Elastic Film Research Articles

Self-Powered, Flexible, Wireless and Intelligent Human Health Management System Based on Natural Recyclable Materials.

Combining wearable sensors with modern technologies such as internet of things and big data to monitor or intervene in obesity-induced chronic diseases, such as obstructive sleep apnea, type II diabetes, cardiovascular diseases, and Alzheimer's disease, is of great significance to the self-health management of human beings. This study designed a loofah-conducting graphite four friction layer enhanced triboelectric nanogenerator (LG-TENG) and developed a health management system for human motion recognition and early warning of sleep breathing abnormalities. By uniformly spraying and depositing conductive graphite on the surface of the loofah and the elastic film cross-interlocking bending structure design, the signal strength of the LG-TENG has been improved by 390%. The stable output signal is still maintained after 1500 s of continuous operation at a frequency of 2 Hz. LG-TENG can realize accurate motion analysis by muscle contraction state. Combining different deep learning models resulted in 98.1% accuracy in recognizing seven categories of displacement speeds for an individual and 96.46% accuracy in recognizing seven categories of displacement speeds for three individuals. In addition, the sleep breathing monitoring early warning system was developed by integrating Bluetooth wireless transmission and upper computer analysis technology. This system aims to analyze and provide real-time warnings for sleep-breathing abnormalities. This research promotes an innovation of TENG technology based on the advantages of natural materials, recyclability and low cost. It offers new ideas for self-health management and scientific exercise for obese people, showing a broad application prospect.

Dynamic characteristic analysis of the elastic ring squeeze film damper-rotor system considering coupling angular misalignment

Dynamic characteristic analysis of the elastic ring squeeze film damper-rotor system considering coupling angular misalignment

Finite element simulations of quartz crystal microbalances (QCM): from Sauerbrey to fractional viscoelasticity under water

2D finite element simulations are performed on QCM working in the thickness-shear mode and loaded with different homogeneous films. They include a purely elastic film, a viscoelastic Maxwellian liquid, viscoelastic-Voigt solid, and the fractional viscoelastic (power-law) version of each case. Unlike single-relaxation kind models, fractional viscoelasticity considers the relaxation-time spectrum often found in polymeric materials. The films are tested in air or covered with liquids of different viscosities. Two substrate thicknesses are tested: 100 nm and 500 nm, the latter being close to the condition that promotes the resonance of the adsorbed film. In all cases the simulations are compared with small-load approximation theory (SLA). The 100 nm films follow the theory closely, although significant deviations of the SLA are observed as the overtone number n increases, even in purely elastic films. We also show that it is possible to identify the viscoelastic ‘fingerprint’ of the 100 nm films in air using raw data and Sauerbrey’s equivalent thickness obtained with the QCM in the 3 < n < 13 range. These numerical data are validated by experimental measurements of crosslinked polydimethylsiloxane films with thicknesses ∼150 nm. In contrast, the 500 nm films deviate notoriously from the SLA, for all viscoelastic models and overtones, with the largest deviation observed in the elastic film. When a liquid layer covers the QCM without an adsorbed film, the only overtone that numerically reproduces the theoretical value is the fundamental, n = 1. For n > 1, strong coupling between the solid and liquid is detected, and the original vibration modes of the crystal are altered by the presence of the liquid. Finally, the numerical simulations suggest that it is possible to detect whether a viscoelastic film is formed under a liquid layer using only the information from n = 1. In these film/liquid systems we also observe the so-called missing-mass effect, although the theory and simulations exhibit different levels of impact of such effect when the liquid viscosity is high.

Low-Foaming Nonionic Gemini Surfactants Containing Hydrophilic Poly(oxyethylene) Chain and Hydrophobic Di-tert-pentylbenzenes Groups.

Low-foaming nonionic gemini surfactants have a wide range of applications in industrial cleaning and photoresist development. In this study, three low-foaming nonionic gemini surfactants (S1, S2, and S3) with different poly(oxyethylene) chain lengths have been synthesized by using methoxy poly(ethylene glycol) and 2,5-di-tert-pentylhydroquinone. The chemical structures of the novel surfactants are confirmed by 1H NMR, Fourier transform infrared, and gel permeation chromatography (GPC), and their properties such as surface tension, wetting properties, emulsifying properties, and foaming properties are investigated. The surface tension values of S1, S2, and S3 at the critical micelle concentration are 40.29, 37.14, and 41.64 mN/m, exhibiting good surface activity. When the surfactant concentration is higher than 2 mM, the contact angles of S1 and S2 no longer change and can maintain 62 and 64°, showing good wetting properties. In addition, S3 can keep an emulsion state for 2 months at high concentrations, exhibiting good emulsion stability. Furthermore, all the prepared surfactants show good low-foaming properties. The initial foaming volumes of S1 are very low, less than 0.1 mL at various concentrations, less than 2% of the conventional surfactant sodium dodecyl sulfate. For S2, the initial foaming volumes at the concentration of 0.1, 1, 2, and 3 g/L are 1, 0.5, 0.55, and 0.45 mL, respectively. For S3, the initial foaming volumes show a general trend of increasing with concentration. The surfactants with longer poly(oxyethylene) chains possess more initial foaming volumes at the same concentration, which is because the greater cohesion between the surfactant molecules can increase the elasticity of the bubble film. Our study enriches the design rationales for low-foaming surfactants and motivates researchers to develop more advanced surfactants for industrial cleaning and photoresist development.

Polymerizable deep eutectic solvent enables flexible gel formation for motion sensor and anti-UV film

Specific applications of gels can raise multiple demands, including low cost, elasticity, adaptability to wide temperature ranges, conductivity, and reduced hazards, thereby presenting diverse challenges for one material. Deep eutectic solvents (DESs) offer unexpected solutions to tackling the challenging task. Here, we mixed anhydrous diallyldimethylammonium chloride (DMDAAC) and urea to synthesize a polymerizable DES with a wide range of solubility. It can polymerize to form versatile DES gel upon photoinitiation. The gel exhibited high transparency (∼94 %), a wide range of temperature tolerance (−40 ∼ 100 °C), outstanding elastic properties (ε > 2400 %), good conductivity (0.05 mS·cm−1) and self-healing capability. The pristine gel film was successfully applied to motion sensors, while the DES gel with lignin was also employed as an elastic anti-UV film. Moreover, its water-solubility and non-hazardous compositions suggest the minimize environmental impact of the DES gel. This polymerizable DES can not only boost the development of electronic devices like motion sensors, but also inspire more creative ideas in promising applications of DESs and DES gels.

Mechanically Driven Self-Healing MXene Strain Gauges for Overstrain-Tolerant Operation.

Compliant strain gauges are well-suited to monitor tiny movements and processes in the body. However, they are easily damaged by unexpected impacts in practical applications, limiting their utility in controlled laboratory environments. This study introduces elastic microcracked MXene films for mechanically driven self-healing strain gauges. MXene films are deposited on soft silicone substrates and intentionally stretched to create saturated microcracks. The resulting device not only has high sensitivity but also can recover its original sensing capability even after experiencing failure-level overstrains. This electrical self-healing ability is achieved through the elastic rebound of the substrate, which autonomously restores the microcracked morphology of the MXene film. The MXene strain gauge can withstand overextension, twisting, impact forces, and even car rolling. The device is also resilient to touch-induced damage during monitoring of physiological motions. The mechanically driven self-healing strategy may effectively improve the durability of highly sensitive strain sensors.

A transfer matrix model to predict acoustic attenuation of earplug filters made up of elastic film and air cavity

The sound attenuation of earplugs, commonly used for noise protection, can be improved by adding acoustic filters. However, the effect of acoustic filters featuring an elastic film and cylindrical air cavities on sound attenuation needs to be better understood. This study seeks to predict acoustic attenuation of an elastic film filter via the development of an analytical model. Its advantage, as compared to numerical simulations, is to offer quicker solutions and a more profound comprehension of each physical parameter's impact. The total acoustic transfer matrix of the filter has been established by coupling the air cavity with the film under assumption of plane wave. The transfer matrix of the vibrating elastic film is based on the Kirchhoff-Love theory and could take into account all its dynamic behaviors, including possible in-plane tension. The model is then validated by comparison with numerical simulations using the finite element method. It is found that the plane wave assumption is valid in almost practical geometries of the air cavity such that the sound attenuation obtained from the analytical model align consistently with those from simulations. Potential limitations are addressed and evaluated.

Antibacterial gelatin/tragacanth gum films containing galbanum essential oil for in vitro scratch-healing

Natural substances and bioactive agents possess great potential in wound care based on their ability to promote healing and prevent infection. This study focused on the fabrication of antibacterial wound dressings by combining gelatin (G), tragacanth gum (TG), and galbanum essential oil (GEO) as a loaded drug. TG addition resulted in more elastic and flexible films besides enabling encapsulation of the hydrophobic GEO into the biopolymeric matrix. GEO was utilized as an antibacterial and a wound-healing enhancer for open wounds such as incisions. Field emission scanning electron microscopy (FE-SEM) analysis revealed a porous film structure after GEO incorporation. Higher GEO concentration caused reduced swelling and slower degradation. Water vapor transfer rate varied from 596 to 894 g/m2.day, making the films suitable for wound dressings. GEO release exhibited a two-phase profile with prolonged diffusion-controlled release for a higher content of GEO. The films demonstrated dose-dependent antimicrobial activity against S. aureus and E. coli strains. Effectiveness and noteworthy application of this research were approved by scratch assay on human dermal fibroblast cells, and films with 3 % GEO showed 79.42 % wound closure, which is significantly higher than the control sample (55.15 %), indicating promoted cell migration and promising wound healing properties.

Study on UV-Curable Acrylic Clear Viscoelastic Materials with Grafted Structures

Flexible substrates are crucial for wearable electronic strain sensors, but achieving biocompatibility, low cost, and aesthetic appeal alongside good mechanical performance remains challenging. Acrylic-based clear viscoelastic films (CVFs) are gaining attention due to their excellent transparency and potential for enhanced mechanical properties. This study synthesized copolymers CVF1-4 with varying branch content using soft monomers 2-ethylhexyl acrylate (2-EHA), butyl acrylate (n-BA), and functional monomer acrylic acid (AA). Employing a "grafting-through" strategy, small molecule monomers, ATRP-synthesized oligomer pBA25, and photoinitiator 1,6-hexanediol diacrylate (HDDA) were in-situ polymerized under UV light to form transparent, flexible elastic films CVF1-4. Between -20 to 80 C, CVF1-4 demonstrated excellent mechanical properties such as low modulus (in the kPa range), low glass transition temperature (below -20 C), large deformation (500-600%), and high strain recovery rate (&gt;95%). Among them, CVF3 with 15% branching showed a balanced comprehensive performance, exhibiting primarily elastic behavior at room temperature. Therefore, selecting appropriate molecular composition and grafting structure provides a simple and customizable solution for optimizing CVF properties.

Enhanced O/W emulsifying properties of pea proteins via deamidation: Insights into interfacial behavior

This study examines the effects of protein glutaminase modification on the interfacial properties and emulsion stability of pea protein isolates (PPI). Emulsions were prepared using native (NPPI) and deamidated PPI (DPPI) at concentrations from 0.5 wt% to 3.6 wt%. The stability of these emulsions was evaluated by examining droplet size distribution, flocculation index, ζ-potential, and CLSM. DPPI demonstrated superior emulsifying ability and stability, requiring only 2.0 wt% to prevent flocculation compared to NPPI's 3.6 wt%. Interfacial properties, such as protein coverage, composition, thickness, tension, and rheology, were characterized. Large Amplitude Oscillatory Dilatation analysis showed minimal differences between NPPI and DPPI-stabilized interfaces at 1 wt%. However, at 3.6 wt%, NPPI interfaces demonstrated abrupt intra-cycle yielding and viscous behavior, whereas DPPI interfaces exhibited gradual softening and a higher maximum linear strain. Additionally, DPPI showed higher interfacial protein coverage and lower interfacial tension. NPPI formed dense, brittle films prone to rupture under dynamic deformation, leading to poor stability. Deamidation of PPI unfolded the protein structure, exposing hydrophobic groups and increasing carboxyl groups, which reduced aggregation. This resulted in a uniform, extensible, and elastic interfacial film resistant to large deformations. Thus, DPPI-stabilized emulsions demonstrated superior stability, showcasing their potential for industrial applications.

90-degree peeling of elastic thin films from elastic soft substrates: Theoretical solutions and experimental verification

Peeling of thin films has been widely used in adhesion measurement, film transfer and bio-inspired design. Most previous studies focused on the peeling of thin films from rigid substrates, but soft substrates are common in practical applications. Herein, we propose a two-dimensional model based on the bilinear cohesive law to characterize the 90-degree peeling of elastic thin films from elastic soft substrates, and obtain theoretical solutions expressed in terms of the Chebyshev series. The theoretical solutions match well with the finite element method results, including the load-displacement curves and the bulging deformation of soft substrates. We find that with decreasing substrate modulus, the maximum peeling force (Pmax) decreases but the steady-state peeling force remains unchanged. With the present solutions, the interfacial strength and fracture energy can be extracted simultaneously from the 90-degree peeling experiments of thin film/soft substrate systems, and then the experimentally measured Pmax for different film thicknesses can be well predicted. Furthermore, we obtain a new power scaling law of Pmax, where the scaling exponent depends on substrate elasticity. These results can help us measure the interfacial properties of thin film/soft substrate systems via peel tests, and regulate their peeling behaviors by interface design.

Modeling of Flexural-Gravity Waves in Ice Cover on Elastic Films

Modeling of Flexural-Gravity Waves in Ice Cover on Elastic Films

The Hydrogen Bonding in the Hard Domains of the Siloxane Polyurea Copolymer Elastomers.

For probing the structure-property relationships of the polyurea elastomers, we synthesize the siloxane polyurea copolymer elastomer by using two aminopropyl-terminated polysiloxane monomers with low and high number-average molecular weight (Mn), i.e., L-30D and H-130D. To study the influence of the copolymer structures on the film properties, these films are analyzed to obtain the tensile performance, UV-vis spectra, cross-sectional topographies, and glass transition temperature (Tg). The two synthetic thermoplastic elastomer films are characterized by transparency, ductility, and the Tg of the hard domains, depending on the reacting compositions. Furthermore, the film elasticity behavior is studied by the strain recovery and cyclic tensile test, and then, the linear fitting of the tensile data is used to describe the film elasticity based on the Mooney-Rivlin model. Moreover, the temperature-dependent infrared (IR) spectra during heating and cooling are conducted to study the strength and recovery rate of the hydrogen bonding, respectively, and their influence on the film performance is further analyzed; the calculated Mn of the hard segment chains is correlated to the macroscopic recovery rate of the hydrogen bonding. These results can add deep insight to the structure-property relationships of the siloxane polyurea copolymer.

CHARACTERIZATION OF COATINGS PREPARED FROM PREVULCANIZED NR/POLYANILINE LATEX

ABSTRACT Latex consisting of a NR/polyaniline (NR/PAni) blend is used in the preparation of thin elastic films. In this study, NR/PAni latex blends with different amounts of doped PAni and surfactants (sodium dodecylbenzene sulfonate [SDBS] and sodium dodecyl sulfate [SDS]) were prepared through prevulcanization. The films were prepared from prevulcanized latexes by casting in a petri dish or with the spin coating method. The conditions suitable for prevulcanization were investigated. The effect of doped PAni amounts and the surfactants SDBS and SDS on the mechanical, electrical conductivity, and physico-chemical surface properties and morphologies of NR/PAni films were characterized. The results indicated that PAni doped with dodecylbenzene sulfonic acid (DBSA) was well dispersed in NR latex in the presence of 0.01 mol/w% of SDBS. The highest amount of doped PAni that was dispersed was 17 w/w%. The properties of the blend of NR and DBSA-doped PAni were superior to those of the other blends. The compatibility between SDBS and DBSA was the dominant factor in improving the properties of the film prepared from the prevulcanized NR/PAni latex blend.

Effect of heat treatment on the stability of ultrasound-assisted cross-linked myofibrillar protein-stabilized emulsion filler phases via rheology and tribology

This work aimed to reveal the effect of heat treatment on the stability of ultrasound-assisted cross-linked myofibrillar protein-stabilized emulsion and its potential application as a filler phase. The interfacial dilatational rheology, emulsion droplets, linear and nonlinear shear rheological properties, microrheological properties, and tribological properties of emulsion fabricated by the original myofibrillar protein (MP) (NA), crosslinked MP (NAG), and sonication after crosslinked MP (MPGU) were determined at the heat temperature of 40 °C, 60 °C, and 80 °C. Results indicated that heat treatment would affect the stability and processing adaptability of the emulsion. The elasticity and strength of the interfacial film were enhanced with the treated temperature increased from 40 °C to 80 °C, and the MPGU group showed a more linear shape of interfacial Lissajous plot than the other groups even at large amplitudes. Based on the good interfacial properties, the MPGU group had the smaller emulsion droplets with more protein-coated, and the network structure was formed only at 80 °C. For the rheological properties, the lower apparent viscosity, elastic index (EI), and macroscopic viscosity index (MVI) in the MPGU group indicated the formation of a more stable emulsion. Furthermore, the lower closed area of Lissajous curves and friction coefficient for the MPGU group also proved the highest stability and lubrication of the emulsion after heat treatment. Therefore, this study indicated that ultrasound-assisted cross-linked myofibrillar protein-stabilized emulsions had good thermal stability and processing adaptability, which contributed to the fabrication of stable emulsion-filled foods.

How specific ion effects influence the mechanical behaviors of amide macromolecules? A cross-scale study.

The mechanisms of specific ion effects on the properties of amide macromolecules is essential to understanding the evolution of life. Because most biological macromolecules contain both complex hydrophilic and hydrophobic structures, it is challenging to accurately identify the contributions of molecular structure to macroscopic behaviors. Herein, we investigated the influence of specific ion effects on the mechanical behaviors of poly(N-isopropylacrylamide) and neutral polyacrylamide (i.e., PNIPAM and NPAM), through a cross-scale study that includes single-molecule force spectroscopy, molecular dynamics simulation and macro mechanical method. The results indicate that the molecular conformation can be markedly influenced by the hydrophilicity (or hydrophobicity) of both macromolecule chain and ions. An extended chain conformation can be obtained when the side groups and ions are relatively hydrophilic, which can also increase the elasticity of a macromolecule chain and film materials. The relatively hydrophobic components promote the collapse of macromolecule chains and reduce the molecular elasticity. It is believed that the hydrogen bonding intensity between a macromolecule chain and aquated ions controls the chain conformation and the elasticity of molecules and films. This study is not only helpful for understanding the self-assembly mechanism of organisms but also provides a way to associate the molecular properties with the macroscopic performance of materials.

Exploiting interfacial instability during peeling a flexible plate from elastic films

Adhesive interactions between soft materials are prevalent in both biological systems and various engineering applications, including soft robots, flexible electronics, and antifouling coatings. Many studies have demonstrated that cavitation and fingering instabilities emerge at the adhesive interface between rigid objects and soft films, owing to the geometric attributes of the contact region. However, in the context of peeling configurations, defining the geometric features is challenging, resulting in relatively scant exploration of interfacial instabilities. Hence, the modulation of instability patterns during the peeling process of a flexible plate from a thin elastic film, alongside the consequential effects on mechanical responses, remains poorly understood. To elucidate the mechanisms underlying interfacial instability during peeling process and its impacts on peel-off force, we use finite element methods to simulate the evolution of interface separation. Consistent with previous experimental observations, we find that the interfacial instability will occur when the bending stiffness of the flexible plate is bigger than a critical value. We show that the interfacial instability is mainly induced by the competition between the adhesion energy and the strain energy of the film, and the incompressibility of the thin film is critical for the appearance of the interfacial instability. Combining theory and finite element simulation, we propose the scaling laws for the critical peel-off force for stable and unstable peelings, respectively, and show that the critical peel-off force will decrease when the interfacial instability occurs. Finally, we demonstrate that weakening the tangential adhesion strength and loosening the constraints between the film and the rigid substrate effectively suppress fingering instability. Collectively, our findings elucidate the pivotal factors influencing interfacial instability, offering invaluable insights for the design of structures or systems involving soft materials.

Формирование свойств биодеградируемых пленок на основе рыбного желатина

Nowadays in the food and nutrition industry special attention is paid to the creation of non-toxic, easily recy-clable packaging materials of a new assortment, capable of providing reliable protection of products from harmful factors. The object of the study was biodegradable film compositions based on fish gelatin and agar, with the addition of plasticizing agent - glycerol. Experimental and analytical studies were carried out using standard and original methods. Modeling of the process of thermal treatment of film compositions was carried out, the experimental dependence of moisture absorption of films on temperature (range 120-160 °C) and duration of the thermal modification process (10-30 minutes) was established. The possibility of thermal modification of biodegradable film compositions was determined. The rational mode of thermal treatment of films is the temperature interval of 140 °C for 20 minutes, which allows to keep the moisture absorption index at the maximum level (842%), exceeding the initial index by 8.4 times, during 120 hours. The established parameters of thermal structuring allow to keep organoleptic quality indicators of films at a high level and to obtain a homogeneous, porous and elastic film. Thermally modified films at temperatures of 140 and 160 °C are characterized by increased dissolution time up to 40 and 70 minutes respectively at dissolution temperature of 60 °C and up to 15 and 30 minutes respectively at dissolution temperature of 75 °C. It is shown that thermal modification of biodegradable films will contribute to compliance with safety requirements, environmental friendliness, absence of toxicity. Thermal modification allows to increase functional and technological properties of composite biodegradable films, which can be used to create a wide range of modern packaging barrier materials.

Understanding the textural enhancement of low-salt myofibrillar protein gels filled with pea protein pre-emulsions through interfacial behavior: Effects of structural modification and oil phase polarity

This study investigated the effects of pea protein pre-emulsions containing triglyceride- or diglyceride-oil on the emulsifying and gelling properties of low-salt myofibrillar protein (MP). Pea protein isolates treated with pH12-shifting (PPIpH) or ultrasonication (PPIU) demonstrated superior initial interfacial adsorption and higher final interfacial pressure than native pea protein. Within MP/PPI blends, an increased ratio of MP led to a decrease in interfacial pressure, while simultaneously enhancing film elasticity at both polar and non-polar interfaces. Polar diglyceride promoted protein adsorption and fostered interfacial interactions between modified pea proteins and MP, enhancing the cross-linking of transglutaminase (TG) in the composite emulsion gels. Combining diglyceride-type PPIU and PPIpH emulsions with TG increased gel strength to 0.58 N and 0.63 N, respectively, from an initial 0.33 N, yielding a denser protein network with uniformly dispersed oil droplets. Therefore, the utilization of diglyceride and modified PPI can serve as structural enhancers in comminuted meat products.

Technical-functional and surface properties of white common bean proteins (Phaseolus vulgaris L.): Effect of pH, protein concentration, and guar gum presence

Legumes are abundant sources of proteins, and white common bean proteins play an important role in air–water interface properties. This study aims to investigate the technical-functional properties of white common bean protein isolate (BPI) as a function of pH, protein concentration, and guar gum (GG) presence. BPI physicochemical properties were analyzed in terms of solubility, zeta potential, and mean particle diameter at pH ranging from 2 to 9, in addition to water-holding capacity (WHC), oil-holding capacity (OHC), and thermogravimetric analysis. Protein dispersions were evaluated in terms of dynamic, interfacial, and foam-forming properties. BPI showed higher solubility (>80 %) at pH 2 and above 7. Zeta potential and mean diameter ranged from 15.43 to −34.08 mV and from 129.55 to 139.90 nm, respectively. BPI exhibited WHC and OHC of 1.37 and 4.97 g/g, respectively. Thermograms indicated decomposition temperature (295.81 °C) and mass loss (64.73 %). Flow curves indicated pseudoplastic behavior, with higher η100 values observed in treatments containing guar gum. The behavior was predominantly viscous (tg δ > 1) at lower frequencies, at all pH levels, shifting to predominantly elastic at higher frequencies. Equilibrium surface tension (γeq) ranged from 43.87 to 41.95 mN.m−1 and did not decrease with increasing protein concentration under all pH conditions. All treatments exhibited ϕ < 15°, indicating predominantly elastic surface films. Foaming properties were influenced by higher protein concentration and guar gum addition, and the potential formation of protein-polysaccharide complexes favored the kinetic stability of the system.