Multilayer Films Research Articles

Development of multilayer films based on PLA/PBAT and sodium alginate for active packaging

AbstractIn this study, polylactic acid (PLA) and polyadipic acid/butylene terephthalate (PBAT) blend polymer were used as matrix to prepare PLA/PBAT substrate film by twin‐screw extruder. A series of multilayer films were prepared by starch‐based adhesive by loading 1% chitosan (CS), 1% zinc oxide nanoparticles (ZnONPs) or 1% silver nanoparticles (AgNPs) with sodium alginate (SA) as three different coatings. Compared with PLA/PBAT, the combination of adhesive and SA‐based antibacterial coating significantly improved the water vapor barrier, oxygen barrier and mechanical properties of the film, regardless of the type of antibacterial agent. The water vapor transmission of SA‐based AgNPs coating film decreased from the original 5.77 × 10−14 to 3.41 × 10−14 g·cm·cm−2·Pa−1·s−1. The oxygen permeability of SA‐based chitosan coating decreased from the original 74.35 × 10−14 to 6.40 × 10−14 cm3·cm·cm−2·Pa−1·s−1. The tensile strength of the SA‐based AgNPs coating film increased from the original 264.79 to 286.22 MPa. The film is yellow and has good ultraviolet absorption capacity. Membranes doped with CS, ZnONPs or AgNPs inhibited the growth of Escherichia coli and Staphylococcus aureus. Among them, chitosan doped membrane has weak antibacterial activity, AgNPs doped membrane has the best antibacterial activity against E. coli and S. aureus, and has potential application prospects in active packaging.

Design of a multi-physics coupling MEMS pressure sensor

The pressure measurement of explosion shock wave puts forward high requirements on the temperature resistance and response speed of the sensor. In this paper, a multi-physics coupling pressure sensor is designed to meet requirements. The sensor mainly consists of a Fabry-Perot cavity optical fiber sensing unit, a piezoelectric pressure sensing unit and a thermometric resistance temperature measurement module. Firstly, the structure of the sensor is designed. The top and bottom surfaces of the Fabry-Perot cavity are composed of a silicon diaphragm and a quartz glass. The piezoelectric pressure sensing unit is an AlN film including its electrodes. Pt thermometric resistance is developed to realize real-time temperature monitoring. Secondly, the fabrication process of the sensor is discussed, especially three key technologies. An Al film is sputtered to increase the reflectivity of the quartz glass. The SU-8 photoresist is applied to accurately control the thickness of Fabry-Perot cavity. Etching is adopted to work out the graphics of the AlN piezoelectric film. At last, a complete fabrication process of the sensor is described. The fabrication of multilayer films begins with a double-sided polishing silicon wafer, while Fabry-Perot cavity was from a double-sided polishing quartz glass. Then two parts of the sensor are combined to ensure the multi-physics coupling sensor to achieve complete function.

Application of ZIF-8/ZIF-67 Multilayer Films for NO2 and CO Detection

Application of ZIF-8/ZIF-67 Multilayer Films for NO2 and CO Detection

The rooftop cooling potentials of evaporative cooling porous tiles and high reflective coatings in hot and humid regions

Altering the reflectivity and permeability of surfaces in high-density cities is a key approach to mitigate rising urban heat islands. High Reflectance Coatings (HRC) and Evaporative Cooling Porous Tiles (ECPT) offer potential solutions for urban cooling. However, previous studies have mainly focused on roof surface temperatures, neglecting changes in near-roof air temperature. ECPT, a new permeable material, is mostly used in urban pavements and ignoring the underutilized rooftops, with limited research on its cooling effects in these settings. Therefore, this study investigates the impact of HRC and ECPT on near-roof air temperatures in the Pearl River Delta through observational experiments under various weather conditions. The results show that both HRC and ECPT significantly reduce near-roof air temperatures, but their effectiveness decreases above 1.8 m. In rainy conditions, these strategies are less effective due to their dependence on solar radiation. HRC works by reflecting short-wave radiation, while ECPT cools by evaporation. A key advantage of ECPT is its ability to be actively watered, quickly reducing temperatures by 2.14 °C at 0.3 m. This research is valuable for developing urban cooling strategies in high-density areas during extreme temperature conditions.

Neural network analysis of neutron and X-ray reflectivity data incorporating prior knowledge.

Due to the ambiguity related to the lack of phase information, determining the physical parameters of multilayer thin films from measured neutron and X-ray reflectivity curves is, on a fundamental level, an underdetermined inverse problem. This ambiguity poses limitations on standard neural networks, constraining the range and number of considered parameters in previous machine learning solutions. To overcome this challenge, a novel training procedure has been designed which incorporates dynamic prior boundaries for each physical parameter as additional inputs to the neural network. In this manner, the neural network can be trained simultaneously on all well-posed subintervals of a larger parameter space in which the inverse problem is underdetermined. During inference, users can flexibly input their own prior knowledge about the physical system to constrain the neural network prediction to distinct target subintervals in the parameter space. The effectiveness of the method is demonstrated in various scenarios, including multilayer structures with a box model parameterization and a physics-inspired special parameterization of the scattering length density profile for a multilayer structure. In contrast to previous methods, this approach scales favourably when increasing the complexity of the inverse problem, working properly even for a five-layer multilayer model and a periodic multilayer model with up to 17 open parameters.

Research on Dry Chemical Detection TechnologyBased on Reflectance Photometry

In response to the issues of insufficient stability and accuracy in dry chemical detection using reflectance photometry, caused by the divergence and multiple internal reflections of the reflected light signal from the sample and the multilayer dry film test strip, a dry chemical reflectance photometry detection system based on an integrating sphere is designed. Firstly, an integrating sphere device is incorporated to reduce signal divergence and loss, ensuring even detection of the sample's reflected light signal and improving detection stability. Secondly, Light Tools optical simulation analysis is performed, and an integrating sphere detection model is established. Thirdly, the Williams-Clapper equation is employed to correct the error in reflectance density caused by multiple internal reflections, enhancing detection accuracy. Experimental validation demonstrates that the developed integrating sphere-based dry chemical reflectance photometry detection system improves the stability and accuracy of the detection system.

A New Method for Evaluating the Influence of Coatings on the Strength and Fatigue Behavior of Flexible Glass

Flexible glass is an interesting substrate for a variety of displays, especially bendable or foldable ones, as it shows excellent surface properties and appealing haptics. With the necessary skill, flexible glass can be coated with thin films of different functionality, such as electrical or optical thin films, using plasma processes. In displays, thin film coatings such as transparent conductive electrodes and/or antireflective layer stacks are of major importance. Despite its attractive surface properties, however, flexible glass is still brittle, and its strength must be examined and monitored during any functionalization process, especially with regard to the fatigue behaviour. Currently, specific setups for cyclic fatigue testing of coated flexible glass are not available. Therefore, a new test method is presented herein for easy-to-handle rapid strength and fatigue testing using an endurance testing machine. This method overcomes two issues with the commonly used two-point bending test: the correct insertion of specimens is much easier, and both strength and fatigue testing using the same setup are now possible. Finite element method (FEM) simulation outcomes and first experimental simple fracture tests show that results comparable to those with a two-point bending test setup can be achieved with less effort. This makes it possible to analyze the fracture behaviour of flexible glass under cyclic loading and to evaluate the influence of thin film stress and other coating properties on its performance.Graphical

The impact of copper and silver as interlayers of zinc telluride films on the physical properties and antifungal efficacy of zinc telluride films

The study aimed to investigate the structure, physical properties, and antifungal activity of ZnTe single-layer, ZnTe/Cu/ZnTe (ZCZ), and ZnTe/Ag/ZnTe (ZAZ) multilayer films. The ZAZ multilayer had the greatest antifungal efficacy, with ZCZ and ZnTe following in descending order of effectiveness. We observed that ZCZ had a MIC of 0.30 mol/ML and that ZAZ had a MIC of 20 mol/L. An X-ray diffraction (XRD) test confirmed a cubic crystal structure for all films, indicating that the crystals were mainly arranged along the (111) plane. For ZnTe films, the average size of crystallites was estimated to be roughly 15 nm, while for ZAZ and ZCZ films, it remained relatively constant at around 14.2 nm and 14.1 nm, respectively. We determined the particle size of ZnTe, ZCZ, and ZAZ using a scanning electron microscope (SEM) and ImageJ analysis. The obtained sizes were 98 nm, 200 nm, and 81 nm for ZnTe, ZCZ, and ZAZ, respectively. We used Swanepoel method and the Cauchy equation to determine the refractive index (n), film thickness (d), and refractive index as a function of wavelength. We used the Tauc equation to find that the optical band gaps (Eg) of the films were 1.67 eV for ZnTe, 1.5 eV for ZCZ, and 1.55 eV for ZAZ. We analyzed six new frequency bands found through FTIR analysis. These bands showed important information about the chemical structure of the films.

Lamellar Microphase Separation and Phase Transition of Hydrogen-Bonding/Crystalline Statistical Copolymers: Amide Functionalization at the Interface.

Microphase separation of random copolymers, as well as that of high χ-low N block copolymers, is promising to construct sub-10-nm structures into materials. Herein, we designed statistical copolymers consisting of 2-hydroxyethyl acrylate (HEA) and N-octadecylacrylamide (ODAAm) to produce crystallization and hydrogen bond-assisted lamellar structure materials. The copolymers not only formed a crystalline lamellar structure with 3-4 nm domain spacing but also maintained an amorphous lamellar structure via phase transition above the melting temperature up to approximately 100 °C. The key is to introduce hydrogen-bonding amide junctions between the octadecyl groups and the polymer backbones, by which the polymer chains are physically fixed at the interface of lamellar structures even above the melting temperature. The stabilization of the lamellar structure by the amide units is also supported by the fact that the lamellar structure of all-acrylate random copolymers bearing hydroxyethyl and crystalline octadecyl groups is disordered above the melting temperature. By spin-coating on a silicon substrate, the HEA/ODAAm copolymer formed a multilayered lamellar thin film consisting of a hydrophilic hydroxyethyl/main chain phase and a hydrophobic octadecyl phase. The structure and order-disorder transition were analyzed by neutron reflectivity.

Design, preparation, and property analysis of metal/dielectric multilayer film with wavelength selectivity

Metal/dielectric multilayer films have important applications in energy-saving glass, stealth materials, solar energy utilization and other fields. In the current study, the thickness of each layer of TiO2/Ag/TiO2/Ag/TiO2 film is optimized. The effects of the number of metal/dielectric multilayer films and the incident light angle on their optical properties were investigated. The TiO2/Ag/TiO2/Ag/TiO2 film was prepared by electron beam evaporation coating technology, and their reflectance and transmittance were measured. The measurement results show that the visible light transmittance (380–780 nm) of the film can achieve 68.7%, and the infrared reflectance (780–2500 nm) can reach 95.9%. Compared with the traditional dielectric/metal/dielectric three-layer film, the visible light transmittance of the film is higher, and the solar infrared reflectance is greatly improved. In the solar radiation band (280–2500 nm), the average error between the experimental reflectance and transmittance and the theoretical prediction results is less than 0.03. The distribution of electric and magnetic fields inside the film was simulated by finite-difference time-domain method. The simulation results show that the high visible light transmittance is due to the interference resonance of electromagnetic waves inside the film. Taking Shanghai as an example, under our calculation conditions, compared with ordinary SiO2 glass, TiO2/Ag/TiO2/Ag/TiO2 film can reduce the total energy consumption of buildings by 14.3% and refrigeration energy consumption by 17.2%.

A hybrid finite difference level set–implicit mesh discontinuous Galerkin method for multi-layer coating flows

A mathematical model and numerical framework are presented for computing multi-physics multi-layer coating flow dynamics, with applications to the leveling of multi-layer paint films. The algorithm combines finite difference level set methods and high-order accurate sharp-interface implicit mesh discontinuous Galerkin methods to capture a complex set of multi-physics, incorporating Marangoni-driven multi-phase interfacial flow and the transport, mixing, and evaporation of multiple dissolved species. In particular, we develop several numerical methods for this multi-physics problem, including: high-order local discontinuous Galerkin methods for Poisson problems with Robin boundary conditions on implicitly-defined domains, to capture solvent evaporation; finite difference surface gradient methods, to robustly and accurately incorporate Marangoni stresses; and a coupled multi-physics time stepping approach, to incorporate all the different solvers at play including quasi-Newtonian fluid flow. The framework is applicable to an arbitrary number of layers and dissolved species; here, we apply it in a variety of settings, including multi-solvent evaporative paint dynamics, the flow and leveling of multi-layer automobile paint coatings in both 2D and 3D, and an examination of interfacial turbulence within a multi-layer matter cascade. Our results reproduce several phenomena observed in experiment, such as the formation of Marangoni plumes and Bénard cells. We also use the model to study the impact of long-wave deformational surface modes on immersed interfaces as well as the emergence of the final multi-layer film profile.

Stability Analysis of the Rapid Heating Multilayer Structure Mold by the Contact Error and Thickness of Layers

Rapid heating of the mold surface is necessary for the high-gloss, high-productivity injection molding process. A rapid heating mold system that uses a carbon nanotube (CNT) as a heating element was investigated because of its structure. For CNT web film to be utilized in the injection molding process, heating must be applied inside the mold. That can cause poor contact at the contact area between the mold and the CNT heating element, leading to local temperature deviation and resistance changes that reduce the heating stability of the CNT surface element. Additionally, the multilayer structure of the CNT web film can cause heat-transfer performance variations due to the different layer thicknesses. To address these issues, an adjustable flush was constructed at the contact area between the electrode inside the mold and the insulator to analyze the heating behavior of the CNT heating element as a function of dimensional deviation. The thermal durability of the CNT web film was also evaluated by analyzing the Raman spectra and measuring resistance changes caused by local overheating. The film can withstand high temperatures, with a flush limit value of 0.3 mm. An optimization analysis was conducted to determine the ideal thicknesses of the multilayer CNT web film, insulator, and electrical insulator. Optimal layer thicknesses were found to be 10 μm, 5 mm, and 0.5 mm, respectively. The main variables of the rapid heating mold required for application to the injection process were identified and reflected in the mold design to suggest directions for commercialization.

The effect of sputtering parameters and doping on the properties of CrN‐based coatings—A critical review

Chromium‐based coatings have been of interest to researchers for the last two decades because of their extraordinary properties like high hardness, high wear, and corrosion resistance properties. However, it is in practice and research to increase the properties of Cr‐based coatings for high‐temperature applications. Numerous dopants like silicon (Si), titanium (Ti), vanadium (V), aluminum (Al), and zirconium (Zr) have been used together with Cr to achieve enhanced properties. The plasma‐based sputtering process is one of the popular and reliable techniques to deposit thin film coatings. The substrate material, processed gas and pressure, substrate temperature, film thickness, and so on also play a significant role in varying the properties and microstructure of the deposited film. Several researchers have deposited Cr/CrN‐based thin films via the chemical vapor deposition technique (CVD) and physical vapor deposition technique (PVD) to study their properties and behavior at room temperature as well as for high‐temperature applications. This work reflects the review of work done to deposit Cr/CrN‐based coatings deposited via PVD: more specifically sputtering technique. The effect of doping in the CrN matrix and variation in sputtering parameters on the properties of CrN‐based coatings have also been studied.

Luminescence enhancement of Y2O3 thin films based on LSPR effect of Ag nanolayers

Based on the local surface plasmon resonance effect of Ag nanolayer, the luminescence enhancement in the visible light range of multilayer thin film has been investigated combined with metal/spacer molecule/photoluminescence material structure. The luminescence enhancement effect of multilayer thin films can be improved by adjusting the spin-coating number of Ag nanolayer and SiO2 spacer in the multilayer structure. At the same time, the mechanism of enhanced luminescence has been analyzed according to the change in fluorescence lifetime. The effect of the coupling between Ag nanolayer and luminescence layer on the radiative transition rate and fluorescence quantum yield have been discussed. The up-conversion luminescence intensity of the noble metal-modified multilayer thin film can be further improved by combining the multilayer structure with sensitized layer.

Effect of polyacid architecture and polycation molecular weight on lateral diffusion within multilayer films.

Despite the potential use of polyelectrolyte multilayers for biomedical, separation, and energy applications, their dynamic properties are not sufficiently understood. In this work, center-of-mass diffusion of a weak polyacid-poly(methacrylic acid) (PMAA) of linear and 8-arm architecture (L-PMAA and 8-PMAA, respectively) and matched molecular weight-was studied in layer-by-layer (LbL) assemblies with poly(diallyldimethylammonium) chloride (PDADMAC) of varied molecular weight. The film deposition at low-salt, acidic conditions when PMAA was only partially ionized yielded thicker, more diffused layers with shorter PDADMAC chains, and bilayer thickness decreased for multilayers constructed with longer PDADMAC. The molecular architecture of PMAA had a weak effect on film growth, with bilayer thickness being ∼20% larger for L-PMAA for the films constructed with the shortest PDADMAC (35 kDa) and identical film growth for L-PMAA and 8-PMAA with the longest PDADMAC (300 kDa). The exposure of the multilayer films to 0.2M NaCl triggered a reduction in PMAA ionization and significant lateral diffusivity of fluorescently labeled PMAA molecules (PMAA*), with diffusion coefficients D ranging from 10-13 to 10-12cm2/s, as determined by the fluorescence recovery after photobleaching technique. For all the films, polymer mobility was higher for star polyacids as compared to their linear counterparts, and the dependence of PMAA diffusion coefficient D on PDADMAC molecular weight (D ∼ M-n) was relatively weak (n < 0.6). However, 8-PMAA demonstrated an approximately doubled power exponent compared to the L-PMAA chains, suggesting a stronger effect of the molecular connectivity of the partner polycation molecules on the diffusion of star polyelectrolytes.

Investigation of the Tribological Properties and Corrosion Resistance of Multilayer Si-DLC Films on the Inner Surfaces of N80 Steel Pipes

In order to solve the problem of the corrosion and wear of N80 metal pipelines exposed to corrosive media and abrasive sand during the development of petroleum resources, the proposed solution involves utilizing HC-PECVD technology to deposit a series of multilayer Si-DLC films with varying thicknesses on the inner surfaces of the N80 steel pipes. This investigation systematically explored the microstructure, mechanical properties, tribological features, and corrosion resistance of the multilayer Si-DLC films. Remarkably, after coating the multilayer (Si-DLC)40 film on the inner wall of the N80 tube, the friction coefficient decreased from 0.7~0.75 to 0.2~3, and the wear rate decreased by two orders of magnitude. In addition, the corrosion current decreased by 50%, and the impedance doubled in a 3.5 wt% NaCl solution saturated with CO2. Thus, the multilayer (Si-DLC)40 film on the inner wall of the N80 tube exhibited superior tribological properties and exceptional corrosion resistance. These findings are anticipated to furnish valuable data and technical insights for mitigating corrosion in N80 steel pipes during petroleum exploitation.

Analysis of Mechanical Properties of EVOH/LDPE Films Produced with Waste EVOH and LDPE

The importance of plastic materials continues to develop more and more every year from past to present. As important as the plastics used in almost every area of life are, it is equally important to keep these materials in the environmental cycle. Since 1970, the use and consumption of plastic has increased almost 10 times. A large share of the use of these plastics occurs in the flexible packaging sector. In the multi-layer films used on flexible packaging in the packaging industry, one of the most important issues of the future is the crisis of raw materials, and the other is recycling and sustainability. In this study, it is aimed to evaluate the low density polyethylene/ poly(ethylene-co-vinyl alcohol)/low polyethylene (LDPE/EVOH/LDPE) structured flexible packaging film waste produced by multilayer blown extrusion method within the same LDPE/EVOH/LDPE flexible packaging film and to examine the mechanical property changes of the material. Sustainable environment and economy, reducing the cost of raw materials, obtaining approximately similar mechanical properties are among the objectives of the study. The wastes released from the LDPE/EVOH/LDPE film were granulated in a single screw extruder. Then, the amount of these waste EVOH granules was 5%, 10%, 20% and 25% by weight in the total film, and their production was carried out with reference to the pure EVOH film in a 7-layer blown film extruder. Samples were taken from the films produced in 50µm thickness in accordance with the standards. Tensile test, tear test, puncture resistance test, sealing force test, shrinkage tests were performed. According to the results of the tests, analyzes on the use of scrap EVOH were concluded.

Segmental dynamics of polystyrene near polymer-polymer interfaces.

This study investigated the segmental dynamics of polymers near polymer-polymer interfaces by probing the rotation of polymer-tethered fluorescent molecules using imaging rotational fluorescence correlation microscopy. Multilayered films were utilized to provide spatial selectivity relative to different polymer-polymer interfaces. In the experimental setup, for the overlayer polymer, polystyrene (PS) was employed and a 15 nm-thick probe-containing layer was placed ≈25nm apart from different underlayer polymers with glass transition temperatures (Tg) either lower or higher than that of PS. The underlayer of poly-n-butyl methacrylate had 72K lower Tg than that of PS, whereas polymethyl methacrylate and polysulfone had 22 and 81K higher Tg, respectively, than that of PS. Two key dynamic features of the glass transition, the non-Arrhenius temperature dependence and stretched relaxation, were examined to study the influence of soft and hard confinements on the segmental dynamics of the overlayer polymer near the polymer-polymer interfaces. Although complications exist in the probing location owing to the diffusion of the polymer-tethered probe during the annealing protocol to consolidate the multilayers, the results suggest that either the segmental dynamics of the polymer near the polymer-polymer interface do not change owing to the soft and hard confinements or the interfacial perturbation is very short ranged.

Enhancement of corrosion resistance and superparamagnetic property by structural modulation in (Co-DLC)/DLC multilayered nanocomposite films

A structure of {[(Co-DLC)/DLC]X}n Multilayered Nanocomposite Films (MNF) is designed by inserting pure DLC high-resistance layers into Co-DLC nanocomposite film, which consists of alternating Co-DLC and DLC layers were prepared by magnetron sputtering. The electrochemical behavior and magnetic property of the films are modulated by varying the number of deposition cycles (n) and the thickness of one single-cycle (X). The electrochemical results show that this MNF structure significantly improves the corrosion resistance of the films owing to the clear interfaces, which block the micropores penetrating the films. Compared to the co-sputtering film, as the number of cycles n increases to 7, the corrosion resistance is enhanced by one order of magnitude from 2.3 × 104 to 2.2 × 105 Ω·cm2. However, the interfaces between the Co-DLC and DLC layer become blurred when the thickness of one single-cycle X is lower than 30 nm, and the corrosion resistance decreases to 3.7 × 104 Ω·cm2. In terms of magnetism, the multilayer structure helps to regulate the homogeneity of Co particle size. As X increases from 30 to 100 nm, the Co particle size increases from 2.7 to 4.7 nm, and the saturation magnetization intensity (Ms) of superparamagnetic property in the films increases from 2.8 to 8.2 mT. As X increases, the remanent magnetization ratio (Mr/Ms) decreases and reaches 0.011 at X = 100 nm, which is about one order of magnitude smaller than that of the co-sputtering film. This result indicates that the MNF have better superparamagnetic property. It is noteworthy that {[(Co-DLC)/DLC]X}n MNF with X ranging from 100 to 40 nm and n ranging from 3 to 7 can achieve high corrosion resistance and superparamagnetic property, simultaneously.

Nano-imprint lithography of broad-band and wide-angle antireflective structures for high-power lasers.

We demonstrate efficient anti reflection coatings based on adiabatic index matching obtained via nano-imprint lithography. They exhibit high total transmission, achromaticity (99.5% < T < 99.8% from 390 to 900 nm and 99% < T < 99.5% from 800 to 1600 nm) and wide angular acceptance (T > 99% up to 50 degrees). Our devices show high laser-induced damage thresholds in the sub-picosecond (>5 J/cm2 at 1030 nm, 500 fs), nanosecond (>150 J/cm2 at 1064 nm, 12 ns and >100 J/cm2 at 532 nm, 12 ns) regimes, and low absorption in the CW regime (<1.3 ppm at 1080 nm), close to those of the fused silica substrate.