Multifunctional Devices Research Articles

New System for Green EMI shielding: Organohydrogel with Multi-band Green Electromagnetic Shielding, Sensing, and Infrared-Stealth Capacity

Current research on green EMI shielding materials is often based on the misconception that absorption-dominated shielding is achieved when reflection loss (SER) exceeds absorption loss (SEA). Although this misconception has been corrected by a large body of literature, few studies have actually achieved absorbed power (A) greater than reflected power (R). In this study, PVA, glycerol and MXene were combined to form an organohydrogel (PMG) with oriented pores. The gel displays remarkable flexibility and strength, attributed to its robust network of hydrogen bond cross-links (the hysteresis return line remains stable under 1000 compression cycles). The PMG20-3 organohydrogel (0.78 wt% MXene) demonstrates a shielding performance of 42.34 dB (A/R=1.38) in the X-band and absorbs 99.9% of power in the terahertz band. This performance exceeds that of most previously reported systems and represents a new system for green electromagnetic shielding materials. Additionally, the PMG organohydrogel has flexible sensing and infrared stealth capabilities. These findings hold great promise for the development of green electromagnetic shielding multifunctional devices.

Realization of topological Bragg and locally resonant interface states in one-dimensional metamaterial beam-resonator-foundation system

Abstract In this study, the one-dimensional (1D) metamaterial beam-foundation system is innovatively improved into a metamaterial beam-resonator-foundation system by inserting resonators into the elastic foundation for ultra-low frequency vibration attenuation and enhanced topological energy trapping. Abundant band gap characteristics are obtained including quasi-static band gap starting from 0 Hz, Bragg scattering band gaps (BSBGs), and local resonance band gaps (LRBGs). Five band folding points are obtained through the band folding mechanism which can be opened by tuning inner and outer resonance parameters. However, only three band folding induced band gaps support mode inversion and Zak phase transition, including one BSBG and two LRBGs. The topological inversion in LRBGs is rarely reported in the 1D mechanical system, which can induce topological locally resonant interface states. The underlying physical mechanism of the topological phase transition in LRBG is revealed, which results from the topological inversion band gap transition from an initial BSBG to a LRBG with resonance parameters changes. Different from conventional 1D topological metamaterials that merely utilize local resonance to lower the band frequency and achieve subwavelength topological states in BSBGs, the topological interface states in LRBGs can localize wave energy to fewer unit cells near the interface, exhibiting enhanced energy localization capacity. The topologically protected interface states are validated with defective cases, demonstrating the potential of topological metamaterials for robust energy harvesting. This study provides new insights into the topological theory of 1D mechanical systems and contributes to the development and implementation of multi-functional devices integrating vibration attenuation and energy trapping.

A Review of Advanced Sensor Technologies for Aquatic Products Freshness Assessment in Cold Chain Logistics.

The evaluation of the upkeep and freshness of aquatic products within the cold chain is crucial due to their perishable nature, which can significantly impact both quality and safety. Conventional methods for assessing freshness in the cold chain have inherent limitations regarding specificity and accuracy, often requiring substantial time and effort. Recently, advanced sensor technologies have been developed for freshness assessment, enabling real-time and non-invasive monitoring via the detection of volatile organic compounds, biochemical markers, and physical properties. The integration of sensor technologies into cold chain logistics enhances the ability to maintain the quality and safety of aquatic products. This review examines the advancements made in multifunctional sensor devices for the freshness assessment of aquatic products in cold chain logistics, as well as the application of pattern recognition algorithms for identification and classification. It begins by outlining the categories of freshness criteria, followed by an exploration of the development of four key sensor devices: electronic noses, electronic tongues, biosensors, and flexible sensors. Furthermore, the review discusses the implementation of advanced pattern recognition algorithms in sensor devices for freshness detection and evaluation. It highlights the current status and future potential of sensor technologies for aquatic products within the cold chain, while also addressing the significant challenges that remain to be overcome.

Dislocation evolution in anisotropic deformation of GaN under nanoindentation

The exceptional performance of GaN semiconductors in lasers, wireless communication, and energy storage systems makes them crucial for future multi-functional devices. However, during the polishing of GaN wafers, abrasive particles can induce subsurface damage, compromising device performance. This study investigates dislocation loops in GaN single crystal to understand dislocation nucleation and glide under external stress. Using nanoindentation for compressive stress, we confirmed multiple slip system activation via transmission electron microscopy after pop-in. We also performed molecular dynamics to simulate the nucleation and multiplication of U-shaped dislocation loops. Furthermore, we developed a theoretical model using Peierls–Nabarro stress to quantify GaN's critical shear stress. Raman spectroscopy was also used to analyze shear stress on U-shaped loops, supporting our model. This study provides insights into GaN dislocation dynamics under mechanical stress, aiding in wafer defect evaluation during machining and offering guidance for dislocation evolution.

Fully Implantable Wireless Cardiac Pacing and Sensing System Integrated with Hydrogel Electrodes.

Cardiac pacemakers play a crucial role in arrhythmia treatment. Existing devices typically rely on rigid electrode components, leading to potential issues such as heart damage and detachment during prolonged cardiac motion due to the mechanical mismatch with cardiac tissue. Additionally, traditional pacemakers, with their batteries and percutaneous leads, introduce infection risks and limit freedom of movement. A wireless, battery-free multifunctional bioelectronic device for cardiac pacing is developed. This device integrates highly conductive (160Sm-1), flexible (Young's modulus of 80kPa is similar to that of mammalian heart tissue), and stretchable (270%) soft hydrogel electrodes, providing high signal-to-noise ratio (≈28dB) electrocardiogram (ECG)recordings and effective pacing of the beating heart. The versatile device detects physiological and biochemical signals in the cardiac environment and allows for adjustable pacing in vivo studies. Remarkably, it maintained recording and pacing capabilities 31 days post-implantation in rats. Additionally, the wireless bioelectronic device can be fully implanted in rabbits for pacing. By addressing a major shortcoming of conventional pacemakers, this device paves the way for implantable flexible bioelectronics, which offers promising opportunities for advanced cardiac therapies.

Flexible PVDF-Ba0.97Ca0.03TiO3 polymer-ceramic composite films for energy storage, biosensor, mechanosensor, and UV–visible light protection

Multifunctional piezoelectric devices, which can detect pressure, store electrostatic energy, block UV radiation, and generate electricity from body movements, are highly beneficial for enhancing individual well-being. To achieve these capabilities, polyvinylidene fluoride (PVDF) composite films with Ba0.97Ca0.03TiO3 (BCT3) filler were prepared, varying the BCT3 content from 0 to 50 wt.%. The BCT3 ceramic, prepared using a modified solid-state reaction, exhibits a tetragonal phase at room temperature with a d33 value of 105 pC/N. X-ray diffraction confirms composite formation. The beta phase ranges from 75 to 86.9 %. At 40 wt.% BCT3, the dielectric constant, energy density, and piezoelectric properties peak, yielding maximum Wrec and Wtot of 138.1 and 284.7 mJ/cm3 (@ 250 kV/cm), respectively. PVDF-BCT3-40 (40 wt.%) shows maximum voltage, current, and power density of 25 V, 26.8 nA, and 19.8 μW/cm3 under a 50 N load. Increasing BCT3 content enhances UV–visible absorbance, making the composites effective for light shielding.

Enhanced Epoxy Composites Reinforced by 3D-Aligned Aluminum Borate Nanowhiskers.

Recently, the durability of high-performance and multifunctional portable electronic devices such as smartphones and tablets, has become an important issue. Electronic device housing, which protects internal components from external stimuli, such as vibration, shock, and electrical hazards, is essential for resolving durability issues. Therefore, the materials used for electronic device housing must possess good mechanical and electrical insulating properties. Herein, we propose a novel high-strength polymer nanocomposite based on 3D-aligned aluminum borate nanowhisker (ABOw) structures. ABOw was synthesized using a facile hydrothermal method, and 3D-aligned ABOw structures were fabricated using a freeze-casting process. The 3D-aligned ABOw/epoxy composites consist of repetitively layered structures, and the microstructures of these composites are controlled by the filler content. The developed 3D-aligned ABOw/epoxy composite had a compressive strength 56.72% higher than that of pure epoxy, indicating that it can provide high durability when applied as a protective material for portable electronic devices.

A Polyimide Composite-Based Electromagnetic Cantilever Structure for Smart Grid Current Sensing.

Polyimides (PIs) have been extensively used in thin film and micro-electromechanical system (MEMS) processes based on their excellent thermal and mechanical stability and high glass transition temperature. This research explores the development of a novel multilayer and multifunctional polymer composite electro-piezomagnetic device that can function as an energy harvester or sensor for current-carrying wires or magnetic field sensing. The devices consist of four layers of composite materials with a polyimide matrix. The composites have various nanoparticles to alter the functionality of each layer. Nanoparticles of Ag were used to increase the electrical conductivity of polyimide and act as electrodes; lead zirconate titanate was used to make the piezoelectric composite layer; and either neodymium iron boron (NdFeB) or Terfenol-D was used to make the magnetic and magnetostrictive composite layer, which was used as the proof mass. A novel all-polymer multifunctional polyimide composite cantilever was developed to operate at low frequencies. This paper compares the performance of the different magnetic masses, shapes, and concentrations, as well as the development of an all-magnetostrictive device to detect voltage or current changes when coupled to the magnetic field from a current-carrying wire. The PI/PZT cantilever with the PI/NdFeB proof mass demonstrated higher voltage output compared to the PI/Terfenol-D proof mass device. However, the magnetostrictive composite film could be operated without a piezoelectric film based on the Villari effect, which consisted of a single PI-Terfenol-D film. The paper illustrates the potential to develop an all-polymer composite MEMS device capable of acting as a magnetic field or current sensor.

The impact of cellulose nanocrystals on the properties of poly(2‐hydroxyethyl methacrylate)‐based contact lenses

AbstractContact lenses are widely used corrective devices for addressing vision impairments. In addition to their traditional role, these lenses are increasingly applied in personalized care, biosensing, and drug release, thus broadening their application as multifunctional devices. Nanoparticles are often used to introduce new functionalities to these materials. In this context, the role played by different nanoparticles requires attention to ensure that lens manufacture and patient comfort meet the desired criteria. This study investigates the properties of contact lenses prepared by incorporating cellulose nanocrystals into the poly(2‐hydroxyethyl methacrylate) matrix. Using photopolymerization reactions, polyHEMA‐based lenses and nanocomposites containing freeze‐dried and never‐dried nanoparticles were obtained. Fundamental properties of these lenses were evaluated to verify whether the nanoparticles could have a negative effect on the materials. Subsequently, the potential impact of these nanoparticles on the adsorption of model amino acids was investigated. Our findings reveal that the presence of cellulose nanocrystals modifies on lens thickness, light transmittance, mechanical properties, refractive index (RI), and the uptake of amino acids by the contact lenses. This could potentially affect patient comfort and modify the uptake and release of pharmaceutical ingredients by the material. Additionally, it could impact how these materials interact with biomolecules present in the lacrimal fluid.

The Carrying Behavior of Water-Based Fracturing Fluid in Shale Reservoir Fractures and Molecular Dynamics of Sand-Carrying Mechanism

Water-based fracturing fluid has recently garnered increasing attention as an alternative oilfield working fluid for propagating reservoir fractures and transporting sand. However, the low temperature resistance and stability of water-based fracturing fluid is a significant limitation, restricting the fracture propagation and gravel transport. To effectively ameliorate the temperature resistance and sand-carrying capacity, a modified cross-linker with properties adaptable to varying reservoir conditions and functional groups was synthesized and chemically characterized. Meanwhile, a multifunctional collaborative progressive evaluation device was developed to investigate the rheology and sand-carrying capacity of fracturing fluid. Utilizing molecular dynamics simulations, the thickening mechanism of the modified cross-linker and the sand-carrying mechanism of the fracturing fluid were elucidated. Results indicate that the designed cross-linker provided a high viscosity stability of 130 mPa·s and an excellent sand-carrying capacity of 15 cm2 at 0.3 wt% cross-linker content. Additionally, increasing reservoir pressure exhibited enhanced thickening and sand-carrying capacities. However, a significant inverse relationship was observed between reservoir temperature and sand-carrying capacity, attributed to changes in the drag coefficient and thickener adsorption. These results verified the effectiveness of the cross-linker in enhancing fluid viscosity and sand-carrying capacity as a modified cross-linker for water-based fracturing fluid.

Wearable SERS sensor based on Bionic Sea urchin-Cavity structure for dual in-situ detection of metabolites and VOCs gas

Diagnosis of diseases by monitoring the metabolite concentration on the skin surface and volatile organic compounds (VOCs) in exhaled gas is an active area of research with great potential for development and application. Therefore, the development of a sensor that can monitor in real time slight changes in metabolite concentrations on the surface of the skin in the resting state and accurately detect VOCs gases in exhaled gas is of significant practical value. To address these challenges, we designed and fabricated the wearable Bionic Sea urchin-Cavity (BSC) SERS sensor with high sensitivity and adaptability. Our testing revealed that the SERS sensor exhibited strong responsiveness to human metabolites. The subtle concentration changes in urea on the resting state skin surface also successfully detected. Furthermore, the SERS sensor successfully detected trace acetone gas volatilized from the 30 mmol/L aqueous acetone solution similar to the acetone concentration in diabetic blood. We anticipate that this SERS sensor could serve as a multi-functional wearable device for medical applications and provide a new platform for the field.

Design and Application of the New Multi-functional Moxibustion Box

Our team is dedicated to exploring new models for the treatment of spleen and stomach diseases using external therapy techniques of Traditional Chinese Medicine (TCM). We have developed a new multi-functional external therapy device for TCM that innovatively combines the concept of combined therapy with moxibustion. Additionally, through the application of artificial intelligence and new cross-industry intelligent manufacturing technologies, we have creatively incorporated an intelligent anti-burning system, enhancing the automation and informatization level of the product. We have implemented the concept of digitalization from the design stage, thus truly realizing an in-depth exploration of moxibustion, a method of external therapy in TCM. This chapter will summarize the design and application of a new multi-functional moxibustion box, aiming to provide a comprehensive reference for improving the symptoms of spleen and stomach diseases through moxibustion therapy.

Dual-Electrically Configurable MoTe2/In2S3 Phototransistor toward Multifunctional Applications.

Photodetectors, essential for a wide range of optoelectronic applications in both military and civilian sectors, face challenges in balancing responsivity, detectivity, and response time due to their inherent unidirectional carrier transport mechanism. Multifunctional photodetectors that address these trade-offs are highly sought after for their potential to reduce costs, simplify system design, and surpass Moore's Law limitations. Herein, we present a multimodal phototransistor based on a 2D MoTe2/In2S3 heterostructure. Through dual electrical modulation employing bias voltage and gate voltage, we engineer the energy band to achieve switchable photoresponse mechanisms between photoconductive and photovoltaic modes. In photoconductive mode, the device exhibits a responsivity of 320 A/W and a specific detectivity of 1.2 × 1013 Jones. Meanwhile, in photovoltaic mode, it exhibits a light on/off ratio of 2 × 105 and response speed of 0.68/0.60 ms. These capabilities enable multifunctional applications such as high-resolution imaging across various wavelengths, a conceptual optoelectronic logic gate, and dual-channel optical communication. This work makes an advancement in the development of future multifunctional optoelectronic devices.

Modulation of solid solution in MgxMn1−xAl2xFe2(1−x)O4 spinel ceramics for multifunctional devices

AbstractSolid solution modulation is an ideal method for combining the advantages of different parent compounds while mitigating their disadvantages. Here, we investigated the thermal sensitivity, magnetic properties, and microwave absorption of MgxMn1−xAl2xFe2(1−x)O4 (0.2 ≤ x ≤ 0.8) spinel solid solution ceramics for application in multifunctional devices. The electrical transport and magnetic properties can be modulated by adjusting the solution ratio. The ceramics exhibit negative temperature coefficient characteristic. The B‐values from 5065–8056 K, suggesting accurate temperature measurements over a wide temperature range. As a type of soft magnetic material, it has a narrow hysteresis loop and high resistivity. Vector network analyzer studies indicate Mg0.2Mn0.8Al0.4Fe1.6O4 could be a candidate for microwave absorption in S‐band. This study successfully extends the applicability of MgxMn1−xAl2xFe2(1−x)O4 ceramics for high‐temperature thermistors and also confirms potential for multifunctional device.

Janus Swarm Metamaterials for Information Display, Memory, and Encryption.

Metamaterials are emerging as an unconventional platform to perform computing abstractions in physical systems by processing environmental stimuli into information. While computation functions have been demonstrated in mechanical systems, they rely on compliant mechanisms to achieve predefined states, which impose inherent design restrictions that limit their miniaturization, deployment, reconfigurability, and functionality. Here, a metamaterial system is described based on responsive magnetoactive Janus particle (MAJP) swarms with multiple programmable functions. MAJPs are designed with tunable structure and properties in mind, that is, encoded swarming behavior and fully reversible switching mechanisms, to enable programmable dynamic display, non-volatile and semi-volatile memory, Boolean logic, and information encryption functions in soft, wearable devices. MAJPs and their unique swarming behavior open new functions for the design of multifunctional and reconfigurable display devices, and constitute a promising building block to develop the next generation of soft physical computing devices, with growing applications in security, defense, anti-counterfeiting, camouflage, soft robotics, and human-robot interaction.

Sliding Ferroelectricity Induced Ultrafast Switchable Photovoltaic Response in ε-InSe Layers.

2D sliding ferroelectric semiconductors have greatly expanded the ferroelectrics family with the flexibility of bandgap and material properties, which hold great promise for ultrathin device applications that combine ferroelectrics with optoelectronics. Besides the induced different resistance states for non-volatile memories, the switchable ferroelectric polarizations can also modulate the photogenerated carriers for potentially ultrafast optoelectronic devices. Here, it is demonstrated that the room temperature sliding ferroelectricity can be used for ultrafast switchable photovoltaic response in ε-InSe layers. By first-principles calculations and experimental characterizations, it is revealed that the ferroelectricity with out-of-plane (OOP) polarization only exists in even layer ε-InSe. The ferroelectricity is also demonstrated in ε-InSe-based vertical devices, which exhibit high on-off ratios (≈104) and non-volatile storage capabilities. Moreover, the OOP ferroelectricity enables an ultrafast (≈3ps) bulk photovoltaic response in the near-infrared band, rendering it a promising material for self-powered reconfigurable and ultrafast photodetector. This work reveals the essential role of ferroelectric polarization on the photogenerated carrier dynamics and paves the way for hybrid multifunctional ferroelectric and optoelectronic devices.

A solar-powered multi-functional portable charging device (SPMFPCD) with internet-of-things (IoT)-based real-time monitoring—An innovative scheme towards energy access and management

In the absence of portable charging devices, sectors such as transportation, communication, and emergency services deal with various challenges towards electric power needs while compromising on (1) operational efficiency, (2) insufficient portable charging solutions, and (3) limited versatility. This highlights the critical need for reliable and multi-functional power solutions. To provide a portable charging solution across diverse sectors, this paper proposes an innovative development of a solar-powered multi-functional portable charging device (SPMFPCD) with internet- of-thing (IoT)-based monitoring capabilities. The proposed scheme introduces a comprehensive model integrating advanced technologies which include a highly efficient solar panel, charge controller, sensors, and IoT module. The proposed system facilitates versatile charging solutions for a wide range of power requirements with real-time monitoring and data analysis through the IoT platform. Moreover, the proposed work explores the applications of the SPMFPCD in (1) emergency medical scenarios, (2) outdoor adventures, (3) disaster management, and 4) public spaces. Performance evaluation was made by proposing case studies to validate the (1) economic viability, (2) power management, and (3) environmental impact of widespread deployment of SPMPFCD in public spaces. Furthermore, detailed analysis of battery energy storage system (BESS) and photovoltaic (PV) integration for load management, seasonal dynamics, and renewable energy integration (REI) contribute to a comprehensive understanding of the proposed solution.

Analog and digital resistive switching in W/TiO2/ITO devices: the impact of crystallinity and Indium diffusion

The resistance-switching memristor with capabilities of information storage and brain-inspired computing has prime importance in recent research. In this study, the impact of crystallinity and Indium diffusion on the existence of analog and digital resistive switching in a W/TiO2/ITO device has been reported. The memristor devices are fabricated by depositing titania films by sol–gel and spin-coating techniques. The films annealed at 250 °C and 400 °C were characterized using x-ray diffraction, Raman spectroscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy (XPS). The characteristic anatase phase started appearing after annealing at 400 °C, whereas the 250 °C annealed sample was in the amorphous state. The electrical characterization revealed significant differences in the switching characteristics of amorphous and crystalline samples, especially in the switching interface, compliance properties, and current conduction mechanism. The grain boundary assisted oxygen vacancy migration, and the diffusion of indium ions from the ITO bottom electrode helped the crystalline sample to show highly stable and reproducible resistive switching compared to amorphous film. The XPS studies confirmed the indium ion diffusion in the crystalline sample. The oxygen vacancy-induced barrier modulation and conductive filament formation caused characteristic switching in amorphous and crystalline samples, respectively. Schottky emission in the amorphous film and SCLC mechanism in the crystalline film confirmed the experimental results. This study provides a distinctive viewpoint and an innovative strategy for developing multifunctional resistive switching devices.

Inorganic film materials for flexible electronics: A brief overview, properties, and applications

AbstractThe field of flexible electronics has experienced remarkable expansion in response to the escalating demand for lightweight, bendable, and multifunctional electronic devices. As the world increasingly integrates electronics seamlessly into everyday life, the importance of flexible electronics becomes more apparent. While existing reviews have examined materials used in flexible devices, they often overly focus on specific materials or provide broad generalizations about different material types. Thus, this review offers a concise yet comprehensive overview of critical inorganic film materials crucial to the advancement of flexible and wearable devices. Each material is introduced with a succinct overview of its structure and production processes. This review elucidates their unique characteristics and potential applications in flexible electronics by comparing their mechanical, electrical, and thermal properties. This review is a valuable resource for researchers entering this emerging field of flexible electronics, providing a concise yet comprehensive insight and property comparisons. Accompanied by figures illustrating material structures and applications, readers will gain access to summarized discussions. Comparative figures of material properties will enhance comprehension. Additionally, discussions on diverse applications will offer insight into their versatility across various fields of flexible electronics.

Growth Conditions and Interfacial Misfit Array in SnTe (111) Films Grown on InP (111)A Substrates by Molecular Beam Epitaxy.

Tin telluride (SnTe) is an IV-VI semiconductor with a topological crystalline insulator band structure, high thermoelectric performance, and in-plane ferroelectricity. Despite its many applications, there has been little work focused on understanding the growth mechanisms of SnTe thin films. In this manuscript, we investigate the molecular beam epitaxy synthesis of SnTe (111) thin films on InP (111)A substrates. We explore the effect of substrate temperature, Te/Sn flux ratio, and growth rate on the film quality. Using a substrate temperature of 340 °C, a Te/Sn flux ratio of 3, and a growth rate of 0.48 Å/s, fully coalesced and single crystalline SnTe (111) epitaxial layers with X-ray rocking curve full-width-at-half-maxima of 0.09° and root-mean-square surface roughness as low as 0.2 nm have been obtained. Despite the 7.5% lattice mismatch between the SnTe (111) film and the InP (111)A substrate, reciprocal space mapping indicates that the 15 nm SnTe layer is fully relaxed. We show that a periodic interfacial misfit (IMF) dislocation array forms at the SnTe/InP heterointerface, where each IMF dislocation is separated by 14 InP lattice sites/13 SnTe lattice sites, providing rapid strain relaxation and yielding the high quality SnTe layer. This is the first report of an IMF array forming in a rock-salt on zinc-blende material system and at an IV-VI on III-V heterointerface, and highlights the potential for SnTe as a buffer layer for epitaxial telluride film growth. This work represents an important milestone in enabling the heterointegration between IV-VI and III-V semiconductors to create multifunctional devices.