation smoothing at the substation level. Finally, the feasibility and effectiveness of the power fluctuation smoothing control model are verified through simulations on an improved standard distribution system.

Property optimization of Er/Yb-codoped LiNbO3 crystals for LNOI lasers and amplifiers

Lithium-niobate-on-insulator (LNOI) is regarded as an ideal platform for integrated photonics. As an essential part, active devices based on rare-earth (RE) doped LNOI have made significant progress, with erbium/ytterbium-codoped lithium niobate (Er/Yb-codoped LN) showing great potential. In this paper, a series of Er/Yb-codoped LN crystals were successfully grown by the Czochralski method, featuring a fixed Er3+ concentration with various Yb3+ doping levels and a fixed RE3+ (RE3+ = Er3+ + Yb3+) concentration. The absorption and emission spectra were measured, and the transfer efficiencies along with relative conversion efficiencies were also displayed. It was concluded that the optimal composition of codoped LN is ∼1.0 mol. % Er3+ and 1.0 mol. % Yb3+, which can enhance active devices by providing lower threshold power, reduced transmission loss, higher transfer efficiency, and improved conversion efficiency. These results will advance the development of high performance LNOI lasers and amplifiers.

대학생의 디지털 기기를 활용한 학습 유형 : 잠재집단 분류 및 영향요인

The purpose of this study is to identify the types of learning based on university students' use of digital devices and to analyze the differences in predictive factors and performance variables across these types. For this, Latent Class Analysis (LCA) was conducted using data from 489 students at S University who participated in the ‘2023 K-NSSE’. The analysis results are as follows: First, the types of learning based on university students' use of digital devices were classified into (1) the digitally marginalized, (2) the communication-oriented, (3) data utilization, and (4) active digital device usage. Second, gender, reflective learning, collaborative learning, and effective class were found to be key predictors for students' digital device usage types. Lastly, the 'active digital device usage group' showed significantly higher results in both digital competence and student outcomes compared to other groups. Based on these findings, academic and practical implications are suggested for developing effective teaching and learning strategies to enhance university students' digital competence.

Developing a method to generate an adaptive real-time camouflage pattern based on electro-chromic active devices

Traditional camouflage faces limitations in modern combat, especially with moving targets or rapidly changing backgrounds. Adaptive camouflage, which adjusts colors and patterns in real time, provides a more flexible and effective solution. This paper presents a comprehensive study of popular adaptive camouflage principles worldwide and proposes a camouflage model for the visible light spectrum based on active electro-chromic principles. Evaluation results indicate that adaptive patterns achieve the lowest Camouflage Similarity Index (CSI) and the highest Universal Image Quality Index (UIQI) across various backgrounds, demonstrating the clear effectiveness of the proposed model. With 3 to 5 dominant colors, pattern generation time is under 1 second, and adaptive patterns exhibit the highest similarity to the background compared to fixed patterns.