Polyethylene Thin Films Research Articles

Management of lagopthalmus with gold implant: A case report

Blinking covers the eye with a thin layer of tear fluid, thereby promoting a moist environment necessary for the cells of the exterior part of the eye. The tears also flush out foreign bodies and wash them away. This is crucial to maintain lubrication and proper health of the eye. In lagophthalmus, there is inability to close the eyelid and loss of blinking mechanism, thereby resulting in corneal dryness, ulceration, abrasion and infection. It may occur due to facial nerve damage secondary to trauma, iatrogenic due to surgery, tumour or Bell’s palsy. Initial symptomatic management is directed towards ocular surface lubrication. Viscous artificial tears are used or thin polyethylene film may be applied over the eyes to reduce evaporative drying. Temporary or permanent tarsorrhaphy may be required in some cases. Changing the position of either the top or bottom eyelid can help relieve the symptoms of lagopthalmus. A prosthetic procedure involves implanting gold weights into the upper eyelid, which allows the eyes to close by gravity. A case report of management of Lagophthalmus is presented here.

The Role of Inorganic-Organic Bio-Fillers Containing Kraft Lignin in Improvement in Functional Properties of Polyethylene.

In this study, MgO-lignin (MgO-L) dual phase fillers with varying amounts of lignin as well as pristine lignin and magnesium oxide were used as effective bio-fillers to increase the ultraviolet light protection and enhance the barrier performance of low density polyethylene (LDPE) thin sheet films. Differential scanning calorimetry (DSC) was used to check the crystalline structure of the studied samples, and scanning electron microscopy (SEM) was applied to determine morphological characteristics. The results of optical spectrometry in the range of UV light indicated that LDPE/MgO-L (1:5 wt/wt) composition exhibited the best protection factor, whereas LDPE did not absorb ultraviolet waves. Moreover, the addition of hybrid filler decreased the oxygen permeability factor and water vapor transmission compared with neat LDPE and its composites with pristine additives, such as lignin and magnesium oxide. The strong influence of the microstructure on thin sheet films was observed in the DSC results, as double melting peaks were detected only for LDPE compounded with inorganic-organic bio-fillers: LDPE/MgO-L.

Buoyant flames in near the lower flammability limit hydrogen–air mixtures

The paper presents the results of large-scale experimental and simulation study of the propagation of premixed near the lower flammability limit hydrogen–air spherical flame. Experiments were carried out in a cylindrical volume of 4.5 m3 covered with thin polyethylene film. The effect of buoyancy and stability of the flame ball in the unconfined volume are studied experimentally and numerically. Numerical analysis of the problem shows that the flame ball becomes unstable after some period of stable propagation that qualitatively corresponds with experimental results. The effect of chemistry in a flame ball propagation process is studied numerically. A comparison of experimental results and numerical simulations are presented. A comparison of numerical simulations with and without chemistry is shown. The subject and results of the study are of critical importance for the industrial explosion safety and hydrogen safety of nuclear power plants.

Unique calibration of passive air sampling for field monitoring of PAHs with polyethylene thin films across seasons and locations

For better insight into passive air sampling, we monitored PAHs with PE sheets during 8 seasons at 3 locations. A numerical model was applied to fit the limiting air-side boundary layer, which was surprisingly stable around 1 mm in all locations.

Photoelectric dye-based retinal prosthesis (OUReP) as a novel type of artificial retina

We have developed the world's first novel type of artificial retina, OUReP (Okayama University Retinal Prosthesis), in which a photoelectric dye that converts light energy into electric potential is covalently bonded to the surface of a polyethylene thin film as an insulator. The receptor that absorbs light and the output device that generates displacement current to stimulate nearby neurons are integrated in a sheet of thin film. It has become possible to measure the surface potential of the artificial retina OUReP using a Kelvin probe that measures the surface potential of semiconductors. When light is turned on and off to the artificial retina OUReP, the surface potential changes rapidly. As the light intensity is increased, the potential change on the surface of the artificial retina becomes larger. As for safety, the artificial retina OUReP was not toxic in all tests for biological evaluation of medical devices. As for efficacy, the artificial retina OUReP was implanted under the retina by vitreous surgery in monkey eyes which had chemically-induced macular degeneration with photoreceptor cell loss. Over the next 6 months, retinal detachment did not occur during the course, and the artificial retina was in contact with the retinal tissue. The amplitude of the visual evoked potential attenuated by macular degeneration recovered 1 month after implantation of the artificial retina, and the recovery of amplitude was maintained until 6 months after the implantation. By using multielectrode array-mounted dish recording system, it has been proved that action potential spikes are induced when the artificial retina is placed on degenerative retinal tissue of retinal dystrophic rats or mice and exposed to light, which is used as an index of the effectiveness of the artificial retina. We have established manufacturing and quality control of the device in a clean room facility, proved the safety and efficacy, and are preparing for first-in-human investigator-initiated clinical trials.

Molecular Dynamics Simulations of Polyethylene Bilayers

By conducting molecular dynamics (MD) simulations of polyethylene (PE) melts consisting of two different films, each comprised of chains of different molar mass, in molecular contact with each other, we compare the structural and dynamical properties between these subsystems. Joining layers of the same chemical constitution but different molecular weights is explored as a route towards packaging materials that combine good mechanical and barrier properties with recyclability and therefore provide more sustainable solutions for contemporary industrial needs. Initially, we construct two independent PE thin films characterized by periodic boundary conditions in two directions, but of finite thickness in the third direction. An “amorphous builder” is used for this purpose, which constructs the chains bead by bead (united atom), using the TraPPE force field. A slab is made by joining the two films in the thickness direction and periodic boundaries are introduced in this direction. The slab is energy minimized and then subjected to NPT molecular dynamics (MD) simulation at 350 K and 1 bar, over times longer than the longest relaxation times of both films. Both structural and dynamical properties of the films are calculated, including the self-diffusion coefficient for the chain centers of mass.

An AFM-IR study on surface properties of nano-TiO2 coated polyethylene (PE) thin film as influenced by photocatalytic aging process

Most plastic wastes undergo extensive photo-aging in the environment, and the aged plastics exhibit different surface properties from pristine ones. Here, we investigate the surface properties of a nano-TiO2 coated polyethylene (PE) film as influenced by photocatalytic aging process using an atomic force microscopy coupled with infrared spectroscopy (AFM-IR) technique. Results showed that the height range of the as-prepared samples was about 30 nm, and the equivalent diameter of nano-TiO2 was ~70 nm. The photo-induced oxidation of the CH2 bond occurred on the surface of the PE film. Photo-aging mainly affected the thermal properties of PE film in a local area, especially affecting the components surrounding the nano-TiO2 particle. The glass transition temperature of unaged PE film mainly changed in the range of 93.9–96.5 °C, but after aging the temperature gradually increased with the distance to nano-TiO2 increasing from near to far. The plastic film surrounding the nano-TiO2 particle became stiffer after photo-aging, and the photocatalytic reaction had an effect on the stiffness of the film material. The second characteristic peaks with resonance deviations (i.e., 110, 112, and 115 kHz) were used for Lorentz contact resonance (LCR) measurements. The mechanical properties of PE film after photo-aging were closely related to the distance between nano-TiO2 and film surface. These research findings are conducive for us to understand better the photo-induced aging process of functional plastic film.

Development of a method for positron annihilation lifetime measurement in thin polyethylene films using a Na-22 source

Positron annihilation lifetime measurements were performed on polyethylene films [low-density polyethylene and ultra-high molecular weight polyethylene (UHMWPE)] with a thickness of 15–2000 μm using a Na-22 positron source enclosed in a Kapton film. For thin films, some positrons will pass through the film and annihilate behind it. Using a single film in a commercial anti-coincidence system, by placing an annealed stainless steel (SUS304) cover behind the sample, it is possible to sufficiently measure the long-lifetime ortho-positronium (o-Ps) component even in thin films. Additionally, calculated intensities of the o-Ps component determined from the estimated film transmittance agreed well with the measured values. Furthermore, by applying this method to uniaxially stretched UHMWPE, we were able to observe structural changes owing to the stretching consistent with shorter measured o-Ps lifetime and increased o-Ps intensity.

Rapid characterization of heavy metals in single microplastics by laser induced breakdown spectroscopy

Microplastics (MPs) in aquatic environment usually carry hazardous matters, including toxic heavy metals. Quantification of heavy metals in MPs is crucial for the comprehensive understanding of their ecotoxicology in field environment. However, conventional methods for heavy metal determination either are applicable only to bulk/collective samples or require strict operation environment. Here we demonstrated that laser induced breakdown spectroscopy (LIBS) is a robust tool for the characterization of heavy metals in single MPs. Single-particle LIBS selects individual MPs with specific sizes (down to tens of microns), shapes, and morphologies and analyzes simultaneously multiple elements in milliseconds without sample pretreatment. In addition to the elaborate optical design, we also used stretched thin polyethylene film as a substrate, which significantly suppress the matrix interference to the particles' spectra. The single particle LIBS was demonstrated to be a quantitative analytical method, and was applied to heavy metal analysis of the MPs collected in the seawaters of the Beibu Gulf of China. Positive correlation between the spectral intensities and the local marine pollutions as well as significant heterogeneity in the elemental compositions were observed. The results demonstrate that single-particle LIBS is a promising method for MPs characterization and is suitable for studying pollutant transportation by using MPs as vectors.

Impacts of Nanoplastics on the Viability and Riboflavin Secretion in the Model Bacteria Shewanella oneidensis

Characterizing the impact of nanoplastics to organism health is important to understand the consequences of the environmental plastic waste problem. This article examines the impact of nano-polystyrene (nano-PS; 159±0.9 nm diameter) to ecologically relevant bacteria Shewanella oneidensis. Bacterial viability was evaluated using a growth-based assay. Riboflavin secretion is a critical cell function of S. oneidensis, serving as an electron mediator in anaerobic respiration and/or as a signaling molecule when the bacteria are under stress. Thus, changes in cellular function were monitored through riboflavin secretion in order to evaluate toxic responses that may not result in cell death. Under aerobic and anaerobic exposures (4, 8 or 12 h), the viability of the S. oneidensis was minimally changed as compared to the control, while the concentration of riboflavin secreted varied with exposure dose. In order to determine if this was a specific response to nanoplastic particles, opposed to a response to either particles or plastic more generally, we exposed the system to colloidal TiO2 nanoparticles and polystyrene and polyethylene thin films. We confirmed that riboflavin secretion trends were specific to nano-PS and not to these other materials, which showed no significant changes. We investigated the association of the nano-PS with ICP-MS using Pd that was chemically incorporated into the model nanoplastics. While 59.2% of the nano-PS were found in the non-cellular culture media, 7.0% and 6.6% was found associated with the loosely and tightly bound extracellular polymeric substance, respectively. There was significantly more nano-PS (10.9%) strongly associated with the cells. Taken together, we found that nano-PS had minimal impacts to viability but caused a significant change in the function of S. oneidensis that can be related to the nano-PS attached or in proximity to the bacterium. These trends are consistent between aerobic and anaerobic cultures, signifying that the stress response of S. oneidensis can be generalized between different environmental compartments. This work highlights that the association of nanoplastic materials with microorganisms may modify the cellular function that could ultimately be an impact to ecosystem health.

In situ tailoring the hierarchical microstructures in polyethylene films fabricated by thermally induced phase separation via temperature gradient fields

In this study, a series of polyethylene thin films were prepared by thermally induced phase separation (TIPS) method with di(2-ethylhexyl)phthalate as the diluent. Morphological observations showed that the microstructures at different locations were fairly distinct and could generally be divided into three layers. When the polymer concentration was lower than the monotectic point (Φm), both pore size and porosity in TIPS films were heavily determined by growth time and growth rate of the diluent droplets. At relatively higher polymer concentration, cooling rate heavily affected the pore size in the films primarily through its influence on polymers’ crystallization process. The relationship between the film microstructure and cooling rate was quantitatively investigated (especially the effect of quenching conditions on the evolution of film morphology) with the aid of an enthalpy transformation method, which established the three-dimensional temperature profiles and supplied an insight into the competition between phase separation kinetics and polymer crystallization. In addition, our findings showed that the pore size, porosity and thermal stability of films all increased with an increasing quenching temperature, which was significantly different from the trends of variation in water vapor transmission rate as well as the $$ E^{\prime}_{ \hbox{max} } $$ and $$ E^{\prime\prime}_{ \hbox{max} } $$ values of dynamic mechanical analysis as the quenching temperature increased. The present work presents a facile way of in situ tailoring hierarchical microstructures in TIPS films of crystalline polymers, which will be very useful to the design of polymer porous films with specific properties.

Response of PE films to low energy electron beam irradiation

In the past few years low energy electron beam units with energies in the range from 80 to 300 keV have been developed as a convenient and non-expensive alternative to high-energy electron accelerators. Some of these applications like surface decontamination or sterilization of medical supplies need the measurement of the dose in order to be in compliance with regulatory agencies. The demand to have dosimetry systems capable to deliver the irradiation dose using a simple procedure and having an appropriate calibration procedure will grow as these applications increase. Having a dosimeter with a response independent of the energy of the incident radiation would allow to calibrate it using high energy radiation sources and then use it at low-energy electron irradiations. In this paper the response of polyethylene (PE) thin films irradiated with low-energy electrons in the interval from 100 to 200 keV has been investigated with the main purpose of using them as dosimeters in low-energy electron irradiations. The response of the films was obtained from their infrared spectrum measured at their surface using the attenuated total reflectance technique (ATR). Analysis of the data obtained using the statistical technique ANOVA was performed to determine whether the energy of the radiation affects the response of the film. The results show that the response of the films depends on the energy of the electron beam used. The conclusion of this research points out that in order to use the PE film in low-energy electron irradiations the films need to be calibrated under the same conditions in which they will be used.

Printable Highly Stable and Superfast Humidity Sensor Based on Two Dimensional Molybdenum Diselenide

Transition metal dichalcogenides (TMDCs) are promising materials for sensing applications, due to their exceptional high performance in nano-electronics. Inherentely, the chemical and thermal responses of TMDCs are highly stable, hence, they pave way for real time sensor applications. This article proposes inceptively a stable and superfast humidity sensor using two-dimensional (2D) Molybdenum diselenide (MoSe2) through printed technlogies. The 2D MoSe2 ink is synthesized through wet grinding to achieve few-layered nano-flakes. Inter digital electrodes (IDEs) are fabricated via screen-printing on Polyethylene terephthalate (PET) substrate and thin film of MoSe2 nano-flakes is fabricated through spin coating. The impedance and capacitance response are recorded at 1 kHz between temperature levels ranging from 20–30 °C. The impedance and capacitance hysteresis results are recorded <1.98% and <2.36%, respectively, ensuring very good repeatability during humidification and dehumidification. The stability of impedance and capacitance response are recorded with maximum error rate of ~ 0.162% and ~ 0.183%, respectively. The proposed sensor shows fast impedance response time (Tres) of ~ 0.96 s, and recovery time (Trec) of ~ 1.03 s, which has Tres of ~ 1.87 s, and Trec of ~ 2.13 s for capacitance. It is aimed to develop a high performance and stable humidity sensor for various monitoring applications.

Single cell imaging with near-field terahertz scanning microscopy.

ObjectivesTerahertz (THz)‐based imaging techniques hold great potential for biological and biomedical applications, which nevertheless are hampered by the low spatial resolution of conventional THz imaging systems. In this work, we report a high‐performance photoconductive antenna microprobe‐based near‐field THz time‐domain spectroscopy scanning microscope.Materials and methodsA single watermelon pulp cell was prepared on a clean quartz slide and covered by a thin polyethylene film. The high performance near‐field THz microscope was developed based on a coherent THz time‐domain spectroscopy system coupled with a photoconductive antenna microprobe. The sample was imaged in transmission mode.ResultsWe demonstrate the direct imaging of the morphology of single watermelon pulp cells in the natural dehydration process with our near‐field THz microscope.ConclusionsGiven the label‐free and non‐destructive nature of THz detection techniques, our near‐field microscopy‐based single‐cell imaging approach sheds new light on studying biological samples with THz.

Thermal conductivity of Nylon 46, Nylon 66 and Nylon 610 characterized by Flash DSC measurement

We recently developed Flash DSC application to characterize the cross-plane thermal conductivity of polyethylene thin films (Thermochimica Acta 2019, 677, 21–25). We hereby applied this method to measure the thermal conductivities of Nylon 46, Nylon 66 and Nylon 610 after their complete crystallization at 156.6 °C, i.e. the temperature around the melting points of Indium particles. The melting point differences of two Indium particles separately placed on the top of the Nylon samples and on the reference cell exhibit a linear dependence of the heating rates, demonstrating the Fourier’s heat conduction law. From the slope, we further derived the thermal conductivity after we measured the specific heat capacity via conventional DSC and measured the sample thickness via the laser confocal fluorescence microscope. The obtained thermal conductivities of three Nylon samples increase with their hydrogen-bonding densities, which are consistent with conventional experimental approaches. The observations validated the general application of our method for the measurement of thermal conductivity of bulk materials.

Insights into the evaluation of the abiotic and biotic degradation rate of commercial pro-oxidant filled polyethylene (PE) thin films

In this study, commercial products formulated from polyethylene (PE) with pro-oxidant additives, were subjected to abiotic and biotic environments. The materials were presumed to be oxo-biodegradable plastics with thicknesses varying between 30 and 70 μm, and calcium carbonate (CaCO3) filler content reaching up to 11 wt%. Accelerated (aging) weathering tests conducted revealed that UV radiation triggered the biodegradation mechanism. Weight loss reached 50% after exposure to weathering which was attributed to triggering the fragmentation of the plastic films. Furthermore, some 83% of weight loss was estimated after 12 months of soil burial. Fluctuation of weight in mid exposure time spans was related to the cross-linking reaction within the polymeric matrix. The mechanical properties investigated along with the thermal stability profile determined for the materials showed that weathering was more severe than soil burial. Thermogravimetry revealed that onset temperature (Tos) was lower than conventional PO products by 25 °C. This could be attributed to the thermal response of the materials due to presence of ion salts and sterates within their composition. The claims by the manufacturing companies which provided the original specimens under an environmentally friendly pretence is disputed due to the fact that none of the products actually showed evidence of major fragmentation or deterioration after exposure to harsh environments. The work also paves the way in standardising assessment methodology for examining biodegradable plastics.

Detection of alpha particles from 7Li(p,α)4He and 19F(p,α)16O reactions induced by laser-accelerated protons using CR-39 with potassium hydroxide-ethanol-water etching solution.

Alpha particles generated by 7Li(p,α)4He and 19F(p,α)16O reactions are selectively detected in the presence of abundant primary protons by reducing the proton sensitivity of CR-39 using a potassium hydroxide-ethanol-water (PEW) etching solution. These nuclear reactions are induced in a LiF crystal using the laser-accelerated protons (4 × 1011 protons/pulse with a maximum energy of 3.3 MeV) generated and accelerated by the interaction of a 40-fs laser pulse with a polyethylene thin film target at a peak intensity of 5 × 1019 W/cm2. Subsequent etching of the CR-39 in the PEW solution (KOH: 17 wt. %; C2H5OH: 25 wt. %; H2O: 58 wt. %) permits the selective detection of 4.0 MeV alpha particles, which is independently confirmed by an experiment using alpha particles from an 241Am source. The described method is expected to be useful for research into nuclear reactions in laser plasma.

Investigation of current density, recombination rate and space charge density in polyethylene thin films based on bipolar charge transport model

Bipolar charge transport model has been widely used to simulate the behavior of space charge in polymeric materials. In order to reduce the error of splitting method three-order flux limiter is adopted to solve the advection-reaction equations. The simulation results are compared with the experimental results and simulation results of Le Roy et al, validating the feasibility of the numerical scheme. The recombination rates and charge densities during polarization and depolarization are deeply analyzed for polyethylene at 40 kV mm−1. The effects of electric field on charge transport are also presented. It is found that the net charge density during polarization increases with the increase of the electric field. Negative charges are observed in the vicinity of the cathode, which disagrees with the experimental results.

Lean hydrogen-air premixed flame with heat loss

In this paper results of large-scale experiments and numerical simulations of premixed lean hydrogen-air spherical flame propagation with and without high heat losses are presented. Experiments were carried out in a cylindrical volume of 4.5 m3 covered with thin polyethylene film. The heat loss surface is a 50 mm layer of steel wool. Analysis of heat loss effect on combustion products expansion and flame surface density is done. The combination of these parameters governs the manner in which the flame accelerates. It is shown that the loss of heat released at the combustion can significantly reduce the speed of flame propagation and suppress the acceleration of the flame front. Comparison of experimental results and numerical simulations are presented. The subject and results of the study are of critical importance for the industrial explosion safety and may be applied in the areas of internal combustion engines and detonation suppression devices.

Quality Mapping of Offset Lithographic Printed Antenna Substrates and Electrodes by Millimeter-Wave Imaging

Offset lithographic printed flexible antenna substrate boards and electrodes have attracted much attention recently due to the boost of flexible electronics. Unmanned quality inspection of these printed substrate boards and electrodes demands high-speed, large-scale and nondestructive methods, which is highly desired for manufacturing industries. The work here demonstrates two kinds of millimeter (mm)-wave imaging technologies for the quality (surface uniformity and functionality parameters) inspection of printed silver substrates and electrodes on paper and thin polyethylene film, respectively. One technology is a mm-wave line scanner system and the other is a terahertz-time domain spectroscopy-based charge-coupled device (CCD) imaging system. The former shows the ability of detecting transmitted mm-wave amplitude signals only; its detection is fast in a second time scale and the system shows great potential for the inspection of large-area printed surface uniformity. The latter technology achieves high spatial resolution images of up to hundreds of micrometers at the cost of increased inspection time, in a time scale of tens of seconds. With the exception of absorption rate information, the latter technology offers additional phase information, which can be used to work out 2D permittivity distribution. Moreover, its uniformity is vital for the antenna performance. Additionally, the results demonstrate that compression rolling treatment significantly improves the uniformity of printed silver surfaces and enhances the substrate’s permittivity values.