Multilayer Design Research Articles

LTCC-Based DC-DC Converter for Reduction of Switching Noise and Radiated Emissions

In this study, a low-temperature co-fired ceramic (LTCC)-based direct current (DC)-DC converter is proposed for reducing stray inductance and mitigating electromagnetic interference. The dominant radiating loop of the proposed LTCC-based DC-DC converter features a multilayer design, which helps suppress noise sources and reduce radiated emissions. The peak voltage of switching noise for the proposed DC-DC converter at the frequency of 500 kHz is approximately 8.98% lower than that of a conventional DC-DC converter. In addition, the radiated emission level of the proposed DC-DC converter is lower than that of the conventional DC-DC converter. In sum, the proposed LTCC-technology-based multilayer design reduces the peak voltage of switching noise and the radiated emission of the DC-DC converter.

Multifunctional and switchable metamaterial for terahertz polarization modulation in the reflection mode.

In this paper, a broadband multi-layered active metamaterial design is investigated, which can achieve a high polarization conversion efficiency over a wide band of frequencies in the terahertz regime. The design can be switched to an efficient metamaterial absorber using the phase transition property of vanadium dioxide (V O 2). Additionally, the designed structure can convert the linear polarization of the incoming wavefronts to its cross-polarization and linear polarization to circular polarization in the reflection mode. The broadband characteristic is achieved due to the strong anisotropic behavior of the metasurface. The structure is robust to a wide range of incident angles as well. The proposed switchable multifunctional design can contribute to the development of active plasmonic polarization devices and metamaterial absorbers.

An optimized B/Ir supermirror for Einstein Probe focusing mirrors in x-ray region of above 8 keV

The Einstein Probe (EP) focusing mirrors is a main load to focus and image x-rays. A single-layer which adopts Nickel substrates and Gold reflective coatings has been used for the EP focusing mirrors and has excellent performance below 8 keV. It is a possibility to enhance the effective area of higher x-ray regions by using the multilayer design. The multilayer with single block is designed and has excellent reflectance at specific x-ray energies above 8 keV. 54 multilayers are used for all mirror shells with different incident angles. The optimized B/Ir supermirror design for focusing mirrors with short focal length shows an effective area of up to 152 cm2 in 9 keV. And, the method can be used to design supermirror for higher x-ray regions, which will achieve hard x-ray detection with short focal length focusing mirrors and small hard x-ray detection satellite.

Development of Multiple Ceramic Coatings on Porous Tubular Metal Support

Dip coating was used to develop anodic half-cell for micro-tubular metal-supported solid oxide fuel cells (MS-SOFCs) economically. Ni–scandia-stabilized zirconia (SSZ) and SSZ were used as anode functional layer and electrolyte, respectively. Successive coatings of the SOFC functional layers were applied onto the porous metallic support using a dip coating technique. Additionally, to prevent delamination between the metal support and anode functional layer, an intermediate layer consisting of stainless steel powder, Ni, and yttria-stabilized zirconia (YSZ) was introduced. After coating, the individual layers were fired in a reducing atmosphere at 1000 °C followed by co-sintering of metal/anode/electrolyte multilayers at 1350°C. Microstructure of the sintered cells was characterized using scanning electron microscopy (SEM). General problems encountered during the fabrication of anodic half-cell for MS-SOFCs by a cost-effective dip coating followed by co-sintering route have been investigated. The sintering conditions and multilayer designs were studied to minimize the metal support oxidation and ceramic layer peeling during co-sintering.

Recent Methods for Modifying Mechanical Properties of Tissue-Engineered Scaffolds for Clinical Applications.

The limited regenerative capacity of the human body, in conjunction with a shortage of healthy autologous tissue, has created an urgent need for alternative grafting materials. A potential solution is a tissue-engineered graft, a construct which supports and integrates with host tissue. One of the key challenges in fabricating a tissue-engineered graft is achieving mechanical compatibility with the graft site; a disparity in these properties can shape the behaviour of the surrounding native tissue, contributing to the likelihood of graft failure. The purpose of this review is to examine the means by which researchers have altered the mechanical properties of tissue-engineered constructs via hybrid material usage, multi-layer scaffold designs, and surface modifications. A subset of these studies which has investigated the function of their constructs in vivo is also presented, followed by an examination of various tissue-engineered designs which have been clinically translated.

Multilayer design of core–shell nanostructure to protect and accelerate sulfur conversion reaction

Although a core–shell design has been suggested to maximize reversible redox reaction of conversion–type electrode materials inside a shell, it is challenging to fulfill the complicated prerequisites collectively. This paper proposes a rational core–shell design composed of single–atom catalytic and protective multilayers for sulfur conversion reaction. A hydrogen bond–based supramolecular network incorporates Fe ions by metal–phenolic coordination, accelerating sluggish kinetics. The polypyrrole layer protects the entire structure to suppress the migration of polysulfides and withstand large volume changes. Comprehensive investigation demonstrates that core–shell sulfur nanostructures preserve the structural integrity and electrocatalytic effect during discharge/charge. The resulting electrodes enable outstanding rate capability and stable cycling performance. Furthermore, the areal capacity of higher sulfur loading cells surpasses current Li–ion batteries even at 1 C. This work reactivates the core–shell strategy as a design guideline for viable next–generation electrode materials.

Miniaturized thin-film filters to connect multiple self-written waveguides

Self-written waveguides (SWWs) have been well investigated within the last decades. In most cases, they are used as low-loss coupling structures, i.e., to connect buried optical structures in photonic integrated circuits. In this work, we extend the field of possible applications for SWWs by embedding a novel thin-film filter to split the beam and connect multiple output ports simultaneously. The multilayer design of the dielectric filter can be customized to enable its application as a dichroic beamsplitter for photonic networks. The embedded thin-film filter was characterized in detail and used to connect an additional optical sensing element, which is also based on SWWs, to demonstrate its usability for measurement of physical quantities.

Corrosion of plasma sputtering medium entropy alloy thin film: A multidisciplinary perspective

Plasma sputtering multi-principal element alloys (MPEAs) thin film is critical to functional multi-layer material design for a wide range of applications. To investigate its electrochemical stability, we established a multidisciplinary approach including in-situ optical microscope integrated EC-SPR coupled with ICPMS, and ex-situ XPS and XAS analysis. Compared to our previous work in bulk material, we observed a significant reactivity change of plasma sputtering thin film on gold. Based on XPS, XAS and SPR results, we propose that the formation of Cr(OH)3 at the edge and the interface between alloys and gold layers is responsible for weakening the corrosion resistance of an NiCoCr/Au system.

Light-Writing & Projecting Multicolor Fluorescent Hydrogels for On-Demand Information Display.

Intelligent rewritable display systems have been long-expected to reduce the heavy consumption of single-use or transient devices in the age of Internet-of-Things. However, it remains challenging to construct such systems with integrated functionality of remote control, rapid activation, multicolor and multimode display. Herein, by learning from the unique multilayer arrangement of chromatophores in chameleon skins, we present a promising kind of rewritable hydrogel multicolor systems that can combine the merits of near-infrared (NIR) light-writing & projecting modes for on-demand information display. Specifically, the systems have typical multilayer layout consisting of PDMS-sealed carbon nanotubes (CNTs) film as photothermal control unit and embedded fluorescent hydrogels as multicolor display unit, in which thermo-responsive hydrogel is constrained within non-responsive hydrogel. Such rational structure design results in the establishment of one promising display mechanism via the cascading "light trigger-heat generation-fluorescence output" process. On this basis, rapid and reversible hand-written display of arbitrary information is achieved within 5 s. Also, sustainable light-projecting display of predesigned multicolor patterns is demonstrated due to the multilayer design that ensures easy patterning of photothermal control or hydrogel display layer. This study brings functional-integrated merits for novel rewritable display systems and open new possibility to construct high-end products for information display/transmission. This article is protected by copyright. All rights reserved.

Effect of Gradient Multilayer Design on Tribological Performance of TiN/TiSiN Coatings Prepared by Cathodic Arc Ion Plating

Hard coatings, such as transition metal nitrides, have been widely applied to improve the mechanical properties and tribological performance of cutting tools. The coatings in various multilayered or gradient structures have been designed to meet the demands of more severe service environments and more precise processing requirements. In this work, TiN/TiSiN coatings in several gradient and multilayered structures were deposited on cemented carbides by cathodic arc ion plating using Ti and TiSi alloy targets. The modulation period (Λ) of the multilayer gradually varies with thickness, ranging from 6 to 46 nm. The gradient multilayer coatings consist of a nanocrystalline-amorphous composite with compact growth. The coating with a modulation period first increasing and then decreasing has the highest hardness of 38 GPa, and the maximum residual compressive stress of −2.71 GPa, as well as the minimum coefficient of friction (COF) and wear rate. Gradient and multilayer structures moderate the brittleness caused by the presence of amorphous SiNx phase and optimize the mechanical properties and tribological performances of the coatings.

Three-dimensional lab-on-a-foil device for dielectrophoretic separation of cancer cells.

A simple, low-cost, three-dimensional (3D) lab-on-a-foil microfluidic device for dielectrophoretic separation of circulating tumor cells (CTCs) is designed and constructed. Disposable thin films are cut by xurography and microelectrode array are made with rapid inkjet printing. The multilayer device design allows the studying of spatial movements of CTCs and red blood cells (RBCs) under dielectrophoresis (DEP). A numerical simulation was performed to find the optimum driving frequency of RBCs and the crossover frequency for CTCs. At the optimum frequency, RBCs were lifted 120µm in z-axis direction by DEP force, and CTCs were not affected due to negligible DEP force. By utilizing the displacement difference, the separation of CTCs (modeled with A549 lung carcinoma cells) from RBCs in z-axis direction was achieved. With the nonuniform electric field at optimized driving frequency, the RBCs were trapped in the cavities above the microchannel, whereas the A549 cells were separated with a high capture rate of 86.3%±0.2%. The device opens not only the possibility for 3D high-throughput cell separation but also for future developments in 3D cell manipulation through rapid and low-cost fabrication.

Versatile graphene-alumina nanofibers for microwave absorption and EMI shielding

Carbon-based hybrid nanostructures have shown to be promising candidates as cost-efficient and effective fillers for electromagnetic interference shielding and RF absorption. In this work, hybrids of graphene-augmented inorganic (alumina) nanofibers (GAIN) have been incorporated in epoxy resin to fabricate a multilayer structure with tunable absorption. Highly aligned graphene augmented alumina nanofibers of 10 ± 2 nm in diameter were produced with the help of a hot wall one-step catalyst-free chemical vapor deposition method at 1000 °C. Effective medium approximation has been used to calculate the intrinsic dielectric properties of GAIN nanofibers. The highest loss tangent of 0.4 has been achieved in a 5 mm thick composite containing 1 vol% of randomly oriented nanofibers. Furthermore, aligned graphene augmented nanofibers were embedded in an epoxy resin matrix to examine the effect of fiber alignment on the dielectric properties of the composite. Based on the obtained dielectric data, a superposed three-layer structure has been fabricated, offering an absorption of >90% in the entire X-band and an absorption peak of −25 dB at ∼11 GHz. Several multilayer designs based on finite element method coupled with Monte Carlo simulations have been proposed to tune the absorption characteristics. This work demonstrates the potential of the hybrid nanofibers with a dual loss function for versatile design options in the area of RF absorption.

Multi-objective optimization for improving machining benefit based on WOA-BBPN and a Deep Double Q-Network

To scientifically and reasonably set and adjust the machining parameters, and improve the machining benefit of the batch machining process including machining quality, performance and efficiency, this paper proposes a low cost and high accurate multi-objective optimization framework by integrating intelligent technologies from three perspectives of physical experiment design, objective function construction and multi-objective optimization. In this framework, multilayer design (MLD) which is a computer experiment design method with low redundancy, good uniformity and filling is applied to the machining physics experiment design to reduce the experiment cost. Whale optimization algorithm (WOA) optimized backpropagation neural network (BBPN) is utilized to construct the optimization objective functions to improve the accuracy of functions. And Deep Double Q-Network (DDQN) is employed to achieve multi-objective optimization of machining quality, efficiency, and performance. The effectiveness of MLD, WOA-BBPN and DDQN in multi-objective optimization of machining process are verified by comparisons of common modeling and multi-objective optimization algorithms based on the milling data. These techniques provide a good guidance for the selection of machining parameters to improve the machining benefit and demonstrates some advantages. The research of this paper also offers a good example of applying intelligent technology in machining.

An integrated load-bearing and vibration-isolation supporter with decorated metamaterial absorbers

Vibration sources such as power units transmit vibration and load to equipment via supporters, aggravating equipment vibration and radiating noise to the environment. Therefore, a supporter is a necessary path for vibration transmission, and reducing its vibration transmission capability is essential for attenuating equipment vibration and noise. To overcome the challenges presented by the inability of traditional supporters to conciliate contradictions between high-bearing capacity and vibration-isolation performance, this paper proposes an integrated load-bearing, vibration-isolation design by embedding metamaterial absorbers in the supporter. Arranging absorbers on the vibration transmission path suppresses vibration transmission in a wide frequency band without affecting the bearing capacity and realizes the function of replacing isolation with absorption. The gradient parallel, multi-layered design of the absorbers effectively extends the vibration attenuation bandwidth, further improving its vibration attenuation capacity. The metamaterial units could reduce additional weight for structural vibration suppression due to their sub-wavelength dimensions and lightweight characteristics. The vibration-absorbing units can be embedded in the cavities of hollow support structures or arranged as an additional component in the external spaces of non-hollow support structures, making them broadly applicable. The design of integrated load-bearing, vibration-isolation supporters with decorated metamaterial absorbers helps attenuate and reduce equipment noise, providing vital engineering application value.

Enable thermal insulation improvement of Al2O3 aerogels doped with graded oriented extinction phase-change fiber at large temperature differences

Phase change materials (PCMs) play essential roles in extending transient thermal insulation in the aerospace field; however, the extinction properties variations during the phase change process have seldom been investigated. The present study presents an extinction phase-change fiber (EPCF) design, i.e., composed of extinction material shell as well as the PCM core and dispersed in Al2O3 aerogel. The extinction performance (especially after the phase transition) and the insulation performances at steady and transient states according to specific infrared radiation wavelength modulation are numerically investigated. This study reveals that the extinction characteristic of VO2@SiO2 is superior to that of SiO2 and TiO2 fiber. The extinction performance is improved by ∼8.37% after the phase transition of VO2. Besides, the time constant of VO2@SiO2 increased by ∼2.17 times the pure aerogel at the insulation aspect. Similar conclusions could be self-evidently found in some other EPCFs; furthermore, multi-layer EPCFs design is studied for spectral modulation principle combined with the transient heat transfer characteristic. Our developmental work could inspire some novel ideas on insulation material design in the future and improve the understanding of phase change insulation.

Reconfigurable Soft Pneumatic Actuators Using Extensible Fabric-Based Skins.

The development of the field of soft robotics has led to the exploration of novel techniques to manufacture soft actuators, which provide distinct advantages for wearable assistive robotics. One subset of these soft pneumatic actuators is conventionally developed from silicone, fabrics, and thermoplastic polyurethane (TPU). Each of these materials in isolation possesses limitations of low-stress capacity, low-design complexity, and high-input pressure requirements, respectively. Combining these materials can overcome some limitations and maintain their desirable properties. In this article, we explore one such composite design scheme using a combination of silicone polymer-based bladder and reconfigurable fabric skin made from an anisotropic extensible fabric. The silicone polymer bladder acts as the hermetic seal, while this skin acts as the constraint. Bending and torsional actuators were designed utilizing the anisotropy of these fabrics. The torsional actuator designs can achieve over 540° of twist, significantly larger than previously reported in the literature, owing to the lower mechanical impedance of the extensible fabrics. Actuators with 360° of bending were also fabricated using this method. In addition, the lack of TPU-backed or inextensible fabrics reduces the actuator's stiffness, leading to lower actuation pressures. Skin-based designs also confer the advantage of modularity, reconfigurability, and the ability to achieve complex motions by tuning the properties of the bladder and the skin. For applications with high-force requirements, such as wearable exoskeletons, we demonstrate the utility of multilayer design schemes. A multilayer bending actuator generated 190 N of force at 100 kPa and was shown to be a candidate for wearable assistive devices. In addition, torsional designs were shown to have utility in practical scenarios such as screwing on a bottle cap and turning knobs. Thus, we present a novel fabric-skin-based design concept that is highly versatile and customizable for various application requirements.

Constructing broadband microwave metastructure absorber based on 2D Ti3CNTx MXene magnetic composites

Microwave absorbing materials (MAMs) have been used to address electromagnetic pollution for both civil and military applications, and MAMs with broadband microwave absorption still remain a challenge. The microwave absorption performance of Ti3CNTx MXene is poor due to impedance mismatch. Modification of Ti3CNTx with magnetic materials is an effective way to improve the impedance matching and increase the effective absorption bandwidth (EAB). Here, 2D Ti3CNTx based magnetic composites were successfully prepared by an electrostatic self-assembly method. The microwave absorption properties of the composites were investigated by varying the loading of Ti3CNTx in the composites and the filling ratio of the composites in the absorber. The EAB can reach 4.75 GHz with an absorber thickness of only 1.32 mm. Integrated with a macroscale multilayer periodic gradient design, the FCM (Fe@NC/Ti3CNTx) composites based metastructure exhibits broadband microwave absorption with an EAB of 12.5 GHz ranging from 5.5 GHz to 18 GHz at a total thickness of 4.5 mm. The microwave attenuation mechanisms were studied by dielectric loss, magnetic loss and impedance matching. The multi-scale development of MXene-based magnetic composites makes them possible to applied to broadband microwave absorption.

A low-cost paper-based blood urea nitrogen optical biosensor for renal surveillance in fingertip blood

In this study, we developed a low-cost, handheld optical biosensor for measuring blood urea nitrogen (BUN) levels in fingertip blood. This biosensor can connect to a cloud-enabled smartphone for remote monitoring of renal diseases. The biosensor features a simple, stackable and multilayer paper-based strip design, which not only achieves a linear optical fast response to BUN concentration but also reduces the complexity of the optical reader. Excellent detection performance was obtained via a unique photoelectric detection algorithm. The proportional function for calculating the analyte concentration was established using blood samples with different BUN concentrations, resulting in a wide detection range of 2.46–38.14 mM and a low detection limit of 0.03 mM. Clinical sample testing demonstrated the biosensor’s high reliability, showing strong agreement with the bulky biochemistry analyzer (gold standard), with a correlation coefficient R2 = 0.9635. It is also capable of connecting to a cloud-enabled smartphone via Bluetooth to transmit test data, which has an easy-to-use interface, thus enabling proactive health management or remote diagnosis. We believe that the proposed BUN biosensor can be a big boost to the daily monitoring of renal diseases and has promising prospects in contributing to the development of the IoMT.

Néel Skyrmion Bubbles in La0.7Sr0.3Mn1–xRuxO3 Multilayers

Ferromagnetic La0.7Sr0.3Mn1-xRuxO3 epitaxial multilayers with controlled variation of the Ru/Mn content were synthesized to engineer canted magnetic anisotropy and variable exchange interactions, and to explore the possibility of generating a Dzyaloshinskii-Moriya interaction. The ultimate aim of the multilayer design is to provide the conditions for the formation of domains with nontrivial magnetic topology in an oxide thin film system. Employing magnetic force microscopy and Lorentz transmission electron microscopy in varying perpendicular magnetic fields, magnetic stripe domains separated by Néel-type domain walls as well as Néel skyrmions smaller than 100 nm in diameter were observed. These findings are consistent with micromagnetic modeling, taking into account a sizable Dzyaloshinskii-Moriya interaction arising from the inversion symmetry breaking and possibly from strain effects in the multilayer system.

The enhancement of mechanical properties and uniform degradation of electrodeposited Fe-Zn alloys by multilayered design for biodegradable stent applications.

Pure Fe is a potential biodegradable stent material due to its better biocompatibility and mechanical properties, but its degradation rate needs to be improved. Alloying with Zn to form Fe-Zn alloy is anticipated to meet the degradation rate requirements while retaining the iron's inherent properties. Therefore, Fe-Zn alloys with monolayered and multilayered structures were prepared by electrodeposition. The alloys' composition, microstructure, mechanical properties, in vitro degradation and biocompatibility were assessed. Results showed that the Zn content ranged from 2.1 wt% to 11.6 wt%. After annealing at 450°C, all the alloys consisted of α(Fe) solid solution and Zn-rich B2 ordered coherent phase, except for the alloy with 11.6 wt% Zn content, in which a Fe3Zn10 phase appeared. The layered structure consisted of alternating columnar-grain and nano-grain layers, which compensated for the intrinsic brittleness of electrodeposited metals and improved the galvanic effect of the alloy, thus increasing the strength and plasticity and changing the corrosion from localized to uniform while augmenting the corrosion rate. The yield strength of the multilayered alloy exceeded 350 MPa, its elongation was more than 20%, and its corrosion rate obtained by immersion test in Hank's solution reached 0.367 mm·y-1. Fe-Zn alloys with lower Zn content had good cytocompatibility with the human umbilical vein endothelial cells and good blood compatibility. The above results verified that the multilayered Fe-Zn alloy prepared by electrodeposition presented enhanced mechanical properties, higher degradation rate, uniform degradation mechanism and good biocompatibility. It should be qualified for the application of biodegradable stents. STATEMENT OF SIGNIFICANCE: A potential biodegradable Fe-Zn alloy, which is difficult to be obtained by the metallurgical method, was prepared by electrodeposition to solve the low degradation rate of iron-based biomaterials. A multilayered microstructure design composed of alternating columnar-grain and nano-grain layers was achieved by changing the electrical parameters. The layered design compensated for the intrinsic poor plasticity of electrodeposited metals. It increased the galvanic effect of the alloy, thus augmenting the corrosion rate and changing the corrosion mode of the alloy from localized to uniform corrosion. The yield strength of multilayered alloy exceeded 350 MPa; its elongation was more than 20%. Moreover, the layered alloy had good cytocompatibility and blood compatibility. It indicates that the alloy is qualified for biodegradable stent application.