Elastic Film Research Articles

Preparation and properties of highly flexible cholesteric side-chain liquid crystalline elastomers with selective reflective properties in the visible region

ABSTRACT In this paper, we have synthesised cholesteryl 4-allyloxybenzoate (MB), crosslinking agent dodecane-1,12-diyl bis(undec-10-enoate) (MG), and A’BGF series liquid crystalline elastomer (LCE) films which take polymethylhydrosiloxane (A’) as the backbone, MB as the cholesteric liquid crystal (LC) monomer, and MG and bis-vinyl silicone oil (MF) with different reactivities as cross-linking agent for exploring the effect of the change of MF content on the properties of the elastomeric films. The experimental results show that the synthesised MB, MG, and the LCE films are all consistent with the molecular design; MB is an enantiotropic cholesteric LC. The synthesised LCE films are cholesteric LCs, have certain selective reflection characteristic, higher thermal stability, and their Tg decreased down to 3.9°C as MF increasing. During the heating and cooling, the liquid crystalline properties of the LCE films have a good reversibility. Among the synthesised LCE films, A’BGF-2 has stretching radio of 264.8% at room temperature, with the best elastic properties. By adjusting the ratio of MF, the content of small-molecule MB remained in the films can be changed, which will affect the optical properties and elasticity of the LCE films. The experiments provide a method for the preparation of highly elastic side chain LCE film.

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

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

Improving emulsion stabilizing capacity of sodium caseinate by colloidal lignin particles near the isoelectric point

Sodium caseinate (Cas) is an attractive candidate for food emulsion formulation due to its surface-active properties as well as the ability to prevent the oxidation of encapsulation oils. However, the emulsions underwent destabilization near its isoelectric point (pI, around pH 4.8) due to the lack of enough electronic repulsion. To overcome the drawback, colloidal lignin particles (CLPs) fabricated from dietary fiber with superior negative repulsion and abundant surface active sites will be inspiring as the patch of Cas-based emulsion. This study systemically explored the modified effect of varied CLPs concentrations in the Cas-based emulsions prepared at pH 4.8. Due to hydrophobic attractions and hydrogen bonds between protein and CLPs, the CLPs significantly increased the negative charge and viscosity of composites while reduced surface hydrophobicity of Cas. Thus, in contrast to Cas, Cas/CLPs complex can fabricate a more elastic oil-water interfacial film, accompanying with a reduced droplet size (52–136 μm). Despite the inhibition of Cas adsorption at interfacial film, Cas/CLPs complex increase the stability of emulsion mainly by increasing electrostatic repulsion, enhancing film elasticity, and thickening continuous phase. Emulsions fabricated with Cas/CLPs complex effectively protected polyunsaturated fatty acids from deterioration, with the lowest levels of hydroperoxide and malondialdehyde observed in Cas/1.00 %CLPs emulsion. This study uncovered the facts behind the non-covalent interactions of Cas and lignin and proposed a novel strategy to stabilize Cas-based emulsions in acidic conditions.

Natural resin as a biosource and bio-based plasticizer for edible resin/ethylcellulose composite film preparation.

Nowadays, finding natural and inexpensive resources that can be easily used to make food films has been considered. Despite the widespread use of synthetic resins, natural resins are rarely used. Opopanax resin (OR) was used in this study as a new biosource to prepare the hydrophobic edible film. Ethylcellulose (EC) was blended well with the resin, allowing the formation of a composite film. Film preparation was possible using different amounts of OR and EC. It was interesting that OR had a plasticizing effect on EC film. While using up to 33% w/w glycerol could not produce an elastic EC film, using only 8.5% w/w OR produced a stiff and flexible EC film with lower water sensitivity. Fourier transform infrared (FTIR) spectroscopy analysis showed that the strength of C-O-C and CH bonds in OR + EC film was higher than in EC film. Despite the higher water sensitivity of OR-based composite films than EC-based composite films, they had lower water vapor permeability (WVP) and higher contact angle due to their smoother and more homogeneous film structures with lower porosity, confirmed by scanning electron microscopy (SEM) images. The mechanical properties showed that the film with the highest resin content had the lowest tensile strength (~ 0.4MPa) and the higher elongation at break (~ 67%) and, therefore, the highest flexibility. The use of natural resins as a biosource is a promising approach in food packaging to prepare hydrophobic films with desirable mechanical properties.

A comparative study on the speed-up dynamics of drop spreading on floating and glass-supported polystyrene thin films

The enhanced spreading of a 2D drop on a stiff and free-standing elastic thin film theoretically investigated by Shanahan (Rev. Phys. Appl. 1988, 23, 1031–1037) has not been studied and verified experimentally. To shed a light on this interesting problem, herein, we perform comparison studies on the spreading behavior of a silicone oil drop on stiff polystyrene thin films supported by two different substrates: glass vs. water. Scaling analysis on the time evolution of the contact radius for the drop spreading on the films of varied thickness (∼40 nm to ∼600 nm) reveals the difference on the dynamics for the drop spreading on glass-supported and floating films. Upon fitting the spreading data by using the spreading model developed by de Ruijter et al. (Langmuir 1999, 15, 2209–2216), we are able to identify the speed-up effect for the drop spreading on water supported floating films, which progressively decreases with film thickness and diminishes when the thickness is greater than ∼200 nm. The elastic driving force that is responsible for the speed-up of the drop spreading on the floating film is evaluated empirically, which is found to decay exponentially with contact radius of the drop. The pre-factor and the decay length of the decay function are determined by film thickness and drop volume, resepctively. Our findings expect to facilitate developing new theories with practical relevance on the spreading dynamics of a liquid drop on elastic films.

Effects of catechin on the stability of myofibrillar protein-soybean oil emulsion and the adsorbed properties of myosin at the oil–water interface

The effects of different concentrations of catechin on the stability of myofibrillar protein-soybean oil emulsions and the related mechanisms were investigated. Adding 10 μmol/g catechin had no obvious effects on the emulsion stability and myosin structure, but 50, 100 and 200 μmol/g catechin decreased the emulsion stability. The microstructure observations showed that 10 μmol/g catechin caused a dense and uniform emulsion to form, whereas 50, 100 and 200 μmol/g catechin induced the merging of oil droplets. The addition of 50, 100 and 200 μmol/g catechin caused a decline in both the total sulfhydryl content and surface hydrophobicity, suggesting protein aggregation, which decreased the adsorption capacity of myosin and the elasticity of interfacial film. These results suggested that higher concentrations of catechin were detrimental to the emulsifying properties of myosin and that the dose should be considered when it is used as an antioxidant.

Hit two birds with one stone: A bi-functional selenium-substituted organosulfur polymer additive for high-performance lithium-sulfur batteries

Sluggish reaction kinetics of sulfur cathode and high reactivity of lithium anode hinder the commercialization of Li-S batteries. Employing the electrolyte additive to regulate the states of active material is a facile and effective way to solve the above issues. Herein, the bifunctional selenium substituted lithium polythioctic acid (PTA-Se) was prepared as an additive of electrolyte via in-situ polymerization and substitution method. Such additives can promote the conversion of polysulfides and facilitate the homogenization of Li-ion flux. The active selenium sites provide a kinetically favorable pathway for polysulfide conversion. The introduction of additives also facilitates the formation of elastic and uniform solid electrolyte phase interface (SEI) film on the surface of lithium anode. As results, Li-S batteries assembled with PTA-Se additive demonstrates a high initial capacity of 1319 mAh g−1 at 0.2C with 1000 mAh g−1 remaining after 150 cycles, corresponding to a 0.16 % capacity decay per cycle. At a high rate of 5C, the cell still achieves a reversible capacity of 517 mAh g−1. This work opens a new avenue for designing effective electrolyte additive and achieving high-performance Li-S batteries.

Altering the interfacial rheology of Pseudomonas aeruginosa and Staphylococcus aureus with N-acetyl cysteine and cysteamine.

Chronic lung infection due to bacterial biofilms is one of the leading causes of mortality in cystic fibrosis (CF) patients. Among many species colonizing the lung airways, Pseudomonas aeruginosa and Staphylococcus aureus are two virulent pathogens involved in mechanically robust biofilms that are difficult to eradicate using airway clearance techniques like lung lavage. To remove such biological materials, glycoside hydrolase-based compounds are commonly employed for targeting and breaking down the biofilm matrix, and subsequently increasing cell susceptibility to antibiotics. In this study, we evaluate the effects of N-acetyl cysteine (NAC) and Cysteamine (CYST) in disrupting interfacial bacterial films, targeting different components of the extracellular polymeric substances (EPS). We characterize the mechanics and structural integrity of the interfacial bacterial films using pendant drop elastometry and scanning electron microscopy. Our results show that the film architectures are compromised by treatment with disrupting agents for 6 h, which reduces film elasticity significantly. These effects are profound in the wild type and mucoid P. aeruginosa, compared to S. aureus. We further assess the effects of competition and cooperation between S. aureus and P. aeruginosa on the mechanics of composite interfacial films. Films of S. aureus and wild-type P. aeruginosa cocultures lose mechanical strength while those of S. aureus and mucoid P. aeruginosa exhibit improved storage modulus. Treatment with NAC and CYST reduces the elastic property of both composite films, owing to the drugs' ability to disintegrate their EPS matrix. Overall, our results provide new insights into methods for assessing the efficacy of mucolytic agents against interfacial biofilms relevant to cystic fibrosis infection.

Bio‐Disintegrable Elastic Polymers for Stretchable Piezoresistive Strain Sensors

AbstractThe fast‐growing usage of electronics is creating large amounts of e‐waste (electronic waste), most of which are directly sent into landfills or incinerated as recycling is either impractical or too costly. Therefore, it is believed that degradable, environmentally friendly materials are the solution to this pressing issue. Herein, disintegrable, durable, and highly stretchable strain sensors are developed based on elastic thin films made of sodium carboxymethyl cellulose, glycerol, and polyvinyl alcohol. The polymer thin films show a failure strain up to ≈ 330% and low hysteresis (5.74% at the second cycle) when subjected to 50% cyclic strain, due to the formation of inter or intramolecular hydrogen bonds. Carbon nanofibers with Au thin film are deposited on the elastic thin film, resulting in highly stretchable piezoresistive strain sensors with a maximum gauge factor of 1.7. More interestingly, the as‐developed sensors can be completely broken down in hot water (at ≈ 95 °C) within ≈ 25 min, indicating their remarkable disintegrability. This unique characteristic is expected to contribute to environmental sustainability. The applications of the sensor for joint bending recognition as well as physiological sign measurement have been demonstrated.

Growth-induced delamination of an elastic film adhered to a cylinder

We study the delamination induced by the growth of a thin adhesive sheet from a cylindrical, rigid substrate. Neglecting the deformations along the axis of the cylinder, we treat the sheet as a one-dimensional flexible and compressible ring, which adheres to the substrate by capillary adhesion. Using the calculus of variations, we obtain the equilibrium equations and in particular arrive at a transversality condition involving in a non-trivial way the curvature of the substrate, the extensibility of the ring and capillary adhesion. By numerically solving the equilibrium equations, we show that delamination by growth occurs through a discontinuous transition from the fully adherent solution to the partially delaminated one. The shape of the delaminated part can take the form either of a ruck, with a small slope, or a fold, with a large slope. Furthermore, in the weak adhesion regime, complete delamination may occur. We construct the phase diagram between the different solutions in the parameter space. In the quasi-incompressible limit, numerical results are also supported by asymptotic calculations both in the strong and weak adhesion regimes.

COTINUS COGGYGRIA ETHANOL EXTRACT AS CROSSLINKING AGENT IN FORMULATION OF THE PROTEIN FILMS

The study explores the potential application of smoketree (Cotinus coggygria Scop) ethanol extract (STE) as a natural cross-linking and active component in the formulation of films based on collagen (CL), gelatin (GL) and soy protein isolate (SPI). After casting and drying of the respective film-forming solutions, elastic and homogeneous films were obtained. A significant color difference was found for all protein films with added STE compared to the control series (mainly due to an increase in yellowness). The degree of cross-linking was highest in CLSTE (60 %), followed by GLSTE (27 %) and SPISTE (18 %). The antioxidant activity of the films, determined by the DPPH radical scavenging assay, increased significantly after the addition of STE. The observed increase in tensile strength (TS) for the films with STE ranged from double (CLSTE and SPISTE) to more than 4 times (GLSTE). In addition, there was a significant improvement in the light barrier properties of the extract-incorporated films, but also a reduction in their transparency up to 1.5 times compared to their respective controls. No significant influence was observed on physical characteristics such as thickness, moisture absorption and total soluble matter. Research results show that STE can be successfully used as a natural cross-linking agent in protein films, resulting in improved light barrier properties as well as increased strength and antioxidant activity.

A flexible droplet-based triboelectric-electromagnetic hybrid generator for raindrop energy harvesting

Dispersed raindrop energy harvesting has recently attracted extensive interest owing to the huge amount of energy contained in the water. However, most raindrop-based electromagnetic generators (EMGs) and triboelectric generators (TEGs) are unable to efficiently convert raindrop energy into electricity due to the rigid, bulky, and complex structures of EMGs with low output voltage, as well as the unstable and low current output of TEGs. Herein, we developed a flexible droplet-based triboelectric-electromagnetic hybrid generator (D-TEHG) including a droplet-based electromagnetic generator (D-EMG) and a droplet-based triboelectric generator (D-TEG) for efficiently harvesting raindrop energy. A flexible magnetically responsive hydrophobic film (MRHF) fabricated by a simple spray coating method was used in a hybrid power output system for raindrop energy conversion, serving as a "spring-like" structure for contacting and separating the electrodes in the D-TEG part, and as an excitation structure for moving the coil in the D-EMG part. When the D-TEHG was excited by a water droplet, the vibration of the elastic film induced the contact and separation of the two electrodes in the D-TEG part and the magnetic flux change through the coil in the D-EMG part, thus generating a dual electrical signal. When a 58.2 µL droplet was dropped from a height of 50 cm and impacted the D-TEHG, the D-TEG generated a peak open-circuit voltage (VOC) of ∼3.01 V and the D-EMG output a peak short-circuit current (ISC) of ∼11.21 mA. The integrated D-TEHG could generate high-performance power for charging capacitors and driving "DUT" LED arrays. By employing advanced flexible materials and structures, the hybrid generator might open up an avenue that makes efficient collection and utilization of large-area raindrop energy a reality.

Bioactive Ag(I) coordination complexes as dopants for castor oil plasticized ethylcellulose films.

The effects exerted by new bioactive acylpyrazolonate Ag(I) derivatives of the general formula [Ag(QPy,CF3)(R-Im)] containing different substituents on the imidazole (R-Im) ancillary ligands and the natural plasticizer castor oil when both are added to the ethylcellulose (EC) biopolymer in the preparation of thin films as potential active food packaging materials are presented. The Ag(I) complexes [Ag(QPy,CF3)(Bn-Im)] and [Ag(QPy,CF3)(Bu-Im)], having benzyl and butyl substituents, whose single crystal molecular structures are reported, have proved to be highly compatible for efficient incorporation between the EC polymer and the hydrophobic plasticizer chains, giving rise, even at low concentrations, to homogeneous, robust and elastic films. The concomitant presence of these Ag(I) complexes and castor oil in the polymer EC matrix gives rise to thin films with improved antibacterial activity against Escherichia coli (E. coli) as a model of Gram-negative bacterial strains when compared to the non-plasticized ones, with very low Ag(I) migration in the three food simulants used (distilled water, ethanol 10% v/v and acetic acid 3% v/v) under two assay conditions (70 °C for 2 h and 40 °C for 10 days).

Microscale damper prototype: A preliminary study on suppressing air flow oscillations within microchannels

This research introduces a novel micro-damper designed to mitigate pressure and velocity oscillations from a piezoelectric micropump in microfluidic environments. Unlike existing research focusing on damping in incompressible liquid flows with methods like elastic films and PDMS membranes, this study proposes a novel micro-damper prototype. Integrated into a microdevice for particle granulometric separation and detection, the damper connects to a piezoelectric micropump outlet and to a focusing microchannel inlet, followed by a capacitive sensor for size-based particle counting. Preliminary analysis determined an optimal airflow velocity at w = 0.5 m/s for accurate focusing and counting under laminar conditions. The micro-damper, constrained by the piezoelectric pump’s geometry, features a 27 µm high and 1000 µm wide cross section. Its outlet supports two potential focusing microchannel inlet configurations of 30 µm or 40 µm. Distinctively, it incorporates two symmetrical backward micro-channels connecting to the atmosphere, allowing direct piezometric contact between the main flow and an infinite compliant volume. OpenFOAM simulations confirm the damper’s effectiveness in maintaining laminar outlet flow and suppressing micropump disturbances. Thus, the proposed micro-damper ensures optimal inlet conditions for subsequent microchannel processes, enabling stable particle separation and detection in controlled airflow samples.

Fibre-based stretchable electrodes for flexible metamaterial electronics: A review

Abstract Flexible electronics researchers have been conducting studies to explore the response of flexible stretchable electrodes to strain. The regulation of strain response in current flexible stretchable electrodes relies primarily on altering the material system, interfacial adhesion, or electrode structure. However, modifying the material system or interfacial adhesion can negatively disrupt the stretchable electrode preparation process, making commercialization a significant challenge. Additionally, the material system may be inadequate in extreme environments such as high temperatures. Hence a systematic structural design approach is crucial for effective response modulation of stretchable electrodes. One potential solution is the design of fibre structures from the micro to macro scale. This article focuses on discussing how the response of stretchable electrodes can be modulated by fibres in different states. The discussion includes fibres on elastic films, fibres directly constituting fibrous membranes at the microscopic level, and fibres constituting metamaterials at the fine level. The modulation can be achieved by altering the orientation of the fibres, the geometrical structure of the fibres themselves, and the geometrical structure formed between the fibres. Additionally, the article analyses the current situation of stretchable electrodes in extreme environments such as high temperatures. It also reviews the development of ceramic fibre membranes that can be stretched in high-temperature environments. The authors further discuss how the stretchability of ceramic fibre membranes can be improved through the structuring of ceramic fibre membranes with metamaterials. Ultimately, the goal is to realize stretchable electrodes that can be used in extreme environments such as high temperatures.

A thin, intrinsically stretchable MXene-MWCNTs/polymer current collector for deformable aqueous Li-ion batteries

By integrating Ti3C2Tx with MWCNTs on an elastic SEBS film, a thin, intrinsically stretchable hybrid conductor was constructed and used to fabricate deformable aqueous Li-ion batteries.

A Novel Approach for Glycero-(9,10-trioxolane)-Trialeate Incorporation into Poly(lactic acid)/Poly(ɛ-caprolactone) Blends for Biomedicine and Packaging.

The product of ozonolysis, glycero-(9,10-trioxolane)-trioleate (ozonide of oleic acid triglyceride, [OTOA]), was incorporated into polylactic acid/polycaprolactone (PLA/PCL) blend films in the amount of 1, 5, 10, 20, 30 and 40% w/w. The morphological, mechanical, thermal and antibacterial properties of the biodegradable PLA/PCL films after the OTOA addition were studied. According to DSC and XRD data, the degree of crystallinity of the PLA/PCL + OTOA films showed a general decreasing trend with an increase in OTOA content. Thus, a significant decrease from 34.0% for the reference PLA/PCL film to 15.7% for the PLA/PCL + 40% OTOA film was established using DSC. Observed results could be explained by the plasticizing effect of OTOA. On the other hand, the PLA/PCL film with 20% OTOA does not follow this trend, showing an increase in crystallinity both via DSC (20.3%) and XRD (34.6%). OTOA molecules, acting as a plasticizer, reduce the entropic barrier for nuclei formation, leading to large number of PLA spherulites in the plasticized PLA/PCL matrix. In addition, OTOA molecules could decrease the local melt viscosity at the vicinity of the growing lamellae, leading to faster crystal growth. Morphological analysis showed that the structure of the films with an OTOA concentration above 20% drastically changed. Specifically, an interface between the PLA/PCL matrix and OTOA was formed, thereby forming a capsule with the embedded antibacterial agent. The moisture permeability of the resulting PLA/PCL + OTOA films decreased due to the formation of uniformly distributed hydrophobic amorphous zones that prevented water penetration. This architecture affects the tensile characteristics of the films: strength decreases to 5.6 MPa, elastic modulus E by 40%. The behavior of film elasticity is associated with the redistribution of amorphous regions in the matrix. Additionally, PLA/PCL + OTOA films with 20, 30 and 40% of OTOA showed good antibacterial properties on Pseudomonas aeruginosa, Raoultella terrigena (Klebsiella terrigena) and Agrobacterium tumefaciens, making the developed films potentially promising materials for wound-dressing applications.

High-Sensitivity Mechanochromic Sensor Using Core-Shell Colloidal Crystals

The Colloidal Crystals-based mechanochromic sensor changes color as the arrangement of colloidal particles changes in response to mechanical deformation, which can be detected through optical measurement. This type of sensor can be used in various applications, such as automobile collision detection, structural deformation detection, and medical equipment, among others. In this study, we prepared a stretchable film by dispersing surface-functionalized colloidal particles in an elastic polymer matrix. Surface of silica colloidal particle was modified with an initiator for Atom Transfer Radical Polymerization (ATRP), followed by surface-initiated ATRP of poly(t-butyl methacrylate) (PtBMA). The core-shell colloidal particles were composited with various acrylic monomers, to fabricate crystalline colloidal array which transforms to elastic film by photopolymerization exhibiting structural color. The prepared film showed a clear color change for deformation within 10%, and the peak reflectance showed more than 30%.

A phase field fracture model for ultra-thin micro-/nano-films with surface effects

Surface effects usually remarkably affect the mechanical response of ultra-thin micro-/nano-structures. However, the mechanisms of surface effects on the fracture characteristics of ultra-thin films are still not fully understood. To this end, this paper develops a modeling framework to investigate the fracture of ultra-thin films at microscales or below. Such a framework couples the Gurtin–Murdoch theory with a phase-field fracture model, in which the former is adopted to introduce the surface effects, i.e., the surface residual stress and surface elasticity of a thin film, and the latter is able to model crack evolution without requiring predefined crack paths or any criteria. Furthermore, a novel crack driving force is introduced, which encompasses the tensile components of both bulk elastic energy and surface elastic energy. Several numerical examples including the biaxial tension test as well as the single-edge notched tension/shear test are performed. The simulation results indicate that the surface strain energy plays a major role in the total elastic strain energy of an ultra-thin film when its thickness is at a micro level, thus demonstrating the significance of surface effects. Moreover, the mode-I fracture test shows that the surface elasticity and surface residual stress have a remarkable influence on the displacement at failure, while for the mode-II fracture test, the surface residual stress significantly influences the fracture characteristics such as the crack path and failure displacement. The developed model paves the way for revealing the fracture mechanisms of ultra-thin micro-/nano-films and conducting their safety assessment.

Recyclable liquid metal – Graphene supercapacitor

Because of their high electrical conductivity, fluidic deformability, self-healing properties, and the possibility of recycling, Ga-based liquid metal alloys like eutectic gallium indium (EGaIn) have tremendous potential as electrodes for stretchable energy storage devices. However, EGaIn droplets could never be used as electrodes in thin-film supercapacitors (SCs) at the desired micro/nano scale, because they rapidly coalesce into bulk EGaIn when contacting acidic/alkaline electrolytes. Here, we show that coating EGaIn droplets with only 0.08 wt% of reduced graphene oxide (GO) nanosheets tremendously improves their chemical stability. We fabricated binder-free GO-coated EGaIn nanocomposite electrodes that show excellent stability in a strong alkaline electrolyte. We demonstrated a symmetric soft-matter pseudo-SC with areal capacitances of 1200mF/cm2@0.3 mA/cm2 and 220mF/cm2@1mA/cm2, which is > 10 × compared to previous SCs based on bulk EGaIn. This SC retains 98.4 % of the initial capacitance after 4000 electrochemical cycles and exhibits comparable self-discharge rates to state-of-the-art flexible pseudo-SCs. Surprisingly, applying mechanical strain results in improved areal capacitance. We demonstrate rapid, laser-based fabrication of a wirelessly chargeable elastic film with an integrated energy harvesting antenna and energy-storage SC that can be used in wearable biomonitoring patches, and e-textiles. Finally, we demonstrate the recovery of the metals from the disposed of SCs through an electrowinning technique.