Polyethylene Terephthalate Membranes Research Articles

Ultra-low concentrations of detection for fluoride and trivalent chromium ions by multiple biomimetic nanochannels in a PET membrane

The development of a detection method for fluoride and chromium (III) ions using a PET membrane with multiple biomimetic nanochannels is descibed. An asymmetric chemical etching technique was used to create conical nanochannels with a PET (polyethylene terephthalate) nuclear track membrane. SEM images showed that the pore diameter of the tip and base sides of the nanochannel were ∼40 nm and ∼180 nm, respectively. The compounds (4-aminophenyl) boronic acid (APBA) and 5-amino-2-nitrobenzoic acid (ANBA), with a specific recognition for F− and Cr3+ respectively, were modified by a conventional method with EDC and NHS. The current-voltage (I–V) curves of the modified PET membranes in response to the target ions at different concentrations were measured with a picoammeter. Excellent linear relationships between the current value of the I–V curve at −2 V and the concentration of Cr3+ and F− were established to obtain standard detection curves for Cr3+ and F−. From these relationships unknown concentrations of Cr3+ and F− can be quantitatively detected, and the results showed that the detection limits of Cr3+ and F− were as low as 4.10 nM and 0.46 nM, respectively. The performance of the novel method was compared to conventional ICP-MS analysis by the determination of Cr3+ in tap water and samples of the Jing Mi diversion canal, and good agreement was found between the two methods. The accuracy and reliability of the method has demonstrated its potential applicability to a wide range of other ionic contaminants.

Latent track PET membranes for high-performance Li+/Mg2+ selectivity assisted with trivalent ion

Selective ionic transport in sub-nanometer pores attracts strong interest. It is still limited by the difficulties in large-scale production of uniform membranes with well-defined sub-nanometer pores. The polymer membranes with latent track are excellent candidate materials. However, the Li+/Mg2+ selectivity in latent track polymer membranes is not high. Herein, we optimize the fabrication process and introduce the trivalent coexisting ions to achieve high selectivity. The polyethylene terephthalate membranes are prepared using the sequential steps of swift heavy ion irradiation, UV illumination, and DMF treatment. The DMF extraction can well control the pore diameters ranging from 2.96 to 5.19 Å as a moderate treatment of membranes. It generates high selectivity in latent track membranes. More interestingly, the ionic transport behavior can be significantly regulated by coexisting ions. By optimizing the experimental conditions, the high selectivity of Li+/Mg2+ of 773 can be achieved in the mixture solutions.

A wound dressing based on a track-etched membrane modified by a biopolymer nanoframe: physicochemical and biological characteristics

Ion track membranes (TMs) are obtained by irradiating thin polymer films, which are usually composed of polycarbonate and polyethylene terephthalate (PET). In medicine and biology, TMs are used for the filtration and separation of molecules and cells in addition to studies of cell migration, intercellular interactions, cell proliferation, and differentiation processes. However, the possibilities and prospects of using TMs as components of wound dressings have not been sufficiently explored. In our study, TMs composed of PET were tested since this material is biocompatible and used in prosthetics and reconstructive surgery. The method of combining TM and electroforming nanofibers, which we used in this study, is relatively new and still requires additional research.Thus, it was found that the main structural elements of the TM surface covered with a biolayer of a mixture of collagen and chitosan are fibers. Coating the TM with a bio-layer preserves its gas and water permeabilities. By varying the fixation method of the biopolymer layer, it is possible to regulate the physicochemical and biological functional properties of the wound dressing. The combination of the high biocompatibility of natural polymers and the stability of synthetic materials can be a successful strategy in manufacturing wound dressings of a new type with specified functional properties. Ion-track PET membranes with applied electrospun fibers from a mixture of chitosan and collagen can be used to produce the wound dressing.Abbreviated title: A wound dressing based on a track-etched membrane.

Etching and Doping of Pores in Polyethylene Terephthalate Analyzed by Ion Transmission Spectroscopy and Nuclear Depth Profiling.

This work is devoted to the study of controlled preparation and filling of pores in polyethylene terephthalate (PET) membranes. A standard wet chemical etching with different protocols (isothermal and isochronous etching for different times and temperatures and etching from one or both sides of the films) was used to prepare the micrometric pores. The pores were filled with either a LiCl solution or boron deposited by magnetron sputtering. Subsequent control of the pore shape and dopant filling was performed using the nuclear methods of ion transmission spectroscopy (ITS) and neutron depth profiling (NDP). It turned out that wet chemical etching, monitored and quantified by ITS, was shown to enable the preparation of the desired simple pore geometry. Furthermore, the effect of dopant filling on the pore shape could be well observed and analyzed by ITS and, for relevant light elements, by NDP, which can determine their depth (and spatial) distribution. In addition, both non-destructive methods were proven to be suitable and effective tools for studying the preparation and filling of pores in thin films. Thus, they can be considered promising for research into nanostructure technologies of thin porous membranes.

Characterization of the surface charge property and porosity of track-etched polymer membranes.

As an important property of porous membranes, the surface charge property determines many ionic behaviors of nanopores, such as ionic conductance and selectivity. Based on the dependence of electric double layers on bulk concentrations, ionic conductance through nanopores at high and low concentrations is governed by the bulk conductance and surface charge density, respectively. Here, through the investigation of ionic conductance inside track-etched single polyethylene terephthalate (PET) nanopores under various concentrations, the surface charge density of PET membranes is extracted as ∼-0.021C/m2 at pH 10 over measurements with 40 PET nanopores. Simulations show that surface roughness can cause underestimation in surface charge density due to the inhibited electroosmotic flow. Then, the averaged pore size and porosity of track-etched multipore PET membranes are characterized by the developed ionic conductance method. Through coupled theoretical predictions in ionic conductance under high and low concentrations, the averaged pore size and porosity of porous membranes can be obtained simultaneously. Our method provides a simple and precise way to characterize the pore size and porosity of multipore membranes, especially for those with sub-100nm pores and low porosities.

Intestinal Permeability of Drugs in Caco-2 Cells Cultured in Microfluidic Devices.

Microfluidic devices are attracting attention for their ability to provide a biomimetic microenvironment wherein cells are arranged in a particular pattern and provided fluidic and mechanical forces. In this study, we evaluated drug transport across Caco-2 cell layers in microfluidic devices and investigated the effects of fluid flow on drug transport and metabolism. We designed a microfluidic device that comprises two blocks of polydimethylsiloxane and a sandwiched polyethylene terephthalate membrane with pores 3.0 µm in diameter. When cultured in a dynamic fluid environment, Caco-2 cells were multilayered and developed microvilli on the surface as compared with a static environment. Drugs with higher lipophilicity exhibited higher permeability across the Caco-2 layers, as well as in the conventional method using Transwells, and the fluidic conditions had little effect on permeability. In the Caco-2 cell layers cultured in Transwells and microfluidic devices, the basal-to-apical transport of rhodamine 123, a substrate of P-glycoprotein, was greater than the apical-to-basal transport, and the presence of tariquidar, an inhibitor of P-glycoprotein, completely diminished asymmetric transport. Furthermore, fluidic conditions promoted the metabolism of temocapril by carboxylesterases. On the other hand, we showed that fluidic conditions have little effect on gene expression of several transporters and metabolic enzymes. These results provide useful information regarding the application of microfluidic devices in drug transport and metabolism studies.

Primary and secondary resonance responses of fractional viscoelastic PET membranes

This paper considers nonlinear vibration of fractional viscoelastic Polyethylene Terephthalate (PET) membranes subjected to external excitation. Particular attention has been paid to the effects of parameters associated with the fractional model on the primary and secondary resonance responses. Here, the fractional Kelvin–Voigt constitutive relation is adopted to describe the viscoelastic material. Based on von-Karman theory and Newton’s second law, the governing equation is derived. The Galerkin technique is utilized to discretize the nonlinear equation of motion. The multiple-scale method is employed to assess the forced responses of the membrane system under external excitation. Numerical results reveal that the fractional viscoelastic model strongly affects the resonance response of membranes. In this regard, these results offer insight into further study on the vibration characteristics of fractional viscoelastic membranes and also determine the stable operating regions of the moving system to avoid divergent instability in the fabrication of flexible electronics.

Interrogation on the Cellular Nano-Interface and Biosafety of Repeated Nano-Electroporation by Nanostraw System.

Cell perforation is a critical step for intracellular drug delivery and real-time biosensing of intracellular signals. In recent years, the nanostraws system has been developed to achieve intracellular drug delivery with minimal invasiveness to the cells. Repeated cell perforation via nano-system could allow delivery of multiple drugs into cells for cell editing, but the biosafety is rarely explored. In this work, a nanostraw-mediated nano-electroporation system was developed, which allowed repeated perforation of the same set of cells in a minimally invasive manner, while the biosafety aspect of this system was investigated. Highly controllable fabrication of Al2O3 nanostraw arrays based on a porous polyethylene terephthalate (PET) membrane was integrated with a microfluidic device to construct the nanostraw-electroporation system. The pulse conditions and intervals of nano-electroporation were systematically optimized to achieve efficient cells perforation and maintain the viability of the cells. The cells proliferation, the early apoptosis activities after nanostraw-electroporation and the changes of gene functions and gene pathways of cells after repeated nano-electroporation were comprehensively analyzed. These results revealed that the repeated nanostraw-electroporation did not induce obvious negative effects on the cells. This work demonstrates the feasibility of repeated nano-electroporation on cells and provides a promising strategy for future biomedical applications.

(Invited) Graphene Oxide-Based Membranes: Viscoelastic Properties and Application to Broadband Microspeakers

Graphene and graphene derivatives have attracted attention as materials for acoustic transduction [1-3]. Graphene oxide (GO) membranes and borate cross-linked graphene oxide (X-GO) membranes combine high stiffness, low mass density, and high loss coefficient. We show [4] that these mechanical properties are ideal for efficient, broadband, electro-acoustic transduction, where the acoustic diaphragm should be light, stiff, and internally damped. We present a quantitative comparison of the figure of merit, (E/ρ 3)1/2, where E is Young's modulus and ρ is the mass density, and the material performance index, tan δ (E/ρ 3)1/2, where tan δ is the loss coefficient. GO and X-GO exhibit high figures of merit, comparable to that of wood and exceeding that of aluminum and thermoplastics. The material performance indices of GO and X-GO exceed that of wood, thermoplastics, and aluminum. The latter are common diaphragm materials in acoustic transducers.For acoustic applications, it is important to understand the frequency dependent viscoelastic response. The complex modulus G = G' + iG'' of GO and X-GO membranes was measured by dynamic mechanical analysis and analyzed by the application of the time-temperature superposition (TTS) principle of polymer rheology. We find that X-GO shows a more than 30% increase in storage modulus G’ over the frequency range of 1 to 10 kHz, exceeding 55 GPa at 10 kHz. There is a reduction in loss coefficient tan δ = G''/G' for X-GO of ≈30% over the same frequency range, reaching tan δ = 0.04 at 10 kHz, which is approximately one order of magnitude larger than that of aluminum.A quantitative comparison of microspeaker performance was conducted at a fixed diaphragm mass m = 15-20 g and 14 mm x 8 mm size, including GO, X-GO, oak wood, polyethylene terephthalate (PET), aluminum, and titanium. Scanning laser measurements confirm pistonic operation of X-GO membranes. Microspeaker sound pressure level response was measured in both time and frequency domains. X-GO diaphragms exhibit 45% higher damping than aluminum membranes in microspeaker assemblies. Consequently, X-GO membranes enable the upshift of loudspeaker breakup frequency by 1/6 to 1/2 octave above speakers assembled with oak wood, PET, aluminum and titanium membranes. GO based materials are thus found to be an exceptional material for electro-acoustic transduction.

Universal Printing Technique of Polydopamine onto Versatile Surfaces for High‐Resolution Cell Patterning Using Wet Elastomeric Stamp

AbstractIn this study, a robust and universally applicable polydopamine (PDA) contact‐printing technique is demonstrated on versatile substrates such as glass, polyethylene terephthalate, poly(methyl methacrylate), polystyrene, polycarbonate, copper, and nitrocellulose membrane in a simple and facile manner using a wet elastomeric stamp. Evaporation of the hydration layer on the wet stamp while in contact with substrates substantially increases the patterning efficiency even without placing any weight on the stamp. The hydration layer possibly assists in reducing the mechanical stress caused during the handling of the stamp and enhances the conformal contact between the stamp and the substrate upon drying. The PDA patterning efficiency is approximately fivefold higher compared to using a dry stamp when patterned on polystyrene, and a large‐scale PDA stamping of over 8.5 cm diameter is also achieved. Water contact angle measurements and Fourier‐transform infrared spectroscopy (FTIR) analyses confirms the successful transfer of PDA onto various surfaces. PDA patterns created on the polystyrene are used to culture endothelial cells to evaluate spatially‐defined cell spreading along the defined geometries. The simple procedure and versatility of the substrates used make the introduced strategy highly suitable for creating large‐scale cell micropatterning platforms and possess great potential for manufacturing antibody‐immobilized lateral flow rapid diagnostic kits, without requiring expensive equipment.

A High-Performance Flag-Type Triboelectric Nanogenerator for Scavenging Wind Energy toward Self-Powered IoTs.

Pervasive and continuous energy solutions are highly desired in the era of the Internet of Things for powering wide-range distributed devices/sensors. Wind energy has been widely regarded as an ideal energy source for distributed devices/sensors due to the advantages of being sustainable and renewable. Herein, we propose a high-performance flag-type triboelectric nanogenerator (HF-TENG) to efficiently harvest widely distributed and highly available wind energy. The HF-TENG is composed of one piece of polytetrafluoroethylene (PTFE) membrane and two carbon-coated polyethylene terephthalate (PET) membranes with their edges sealed up. Two ingenious internal-structure designs significantly improve the output performance. One is to place the supporting sponge strips between the PTFE and the carbon electrodes, and the other is to divide the PTFE into multiple pieces to obtain a multi-degree of freedom. Both methods can improve the degree of contact and separation between the two triboelectric materials while working. When the pair number of supporting sponge strips is two and the degree of freedom is five, the maximum voltage and current of HF-TENG can reach 78 V and 7.5 μA, respectively, which are both four times that of the untreated flag-type TENG. Additionally, the HF-TENG was demonstrated to power the LEDs, capacitors, and temperature sensors. The reported HF-TENG significantly promotes the utilization of the ambient wind energy and sheds some light on providing a pervasive and sustainable energy solution to the distributed devices/sensors in the era of the Internet of Things.

Fabrication of double conical PET nanochannel for molecular detection

Polymer nanochannels based on ion-track etching have attracted increasing interests for molecule detection using current blockage because of the easy control of nanochannel with precise geometry at 1 nm scale in recent years. In this work, polyethylene terephthalate (PET) membranes were irradiated with single ions of 2.15 GeV Kr and then the single latent ion track was developed to fabricate nanochannels of several nanometers for lambda-DNA detection. The ion-track etching with DC or AC provided reliable fabrication of double conical nanochannel with similar size of 48 kb λDNA with symmetrical ion transportation. Current blockage experiments demonstrated that the bi-conical PET nanochannel is sensitive for the translocation of 48 kb λDNA biomolecules with the mean translocation blockage factor Δi/i from 0.02 to 0.10 and the ability to differentiate the number of molecules. The nanochannel is more sensitive for biomolecule detection at lower KCl concentration. This investigation demonstrates that latent track etching of energetic heavy ions is a reliable approach in polymer nanochannel fabrication for biomolecule detection with accurate nanoscale control and low-cost mass production.

A simple electrochemical immunosensor based on a gold nanoparticle monolayer electrode for neutrophil gelatinase-associated lipocalin detection

An electrochemical immunosensor for the accurate detection of cat neutrophil gelatinase-associated lipocalin (NGAL) in urine samples based on an electrode with a monolayer of gold nanoparticles (AuNPs) was proposed in this study. To fabricate the sensing electrode, a nickel mold with concave micron hemisphere array was prepared and then used to transfer the micron hemispherical structure onto a polyethylene terephthalate (PET) film using the hot embossing technique. A gold thin film was sputtered onto the micron hemispherical structure array, after which 1,6-hexanedithol and AuNPs were uniformly deposited on the PET membrane to form a sensing electrode. The NGAL concentrations were measured by electrochemical impedance spectroscopy after attaching the anti-NGAL. Results revealed that the proposed sensing scheme exhibited a wide dynamic detection range from 1 to 100 ng/mL, which is far enough to distinguish the healthy (NGAL concentration <10 ng/mL) from the damaged kidney. A low limit of detection and high sensitivity of 0.47 ng/mL and 10261.8 Ω ng−1mL, respectively, were also measured. After performing real sample detection using urine samples from cats collected at a veterinary hospital, the results confirmed that the proposed NGAL detection approach in this research could accurately detect the concentration of NGAL in cat urine samples.

Fabrication of ZnO/y-FeOOH nanoparticles embedded on the polyethylene terephthalate membrane: Evaluation of antifouling behavior and COD removal.

Nanofiltration contributes to the development of advanced treatment of wastewater. An antifouling mixed matrix recycled polyethylene terephthalate (rPET) membrane modified by the hydrophilic ZnO/y-FeOOH nanoparticles (NPs) was fabricated via the electrospinning method. The effect of ZnO/y-FeOOH NPS embedded in rPET as a modifier on the fabrication of nanocomposite membranes was investigated regarding water flux, membrane morphology, permeability, fouling resistance, and COD removal. The surface morphology of the rPET-ZnO/y-FeOOH membrane was evaluated by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), water contact angle (WCA), and porosity and pore structure.Due to the embedding of NPs, the resulting rPET-ZnO/y-FeOOH membrane, with a low WCA of 53.404° angle, conforms significantly improved hydrophilicity and water permeation flux. The FESEM image displayed the distribution of cuboidal and needle-like ZnO and FeOOH NPs on the rPET membrane. The performance of the nanofiltration system related to the removal efficiency of COD was studied. It was deduced that the rPET-ZnO/y-FeOOH membrane had a superior COD removal capability (95.7%) at a pressure of 2 bar. Protein rejection tests were performed on antifouling behavior. The nanocomposite membrane with a high antifouling capability was related to 0.5 wt·% ZnO/y-FeOOH NPs (flux recovery ratio [FRR] = 96.2%, Rr = 90.21%, and Rir = 3.001%). The modification procedure in this study (as a great improving technique) was proposed to fabricate the antifouling nanofiltration membrane.

Surface characterization of polyimide and polyethylene terephthalate membranes toward plasma and UV treatments

This study is to bring an overview on various methods regarding the surface treatment performed on different polymeric membranes in relation to a deference between the treatment mechanism and their chemical structure. Herein, plasma and UV surface treatments (PST and UST) were utilized to treat the surfaces of two commercial membranes, i.e., aromatic polyimide and polyethylene terephthalate for various durations using a discharge electrode and an UV LED curing system, respectively. Based on the effects of PST and UST processes on the surface of these membranes, their surface properties have been characterized to surface morphology and hydrophilicity (or wettability), at same time the changes have probably occurred on their surface during the PST and UST processes. As a result, their hydrophilic behavior was significantly enhanced after conducting these treatment processes based on the investigation of water contact angle. Moreover, Fourier-transform infrared and Raman spectroscopy manifested the changes in the chemical bonds, interactions and orientations of molecules, which confirmed the apparition and insertion of polar functional groups after the surface treatments, and accordingly, their wettability was enhanced significantly. Also, optical microscopy images showed direct impactions on their surface and the evidence of slight surface aging/damage during the treatment processes based on the presentation of the strange streaks on the treated surfaces. In particular, the peel forces exhibited an increase comparing to the initial membranes, which is characteristically for enhancing their adhesion behavior. Hence, these results are needful for improving the surface properties of a material, and obtaining better adhesion behavior on the membrane-like materials and recycling polymer materials.

Porous Polyethylene Terephthalate Nanotemplate Electrodes for Sensitive Intracellular Recording of Action Potentials.

New strategies for intracellular electrophysiology break the spatiotemporal limitation of the action potential and lead a notable advance in the investigation of electrically excitable cells and their network. Although successful applications of intracellular recording have been achieved by 3D micro/nanodevices, complex micro/nanofabrication processes preclude the progress of extensive applications. We address this challenge by introducing porous polyethylene terephthalate (PET) membrane to develop a new type of nanotemplate electrode. This nanotemplate electrode is manufactured following a fabrication process on a porous PET membrane by atomic layer deposition. The 3D nanotemplate electrodes afford intracellular access to cardiomyocytes to report intracellular-like action potentials. These controllable nanotemplate electrodes exhibit sensitive and prolonged intracellular recordings of action potentials compared with free-growing 3D nanoelectrodes. This study indicates that the optimized structure of the nanoelectrode significantly promotes the performance of intracellular recording to assess electrophysiology in the fields of cardiology and neuroscience at an action potential level.

Estimation of the nano-pores diameter by conductometric measurements

s. Ionic transport properties and diameter of asymmetric conical nano-pores in polyethylene terephthalate membranes were calculated. These nano-pores were synthesized by chemical etching method in irradiated polyethylene terephthalate (PET) films. After etching, the transport characteristics weredocumented under stepping voltage with 2M ionic concentrations of Potassium halides i.e. KCl, KBr and KI. The symmetric bathing condition (same temperature and same pH value solution in both side of chamber) in electrochemical cell were accomplished. It is investigated that diameter of nano-pores is also evaluate by measuring the current rectification properties of track etched nano-pores.

An Array of Flag-Type Triboelectric Nanogenerators for Harvesting Wind Energy.

Harvesting wind energy from the ambient environment is a feasible method for powering wireless sensors and wireless transmission equipment. Triboelectric nanogenerators (TENGs) have proven to be a stable and promising technology for harvesting ambient wind energy. This study explores a new method for the performance enhancement and practical application of TENGs. An array of flag-type triboelectric nanogenerators (F-TENGs) for harvesting wind energy is proposed. An F-TENG consists of one piece of polytetrafluoroethylene (PTFE) membrane, which has two carbon-coated polyethylene terephthalate (PET) membranes on either side with their edges sealed. The PTFE was pre-ground to increase the initial charge on the surface and to enhance the effective contact area by improving the surface roughness, thus achieving a significant improvement in the output performance. The vertical and horizontal arrays of F-TENGs significantly improved the power output performance. The optimal power output performance was achieved when the vertical parallel distance was approximately 4D/15 (see the main text for the meaning of D), and the horizontal parallel distance was approximately 2D. We found that the peak output voltage and current of a single flag-type TENG of constant size were increased by 255% and 344%, respectively, reaching values of 64 V and 8 μA, respectively.

Electron Transport Mechanisms in Polyethylene Terephthalate Membranes

This paper describes carrier transport mechanisms in polyethylene terephthalate (PET) films and porous PET-based membranes (PMs) obtained by irradiating pristine PET film with swift heavy ions, with subsequent chemical etching in an alkali (NaOH) solution. The obtained PMs had through nanochannels (pores) with an average diameter of 720-750 nm. We observed that in the temperature range 240-300 K, the current-voltage characteristics I(V) of the initial Cu|PET|Cu structure obeyed the improved Mott--Gurney law, which is based on the Mark--Helfrich model for a space-charge-limited current (SCLC) mechanism for electron transport. It was found for the first time that creation of nanochannels in PMs resulted in a significant increase in the electric current density (by about three orders of magnitude) while maintaining the SCLC mechanism. The enhanced current density is explained by the formation of a highly conductive layer along the inner surface of the walls of the nanochannel that are covered with carboxyl end groups, which are created by alkaline hydrolysis. According to the model, the surface states formed by these groups enable the drift of additional electrons injected from the copper electrodes under the action of the bias voltage. Keywords: polyethylene terephthalate, electron transport, space-charge-limited current mechanism, Mark--Helfrich injection model.

Dual-frequency electrically driven nematic microstructures confined to biaxial porous polymer membranes

We report the study of internal ordering and electro-optical response of dual-frequency nematic liquid crystals (DFNLCs) confined to microporous polyethylene terephthalate (PET) membranes. The DFNLCs are characterized by positive/negative signs of dielectric anisotropy in low/high-frequency electric fields E. Microscopic observations assisted by numerical simulations identified the escaped radial (ER) configurations of the nematic director field within the porous membrane for E = 0. Low/high-frequency electric fields were applied to the PET-DFNLC membrane to manipulate the internal nematic configuration. We found that the low/high-frequency electric fields transform the ER structure to the quasi axial/planar radial, resulting in the suppressed/increased propagation of near-infrared electromagnetic radiation through the composite material. The results are discussed for photonic applications.