Device Applications Research Articles

Multi-Color Spaceplates in the Visible.

The ultimate miniaturization of any optical system relies on the reduction or removal of free-space gaps between optical elements. Recently, nonlocal flat optic components named "spaceplates" were introduced to effectively compress space for light propagation. However, space compression over the visible spectrum remains beyond the reach of current spaceplate designs due to their inherently limited operating bandwidth and functional inefficiencies in the visible range. Here, we introduce "multi-color" spaceplates performing achromatic space compression at three distinct color channels across the visible spectrum to markedly miniaturize color imaging systems. In this approach, we first design monochromatic spaceplates with high compression factors and high transmission amplitudes at visible wavelengths based on a scalable structure and dielectric materials widely used in the fabrication of meta-optical components. We then show that the dispersion-engineered combination of monochromatic spaceplates with suitably designed transmission responses forms multicolor spaceplates that function achromatically. The proposed multicolor spaceplates, composed of amorphous titanium dioxide and silicon dioxide layers, efficiently replace free-space volumes with compression ratios as high as 4.6, beyond what would be achievable by a continuously broadband spaceplate made of the same materials. Our strategy for designing monochromatic and multicolor spaceplates, along with the presented theoretical and computational results, show that strong space-compression effects can be achieved in the visible range. Our findings may ultimately enable a new generation of ultrathin optical devices for various applications.

Magnetoelectric Tuning of 2D Ferromagnetism in 1T-CrTe2 through In2Se3 Substrate.

Electric field control of two-dimensional (2D) materials with optimized magnetic properties is not only of scientific interest but also of technological importance in terms of the functionality of various nanoscale devices. Here, we report the multiferroic control of the 2D ferromagnetism in 1T-CrTe2 monolayer through a ferroelectric In2Se3 sublayer. Our results reveal the effect of polarization switching on the electronic structures and magnetic properties of 1T-CrTe2/In2Se3 heterostructures, enabling effective manipulation of their magnetic anisotropy energy (MAE) and magnetization orientation. Additionally, we also demonstrate the strong dependence of their MAE and switching effect on the external strain and surface hydrogenation. Notably, polarization switching exhibits a reversal modification in the hydrogenated multiferroic structures. These tunable behaviors are primarily attributed to the alteration of p-orbitals near the Fermi level of the interfacial Te atoms due to magnetoelectric coupling. Our findings suggest the potential of 1T-CrTe2/In2Se3 heterojunctions for the practical application of 2D multiferroic spintronic devices.

Two-dimensional valley photonic crystal resonant cavities

Introducing defects in photonic crystals is a common method for manipulating and controlling the propagation of electromagnetic waves. By introducing defects in photonic crystal waveguides, the periodicity of the waveguide structure can be disrupted, local modes can be formed, and resonant cavity functions can be achieved. In this study, we designed two groups of two-dimensional valley photonic crystal waveguides, each of which uses different methods to introduce defects and obtained different resonant cavity structures, and designed a resonant cavity sensor. We conducted a detailed theoretical analysis of the resonant cavity through simulation software. In addition, we fabricated the samples and conducted microwave experiments to demonstrate the accuracy of our theoretical research. Our research provides guidance for the application of photonic crystal devices.

DATA SECURITY IN IOT DEVICES AND SENSOR NETWORKS FOR ROBUST THREAT DETECTION AND PRIVACY PROTECTION

The rapid proliferation of Internet of Things (IoT) devices and sensor networks has revolutionized various industries by enhancing automation, connectivity, and operational efficiency. However, these advancements have also introduced significant security challenges due to the resource constraints and decentralized nature of IoT environments. This paper provides a systematic review of IoT security solutions, focusing on encryption techniques, authentication protocols, and machine learning-based anomaly detection methods. A total of 55 peer-reviewed articles were analyzed following the PRISMA guidelines. The findings reveal that while lightweight cryptographic algorithms, such as elliptic curve cryptography (ECC), offer robust security with low energy consumption, scalability across large IoT networks remains a challenge. Blockchain-based authentication has emerged as a promising decentralized solution, but issues related to energy consumption and latency hinder its widespread adoption. Machine learning techniques have shown high accuracy in detecting threats in real-time, but their resource-intensive nature limits their application in low-power IoT devices. This review underscores the need for multi-layered, integrated security frameworks and highlights gaps in research on quantum-resistant cryptography and interoperable security standards. Future research must focus on developing scalable, energy-efficient security solutions to ensure data integrity and privacy in expanding IoT ecosystems.

Interface defect state induced spin injection in organic magnetic tunnel junctions

This article analytically explores defect assisted spin injection in organic magnetic tunnel junctions (MTJs) [x/rubrene/Co, x = La2O3, LaMnO3, La0.7Ca0.3MnO3 (LCMO), La0.7Sr0.3MnO3 (LSMO)] employing nonequilibrium Green’s function (NEGF). Spin precession at ferromagnet (FM)/organic semiconductor (OSC) interface defect states have been considered while modeling the MTJ devices. Variations in voltage dependent parallel (RP) and antiparallel (RAP) resistances have been attributed to modified spin dependent scattering at modified spin resolved density of states of magnetic electrodes. Moreover, change in distribution of defect state depths at a spin injection interface has also been observed to modify RP/RAP, and hence, tunnel magnetoresistance (TMR) across the devices. Localization of defect state distribution due to a high spin split band may have resulted in large TMR for La2O3 devices. Nonlinear spin transfer torque (STT) in devices other than LSMO indicates compensation of spin damping, resulting in a high TMR response across the devices. Hence, the localization of defect state distribution and the choice of magnetic electrodes with high spin split bands may be exercised to realize spintronic devices for low power spin memory applications.

Enhanced pediatric thyroid ultrasound image segmentation using DC-Contrast U-Net

Early screening methods for the thyroid gland include palpation and imaging. Although palpation is relatively simple, its effectiveness in detecting early clinical signs of the thyroid gland may be limited, especially in children, due to the shorter thyroid growth time. Therefore, this constitutes a crucial foundational work. However, accurately determining the location and size of the thyroid gland in children is a challenging task. Accuracy depends on the experience of the ultrasound operator in current clinical practice, leading to subjective results. Even among experts, there is poor agreement on thyroid identification. In addition, the effective use of ultrasound machines also relies on the experience of the ultrasound operator in current clinical practice. In order to extract sufficient texture information from pediatric thyroid ultrasound images while reducing the computational complexity and number of parameters, this paper designs a novel U-Net-based network called DC-Contrast U-Net, which aims to achieve better segmentation performance with lower complexity in medical image segmentation. The results show that compared with other U-Net-related segmentation models, the proposed DC-Contrast U-Net model achieves higher segmentation accuracy while improving the inference speed, making it a promising candidate for deployment in medical edge devices in clinical applications in the future.

Effect of pressure, temperature, and particle size on cold sintered ZnO for transparent thick films on polymer substrates

AbstractThe role of pressure, temperature, and particle size on cold sintering of ZnO has been investigated with a view to developing transparent thick films for device applications. Coarse ZnO (∼90–250 nm, cZnO) particles exhibited equiaxed grain growth under all conditions eventually achieving grain sizes of ∼ 0.5–1.0 µm at 300°C/375 MPa. In contrast, nano‐ZnO (40–80 nm, nZnO), exhibited grain growth along the c‐axis with a broader grain size distribution (0.5–4 µm) at higher temperatures and pressure (300°C/375 MPa) than cZnO. The broader grain size distribution is attributed to greater dissolution for nZnO compared with cZnO coupled with redistribution of Zn acetate/acetic acid into pores. ZnO continues to dissolve and reprecipitate within the pores throughout the densification process resulting in localized, larger grain sizes. In plane grain growth normal to the pressing direction was observed at and near the sample surface particularly in nZnO, which is attributed to constrained‐sintering. Some abnormal grain growth (10–20 µm) was also sporadically observed near or at the surface of nZnO (300°C/375 MPa) due to greater rates of reprecipitation as the transient solvent volatilizes adjacent to the die wall/plunger. Tape casting was used to fabricate single and multiple layers (≈30 µm) of ZnO on Kapton® to demonstrate the potential for device fabrication. Transparency was achieved by choosing cold sintering conditions (200°C/250 MPa) for nZnO that gave ∼95% relative density while restricting a majority of grain growth to <200 nm so that internal light scattering from grain boundaries was avoided.

Comparative analysis of thermoelectric properties in bulk 2H and monolayer MoS2: a first-principles study at high temperatures

The pursuit of high-efficiency heat-to-electricity conversion is one of the indispensable driving forces toward future renewable energy production. The two-dimensional (2D) transition metal dichalcogenide, such as molybdenum disulfide (MoS2), is at the forefront of research due to its outstanding heat propagation features and potential applications as a thermoelectric material. Using the first-principles density functional theory coupled with the semi-classical Boltzmann transport equation within the constant relaxation time approximation, we present the thermoelectric and energy transport in the bulk 2H and monolayer MoS2 material system. In order to advance the underlying physics, we calculate several crucial transport parameters such as electrical conductivity, electronic thermal conductivity, Seebeck coefficient, and power factor as a function of the reduced chemical potential for different doping types and temperatures, in addition to the electron energy dispersion relation of the material system. Our comprehensive study employs the Shankland interpolation algorithm and the rigid band approximation to attain a high degree of accuracy. This thorough investigation reveals the high Seebeck coefficient of 1534 and 1550 μ V/K at 500 K for the bulk 2H and monolayer MoS2, respectively. Furthermore, the ultrahigh power factor values of 9.21 × 1011 and 3.69 × 1011 Wm −1 K −2 s −1 are shown at 800 K in the bulk 2H and monolayer MoS2, respectively. Based on the power factor results, our in-depth analysis demonstrates that the bulk 2H MoS2, when compared to monolayer MoS2, exhibits great potential as a promising semiconducting thermoelectric material for advanced high-performance energy device applications.

High Efficiency n-Type Doping of Organic Semiconductors by Cation Exchange.

Achieving efficient doping in n-type conjugated polymers is crucial for their application in electronic devices. In this study, an n-type doping method is developed based on cation exchange that maintains a high doping level while ensuring a high degree of structural order, leading to significantly improved electrical conductivity. By investigating various dopants and ionic liquids, it is discovered that the choice of dopant influences doping efficiency, while the selection of ionic liquid affects cation exchange efficiency. Through careful selection of suitable dopants and ionic liquids, High doping levels are achieved remarkably in a short period, resulting in the highest conductivity (nearly 1×10- 2Scm-¹) compared to other doping methods for poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (N2200). The findings highlight the robustness and efficiency of cation exchange doping as an effective approach for achieving high-quality n-type doping in conjugated polymers, thereby opening new avenues for the development of advanced polymer-based electronic devices.

Super-Tough, Non-Swelling Zwitterionic Hydrogel Sensor Based on the Hofmeister Effect for Potential Motion Monitoring of Marine Animals.

Hydrogel-based electronic devices in aquatic environments have sparked widespread research interest. Nevertheless, the challenge of developing hydrogel electronics underwater has not been profoundly surmounted because of the fragility and swelling of hydrogels in aquatic environments. In this work, a zwitterionic double network hydrogel comprisedof polyvinyl alcohol (PVA), poly(sulfobetaine methacrylate) (PSBMA), and sulfuric acid (H2SO4) demonstrates super-tough and non-swelling performance. The Hofmeister effect of H2SO4 and PSBMA induces the PVA chains to form numerous nanocrystalline domains, which serve as the primary physical crosslinking points and provide effective energy dissipation. H2SO4 induces a strong salting-out effect to facilitate PVA crystallization and the formation of a dense and stable network structure that inhibits swelling. The resulting hydrogel exhibits an ultra-high toughness of 4.61MJm-3, non-swelling, and long-term stability for up to a month in pure water and seawater. Based on this, a hydrogel-based seawater strain sensor has been developed to monitor the underwater movements of marine animal models. Reliable and stable sensing performance ensures real-time collection of underwater motion signals, despite the impacts of water flow and the interference of ions. This study provides a facile approach to designing super-tough and non-swelling hydrogels and further expands the application of underwater electronic devices.

Impact of Laser Ablation Strategies on Electrochemical Performances of 3D Batteries Containing Aqueous Acid Processed Li(Ni0.6Mn0.2Co0.2)O2 Cathodes with High Mass Loading

Lithium-ion batteries are currently one of the most important energy storage devices for various applications. However, it remains a great challenge to achieve both high energy density and high-power density while reducing the production costs. Cells with three-dimensional electrodes realized by laser ablation are proven to have enhanced electrochemical performance compared to those with conventional two-dimensional electrodes, especially at fast charging/discharging. Nevertheless, laser structuring of electrodes is still limited in terms of achievable processing speed, and the upscaling of the laser structuring process is of great importance to gain a high technology readiness level. In the presented research, the impact of different laser structuring strategies on the electro-chemical performance was investigated on aqueous processed Li(Ni0.6Mn0.2Co0.2)O2 cathodes with acid addition during the slurry mixing process. Rate capability analyses of cells with laser structured aqueous processed electrodes exhibited enhanced performance with capacity increases of up to 60 mAh/g at high current density, while a 65% decrease in ionic resistance was observed for cells with laser structured electrodes. In addition, pouch cells with laser structured acid-added electrodes maintained 29–38% higher cell capacity after 500 cycles and their end-of-life was extended by a factor of about 4 in contrast to the reference cells with two-dimensional electrodes containing common organic solvent processed polyvinylidene fluoride binder.

Artificial synapses based on HfOx/TiOy memristor devices for neuromorphic applications.

As a result of enormous progress in nanoscale electronics, interest in Artificial Intelligence (AI) supported systems has also increased greatly. These systems are typically designed to process computationally intensive data. Parallel processing neural network architectures are particularly noteworthy for their ability to process dense data at high speeds, making them suitable candidates for AI algorithms. Due to their ability to combine processing and memory functions in a single device, memristors offer a significant advantage over other electronic platforms in terms of area scaling efficiency and energy savings. In this study, single-layer and bilayer metal-oxide HfOx and TiOy memristor devices inspired by biological synapses were fabricated by pulsed laser and magnetron sputtering deposition techniques in high vacuum with different oxide thicknesses. The structural and electrical properties of the fabricated devices were analysed using X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS), and standard two-probe electrical characterization measurements. The stoichiometry and degree of oxidation of the elements in the oxide material for each thin film were determined. Moreover, the switching characteristics of the metal oxide upper layer in bilayer devices indicated its potential as a selective layer for synapse. The devices successfully maintained the previous conductivity values, and the conductivity increased after each pulse and reached its maximum value. Furthermore, the study successfully observed synaptic behaviours with long-term potentiation (LTP), long-time depression (LTD), paired-pulse facilitation (PPF), and spike-timing-dependent plasticity (STDP), showcasing potential of the devices for neuromorphic computing applications.

Polarization Independent Dynamic Beam Steering based on Liquid Crystal Integrated Metasurface

Digital Micromirror Devices, extensively employed in projection displays offer rapid, polarization-independent beam steering. However, they are constrained by microelectromechanical system limitations, resulting in reduced resolution, limited beam steering angle and poor stability, which hinder further performance optimization. Liquid Crystal on Silicon technology, employing liquid crystal (LC) and silicon chip technology, with properties of high resolution, high contrast and good stability. Nevertheless, its polarization-dependent issues lead to complex system and low efficiency in device applications. This paper introduces a hybrid integration of metallic metasurface with nematic LC, facilitating a polarization-independent beam steering device capable of large-angle deflections. Employing principles of geometrical phase and plasmonic resonances, the metallic metasurface, coupled with an electronically controlled LC, allows for dynamic adjustment, achieving a maximum deflection of ± 27.1°. Additionally, the integration of an LC-infused dielectric grating for dynamic phase modulation and the metasurface for polarization conversion ensures uniform modulation effects across all polarizations within the device. We verify the device’s large-angle beam deflection capability and polarization insensitivity effect in simulations and propose an optimization scheme to cope with the low efficiency of individual diffraction stages.

Ceramics for Microelectromechanical Systems Applications: A Review

A comprehensive review of the application of different ceramics for MEMS devices is presented. Main ceramics materials used for MEMS systems and devices including alumina, zirconia, aluminum Nitride, Silicon Nitride, and LTCC are introduced. Conventional and new methods of fabricating each material are explained based on the literature, along with the advantages of the new approaches, mainly additive manufacturing, i.e., 3D-printing technologies. Various manufacturing processes with relevant sub-techniques are detailed and the ones that are more suitable to have an application for MEMS devices are highlighted with their properties. In the main body of this paper, each material with its application for MEMS is categorized and explained. The majority of works are within three main classifications, including the following: (i) using ceramics as a substrate for MEMS devices to be mounted or fabricated on top of it; (ii) ceramics are a part of the materials used for an MEMS device or a monolithic fabrication of MEMS and ceramics; and finally, (iii) using ceramics as packaging solution for MEMS devices. We elaborate on how ceramics may be superior substitutes over other materials when delicate MEMS-based systems need to be assembled or packaged by a simpler fabrication process as well as their advantages when they need to operate in harsh environments.

Review of Liquid Metal Fiber Based Biosensors and Bioelectronics

Liquid metal, as a novel material, has become ideal for the fabrication of flexible conductive fibers and has shown great potential in the field of biomedical sensing. This paper presents a comprehensive review of the unique properties of liquid metals such as gallium-based alloys, including their excellent electrical conductivity, mobility, and biocompatibility. These properties make liquid metals ideal for the fabrication of flexible and malleable biosensors. The article explores common preparation methods for liquid metal conductive fibers, such as internal liquid metal filling, surface printing with liquid metal, and liquid metal coating techniques, and their applications in health monitoring, neural interfaces, and wearable devices. By summarizing and analyzing the current research, this paper aims to reveal the current status and challenges of liquid metal conductive fibers in the field of biosensors and to look forward to their development in the future, which will provide valuable references and insights for researchers in the field of biomedical engineering.

Retraction Note: An efficient deep learning based stress monitoring model through wearable devices for health care applications

Retraction Note: An efficient deep learning based stress monitoring model through wearable devices for health care applications

3D Printing of Hierarchical Structures Made of Inorganic Silicon-Rich Glass Featuring Self-Forming Nanogratings.

Hierarchical structures are abundant in nature, such as in the superhydrophobic surfaces of lotus leaves and the structural coloration of butterfly wings. They consist of ordered features across multiple size scales, and their advantageous properties have attracted enormous interest in wide-ranging fields including energy storage, nanofluidics, and nanophotonics. Femtosecond lasers, which are capable of inducing various material modifications, have shown promise for manufacturing tailored hierarchical structures. However, existing methods, such as multiphoton lithography and three-dimensional (3D) printing using nanoparticle-filled inks, typically involve polymers and suffer from high process complexity. Here, we demonstrate the 3D printing of hierarchical structures in inorganic silicon-rich glass featuring self-forming nanogratings. This approach takes advantage of our finding that femtosecond laser pulses can induce simultaneous multiphoton cross-linking and self-formation of nanogratings in hydrogen silsesquioxane. The 3D printing process combines the 3D patterning capability of multiphoton lithography and the efficient generation of periodic structures by the self-formation of nanogratings. We 3D-printed micro-supercapacitors with large surface areas and a high areal capacitance of 1 mF/cm2 at an ultrahigh scan rate of 50 V/s, thereby demonstrating the utility of our 3D printing approach for device applications in emerging fields such as energy storage.

Elastic mechanical thermodynamic and thermoelectric properties of pristine and titanium doped Mg2Si: a density functional theory study.

Herein, we report a systematic investigation of the effect of Titanium doping on the structural, elastic, mechanical, thermodynamic, and thermoelectric (TE) dynamics of Mg2Si Compounds using first-principle investigation. The present study has been carried out using the FP-LAPW (full potential linearized augmented plane wave)method as implemented in Wien2k code under mBJ exchange potentials. The investigations revealed that Mg2-xTixSi compounds have structural stability with cubic phase (Fm-3m symmetry) and possess degenerate semiconducting nature. The analysis of elastic constants revealed mechanical stability of the investigated compounds following Born criteria. Thermodynamic investigations have been carried out in the temperature range of 100 to 1500 K at zero pressure and the quantities like heat capacity, Debye temperature, Grüneisen constant, and thermal expansion coefficient have been critically analyzed. Lastly, the thermoelectric performance of Mg2-xTixSi compounds has been predicted by estimating the thermopower (S2σ) and thermoelectric figure of merit (zT) in the temperature range of 300 to 1500 K. The predicted value of zTmax for Mg2-xTixSi compound is 0.67 at 800 K for x = 0.25 titanium content, suggesting materials promising application for thermoelectric energy harvesting and mechanical devices.&#xD.

Nanocrystalization effects on the structural, electrical and thermoelectric properties of 10KNbO3-10Fe2O3-50B2O3-30V2O5 glass for non-volatile electronic-memory devices

AbstractThe composition: 10KNbO3-10Fe2O3-50B2O3-30V2O5 (in mol%) is produced using the conventional melt quenching method and their corresponding glass–ceramic nanocomposites were studied. The structural properties of the as-quenched sample and its heat-treated samples were investigated using X-ray diffraction and differential thermal analysis. Density (ρ) was found to decrease with increasing average nanocrystallite size as the molar volume increases. Studies on thermoelectric power have been carried out. The glass–ceramic nanocomposite after 2 h of heating exhibits significant improvement of electrical conductivity. The activation energy (W), polaron radius (rp) and other parameters have been estimated in the non-adiabatic region. The current–voltage (I–V) curve of each sample was measured. A temporal analysis of current & voltage in nonlinear I–V curves show pinched hysteresis loop, which is the memristor’s fingerprint. The glass–ceramic nanocomposite after 2 h of heating exhibits a large switching window. The results of the study enable us to predict that they will be helpful for future applications of non-volatile electronic-memory devices.

Challenges and Opportunities of Stretchable Electroluminescent Devices and Displays

AbstractStretchable electroluminescent (EL) devices have been studied for more than 10 years, and their EL and mechanical performance, such as brightness, efficiency, stretchability, and stretching stability show significant improvement. Stretchable display is considered to be the most promising next‐generation display technology, which has broad application prospects in various emerging fields, such as deformable displays, electronic skins, and biomedical devices, and it attracts much attention from worldwide manufacturers. However, no commercial application cases for stretchable displays are reported to date. There are many reasons for this situation, including deficient device performance, immature preparation process, and diversiform device structures and materials. On the other hand, although researchers devise a number of possible applications for stretchable EL devices, it is still controversial what unique and interesting functions stretchable displays can play in these scenarios, and whether they can be replaced by flexible, bendable, and rollable devices with better EL and mechanical performance. Therefore, the future of stretchable displays is full of both opportunities and challenges. In response to the above concerns, this review summarizes the characteristics, problems, and possible solutions of various types of stretchable EL devices, aiming to promote their development and application.