Polyethylene Terephthalate Foils Research Articles

Rapid low-pressure plasma sintering of inkjet-printed silver nanoparticles for RFID antennas

Abstract

Scalability and stability of very thin, roll-to-roll processed, large area, indium-tin-oxide free polymer solar cell modules

Polymer solar cell modules were prepared directly on thin flexible barrier polyethylene terephthalate foil. The performance of the modules was found to be scalable from a single cell with an area of 6cm2 to modules with a total area of up to 186cm2. The substrate thickness was also explored and the performance was found to be independent of thickness in the range of 20–130μm. The thinner substrates were found to present some challenge regarding handling but were not limited in performance. Large area modules on a substrate thickness of 45μm were finally prepared by full roll-to-roll processing employing P3HT:PCBM as the active material and were found to exhibit a total area efficiency of >1% (1000W/m−2; AM1.5G) with a typical active-area efficiency in the 1.5–1.6% for total module area of >110cm2 due to high fill factors in excess of 50%. The modules were also found to have an active-area efficiency of >1% under low light levels (∼100Wm−2). The modules were then subjected to extensive stability testing for a minimum of 1000h employing several ISOS protocols. The modules presented higher than 80% of the initial performance (T80) in the dark (ISOS-D-1), in dark under elevated temperature of 65°C (ISOS-D-2), under low light (ISOS-LL), under full sunlight (ISOS-L-2), and under outdoor testing (ISOS-O), which was conducted in two locations in India and Denmark. We estimate maximum T80 for those tests to be 2800, 5000, 1300, 1000, and 3500h respectively. The modules showed significant sensitivity to high humidity and had low values for T80 for dark storage tests at 50°C/85%RH (ISOS-D-3) and accelerated operation conditions with 0.7 sun/65 oC/50%RH (ISOS-L-3). We found the modules to be particularly suited for information and communications technology (ICT) and mobile applications where low humidity (<50%) and lower temperatures (<65°C) can be anticipated and we estimate operational lifetimes in excess of 1year.

The characterization of PEEK, PET and PI implanted with Co ions to high fluences

Polyimide (PI), polyetheretherketone (PEEK), and polyethylene terephthalate (PET) foils have been implanted with 40keV Co+ ions at room temperature to the fluences ranging from 0.2×1016cm−2 to 1.0×1017cm−2. Co depth profiles determined by RBS have been compared to SRIM 2008 calculations. The measured projected ranges RP differ slightly from the SRIM simulation because of the compositional changes in polymers implanted to high fluences; especially the widths of the Co profiles are much larger than those simulated by SRIM. Oxygen and hydrogen depletion has been examined using the RBS and ERDA techniques. The surface morphology of the implanted polymers has been characterized using AFM. The PET polymer exhibits lower oxygen escape than the PI and PEEK, but the surface roughness at PET has been affected most significantly after the implantation. Implanted Co atoms tend to aggregate into nanoparticles, the size and distribution of which has been determined from TEM micrographs and using image analysis. The largest diameter of Co particles has been found in implanted PET.

Fast Inline Roll‐to‐Roll Printing for Indium‐Tin‐Oxide‐Free Polymer Solar Cells Using Automatic Registration

AbstractFast inline roll‐to‐roll printing and coating on polyethylene terephthalate (PET) and barrier foil was demonstrated under ambient conditions at web speeds of 10 m min−1 for the manufacture of indium‐tin‐oxide‐free (ITO‐free) polymer solar cells comprising a 6‐layer stack: silver‐grid/PEDOT:PSS/ZnO/P3HT:PCBM/PEDOT:PSS/silver‐grid. The first and second layers were printed at the same time using inline processing at a web speed of 10 m min−1 where flexographic printing of a hexagonal silver grid comprises the first layer followed by rotary‐screen printing of a PEDOT:PSS electrode as the second layer. The third and fourth layers were slot‐die coated at the same time again using inline processing at a web speed of 10 m min−1 of firstly zinc oxide as the electron transport layer followed by P3HT:PCBM as the active layer. The first three layers (silver‐grid/PEDOT:PSS/ZnO) comprise a generally applicable ITO‐free, semitransparent, electron‐selective front electrode for inverted polymer solar cells. This electrode shows a low sheet resistance (∼10 Ω/□) and good optical transmission in the visible range (∼60 %). The solar cell stack was completed by rotary‐screen printing of a hole‐collecting PEDOT:PSS layer at 2 m min−1 and a comb‐patterned silver‐grid back electrode at the same speed. The solar cells were post processed by using fast roll‐to‐roll switching to a functional state.

Electronic behavior of micro-structured polymer foils immersed in electrolyte

The presence of impurities in polymers makes them electroactive. When immersed in electrolytes, polymers can incorporate additional ions, thus changing their electronic properties. The aim of the present work is to characterize the electronic behavior of polymers with microstructures obtained from proton irradiation and etching. To that end, polyethylene terephthalate foils were irradiated with a 2.0×2.0μm2 proton beam of 3MeV. Subsequently, the foils were submitted to an etching procedure with NaOH, leading to microstructures of the order of 1000μm2. Finally, the polymers were immersed in a solution of NaCl and submitted to an AC voltage from a function generator. The results show that the etching procedure after proton irradiation leads to buried structures in the polymers. Pristine and microstructured foils show an Ohmic behavior for frequencies below 1kHz and a capacitive behavior above this frequency up to 1MHz. This behavior is independent of the foil thickness and the area of the structures.

Label-free DNA detection using the narrow side of funnel-type etchednanopores

A sensitive; simple and label-free method for DNA detection is presented. Irradiated polyethylene terephthalate foils were etched to present conical tracks at a density of approximately 5×107 tracks per cm2. Probe DNA was immobilized at the narrow opening of the tracks (2–4nm diameter). The presence of target DNA resulted in changes in both conductance and rectification ratios in a concentration-dependent manner. DNA concentrations as low as 2nM could be detected using this simple two-step detection scheme.

Pulsed Ligh inactivation of Listeria innocua on food packaging materials of different surface roughness and reflectivity

Inactivation of Listeria innocua on food packaging materials by Pulsed Light (PL) treatment was investigated. Coupons of low density polyethylene (LDPE), high density polyethylene (HDPE), polyethylene-laminated ultra-metalized polyethylene terephthalate (MET), polyethylene-coated paperboard (TR), and polyethylene-coated aluminum foil paperboard laminate (EP) were inoculated with L. innocua cells in stationary growth phase. Inoculated coupons (∼8CFU/coupon) were treated with Pulsed Light fluence of up to 8.0J/cm2, and survivors were determined. Reductions up to 7.2±0.29, 7.1±0.06, 4.4±0.85, 4.5±1.32, and 3.5±0.82 log CFU/coupon were obtained on LDPE, HDPE, MET, TR, and EP, respectively. Inactivation data were used to determine Weibull kinetic parameters and predict inactivation in a wide range of fluence. Increasing surface reflectivity and surface roughness appeared to induce lower inactivation. Minimal surface heating was observed for all materials except MET, on which significant heating occurred. These results demonstrate the potential of Pulsed Light as an effective method for decontaminating food packaging materials.

Relaxation of stresses in polystyrene–carbon microcomposite resistive layers

Abstract This paper presents the investigation results on thermoresistive elements made with a styrene–butadiene–styrene (SBS) modified polystyrene binder and carbon filler. Resistive layers were deposited by screen-printing method onto a polyethylene terephthalate (PET) foil. The temperature–resistance dependence of the examined layers was observed. The carbon filler content was precisely selected to obtain high values of TCR, such as 70,000 ppm/°C, for resistive layers with a SBS-modified polystyrene binder in the temperature range from 24 to 100 °C. Because of high TCR the influence of mechanical stresses, which is unfavorable feature of the examined layers, may be omitted. The highest TCR value and stability of electrical parameters during operation were observed for layers containing 42.9% of carbon filler by mass content. The measurements were carried out with the aid of an infrared camera and an oscilloscope because of very fast changes of resistive elements parameters. The analysis of the obtained results allows to draw conclusions about the carbon layer properties and to determine the stress–relaxation rate of the polymer structures.

Non‐destructive lateral mapping of the thickness of the photoactive layer in polymer‐based solar cells

ABSTRACTNon‐destructive lateral mapping of the thickness of the photoactive layer in poly(3‐hexyl‐thiophene) : 1‐(3‐methoxy‐carbonyl)propyl‐1‐phenyl‐(6,6)C61 (P3HT : PCBM) solar cells is demonstrated. The method employs a spatially resolved (XY) recording of ultraviolet‐visible spectra in reflection geometry at normal incidence, using a dense raster defined by a circular probe spot of 800‐µm diameter. The evaluation of the thickness of the photoactive layer at each raster point employs an algorithm‐driven comparison of the measured absorption spectrum with spectral features, as compiled from the corresponding simulated spectrum. For the robustness of the applied algorithm toward noise in the recorded absorption data to be increased, a new minimum finder algorithm is described and implemented. The thickness evaluation relies on the correct assignment of extrema in the experimental absorption spectra to the corresponding extrema in the simulated absorption spectra, and a new algorithm for this is also implemented and described. For a level of confidence for the method to be established, first thickness mapping is performed for a set of reference samples consisting of P3HT : PCBM spin‐coated on indium tin oxide‐coated float glass substrates. After this, two application examples for solar cells processed either by spin coating or slot die coating of the P3HT : PCBM layer follow. The spin‐coated solar cells have glass as the substrate with the P3HT : PCBM spun at different spinning speeds. The slot die‐coated solar cells were processed on polyethylene terephthalate foil in a roll‐to‐roll experiment involving a continuously changing P3HT : PCBM concentration along the printing direction. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Investigations of plasma polymerized SiOx barrier films for polymer food packaging

Nano-scale SiOx layers were deposited on polyethylene terephthalate (PET) foils by plasma enhanced chemical vapor deposition (PECVD) in an electron cyclotron resonance (ECR) plasma process in order to enhance their barrier properties towards water vapor. Oxygen (O2) and hexamethyldisilazane (HMDSN) served as reactive gas and precursor, respectively. The effect of layer thickness and O2:HMDSN (x:1) gas mixture ratio on the water vapor transmission rate was systematically investigated. Measurements by infrared spectroscopy and scanning electron microscopy for the characterization of the chemical composition and of the surface structure of the SiOx layers, respectively, showed that both chemical composition and surface structure of the layers have a noticeable effect on their barrier properties. For low O2 content in the O2:HMDSN gas mixture ratio, organic layers were deposited. When increasing the O2 content, the growing number of inorganic compounds in the SiOx layers found by the infrared spectroscopy gave rise to a decrease in the water vapor transmission rate. A reduction of the water vapor permeation by more than a factor of 2 in comparison with the uncoated PET foil was achieved by the best performing SiOx layer. Further increase of the O2 content led to the onset of a columnar-like layer growth which showed to be causative for the water vapor permeation rising again.Finally, the barrier properties towards water vapor of 100nm thick SiOx films deposited from different O2:HMDSN gas mixtures were contrasted with their corresponding barrier properties towards O2. The minimum water vapor and O2 permeation results were found for the SiOx films plasma deposited from almost identical O2:HMDSN gas mixture ratios in the range of 25≤x≤30.

Specular properties of chemically etched polyethylene terephthalate foils in the soft X-ray region

Results from angular measurements of reflections of radiation at a wavelength of 13.5 nm of poly-ethyleneterephthalate (PETP) foils before and after chemical etching are described. The observed reduction in reflections at grazing incidence in contrast to reflections from ideal smooth sample is due to the characteristics of the surface microrelief of the foils and its changes due to etching. The results of this work can be used to study the spectral transmission of X-ray and UV diffractive filters made on the basis of track membranes.

Effect of humid air exposure between successive helium plasma treatments on PET foils

It is well known that helium plasmas can successfully alter the surface properties of polyethylene terephthalate (PET). However, the influence of humid (atmospheric) air exposure between successive helium plasma treatment steps has not been previously examined. In this work, PET foils are treated in successive short treatment steps of 5s with a DBD operating in helium at medium pressure (5.0kPa). Between every plasma treatment step, the samples are either kept in the plasma chamber at 5.0kPa under helium atmosphere or are exposed to humid air at atmospheric pressure. The plasma-treated samples are examined using contact angle measurements and X-ray photoelectron spectroscopy (XPS). Results clearly show that exposure to humid air between successive helium plasma treatment steps leads to a larger decrease in water contact angle and a more pronounced oxygen incorporation. XPS results have shown that during each helium plasma treatment, O–C═O groups are introduced on the PET surfaces. However, when the samples are exposed to humid air between plasma treatments, also C–O groups are created on the PET surfaces. These C–O groups are mainly introduced during exposure to humid air: every helium plasma treatment creates surface radicals, which can in turn react with oxygen species present in the atmosphere during subsequent humid air exposure, leading to the incorporation of C–O groups.

Development of pH-sensitive indicator dyes for the preparation of micro-patterned optical sensor layers

Functional hydroxyazobenzene dyes for optically monitoring pH in the range from 6 to 10 were synthesised. The p K a values of the dyes have been tailored by appropriate choice of substituents in position para to the hydroxy group, resulting in lower p K a values for electron acceptor substituents and higher p K a for electron donors. Furthermore, substituent effects on absorbance spectra have been evaluated, with expected shifts to longer wavelength in the case of electron donors. For immobilisation, the indicator dyes were covalently linked to cellulose films via vinylsulfonyl chemistry. Mechanical stabilization of the cellulose films was achieved by lamination onto polyethylene terephthalate foils. In order to obtain patterned sensor layers with geometrical defined sensing areas a laser-structured adhesive tape was used as protective mask in the dyeing step.

EUV micropatterning for biocompatibility control of PET

We have investigated the influence of oriented microstructures at modified polyethylene terephthalate (PET) on the adhesion and alignment of Chinese hamster ovary (CHO) cells. For surface modification, the PET foils were exposed to the radiation of a laser-plasma extreme ultraviolet (EUV) source based on a double-stream gas-puff target. The emission of the plasma was focused onto the samples by means of a gold-plated ellipsoidal collector. The spectrum of the focused radiation covered the wavelength range from 9 to 70 nm. The PET samples were irradiated with the EUV pulses at a repetition rate of 10 Hz in a high vacuum. For control experiments, PET samples were also irradiated in air with the light of a 193 nm ArF-excimer laser. Different kinds of surface microstructures were obtained depending on the EUV or laser fluence and pulse number, including oriented wall- and ripple-type structures with lateral structure periods of a few µm. The surface morphology of polymer samples after the irradiation was investigated using a scanning electron microscope (SEM). Changes in chemical surface structure of the irradiated samples were investigated using X-ray photoelectron spectroscopy (XPS). We demonstrated that the cells show good adhesion and align along oriented wall- and ripple-type microstructures on PET surfaces produced by the EUV irradiation.

Silicon oxide diffusion barrier coatings on polypropylene

In this study the influence of process conditions for the plasma-enhanced chemical vapor deposition of SiO x diffusion barrier coatings on polypropylene (PP) is investigated and compared to results obtained on polyethylene terephthalate (PET). It was observed that the thermal load during deposition is much more crucial in the case of PP. If the thermal load is not the limiting factor, the composite parameter (CP) energy input per mass of precursor showed to be valuable to describe plasma conditions at constant oxygen to monomer ratio. Low oxygen transmission rates (OTRs) of 5.1 ± 3.6 and 0.3 ± 0.1 cm 3/m 2day/atm were achieved on PP and PET foil, respectively, for an optimal CP of 4.1 × 10 5 J/g. Fourier transform infrared (FTIR) spectroscopy revealed that low carbon and silanol content is necessary for good barrier performance. Low RF power, necessary to reduce thermal load on PP, can be compensated by increasing the oxygen to monomer ratio. For favorable plasma conditions, the dependence of the OTR on the coating thickness follows a similar trend for both substrate materials with a critical thickness of approximately 12 nm. The residual permeation can be correlated to the defect density at each stage of film growth by means of a simple correlation. Further support for permeation through defects is found by the activated rate theory, since the apparent activation energy of oxygen permeation is below typical values of amorphous glasses and remains unchanged due to the deposition of SiO x on both substrates.

Construction of wireless sensor for harsh environment operation

The paper presents empirical results of wireless and battery less smart sensor system made with three different techniques. The system has been both designed and fabricated to meet harsh environment requirements for sensor operation. In this work FR4 laminate (PCB), Low Temperature Co-fired Ceramics (LTCC) and Polyethylene Terephthalate foil (PET) were used as a sensor electronic board. According to the substrates three different techniques and materials were used to fabricate conductive traces. The paper reports comparison of electrical parameters obtained during tests for each type of board.

Surface charge density of the track-etched nanopores in polyethylene terephthalate foils

Surface charge is one of the most important properties of nanopores, which determines the nanopore performance in many practical applications. We report the surface charge densities of track-etched nanopores, which were obtained by measuring the streaming current and pore conductance, respectively. Experimental results reveal that surface charge densities depend significantly on the salt concentrations. In addition the values obtained with the pore conductance were always several times higher than those calculated with the streaming current, and the gel-like surface layer on the nanopore was considered to be responsible for this discrepancy.

Silicon Oxide Permeation Barrier Coating and Plasma Sterilization of PET Bottles and Foils

AbstractThe results of silicon oxide permeation barrier coating and plasma sterilization are shown using a low‐pressure microwave plasma reactor system based on a Plasmaline antenna developed for the treatment of polyethylene terephthalate bottles and foils. The influence of the coating composition on the barrier properties is analyzed and a good correlation is found. The optimized barrier coatings are analyzed regarding coating defects, which are visualized by means of capacitively coupled oxygen plasma etching of the coated substrates. The capabilities of plasma sterilization are exemplarily demonstrated for spores of Bacillus atrophaeus allowing for a spore reduction according to today's regulations for aseptic food packaging.

Propagation Distance of the α-Particle-Induced Bystander Effect: The Role of Nuclear Traversal and Gap Junction Communication

When cell populations are exposed to low-dose alpha-particle radiation, a significant fraction of the cells will not be traversed by a radiation track. However, stressful effects occur in both irradiated and bystander cells in the population. Characterizing these effects, and investigating their underlying mechanism(s), is critical to understanding human health risks associated with exposure to alpha particles. To this end, confluent normal human fibroblast cultures were grown on polyethylene terephthalate foil grafted to an ultrathin solid-state nuclear track detector and exposed under non-perturbing conditions to low-fluence alpha particles from a broadbeam irradiator. Irradiated and affected bystander cells were localized with micrometer precision. The stress-responsive protein p21(Waf1) (also known as CDKN1A) was induced in bystander cells within a 100-microm radius from an irradiated cell. The mean propagation distance ranged from 20 to 40 microm around the intranuclear alpha-particle impact point, which corresponds to a set of approximately 30 cells. Nuclear traversal, induced DNA damage, and gap junction communication were critical contributors to propagation of this stressful effect. The strategy described here may be ideal to investigate the size of radiation-affected target and the relative contribution of different cellular organelles to bystander effects induced by energetic particles, which is relevant to radioprotection and cancer radiotherapy.

High-voltage glow discharge plasma immersion ion implantation assisted by magnetic field

Plasma immersion ion implantation (PIII) employing high-voltage glow discharge is an effective tool to achieve better material properties without external plasma sources. The efficacy of high-voltage glow discharge can be enhanced by the use of a magnetic field. Our experimental results disclose that the addition of permanent magnets effectively increases the plasma density and decreases the delay time to ignite the glow discharge. The discharge can also be ignited at a lower pressure in the presence of a magnetic field. This helps to improve the implantation energy due to reduced particle collisions. In addition, the process is more flexible since plasma generation depends less on the gas pressure and target bias compared to conventional high-voltage glow discharge PIII. To demonstrate the advantages of this simple, flexible and efficient technique, polyethylene terephthalate (PET) foils are treated by glow discharge PIII to improve the surface properties and smaller water contact angles are observed from the implanted samples.