Bilayer Films Research Articles

The effects of polylactic acid-whey protein isolated bi-layer film incorporated with ZnO nanoparticles on the quality of common carp Cyprinus carpio

The effects of polylactic acid-whey protein isolated bi-layer film incorporated with ZnO nanoparticles on the quality of common carp Cyprinus carpio

Versatile flexible SERS substrate for in situ detection of contaminants in water and fruits based on Ag NPs decorated wrinkled PDMS film.

Flexible surface-enhanced Raman spectroscopy (SERS) substrate has attracted great attention due to its convenient sampling and on-site monitoring capability. However, it is still challenging to fabricate a versatile flexible SERS substrate, which can be used for in situ detection of analytes either in water or on irregular solid surfaces. Here, we report a flexible and transparent SERS substrate based on a wrinkled polydimethylsiloxane (PDMS) film obtained by transferring corrugated structures on the aluminium/polystyrene bilayer film, onto which silver nanoparticles (Ag NPs) are deposited by thermal evaporation. The as-fabricated SERS substrate exhibits a high enhancement factor (∼1.19×105), good signal uniformity (RSD of 6.27%), and excellent batch-to-batch reproducibility (RSD of 7.3%) for rhodamine 6 G. In addition, the Ag NPs@W-PDMS film can maintain high detection sensitivity even after mechanical deformations of bending or torsion for 100 cycles. More importantly, being flexible, transparent, and light, the Ag NPs@W-PDMS film can both float on the water surface and conformally contact with the curved surface for in situ detection. The malachite green in aqueous environment and on apple peel can be easily detected down to 10-6 M with a portable Raman spectrometer. Therefore, it is expected that such a versatile flexible SERS substrate has great potential in on-site, in situ contaminant monitoring for realistic applications.

Structural and magnetic anisotropy in YBa$_2$Cu$_3$O$_7$/La$_{0.67}$Sr$_{0.33}$MnO$_3$ bilayer on SrTiO$_3$ substrate

We study the magnetic properties and emergence of superconductivity in YBa_22Cu_33O_77 (YBCO)/ La_{0.67}0.67Sr_{0.33}0.33MnO_33 (LSMO) heterostructures. Bilayer films of superconducting layer, YBCO, and ferromagnetic layer, LSMO were grown on SrTiO_{3}3 (STO) (001) substrate using ultrahigh vacuum Pulsed Laser Deposition system. Magnetization data at 100 K as a function of applied magnetic field shows ferromagnetic behaviour due to the LSMO layer. Cooling below 100 K leads to superconductivity in this material; the onset of superconductivity occurs at a temperature, T_{c,SC},Tc,SC, of 86 K for H_{ext}\perp cHext⊥c (in-plane) & 84 K for H_{ext}||cHext||c (out-of-plane) under 100 Oe applied field. In-plane magnetic measurements show significant suppression of diamagnetic behaviour as compared to the out-of-plane measurements. The susceptibility signals are higher for out-of-plane direction. Such strong anisotropy in magnetism and the transition temperatures reveal complex interplay of magnetism and superconductivity in this system and calls for further study in this direction.

Sodium alginate/chitosan-based intelligent bilayer film with antimicrobial activity for pork preservation and freshness monitoring

A pH-sensitive bilayer film with antioxidant and antibacterial activities was successfully prepared by anchoring anthocyanins (ACNs) with sodium alginate (SA) as the sensing inner layer and incorporating TiO2 in chitosan (CS) as the protective outer layer. ACNs in the inner layer were immobilized under acidic conditions while released under alkaline conditions because of the pH sensitivity of SA molecules. The incorporation of TiO2 improved the color stability of the ACNs, and the film exhibited a wide range of color variations at pH 2–13 with ΔE>5. FT-IR confirmed the existence of hydrogen bonds among the components, and the tensile strength (TS) and elongation at break (EB) of the film reached 24.32 MPa and 38.58%, respectively. Moreover, the bactericidal rates of the film towards E. coli and S. aureus were 99.23% and 97.49%, respectively. The bilayer film could extend the pork's shelf life for 40 and 96 h at 20 °C and 4 °C, and monitor the pork quality in real-time. Therefore, the [email protected] + CS/TiO2 bilayer film is promising for meat preservation and freshness monitoring.

Tailor-made coextruded blown films based on biodegradable blends for hot filling and frozen food packaging

Biodegradable polymers still have severe limitations in their application over wide temperature ranges. In this study, we developed coextruded bilayer biodegradable packaging suitable for either hot-filling and frozen food products. The films were realized by combining an inner layer, made of Ecovio and amorphous poly(lactide) (PLA4060) blend, providing high ductility and sealability, with an outer layer made of poly(butylene succinate) (PBS) and semicrystalline PLA4032 blend, contributing to barrier properties and thermal resistance. The concentration of each blend was optimized for the target application based on preliminary chemical-physical investigations. Then, three bilayer structures with different relative thicknesses of the layers were realized and analyzed for their mechanical, barrier, wettability, sealability and overall migration properties in the −18÷85 °C temperature range, to check their compliance with the needs of food packaging applications involving both thermal treatment and freezing. The coextruded films had functional performance generally intermediate those of the single layers and weighted on their relative thicknesses, and overall migration values complying the limits of Regulation (EU) No 10/2011 for plastic packaging intended for both hot filling process and long-term frozen food storage. Among all, the most suitable structure for the target application was the bilayer film with the largest thickness of the outer layer (i.e. 50 µm), which showed the best balance between stiffness and ductility in the explored temperature range. In particular, it displayed the lowest lowering of elastic modulus at 85 °C, which becomes equal to 135 MPa, and an elongation at break equal to 40 % at −18 °C.

Interfacial Strain Analysis of Bending Bilayer Silicone Elastomer Films Using a Cholesteric Liquid Crystal Sensor

The analysis of the bending strain at the interface of layered polymer films is significant in the design of flexible electronic devices because conductive materials placed on the interface are degraded by strain. Although theoretical calculations and numerical simulations of the interfacial bending strain of polymer films have been conducted, few experimental analyses have been reported because of the difficulty in measuring the interface strain. In our previous study, the internal strain in a bending polymer film was successfully measured using a cholesteric liquid crystal elastomer (CLCE) sensor. Herein, we report the interfacial strain analysis of a bending bilayer film composed of poly(dimethylsiloxane) (PDMS) films with different Young’s moduli using a CLCE sensor. The experimental strain analysis revealed that the bending strain at the interface depends on the distance between the interface and the neutral mechanical plane (NMP), which experiences no strain. Notably, as the bilayer films bend significantly, the NMP shifts toward the inner bending surface because of the change in the balance between the tensile and compressive stresses in the film. This study enables us to understand the interface bending strain in polymer films, which will aid in the design of flexible electronic devices with conductive materials placed on the interface whose strain is minimized.

Effects of fluoride ions on corrosion performance and surface properties of SS304 in simulated PEMFC cathodic environments

U.S. Department of Energy (DOE) 2025 target proposes lower cost requirements for bipolar plates. To investigate the applicability of using cost-effective 304 stainless steel (SS304) as bipolar plates in proton exchange membrane fuel cell (PEMFC) and assess its corrosion risk, this work systematically investigates the impact of fluoride ions on corrosion performance and surface properties evolution of SS304 in simulated PEMFC cathodic environments. The electrochemical tests and morphological characteristics of polarized SS304 samples (0.6 V, 5 h) reveal that an increase in F− concentration results in the inability of SS304 to passivate spontaneously and exacerbates the uniform dissolution corrosion. However, all polarized samples can be electrochemically passivated, exhibit no obvious pitting, and form bi-layer semiconductive passive films with stable current densities (0.031–0.166 μA cm−2) lower than 1 μA cm−2, satisfying the corrosion criterion of DOE 2025. Additionally, the ascending of F− concentration reduces surface roughness, while increasing the wettability and interfacial contact resistance (ICR) of the polarized SS304 samples. The ICR of all SS304 samples, with or without polarization test, ranges from 258 to 754 mΩ cm2 fails to meet the relevant DOE 2025 target (<10 mΩ cm2).

Photocatalytic antimicrobial and photostability studies of TiO2/ZnO thin films

A nanothin film-based antimicrobial coating has been attractive in response to the rise and spread of pathogenic microbes, which led to the development of low-cost, effective, and rapid disinfection methods for coating material. TiO2/ZnO bilayer thin films have been developed through magnetron sputtering and thermal oxidation. The influence of oxidation temperature on structural, optical, photocatalytic, photostability, and antimicrobial properties of Ti/ZnO thin films has been addressed. X-ray diffraction (XRD) analysis has shown the presence of hexagonal wurtzite ZnO, Ti0.895O.77, and anatase TiO2 in the bilayer films. Increasing the oxidation temperature reveals a certain degree of crystallization and transforms Ti0.895O.77 into the anatase/rutile TiO2 phase. The bottom layer of ZnO provides sufficient oxygen to improve TiO2 crystallinity and prevent transforming anatase to rutile during thermal oxidation process. Moreover, Ti/ZnO thermally oxidized at 550 °C exhibit excellent photocatalytic performance under UV irradiation with high photostability. The inhibition rate increased (p < 0.05) with irradiation time forE. coli,S. aureus, andC. albicans with effectiveness values reaching approximately 97 ± 3.408, 98 ± 2.409, and 95 ± 3.105 %, respectively. This work reveals that magnetron sputtering through a thermal oxidation approach could generate stellar TiO2/ZnO thin films as photocatalysts and antimicrobial agents with cost-effectiveness and efficiency.

Ab initio study of the piezoelectric effects of the 2D semiconductors of IV group monochalcogenides (GeSe, GeS)

In this article, the piezoelectric effects of the 2D semiconductors of IV group monochalcogenides (GeS, GeSe) are studied by methods of the density functional theory and first-principles pseudopotential based on own program code. The spatial distribution of valence electron density, density of states, and Coulomb potential along transverse direction are calculated. It was found that a more significant rearrangement of the electron density was observed during compression of both GeS and GeSe bi-layer films than mono-layer films, but more significant in GeS films.

Entrapment of probiotic (Bifidobacterium longum) in bilayer emulsion film with enhanced barrier property for improving viability

The gelatin/gellan gum based-bilayer emulsion film was developed in this work to improve the survivability of Bifidobacterium longum during the storage process. The baobab seed oil (BO) was added to the gelatin (GE) matrix to develop emulsion film as the barrier outer layer. The blueberry anthocyanin extract (BE) was incorporated into the gellan gum (GG)-based inner layer to enhance the viability of B. longum. The SEM and FTIR results revealed that the probiotics were successfully entrapped in BO/BE-loaded bilayer film. The greatest survivability and viable cell numbers of the B. longum during the storage period were observed in the BO/BE loaded bilayer film. Furthermore, the stability of the colorful patterns by electrochemical writing was also evaluated in this work. Finally, the GE/BO-GG/BE/BM maintain satisfactory probiotic viability in steamed bread coating application. Hence, the GE/BO-GG/BE/BM bilayer film could be considered a novel material to deliver and protect the probiotics in food applications.

Large room temperature electrocaloric effect in PbZrO3/Ca3Mn2O7 heterostructure

Electrocaloric effects of antiferroelectric and ferroelectric films have been intensively studied for the applications in refrigeration. However, achieving high electrocaloric performance near room temperature is still very difficult in films. Herein, we report that large and regulable electrocaloric effects at room temperature are achieved in PbZrO3/Ca3Mn2O7 bilayer films based on PbZrO3 phase transition, and the sign of adiabatic temperature change, ΔT, is determined by Ca3Mn2O7 thickness. The PbZrO3-Ca3Mn2O7 heterojunction formed by carrier diffusions reduces the carrier concentration of the film and establishes a built-in electric field in the junction region, and withstanding voltages of the bilayer films are enhanced greatly. The maximum positive ΔT of 66.5 K was obtained in the bilayer film with a thin Ca3Mn2O7 layer, but a negative ΔT of -9.9 K with a thick Ca3Mn2O7 layer, near room temperature. This work presents a simple and effective approach to designing huge electrocaloric based on antiferroelectric-containing multilayers near room temperature.

PHARMACOKINETIC STUDY IN HUMANS AND IN VITRO EVALUATION OF BIOENHANCED BILAYER SUBLINGUAL FILMS FOR THE MANAGEMENT OF ACUTE MIGRAINE

Objective: Long-lasting migraine pain is one of the most disabling neurological disorders and requires a quick onset of action from the administered dosage form. This study aimed to provide sublingual administration of the frequently used combination of NSAID and triptan in order to trigger their action immediately by escaping the first-pass metabolism, simultaneously improving patient compliance. Methods: In the present research, sublingual bilayer films were developed by joining the two loaded layers with zolmitriptan and piroxicam, respectively. Each layer was prepared and loaded separately using the traditional solvent casting method. Mechanical support was provided by the 1:1 combination of HPMC E-15 and pullulan, which were used as water-soluble film-forming polymers with polyethylene glycol 400 as a plasticizer. Films were evaluated for various physicochemical and mechanical properties. Finally, a pharmacokinetic study was performed on six healthy human volunteers to compare the PK parameters of the best formulation, BSTF-3, with those of a commercially available formulation. Sepitrap 80 and Sepitrap 4000 were used as bio-enhancers to achieve faster systemic delivery. Results: The thin, flexible bilayer films were observed to provide quick action alone with increase patient compliance by preventing the first-pass metabolism and dysphagia. Sepitrap 80 successfully increased the permeation of both drugs. Approximately 92 percent of zolmitriptan was released from the formed bilayer sublingual thin films within 3 min, whereas 92 percent of piroxicam was released within 4.5 min from the best formulation. Within 30 min of the commencement of the pharmacokinetic investigation, plasma concentrations of the active component began to rise rapidly. Conclusion: When compared to commercial formulations, the developed films had a greater AUC and Cmax with a shorter Tmax, indicating a faster trigger of action and higher bioavailability.

Bioinspired Intelligent Solar‐Responsive Thermally Conductive Pyramidal Phase Change Composites with Radially Oriented Layered Structures toward Efficient Solar–Thermal–Electric Energy Conversion

AbstractTo remedy the drawbacks of weak solar‐thermal conversion capability, low thermal conductivity, and poor structural stability of phase change materials, pyramidal graphitized chitosan/graphene aerogels (G‐CGAs) with numerous radially oriented layers are constructed, in which the long‐range radial alignment of graphene sheets is achieved by a novel directional‐freezing strategy. A G‐CGA/polyethylene glycol phase change composite exhibits a thermal conductivity of 2.90 W m−1 K−1 with a latent heat of 178.8 J g−1, and achieves a superior solar‐thermal energy conversion and storage efficiency of 90.4% and an attractive maximum temperature of 99.7 °C under a light intensity of 200 mW cm−2. Inspired by waterlilies, solar‐responsive phase change composites (SPCCs) are designed for the first time by assembling the G‐CGA/polyethylene glycol phase change composites with solar‐driven bilayer films, which bloom by day and close by night. The heat preservation effect of the solar‐driven films leads to a higher temperature of SPCC for a longer period at night. The SPCC‐based solar–thermal–electric generator achieves output voltages of 499.2 and 1034.9 mV under light intensities of 200 and 500 mW cm−2, respectively. Even after stopping the solar irradiation, the voltage output still occurs because of the latent heat release and the heat preservation of the films.

The Interplay between Different Stimuli in a 4D Printed Photo-, Thermal-, and Water-Responsive Liquid Crystal Elastomer Actuator.

Multi-stimuli responsivity in 3D-printed objects is receiving much attention. However, the simultaneous interplay between different environmental stimuli is largely unexplored. In this work, we demonstrate direct ink writing of an oligomeric ink containing an azobenzene photo-switch with an accessible hydrogen bond allowing triple responsivity to light, heat, and water. The resulting printed liquid crystal elastomer performs multiple actuations, the specific response depending on the environmental conditions. Bilayer films formed by printing on a static substrate can rapidly change shape, bending almost 80 degrees if irradiated in air or undergoing a shrinkage of about 50 % of its length when heated. The bilayer film assumes dramatically different shapes in water depending on combined environmental temperature and lighting conditions.

A Sample‐Triggered Microvalve Based on Material Property Regulation Mechanism for Reagent Storage and on‐Demand Release

Prestoring and on‐demand releasing of reagents is an essential feature for further automation and integration of lab‐on‐a‐chip (LOC). The current microvalves rely on external drive to trigger release the prestored reagent. Herein, a novel microvalve that can achieve long‐term prestorage and tested‐sample‐triggered release of reagents is developed. The microvalve functions based on water‐triggered material property regulation mechanism: the waterproof film contributes to the reagent stable storage; the water‐solvable film would lose most of its mechanical strength once triggered by water; then the bilayer film would fracture under the stress of the microspring, releasing the prestored reagent. The functionality of the microvalve is demonstrated in a microfluidic chip. The microvalve is triggered open by the test sample, and the released prestored reagent flows to the reserved reaction area few minutes later. The delay time could be adjusted from 0.1 to 11 min as required by sample reaction, through controlling the structure of the time‐delay valve. Compared to previous reported microvalves that rely on the external drive, the novel microvalve reported herein provides a new approach to realize internal signal‐triggered release of the prestored reagent, thus achieving a real accessory‐free, portable, and user‐friendly self‐contained LOC for rapid and point‐of‐care diagnostics.

Resistive switching characteristics of Ag2O/TiO2 bilayer film based memristor

With the increasing importance of artificial intelligence (AI), significant effort has been devoted to the development of memory device that seek to emulate the energy-efficient information storage and processing. In this work, a memristive device with Ag/Ag2O/TiO2/FTO structure was fabricated by the sol-gel method. The as-prepared memristive device exhibits bipolar resistive switching characteristics under direct-current-voltage sweep. In particular, this memristive device with Ag2O/TiO2 layer annealing at 450 ℃ has a low switching voltage after 150 successive cycles. At the same time, the switching window of the device with Ag2O/TiO2 layer annealing at 450 ℃ is obvious, and the switching resistances are stable and easy to distinguish. This device exhibits some obvious advantages of low power consumption, remarkable repeatability, excellent endurance, and stable memory state. As a result, this Ag2O/TiO2 bilayer film based memristive device has great potential to be used as information storage and processor device for AI applications.

Topotactic, Vapor-Phase, In Situ Monitored Formation of Ultrathin, Phase-Pure 2D-on-3D Halide Perovskite Surfaces.

Two-dimensional (2D) halide perovskites, HaPs, can provide chemical stability to three-dimensional (3D) HaP surfaces, protecting them from exposure to ambient species and from reacting with contacting layers. Both actions occur with 2D HaPs, with the general stoichiometry R2PbI4 (R: long or bulky organic amine) covering the 3D ones. Adding such covering films can also boost power conversion efficiencies of photovoltaic cells by passivating surface/interface trap states. For maximum benefit, we need conformal ultrathin and phase-pure (n = 1) 2D layers to enable efficient tunneling of photogenerated charge carriers through the 2D film barrier. Conformal coverage of ultrathin (<10 nm) R2PbI4 layers on 3D perovskites is challenging with spin coating; even more so is its upscaling for larger-area devices. We report on vapor-phase cation exchange of the 3D surface with the R2PbI4 molecules and real-time in situ growth monitoring by photoluminescence (PL) to determine limits for forming ultrathin 2D layers. We characterize the 2D growth stages, following the changing PL intensity-time profiles, by combining structural, optical, morphological, and compositional characterizations. Moreover, from quantitative X-ray photoelectron spectroscopy (XPS) analysis on 2D/3D bilayer films, we estimate the smallest width of a 2D cover that we can grow to be <5 nm, roughly the limit for efficient tunneling through a (semi)conjugated organic barrier. We also find that, besides protecting the 3D against ambient humidity-induced degradation, the ultrathin 2D-on-3D film also aids self-repair following photodamage.

Improving the current density and reducing the recombination rate of dye sensitized solar cells by modifying the band gap of Titania using Novel heterostructures

Here we report the synthesis of thin films of pristine TiO2, 1% Cd-doped TiO2 (Cd–TiO2), TO2/Cd–TiO2, and Cd–TiO2/TiO2 on FTO glass substrates using the sol-gel dip-coating method. XRD shows that all films have an anatase crystal phase. The maximum intensity and large grain size (48.89 nm) in a 1% Cd–TiO2/TiO2 bilayer film have been observed. Detailed optical properties like absorbance, transmittance, band gap energy (Eg), refractive index (n), dielectric constant, and extinction coefficient (k) have been calculated by UV–Vis. Spectroscopy. According to UV–Vis results, all films absorb UV radiation and transmit visible radiation. The film of 1% Cd–TiO2/TiO2 is a good electrode for solar cell applications due to its low Eg (2.9 eV) and strong transmittance in the visible region. The dye-sensitized solar cells (DSSCs) of these films have been prepared with N719 dye. The cell made up of 1% Cd–TiO2/TiO2 photoanode has the maximum power conversion efficiency (2.47%) in comparison with a pure TiO2 photoanode (1.32%) due to an improvement in the transfer of electrons from the LUMO of dye to the conduction band of TiO2.

Self-Formation of a Ru/ZnO Multifunctional Bilayer for the Next-Generation Interconnect Technology via Area-Selective Atomic Layer Deposition.

This study suggests a Ru/ZnO bilayer grown using area-selective atomic layer deposition (AS-ALD) as a multifunctional layer for advanced Cu metallization. As a diffusion barrier and glue layer, ZnO is selectively grown on SiO2 , excluding Cu, where Ru, as a liner and seed layer, is grown on both surfaces. Dodecanethiol (DDT) is used as an inhibitor for the AS-ALD of ZnO using diethylzinc and H2 O at 120 °C. H2 plasma treatment removes the DDT adsorbed on Cu, forming inhibitor-free surfaces. The ALD-Ru film is then successfully deposited at 220 °C using tricarbonyl(trimethylenemethane)ruthenium and O2 . The Cu/bilayer/Si structural and electrical properties are investigated to determine the diffusion barrier performance of the bilayer film. Copper silicide is not formed without the conductivity degradation of the Cu/bilayer/Si structure, even after annealing at 700 °C. The effect of ZnO on the Ru/SiO2 structure interfacial adhesion energy is investigated using a double-cantilever-beam test and is found to increase with ZnO between Ru and SiO2 . Consequently, the Ru/ZnO bilayer can be a multifunctional layer for advanced Cu interconnects. Additionally, the formation of a bottomless barrier by eliminating ZnO on the via bottom, or Cu, is expected to decrease the via resistance for the ever-shrinking Cu lines.

Unraveling the control of reversibility for actuators based on cellulose nanofibers

In this work, we have prepared cellulose-based actuators taking advantage of the pH-sensitive solubility of chitosan (CH) and the mechanical strength of CNFs. Bilayer films were prepared by vacuum filtration inspired by plant structures that exhibit reversible deformation under pH changes. The presence of CH in one of the layers led to asymmetric swelling at low pH, thanks to the electrostatic repulsion between charged amino groups of CH, and the subsequent twisting with the CH layer on the outside. Reversibility was achieved by substituting pristine CNFs with carboxymethylated CNFs (CMCNFs), that are charged at high pH and thus competed with the effects of amino groups. Swelling and mechanical properties of layers under pH changes were studied by gravimetry and dynamic mechanical analysis (DMA) to quantify the contribution of chitosan and the modified CNFs on the reversibility control. This work evidenced the key role of surface charge and layer stiffness to achieve reversibility. Bending was triggered by the different water uptake of each layer, and shape recovery was achieved when the shrunk layer shower higher rigidity than the swollen layer.