Polyethylene Terephthalate Membranes Research Articles

In English

The plasma-chemical method of track-etched polyethylene terephtalate membranes’ surface modification by monomers with different chemical structure was developed. Physicochemical properties of modified membranes were investigated. The authors showed the possibility of obtaining membranes with the required properties.

Comparison of culture media indicates a role for autologous serum in enhancing phenotypic preservation of rabbit limbal stem cells in explant culture.

In this study, we aimed to compare the effects of six different cell culture media and autologous serum (AS) on the phenotypic characteristics of rabbit limbal epithelial stem cells (LESC) cultivated on porous polyethylene terephthalate (PET) membranes. Limbal explants from rabbit corneas were grown on PET membrane inserts in five different media: DMEM-F12 with fetal bovine serum (FBS) (DMEM-F12-FBS), with pluripotin (DMEM-F12-pluripotin) and with autologous serum (DMEM-F12-AS), Epilife, Keratinocyte Serum Free Medium (KSFM) and Defined-Keratinocyte Serum Free Medium. The effects of different media were evaluated by total cell yield from explants, measuring the expression of proteins by immunofluorescence and gene expression by Real Time PCR. In all five media tested, most of the limbal epithelial cells (LEC) which proliferated from explants were positive for cytokeratin (CK) 14 (85-90%), indicating that all five media support the growth of LESC from explants. The expression of differentiation markers; CK 3 and 12 was highest in DMEM-F12-FBS (56%), was lower in Epilife and KSFM (26 and 19%, respectively), with the lowest values (13%) obtained in DMEM-F12-AS. Gene expression of limbal cultures on PET membrane inserts was compared to fresh limbal tissue. In DMEM-F12-FBS, DMEM-F12-pluripotin, and DMEM-F12-AS, expression of potential LESC markers CXCR4 and polycomb complex protein BMI-1 were similar to limbal tissue. DMEM-F12 with 10% AS maintained a higher percentage of potential stem cell marker genes and lower expression of genes involved in differentiation compared to Epilife or KSFM. Our study shows that rabbit LEC can be cultivated on PET inserts using DMEM-F12 with autologous serum without a requirement for amniotic membrane or feeder cells.

Modification of Track-Etched PET Membranes by Graft Copolymerization of Acrylic Acid and N-Vinylimidazole

Photoinduced graft polymerization of N-vinylimidazole (VI) and graft copolymerization of N-vinylimidazole with acrylic acid (AA) onto track-etched polyethylene terephthalate membranes (PET TeMs) with a pore diameter of 450 ± 15 nm have been systematically studied. The effect of different parameters, such as irradiation time, monomer concentration, and solvent nature, has been examined. The samples have been characterized using the instrumental techniques of FTIR and XPS spectroscopies, thermogravimetry, and scanning electron microscopy. The copolymer composition has been determined spectrophotometrically using the Toluidine Blue and Acid Orange dyes. Optimal conditions of AA and VI copolymerization have been found. It has been shown that the surface of modified PET TeMs is reach in functional groups which makes them a promising material for the development of nanosensors and nanocatalysts.

Selective deposition of Pd nanoparticles in porous PET membrane for hydrogen separation

Hydrogen purification based on Pd deposition in porous polymeric membranes show promising results for hydrogen permeability and selectivity. It is due to high absorption property of Pd nanoparticles. In this work, gas permeability of carboxylic group functionalized Polyethylene terephthalate (PET) membranes with different time of functionalization have been examined. It has been found that PET membrane having more –COOH group shows higher selectivity for Hydrogen (H2). Further to improve the selectivity, these carboxylated PET membranes dipped in Pd nanoparticles solution for 6 h and found more selective for H2 in comparison to Carbon dioxide (CO2) and Nitrogen (N2). As the carboxylation increases selectivity of H2 improves drastically in the beginning and nearly get saturated after 24 h. Similar trend has been observed for these membranes after Pd nanoparticles deposition. Fourier transform infrared spectroscopy (FTIR) spectra of these membranes revealed that intensity of peaks related to –COOH group at 2968 cm−1 & 1716 cm−1 increases with functionalization time. Field Emission Scanning Electron Microscopy (FESEM) was used to study the surface morphology of membranes.

Automatically Turn-Off EOF Pump Based on Conical Nanopores with Lead Sensor

Electroosmotic flow (EOF) is an electrokinetic phenomenon that occurs when an ionic current is passed through a channel or porous material that contains excess surface charge. We have found that net flow through a conical-pore membrane can be achieved by applying a symmetrical sinusoidal voltage waveform across the membrane. This is possible because the alternating current (AC) carried by ions through the nanopore is rectified. Here, the EOF pump based on polyethylene terephthalate (PET) membranes were modified with 18-crown-6 to selectively pump solution without lead ions. As more lead ions bound with 18-crown-6 on the surface, the surface charge was more neutral. Thus, the electroosmotic flow was less rectified. Finally, the net flow was zero meaning the pump was turned off if the lead concentration is high enough. The flow rate of EOF pump in a series of lead ions aqueous solution was investigated. We also reported the selectivity of this EOF pump in the aqueous solution with different metal ions.

Phase Demodulation of Short-Cavity Fabry–Perot Interferometric Acoustic Sensors With Two Wavelengths

A phase interrogation method for a fiber-optic acoustic sensor based on a short-cavity extrinsic Fabry–Perot interferometer (EFPI) is proposed with two wavelengths. A multichannel tunable optical filter is employed, which selects out two monochromatic beams from the broadband interference spectrum of EFPI with fixed wavelength interval. The influence of the wavelength interval on the recovery of the phase signal has been theoretically and experimentally analyzed. To get the best sensitivity, the wavelength interval is fixed at one quarter of the period of sensor interference fringes. An optimized differential cross multiplication algorithm is utilized to demodulate the acoustic signal, which can eliminate the impact of optical power imbalance between the two light paths. This system may be a universal phase demodulation unit for short-cavity EFPI acoustic sensors. The EFPI acoustic sensing head is formed by an aluminum-attached polyethylene terephthalate membrane and a cleaved fiber tip. The sensor interrogated by the proposed demodulation system demonstrated large dynamic range in low-frequency domain under high sound pressure. A signal-to-noise ratio (SNR) of ∼53 dB is obtained at 80 Hz. These features make the sensor especially suitable for noise detection.

Ultrathin Alumina Membranes as Scaffold for Epithelial Cell Culture from the Intestine of Rainbow Trout.

Permeable membranes are indispensable for in vitro epithelial barrier models. However, currently available polymer-based membranes are low in porosity and relatively thick, resulting in a limited permeability and unrealistic culture conditions. In this study, we developed an ultrathin, nanoporous alumina membrane as novel cell culture interface for vertebrate cells, with focus on the rainbow trout (Onchorynchus mykiss) intestinal cell line RTgutGC. The new type of membrane is framed in a silicon chip for physical support and has a thickness of only 1 μm, with a porosity of 15% and homogeneous nanopores (Ø = 73 ± 21 nm). Permeability rates for small molecules, namely lucifer yellow, dextran 40, and bovine serum albumin, exceeded those of standard polyethylene terephthalate (PET) membranes by up to 27 fold. With the final goal to establish a representative model of the fish intestine for environmental toxicology, we engineered a simple culture setup, capable of testing the cellular response toward chemical exposure. Herein, cells were cultured in a monolayer on the alumina membranes and formed a polarized epithelium with apical expression of the tight junction protein ZO-1 within 14 days. Impedance spectroscopy, a noninvasive and real time electrical measurement, was used to determine cellular resistance during epithelial layer formation and chemical exposure to evaluate barrier functionality. Resistance values during epithelial development revealed different stages of epithelial maturity and were comparable with the in vivo situation. During chemical exposure, cellular resistance changed immediately when barrier tightness or cell viability was affected. Thus, our study demonstrates nanoporous alumina membranes as promising novel interface for alternative in vitro approaches, capable of allowing cell culture in a physiologically realistic manner and enabling high quality microscopy and sensitive measurement of cellular resistance.

Tympanic membrane organ culture using cell culture well inserts engrafted with tympanic membrane tissue explants.

Tissue engineering approaches using growth factors and various materials for repairing chronic perforations of the tympanic membrane are being developed, but there are surprisingly few relevant tissue culture models available to test new treatments. Here, we present a simple three-dimensional model system based on micro-dissecting the rat tympanic membrane umbo and grafting it into the membrane of a cell culture well insert. Cell outgrowth from the graft produced sufficient cells to populate a membrane of similar surface area to the human tympanic membrane within 2 weeks. Tissue grafts from the annulus region also showed cell outgrowth but were not as productive. The umbo organoid supported substantial cell proliferation and migration under the influence of keratinocyte growth medium. Cells from umbo grafts were enzymatically harvested from the polyethylene terephthalate (PET) membrane for expansion in routine culture and cells could be harvested consecutively from the same graft over multiple cycles. We used harvested cells to test cell migration properties and to engraft a porous silk scaffold material as proof-of-principle for tissue engineering applications. This model is simple enough to be widely adopted for tympanic membrane regeneration studies and has promise as a tissue-equivalent model alternative to animal testing.

METALLIC NICKEL (Ni) NANOTUBES: INFLUENCE OF DEPOSITION PARAMETERS ON THEIRS STRUCTURE AND MAGNETIC PROPERTIES

The arrays of Ni nanotubes have been synthesized in pores of polyethylene terephthalate membranes by electrochemical method. Morphological and structural characteristics were studied by scanning electron microscopy, gas permeability, energy-dispersive X-ray spectroscopy and X-ray diffraction analysis. It was shown that Ni nanotubes have lateral dimensions corresponding to the membranes pores parameters (length ~12 μm and pores diameters 400 nm) with the tubes walls thickness in the range from 60 nm to 160 nm, depending on the deposition conditions. Ni nanotubes have the face-centered cubic lattice phase. The dependence of crystal structure parameters on temperature and voltage of synthesis was established. Dependences of main magnetic parameters (coercivity value and magnetization of saturation and squatness) on deposition parameters were studied. Significant magnetic anisotropy was found, but any evident influence of deposition parameters on magnetic properties was not found.

Intensity Demodulation Based Fiber Sensor for Dynamic Measurement of Acoustic Wave and Lateral Pressure Simultaneously

In this paper, we propose an intensity demodulation based fiber sensor for dual-parameters sensing of acoustic wave and lateral pressure. The sensor consists of a long period fiber grating (LPFG) inserted into a Sagnac interferometer (SI). The LPFG is kept straight and fixed on a polyethylene terephthalate membrane for acoustic detection. A tunable laser source (TLS) is utilized to illuminate the sensor. The acoustic wave will produce a time-varying intensity signal that consists of an alternating current (ac) component and a direct current (dc) component. The ac component contains the acoustic information, while the dc level is determined by the transmittance of the sensor in the static condition (without acoustic signal applied on the sensor). Since the lateral pressure induced wavelength shift of the SI will change the transmittance at the TLS wavelength, the dc level varies with different lateral pressure applied on the sensor. Therefore, the acoustic wave and lateral pressure can be demodulated, respectively, by monitoring the ac component and dc level in the output signal. In the experiment, output time-domain signals with 500 Hz ac components and different dc values are acquired when 500 Hz acoustic wave and different lateral pressure is applied on the sensor.

Selective Separation of Metal Ions via Monolayer Nanoporous Graphene with Carboxyl Groups.

Graphene-coated plastic substrates, such as polyethylene terephthalate (PET), are regularly used in flexible electronic devices. Here we demonstrate a new application of the graphene-coated nanoporous PET membrane for the selective separation of metal ions in an ion exchange manner. Irradiation with swift heavy ions is used to perforate graphene and PET substrate. This process could create graphene nanopores with carboxyl groups, thus forming conical holes in the PET after chemical etching to support graphene nanopores. Therefore, a monolayer nanoporous graphene membrane with a PET substrate is constructed successfully to investigate its ionic selective separation. We find that the permeation ratio of ions strongly depends on the temperature and H+ concentration in the driving solution. An electric field can increase the permeation ratio of ions through the graphene nanopores, but it inhibits the ion selective separation. Moreover, the structure of the graphene nanopore with carboxyl groups is resolved at the density functional theory level. The results show the asymmetric structure of the nanopore with carboxyl groups, and the analysis indicates that the ionic permeation can be attributed to the ion exchange between metal ions and protons on the two sides of graphene nanopores. These results would be beneficial to the design of membrane separation materials made from graphene with efficient online and offline bulk separation.

Localized Heat Generation from Magnetically Responsive Membranes

Commercial thin film composite nanofiltration NF270 and microfiltration polyethylene terephthalate (PET) track-etched membranes were modified by grafting thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) polymers via surface initiated atom transfer radical polymerization (ATRP). The polymer chain ends were conjugated with superparamagnetic (Fe3O4) nanoparticles. Each tailored superparamagnetic nanoparticle acts as a nanoheater under an external oscillating magnetic field. The localized heat generated induces the lower critical solution temperature (LCST) transition for the PNIPAM in aqueous solution. The phase transition of the polymer leads to the alteration of membrane transport properties. Localized heating affects membrane permeability differently for NF270 and PET membranes based on whether the modification occurs on the membrane surfaces or inside the membrane pores. Filtration of polystyrene latex particles through PET membranes demonstrates that it is possible to modulate the pore size by appl...

Structure and phase composition of thin TiO2 films grown on the surface of metallized track-etched polyethylene terephthalate membranes by reactive magnetron sputtering

We have studied TiO2, Ag, Ag/TiO2, and Cu/TiO2 coatings grown on track-etched polyethylene terephthalate membranes. The metals and oxides were deposited by reactive vacuum sputtering using a planar magnetron. The microstructure of the samples were examined by scanning and transmission electron microscopy techniques. The elemental composition of the coatings were determined by energy dispersive X-ray microanalysis, and their phase composition was determined by X-ray diffraction at different temperatures and by transmission electron diffraction. Titanium dioxide can be present on the surface of track-etched membranes (TMs) in three forms: nanocrystals of tetragonal anatase with orthorhombic brookite and amorphous TiO2 impurities. The copper-metallized TM has been shown to contain cubic Cu2O. The optical properties of the composite membranes and films have been studied by absorption spectroscopy. The energies of direct and indirect allowed optical transitions have been evaluated from measured absorption spectra of the TiO2, Ag/TiO2, and Cu/TiO2 coatings.

Fe – нанотрубки: синтез, структурные и магнитные свойства

The article presents results of investigations of hollow Fe nanotubes obtained by electrochemical deposition into the pores of polyethylene terephthalate membranes. Morphological and structural parameters of the synthesized samples of nanotubes were studied by methods of scanning electron microscopy, X-ray and energy dispersive analysis. The investigations of the magnetic properties of nanotubes were provided by Mossbauer and vibration magnetometer methods. Macro- and micromagnetic parameters of nanotubes were determined. X-ray analysis showed that walls of nanotubes have a BCC structure with non- preferred direction and the crystal lattice parameter a = 2.8627 A. Due to defects formation in the process of electrochemical deposition, the deformation of crystal lattices occurs at crystallites interfaces. It was also found that walls of nanotubes were formed by separate crystallites settled layer by layer. Based on the analysis of the study of dependence of the magnetization on magnetic field, it was found that the basic magnetic characteristics of arrays of Fe nanotubes decreased monotonously in the temperature range from 100 to 300 K.

Capillary pore membranes with grafted diblock copolymers showing reversibly changing ultrafiltration properties with independent response to ions and temperature

Track-etched polyethylene terephthalate membranes with a pore size of 110nm have been modified by a grafted diblock copolymer structure in order to obtain dual-responsive ultrafiltration membranes. The temperature-responsive poly-N-isopropylacrylamide (PNIPAAm) and the ion-responsive poly-N,N-dimethyl-N-methacryloyloxyethyl-N-(3-sulfopropyl) ammonium betaine (PSPE) were grafted from the pore walls by sequential surface-initiated atom transfer radical polymerization. To achieve a well controlled pore functionalization, the polymerization rate had been adjusted to a very slow chain growth. A successful grafting of PSPE as first block and of PNIPAAm as second block could be demonstrated. To study the temperature and ion responsivity, hydraulic permeability and dextran diffusion experiments at 25°C and 40°C with different salt solutions had been carried out. It could be shown that such membranes can change their barrier pore size from a more open to a more closed state in dependency of temperature as well as kind of ions and their concentration in the feed. The grafted layer thickness showed a particularly strong increase in the presence of KClO4. Like expected for a well defined polymer brush, an expanded or collapsed state for each of the individual blocks could be obtained. In presence of KClO4 at 25°C both blocks are expanded and the pores are in a more closed state. If one of these stimuli is changed, for example when temperature is increased to 40°C or ions are removed, the block copolymer brushes collapse partially what leads to more open pores. However, if both stimuli are applied together, i.e. if temperature is 40°C and no ions are in solution, diblock copolymers collapse fully what leads to fully opened pores. It had also been demonstrated that this dual responsivity and the magnitude of the effects depend very strongly on the absolute degree of grafting and the ratio between the two different responsive polymer blocks. Furthermore, the ability of changing effective membrane barrier pore size by ions and temperature has been investigated in more detail by dextran diffusion experiments, and very pronounced and reversible changes of molecular sieving curve and molecular weight cut-off could be obtained.

Study on preparation and surface hydrophility of polyethylene terephthalate (PET) membrane via blending graphene oxide and grafting of nano-silica particles

Polyethylene terephthalate (PET) is one kind of widely used engineering plastics, but its hydrophobic surface hinders the further application in some engineering fields. In this paper, the PET membrane with high hydrophilic surface has been prepared by blending graphene oxide (GO) and then grafting nano-silica. The surface properties of modified PET and pristine PET were also characterised by contact angle measurement and atomic force probe microscopy (AFM). Contact angle measurement results show that surface wetting contact angle of the modified PET membrane is only 14.7°. In protein fouling test, bovine serum albumin (BSA) was used as a protein model solution. Modified membranes exhibited good anti-fouling properties in reducing the irreversible membrane fouling.

A Low-Cost Accelerometer Developed by Inkjet Printing Technology

In this paper, an inkjet-printed sensor in the mesoscale is presented with the aim to investigate its behavior as an accelerometer in the low-frequency domain (up to 20 Hz), which properly fits with the need of typical applications in the field of human and seismic monitoring. The accelerometer consists of a Polyethylene terephthalate membrane clamped by four spring legs to a fixed support. The sensing readout strategy is implemented through four strain gauges directly printed onto the flexible substrate. The advantages of the approach proposed are mainly related to the adopted low-cost direct printing technology, which allows for the realization of cheap and customizable devices. The sensor behavior has been deeply investigated. The device responsivity and resolution are 9.4 mV/g and 0.126 g, respectively, at 10 Hz, and 41.0 mV/g and 0.003 g, respectively, at 35 Hz. The performances obtained encourage the development of the all-inkjet-printed sensor proposed, especially taking into account its low cost and disposable features.

Permeation control in hydrogel-layered patterned PET membranes with defined switchable pore geometry – Experiments and numerical simulation

Permeation through polymeric membranes can be controlled by surface coating of a polyethylene terephthalate (PET) membrane with poly(N-isopropylacrylamide) (PNIPAAm) and inserting pores of defined geometry. When the temperature of the system rises above the volume phase transition temperature, the pores open, which allows permeation of formerly blocked particles. The exact control of the temperature allows defined change of the pore size and therefore enables separation abilities. Free swelling experiments are conducted to obtain the swelling behaviour of PNIPAAm. Then, a temperature expansion model is derived in order to simulate this behaviour with the finite element tool ABAQUS. The gained results are in excellent agreement with the observed shape change. Membranes with permeation control of particles can be used for biomedical application in microfluidics to analyse the size distribution of cells or in chemical information processing as a transistor-like component for an information-bearing chemical species. The possibility to simulate the behaviour of such permeation systems allows computer aided design and prediction of permeation abilities in these areas.

Electrical impedance spectroscopy of a PET chip sandwiched between two disk electrodes: understanding the contribution of the polymer/electrode interface.

This work is devoted to the understanding of the dielectric impedance response of a semi-crystalline polyethylene terephthalate (PET) membrane sandwiched between two disk electrodes under alternate voltage excitation in the frequency range between 1 MHz and 25 mHz. Experimental results obtained for various PET thicknesses (36, 50 and 100 μm) highlighted the influence of the contact resistance at the electrode/polymer interface. For a better understanding of the PET/electrode interface behaviour, the experiments were compared with simulations performed for three different descriptions: the direct use of electrical equivalent circuits, an analytical model accounting for a power-law distribution of resistivity, and a numerical model (finite element simulations of the whole cell). The results highlight that the resistivity distribution obtained using the power-law model provided an appropriate description of the system in the frequency range investigated while the use of the CPE model is only consistent for low-frequencies (below 1 Hz).

Microporous organic network@PET hybrid membranes: removal of minute organic pollutants dissolved in water

Microporous organic networks (MONs) were incorporated into a polyethylene terephthalate (PET) membrane. The resultant MON@PET hybrid membranes showed promising filtration towards aromatic pollutants dissolved in water.