Multilayer Films Research Articles

Double-protein-loaded 3D-printed polyetheretherketone cage for promoting interbody fusion via osteogenic differentiation

Intervertebral disc degeneration (IDD) is a common condition characterized by age-related wear and tear of the spine. In advanced stages or severe cases of IDD, surgical treatment involving the implantation of an interbody cage is often the primary treatment approach. Polyetheretherketone (PEEK) has been widely used in orthopedic and spinal implants due to its remarkable mechanical properties, biocompatibility, and corrosion resistance. However, when used in interbody cages, PEEK exhibits poor processability and biological inertness, which are significant disadvantages that need to be addressed. In this work, we first fabricated the PEEK cage via the fused deposition modeling (FDM) method. To improve its fusion effect, bone morphogenetic protein 2 (BMP2) was loaded onto sulfonated PEEK and sealed with gelatin/chitosan (Gel/Chi) multilayer films. Substance P was then grafted on the surface with a Schiff base. When the cage is implanted, substance P is released first, recruiting bone marrow-mesenchymal stem cells (MSCs) to the implant surface. Subsequently, upon degradation of the Gel/Chi multilayer films, BMP2 is slowly released and promotes osteogenic differentiation of MSCs. In vivo results revealed that the double-protein-loaded PEEK cage exhibited remarkable fusion effects. This work provides a novel approach for the design and fabrication of a PEEK intervertebral fusion device with an excellent fusion effect.

Nanofiber array growth mechanism based on dealloying of Ti-Cu/Cu multilayer precursor film

Metal oxide nanofiber array materials are a type of material with outstanding performance and application potential. Recently, an efficient dealloying method using Ti–Cu/Cu multilayer film as a precursor was proposed to prepare titanium oxide nanofiber array structure. However, the growth mechanism and formation process of such an oxide nanofiber array grown on multilayer-film is not clear. In this work, we use Ti-Cu/Cu multilayer film as the precursor, NaOH solution as the dealloying corrosion solution, and free dealloying at room temperature. On the basis of successfully obtaining TiO2 nanofiber array films, the morphology formation and evolution process of the nanoarray were carefully monitored, and the atomic percentage changes of Ti, Cu and O elements in the dealloying precursor films were tested, as well as the formation and crystalline phase evolution trends of TiO2. Based on the experimental data, we tried to draw a schematic diagram of the formation process of this TiO2 nanofiber array, and proposed that the growth mechanism of the TiO2 nanofiber array is the precipitation growth process both with Ostwald Ripening and Oriented Attachment mechanisms. Then, the photocurrent response characteristics of the obtained nanofiber array structure samples were analyzed, and it was found that the nanofiber array structure had a certain effect on the photocurrent response performance. The completion of the present work is expected to provide a theoretical reference for the preparation and application of other metal oxide nanofiber array by dealloying method.

Effect of the interlayer distribution of ZnO decorated with Ag nanoparticles on the antimicrobial activity of multilayer poly(methyl methacrylate) films

AbstractIncorporating nanoparticles into polymer matrices for enhanced antimicrobial properties is particularly interesting. This study examines how the interlayer distribution of zinc oxide (ZnO) decorated with silver nanoparticles (AgNPs) within poly(methyl methacrylate) (PMMA) films impacts their antimicrobial activity. Various PMMA multilayer films were prepared, with the antimicrobial additive intentionally placed in the outer, core, bottom, or throughout all layers. Their efficacy was tested against gram‐negative (Escherichia coli) and gram‐positive (Staphylococcus aureus) bacteria. Results indicate that E. coli was the strain with the highest sensitivity to the system because it is a gram (−) bacterium, which could generate a lower resistance to AgNPs. On the other hand, S. aureus, being gram (+), presents a thicker lipid membrane, and peptidoglycan wall, which makes it difficult for AgNPs to enter. Films with uniform distribution throughout thickness exhibited the most sustained antimicrobial activity due to high antimicrobial concentration. This study demonstrated that the distribution of the AgNPs/ZnO system in different layers of a PMMA film influences its antimicrobial capacity. Finally, a mechanism for migrating silver ions released from the AgNPs/ZnO system in PMMA films is proposed, highlighting their interactions with bacterial cells and the subsequent antimicrobial effects.Highlights Interlayer distribution influences antimicrobial activity. Outer placement leads to rapid silver ion release. Core distribution controls antimicrobial kinetics. Uniform distribution ensures sustained activity.

Inverse-design laser-infrared compatible stealth with thermal management enabled by wavelength-selective thermal emitter

With the fast development of multi-band detection technology, the demand for multi-band stealth technology with thermal management in military and civilian fields is increasing. Although the metasurfaces can achieve multi-band stealth and thermal management, their fabrication is complex and costly. In this paper, a simple multilayer structure is used to realize laser-infrared compatible stealth with thermal management. More importantly, the traditional method of optimizing metasurface structures by manually scanning parameters consumes a lot of computational time and resources. In order to speed up design of nanostructures, we propose a wavelength-selective thermal emitter (WSTE) composed of ZnS/Ge3Sb2Te6 (GST) multilayer films and a Ni reflector using inverse design method. The simulation results show that, in the crystalline phase, the WSTE has low spectral emissivity (ε3-5μm = 0.12, ε8-14μm = 0.22) in the mid-wave infrared (MWIR) and long-wave infrared (LWIR), high spectral emissivity (ε5-8μm = 0.72) in the non-atmospheric window and high absorptivity (A1.06μm = 0.90, A1.55μm = 0.97, A10.6μm = 0.91) in the laser wavelengths, which indicates that the WSTE can simultaneously achieve MWIR, LWIR and laser stealth with radiative heat dissipation. The method proposed in this paper overcomes the problems of single-band stealth and inefficient. Moreover, by varying the crystallization fraction of the GST, the WSTE can achieve dynamic control of thermal radiation in the wavelength range of 3–14 µm. The simulated infrared images verify that WSTE has good infrared stealth performance. Finally, the effects of incidence angle and polarization angle on the emission spectrum of WSTE are studied, which can demonstrate the infrared stealth is insensitive to both. In conclusion, the WSTE is attractive in advanced photonics applications, such as radiative cooling and infrared stealth.

Integrating all-yarn-based triboelectric nanogenerator/supercapacitor for energy harvesting, storage and sensing

In the burgeoning field of energy harvesting, the integration and miniaturization of triboelectric nanogenerators with supercapacitors (TENG-SC) offers a promising frontier for developing self-powered wearable and portable sensing electronics. However, many TENG-SC systems encounter challenges in meeting wearability, high energy density, and ease of use requirements due to their complex configurations and limited flexibility. Herein, an asymmetric supercapacitor (ASC) was created by rolling up a lamellar multilayer film into a cylindrical yarn-based structure. The lamellar multilayer film comprises energy storage films with sequentially stacked layers of the positive AgNW/MnO2-TPU layer, PP separator layer, and negative AgNW/AC-TPU layer, tightly bonded to create a sandwich-like structure. The yarn-based ASC, functioning as an energy storage unit, demonstrates a high volumetric energy density of 3.2 mWh cm−3 and excellent cyclic stability (10000 cycles). Subsequently, a thinner sheath-core TPU/CB@AgNW/PMMA yarn was produced by combining wet spinning with electrospinning, which was helically wound around the yarn-based ASC to form an all-yarn-based TENG-ASC pressure-sensitive sensor that integrates energy harvesting, storage, and sensing. The miniaturized TENG-ASC yarn can convert various forms of bio-motion energy into electrical signals, with a maximum output voltage of around 3.5 V and a peak power density of 2.14 mW m−2. Simultaneously, this all-yarn-based TENG-ASC device achieves superior sensitivity (30.3 kPa−1) and has a wide pressure detection range of up to 50 kPa. This integrated system can continuously power electronic devices embedded in smart textiles, thereby extending their operational life and functionality.

Wireless optical power transfer system incorporating a wide-field-of-view optical receiver.

This article introduces what we believe to be a novel receiver design featuring a compact, wide-field-of-view receiver and bidirectional gain medium that enables multiple receivers to charge simultaneously. The receiver was tested with a transmitter comprising a bidirectional broadband semiconductor optical amplifier and two wavelength division multiplexing filters. The receiver incorporates a ball-lens retroreflector equipped with anti-reflection and highly reflective coatings on its front and rear surfaces, respectively. The system has an overall efficiency of 1.23%, which can be improved further using suitable gain media. This receiver scheme has potential for seamless integration with various transmission systems that utilize the RBC technique and offers a wide field of view of approximately ±60 degrees.

Optical scattering measurement of highly reflective coatings with the cavity ring-down technique.

Cavity ringdown (CRD) is employed for the first time, to the best of our knowledge, to precisely measure the optical scattering of highly reflective (HR) optics with measurement sensitivity greatly enhanced via power trapping inside the ringdown cavity. The scattering measurement accuracy is significantly improved by calibrating the photo-detector for the scattering measurement with the low transmittance of the cavity mirror or test HR mirror, which is also accurately measured by CRD. The influence of environmental stray light (such as the probe light scattered by optics and mechanical parts outside the ringdown cavity) and other background noises on the scattering measurement is greatly eliminated by the temporal behavior of the scattering CRD signal. A scattering measurement sensitivity of 4.0 × 10-13 is experimentally achieved with a laser with output power of 12 mW.

Reactively Processed Poly(butylene adipate terephthalate) Composite–Based Multilayered Films with Improved Properties for Sustainable Packaging Applications: Structural Characterization and Biodegradation Mechanism

AbstractIn this study, it is attempted to enhance the properties and biodegradability of poly(butylene adipate terephthalate) (PBAT) using nanocomposite technology to meet the demand for sustainable packaging applications. Two nanoclays containing PBAT composites are reactively processed and integrated into the multilayered films. Reactive processing facilitates the dispersion and distribution of nanoclay particles in the PBAT matrix. The multilayered films comprising reactively processed PBAT composites exhibited a 24.5%–31.5% reduction in the oxygen transmission rate and improved dimensional stability and tensile properties. Moreover, the degradability of the multilayered film comprising reactively processed PBAT composites reached 82% in 180 days. In contrast, a neat PBAT film of similar thickness attained only 53% degradation in the same period. The biodegradation mechanism is proposed based on the topology of the disintegrated films studied using scanning electron microscopy, chemical bond vibrations determined by Fourier‐transform infrared spectroscopy, and structural evolution by small‐ and wide‐angle X‐ray scattering (SWAXS). The SWAXS analysis is used to understand the changes in the degree of crystallinity, long‐range periodic order, and crystalline and amorphous layer thickness of the multilayered films before and after degradation. Such multilayered films can find applications where packaging or biomedical devices cannot be recycled.

Effect of interlayer thickness on electrochemical properties and corrosion resistance of sputtered TiNxnm/Tixnm multilayer thin films

Three multilayers [TiNxnm/Tixnm/p-type Si (100)] (x = 2.5, 5, 10) were fabricated using a dc-magnetron sputtering to evaluate surface and interfacial effect on electrochemical properties for possible application in supercapacitor electrode materials. The (111) and (101) planes of TiN and Ti were observed at 36.50° and 40.19° respectively. TA, LA, and TO phonon modes were found at 254.12, 306.15, and 637.94 cm−1, respectively. The defect state distribution of Ti, N, and O was investigated from PL. XPS confirmed the Ti at. % of TiNxnm/Tixnm multilayers decreased from 43.07 to 12.04 and N at. % increased from 42.79 to 72.53 % as the x value decreased from 10 nm to 2.5 nm. The areal specific capacitance (Ca) and energy density (E) of the TiNxnm/Tixnm multilayer electrode increased with decreasing multilayer thickness. E varied from 0.27 to 1.37 mWhcm−2 and the power density (P) from 5.04 to 25.4 mWcm−2 for the multilayers. The diffusion coefficient (D) and total accumulated charge (Qin) decreased from 6.48 × 10−17 to 1.56 × 10−18 cm2/s and 1.82 to 1.64 C/cm2, respectively, for TiNxnm/Tixnm multilayers. The capacitive contribution was the highest in x = 10 (2.181 Av−1s). However, the diffusion-limited contribution was maximum in x = 5 (3.541 Av−1/2s1/2). The cyclic stability maintained at 85.4 % capacitive retention over 1000 cycles and the expansive potential window (up to 0.8 V in 1 M H2SO4) makes the multilayer thin films ideal for supercapacitor electrodes. Among all the samples, the TiN2.5nm/Ti2.5nm exhibited the highest Ca, E, and diffusion coefficient, originating from the smaller layer thickness, leading to more ohmic conductivity and facilitating the supercapacitive performance.

State-of-the-Art Review: Effects of Using Cool Building Cladding Materials on Roofs

Cool roofs are roofing systems designed to reflect significant solar radiation, reducing heat absorption and subsequent cooling energy demands in buildings. This paper provides a comprehensive review of cool roof technologies, covering performance standards, material options, energy-saving potential, and hygrothermal considerations. The review examines provisions in current codes and standards, which specify minimum requirements for solar reflectance, thermal emittance, and solar reflectance index (SRI) values. These criteria often vary based on factors like roof slope, climate zone, and building type. Different cool roof materials are explored, including reflective paints and coatings that can be applied to existing roofs as cost-effective solutions. Several studies have demonstrated the energy performance benefits of cool roofs, showing significant reductions in cooling loads, indoor air temperatures, peak cooling demand, and overall cooling energy consumption compared to traditional roofs. However, hygrothermal performance must be evaluated, especially in cold climates, to optimize insulation levels and avoid moisture accumulation risks, as reduced heat absorption can alter moisture migration patterns within the building envelope. While cool roofs provide substantial energy savings in hot climates, further research is needed to validate modeling approaches against real-world studies, investigate the impact of seasonality and green spaces on cool roof efficacy and urban heat island mitigation, and explore energy-saving potential, moisture control, and condensation risks in cold and humid environments.

Multilayer Film Comprising Polybutylene Adipate Terephthalate and Cellulose Nanocrystals with High Barrier and Compostable Properties.

In the present study, a multilayer, high-barrier, thin blown film based on a polybutylene adipate terephthalate (PBAT) blend with polyhydroxyalkanoate (PHA), and composed of four layers including a cellulose nanocrystal (CNC) barrier layer and an electrospun poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) hot-tack layer, was characterized in terms of the surface roughness, surface tension, migration, mechanical and peel performance, barrier properties, and disintegration rate. The results showed that the film exhibited a smooth surface. The overall migration tests showed that the material is suitable to be used as a food contact layer. The addition of the CNC interlayer had a significant effect on the mechanical properties of the system, drastically reducing the elongation at break and, thus, the flexibility of the material. The film containing CNCs and electrospun PHBV hot-tack interlayers exhibited firm but not strong adhesion. However, the multilayer was a good barrier to water vapor (2.4 ± 0.1 × 10-12 kg·m-2·s-1·Pa-1), and especially to oxygen (0.5 ± 0.3 × 10-15 m3·m-2·s-1·Pa-1), the permeance of which was reduced by up to 90% when the CNC layer was added. The multilayer system disintegrated completely in 60 days. All in all, the multilayer system developed resulted in a fully compostable structure with significant potential for use in high-barrier food packaging applications.

Characterization of RF-Sputtered ZnO Thin Film Coatings on Aluminum (Al6061): Microstructure, Wettability, Cavitation, and Corrosion Analysis

The study focuses on the characterization of Aluminum (Al-6061) coated with RF-sputtered Zinc Oxide (ZnO) thin film, aiming to understand the complex interactions between microstructure, wettability, cavitation resistance, and corrosion performance. The study involves the use of various analytical techniques such as Field Emission Scanning Electron Microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and water contact angle (WCA) measurements. The cavitation erosion testing has been conducted under various factors namely jet velocity (m/s), impingement angle (°), and stand-off distance (cm), respectively, and that too at various levels. Further, with the use of RSM, the study also contributes to the interplay in between factors and acquiring optimized results. Moreover, the findings of the study provide valuable insights into the effectiveness of the ZnO coating in enhancing corrosion resistance and reducing mass loss due to cavitation erosion. The study’s results offer significant implications for the engineering and design of protective coatings for Aluminum surfaces, with the potential to enhance durability and performance in various industrial applications.

Enhancement of spin Hall angle in semimetallic materials α -Sn under voltage regulation

Utilizing current-induced spin–orbit torque (SOT) to control magnetization is essential for the advancement of spintronics. SOT offers high energy efficiency and rapid operation speed. The ideal SOT material should have a high charge-to-spin conversion efficiency and excellent electrical conductivity. Recently, there has been a focus on topological insulator materials with topological surface states in SOT research due to their controllability in spin–orbit coupling, conductivity, and energy band topology. While topological Dirac semimetallic materials show promise for SOT applications, research on voltage regulation of their spin Hall angle is still in its early stages. This paper investigates the multilayer structure of a Dirac semimetallic material. In an α-Sn/Ag bilayer, the voltage regulation effect can increase the spin Hall angle by five times by adjusting the strain on the Fermi level. Experiments explore the role of a silver layer as a transport layer in the electric field control of multilayer films. This material system can enhance its effects under electric field regulation and offer insight for achieving regulation in new spintronic devices.

Design and magnetron sputtering of nanomultilayered W2N/Ag-SiNx films: Microstructural insights and optimized self-lubricant properties from room temperature to 500 °C

Novel multilayered films were engineered by integrating W2N and Ag-SiNx layers in a multilayer structure to obtain improved hardness and tribological properties. The films were fabricated by alternating magnetron sputtering, depositing 40 nm layers of W2N with varying thickness of Ag-SiNx layers varying in thickness from 4 to 20 nm. The effect of the increase thickness of the Ag-SiNx layers in the films microstructure and tribological properties were accessed. Tribological experiments were conducted at room temperature (RT), 500 °C, and RT-500 °C cycling conditions. The results revealed the production of a multilayered structure comprising single fcc-W2N layers interspersed with dual-phase layers consisting of fcc-Ag and amorphous SiNx phases. Tribological results indicated an improvement in the tribological performance with increase thickness of the Ag-SiNx layer up to 12 nm. The tribo-synergistic/combined action of both W2N and Ag-SiNx layers, along with the presence of layered lubricant tribo-phases of WO3 and Ag2WO4, showcased the pivot role in reducing friction and enhancing wear resistance. The optimized multilayered film, featuring a 12 nm Ag-SiNx layer, demonstrated exceptional tribological properties under temperature-cycling from RT to 500 °C.

Design and preparation of Ta33W35Cr15V17 /Al2O3 nano multilayer film based on multi-level construction strategy and its radiation resistance behavior

The microstructure and mechanical properties of Ta33W35Cr15V17/Al2O3 nano-multilayer films with preset defects after He+ ion irradiation were studied to understand the effects of layer interfaces and nano-defects. After irradiation, the growth of He bubbles in the alumina layer was confined to the nanovoids without aggregations. The nanochannel in the high-entropy alloy layer absorbed the deposited energy of He+ and shrank to disappear. In addition, the film was softened after irradiation due to the presence of presetting defects. Based on which a dual absorption source model of interface and pre-set defects was proposed to explain the enhancement of radiation tolerance.

Multilayer Diamond‐Like Carbon Films on Monocrystalline Diamond

Multilayer films of diamond‐like carbon (DLC) on monocrystalline diamond substrates have been for the first time obtained by plasma‐chemical deposition. Their chemical composition and structural and morphological properties are studied. The DLC individual layers differ in their sp3 carbon content. The multilayer nature of the resulting coatings is confirmed by periodic density modulation on the small‐angle X‐ray reflectometry curve and modulations in the CsC8, CsC6, CsC4 lines on the crater depth profile of secondary ions of elements (secondary ion mass spectrometry). The dependence of the deposition rate of multilayer DLC films on diamond, their composition and properties on the argon additive to the reaction gas mixture, as well as on methane flow, pressure and growth time, are studied.

Bone Fracture Healing under the Intervention of a Stretchable Ultrasound Array.

Ultrasound treatment has been recognized as an effective and noninvasive approach to promote fracture healing. However, traditional rigid ultrasound probe is bulky, requiring cumbersome manual operations and inducing unfavorable side effects when functioning, which precludes the wide application of ultrasound in bone fracture healing. Here, we report a stretchable ultrasound array for bone fracture healing, which features high-performance 1-3 piezoelectric composites as transducers, stretchable multilayered serpentine metal films in a bridge-island pattern as electrical interconnects, soft elastomeric membranes as encapsulations, and polydimethylsiloxane (PDMS) with low curing agent ratio as adhesive layers. The resulting ultrasound array offers the benefits of large stretchability for easy skin integration and effective affecting region for simple skin alignment with good electromechanical performance. Experimental investigations of the stretchable ultrasound array on the delayed union model in femoral shafts of rats show that the callus growth is more active in the second week of treatment and the fracture site is completely osseous healed in the sixth week of treatment. Various bone quality indicators (e.g., bone modulus, bone mineral density, bone tissue/total tissue volume, and trabecular bone thickness) could be enhanced with the intervention of a stretchable ultrasound array. Histological and immunohistochemical examinations indicate that ultrasound promotes osteoblast differentiation, bone formation, and remodeling by promoting the expression of osteopontin (OPN) and runt-related transcription factor 2 (RUNX2). This work provides an effective tool for bone fracture healing in a simple and convenient manner and creates engineering opportunities for applying ultrasound in medical applications.

Numerical study of mid-infrared broadband perfect absorber based on dielectric/aluminium doped zinc oxide multilayer films

We propose a lithography-free wide-angle polarization-insensitive ultra-broadband absorber by using multilayer films consist of five pairs of aluminium doped zinc oxide (AZO) and a dielectric film which is supposed to be fabricated on glass substrate. The absorption spectrum of the proposed model is calculated by using transfer matrix method. The analytic results show that the absorptivity is larger than 95% with normal incidence light in the wavelength range from 7.5μm to 20μm and having high transmittance at the visible wavelength range from 0.4μm to 0.8μm range. Further, the effect of incident angle and polarization on the absorption spectrum are also investigated. The absorption spectrum of the proposed design is highly tunable on changing the damping constant of the AZO film. The electric field and magnetic distributions at different wavelengths show that the absorption is mainly originated due to the constructive interference of electromagnetic waves in the multilayer films. Such physical mechanism of broadening bandwidth based on increasing the carrier concentration of the highly visible transparent conducting films have pave a new direction for the design of tunable broadband absorber in different frequency band. Meanwhile, this broadband absorber is a good candidate for the potential applications in daytime radiation cooling system in the mid-infrared frequency band and also used as transparent conducting electrode in solar cell applications.

Modelling and experimental study of surface morphology evolution during layer growth on nanograting structures

Coating nano/micro-structured elements with a single or multi-layered film can greatly enhance their functionality. The experimental enhancement, however, is significantly limited by the smoothing and distortion of the structural profile after coating. This requires a comprehensive understanding of the layer growth behavior on nanoscale non-isotropic surface with a proper model to analyze and predict the structure evolution. Here, a simplified linear growth model with single free parameter was successfully used for analysis of the smoothening of grating grooves. The model enables a quantitative description of the evolution of surface morphology from substrate to the top surface with sub-nanometer accuracy. Based on this, the smoothing behavior of single-Si layer and W/Si multilayer growth on nanoscale gratings (period ∼ 40 nm) and flat substrates were studied experimentally, for applications in X-ray optics. The smoothing effect of the W/Si multilayer coating is more pronounced than that of the single Si layer for both substrate types. The corrugated nanogratings suppressed the smoothing effect as compared to the flat isotropic surface. These works provide new guidance to predict and control the growth of layers on nanostructures.

Consideration of the effect of nanoscale porosity on mass transport phenomena in PECVD coatings

Here we show a novel approach to characterize the gas transfer behavior of silicon-oxide (SiO x ) coatings and explain the underlying dynamics. For this, we investigate the coating on a nm-scale both by measurement and simulation. Positron annihilation spectroscopy (PAS) and quantum mechanical electronic structure-based molecular dynamics simulations are combined to characterize the porous landscape of SiO x coatings. This approach analyses the influence of micropores smaller than 2 nm in diameter on gas permeation which are difficult to study with conventional methods. We lay out the main pore diameter ranges and their associated porosity estimates. An influence of layer growth on pore size and porosity was found, with an increased energy input during layer deposition leading to smaller pore sizes and a reduced porosity. The molecular dynamics simulations quantify the self-diffusion of oxygen and water vapor through those PAS deducted micropore ranges for hydrophilic and hydrophobic systems. The theoretical pore size ranges are fitting to our PAS results and complete them by giving diffusion coefficients. This approach enables detailed analysis of pore morphology on mass transport through thin film coatings and characterization of their barrier or membrane performance. This is a crucial prerequisite for the development of an exhaustive model of pore dominated mass transports in PECVD coatings.