Polyethylene Naphthalate Research Articles

A novel strategy of fabricated flexible ITO electrode by liquid metal ultra-thin oxide film

Flexible transparent conductive films are gaining attention day by day over the last few years due to it is a key component of next generation flexible electronics and optoelectronic devices. Indium tin oxide (ITO) as one of the most widely used transparent conductive material is limited by the traditional deposition approach cannot be achieve ultra-thin, which results in its brittle nature. Herein, a novel strategy for fabricating highly transparent conductive films by liquid metal interface phase separation technique based on low-melting liquid metal of InxSn100-x alloy is reported, during the solid-to-liquid phase transition of alloy, the monolayer of surface oxide film segregated with the bulk phase and was printed on the flexible polyethylene-naphthalate (PEN) substrate under the van der Waals. This novel strategy can directly print the ultra-thin self-oxide with the structure of ITO on PEN substrate, with the resulting of transparency over 97.5% and resistivity as low as 0.21 kΩ cm, providing a new way of low-cost raw ITO material as well as the personalized preparation strategy. The desirable highly transparent conductive films are comparable to recently reported ITO film, together with advantages of pretty steady, make them attractive as various flexible transparent conductive electrodes, for example, an ultra-thin ITO film is developed for luminescent devices.

Low-temperature atomic layer deposition of TiO2 activated by laser annealing: Applications in photocatalysis

This work reports an innovative method to obtain anatase TiO2 films on polymeric substrate. The low temperature atomic layer deposition (LT-ALD) of TiO2 on polymeric substrate was combined with the laser irradiation. TiO2 amorphous films were deposited by LT-ALD on polyethylene naphthalene (PEN) substrate at a temperature of 90 °C. Successively, a KrF excimer laser was used for the annealing of the TiO2 films. The laser annealing induced the crystallization of the films in the form of anatase. A detailed morphological, structural, and chemical characterization was performed by ellipsometry, scanning electron microscopy (SEM), Raman spectroscopy, and transmission electron microscopy (TEM). The photocatalytic aptitude of the investigated films was demonstrated by the degradation of the methylene blue (MB) dye in aqueous solution under UV light irradiation. Simulations of the temperature depth profiles as a function of the time during the laser processes were performed. The results demonstrate that the matching of the extremely low temperature growth by ALD with the laser irradiation allows to synthetize anatase TiO2 films on flexible substrate that could find applications in photocatalysis, especially for wastewater remediation.

R &D of wavelength-shifting reflectors and characterization of the quantum efficiency of tetraphenyl butadiene and polyethylene naphthalate in liquid argon

Detectors based on liquid argon (LAr) often require surfaces that can shift vacuum ultraviolet (VUV) light and reflect the visible shifted light. For the LAr instrumentation of the LEGEND-200 neutrinoless double beta decay experiment, several square meters of wavelength-shifting reflectors (WLSR) were prepared: the reflector Tetratex® (TTX) was in-situ evaporated with the wavelength shifter tetraphenyl butadiene (TPB). For even larger detectors, TPB evaporation will be more challenging and plastic films of polyethylene naphthalate (PEN) are considered as an option to ease scalability. In this work, we first characterized the absorption (and reflectivity) of PEN, TPB (and TTX) films in response to visible light. We then measured TPB and PEN coupled to TTX in a LAr setup equipped with a VUV sensitive photomultiplier tube. The effective VUV photon yield in the setup was first measured using an absorbing reference sample, and the VUV reflectivity of TTX quantified. The characterization and simulation of the setup along with the measurements and modelling of the optical parameters of TPB, PEN and TTX allowed to estimate the absolute quantum efficiency (QE) of TPB and PEN in LAr (at 87K) for the first time: these were found to be above 67 and 49%, respectively (at 90% CL). These results provide relevant input for the optical simulations of experiments that use TPB in LAr, such as LEGEND-200, and for experiments that plan to use TPB or PEN to shift VUV scintillation light.

Mammalian Cell Interaction with Periodic Surface Nanostructures.

Here, we report on the nanopatterning of different aromatic polymer substrates achieved by KrF excimer laser treatment. The conditions for the construction of the laser-induced periodic surface structures, the so-called LIPSS pattern, were established by optimized laser fluence and a number of pulses. The polymer substrates were polyethylene naphthalate (PEN), polyethersulfone (PES), and polystyrene (PS), which were chosen since they are thermally, chemically, and mechanically resistant polymers with high absorption coefficients at the excimer laser wavelength. The surface morphology of the treated substrates was investigated by atomic force microscopy and scanning electron microscopy, and the roughness and effective surface area on the modified samples were determined. Elemental concentration was characterized by energy-dispersive (EDX) analysis, surface chemistry was determined with X-ray photoelectron spectroscopy (XPS). The samples with the formation of LIPSS induced by 10 mJ·cm−2 with 1000, 3000, and 6000 pulses were used for subsequent in vitro cytocompatibility tests using human cells from osteosarcoma (U-2 OS). The LIPSS pattern and its ability of significant cell guidance were confirmed for some of the studied samples. Cell morphology, adhesion, and proliferation were evaluated. The results strongly contribute to the development of novel applications using nanopatterned polymers, e.g., in tissue engineering, cell analysis or in combination with metallization for sensor construction.

Hysteresis Dynamic Modeling and Analysis of Flexible Nano Silver-Polyvinyl Alcohol Humidity Sensor Based on the Microscopic Process and Langmuir-Fick Theory.

In recent years, advances in materials science and manufacturing technologies have facilitated the development of flexible sensors. However, there are still performance gaps between emerging flexible sensors and traditional silicon-based rigid sensors, especially lacking dynamic modeling and optimization analysis for addressing above challenges. This paper describes a hysteresis dynamic modeling method for flexible humidity sensors. Through inkjet printing and coating methods, the polyvinyl alcohol (PVA) sensitive layer and nano silver interdigital electrode are fabricated on flexible polyethylene naphthalate substrates. The performance characterization results show that the sensitivity and maximum hysteresis within the range of 12–98% relative humidity (RH) are −0.02167 MΩ/% RH and 2.7% RH, respectively. The sensor also has outstanding dynamic response ability and stability in a wide range of humidity variation. The hysteresis mechanism of flexible humidity sensors is theoretically analyzed from microscopic hysteresis processes, Langmuir monomolecular adsorption dynamic modeling, and Fick diffusion dynamic modeling. These hysteresis models provide a path for the hysteresis optimization of flexible PVA humidity sensors. Further exploration of the diffusion rate of water molecules and the proportion of PVA in ink represents promising hysteresis optimization directions of flexible humidity sensors based on PVA-sensitive material.

Engineered Cu-PEN Composites at the Nanoscale: Preparation and Characterisation.

As polymeric materials are already used in many industries, the range of their applications is constantly expanding. Therefore, their preparation procedures and the resulting properties require considerable attention. In this work, we designed the surface of polyethylene naphthalate (PEN) introducing copper nanowires. The surface of PEN was transformed into coherent ripple patterns by treatment with a KrF excimer laser. Then, Cu deposition onto nanostructured surfaces by a vacuum evaporation technique was accomplished, giving rise to nanowires. The morphology of the prepared structures was investigated by atomic force microscopy and scanning electron microscopy. Energy dispersive spectroscopy and X-ray photoelectron spectroscopy revealed the distribution of Cu in the nanowires and their gradual oxidation. The optical properties of the Cu nanowires were measured by UV-Vis spectroscopy. The sessile drop method revealed the hydrophobic character of the Cu/PEN surface, which is important for further studies of biological responses. Our study suggests that a combination of laser surface texturing and vacuum evaporation can be an effective and simple method for the preparation of a Cu/polymer nanocomposite with potential exploitation in bioapplications; however, it should be borne in mind that significant post-deposition oxidation of the Cu nanowire occurs, which may open up new strategies for further biological applications.

Substrate Selection Framework for Organic Thin-Film Transistor Based on Flexibility and Reliability Issues

Flexibility is an important feature of organic thin-film transistor (OTFT) technology. The need for flexibility adds challenges to the mechanical reliability of the OTFTs. This work focuses on mechanical and thermal failure mechanisms in an OTFT and their relation with the substrate properties. It is observed that four material parameters of the substrate, namely, Young’s modulus, thermal conductivity, coefficient of thermal expansion, and glass transition temperature, are crucial in determining the reliability and flexibility of the OTFT. Further more, using an interval-based technique for order preference by similarity to ideal solution (TOPSIS) technique, five polymer substrates including polycarbonate (PC), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyimide (PI), and polyethersulfone (PES) are analyzed. It is concluded that PI is the most suitable substrate material for OTFTs to improve flexibility and reliability.

Measurement of electric field distribution in 2μm thick Polyethylene naphthalate film

Measurement of electric field distribution in 2μm thick Polyethylene naphthalate film

Dielectric, structural and mechanical properties of thermally aged biaxially oriented polymeric substrates for flexible electronics

Two materials, polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), which are often used as flexible substrates for electronics, were exposed to accelerated thermal aging at temperatures of 190 °C and 210 °C for 5000 and 2000 h, respectively. Changes in their thermal, dielectric, and mechanical properties were investigated. The results revealed that dielectric losses increase slower for PET than for PEN at lower aging temperatures. In contrast, at higher aging temperatures, similar behavior was observed for both materials. During aging, the dissipation factors of PET and PEN increased by one order of magnitude over those of the original states. The dielectric frequency-temperature characteristics obtained by broadband dielectric spectroscopy (BDS) shifted and indicated changes in the individual dielectric relaxation mechanisms (i.e., α, β, β*). Discoloration induced by thermal aging and quantified by ultraviolet–visible spectroscopy by the peak at 453 nm was detected primarily in the spectrum of PEN. The mechanical tensile strength of PET deteriorated considerably (10 times) after only a few hundred hours, whereas PEN was stable after even longer exposure times. It was found that all of the changes mentioned above are primarily related to the change in the crystalline-to-amorphous phase ratio, as demonstrated by differential scanning calorimetry (DSC) and supported by density measurements.

Performance Enhancements of Fully Inkjet-Printing Technology for Antenna-in-Package and Substrate Integrated Waveguides

A fully inkjet-printing technology is applied to antenna-in-package (AiP) and substrate integrated waveguide (SIW) to enhance the performance of three components, including via holes, wire bonding, and flexible antenna arrays. First of all, earlier studies utilize shorting pins for the conductive pathway in high-density AiP and SIW, but this requires an additional procedure to plate the conductor. We propose a mechanical approach to form a cylindrical hole, plating the surface with silver nanoparticles and realizing the equivalent circuit model of the shorting pin. The proposed approach does not require high alignment sensitivity or the precise control of laser power level. Second, fully inkjet-printed wire bonding is proposed for the system on the package. The proposed technique not only reduces the discontinuity but also enables a fabrication without additional assembly. Third, the proposed technique is implemented for antenna development, which shows desirable performance with reduced fabrication complexity. The proposed technology is validated by microstrip lines, SIWs, SIW cavity slots, and flexible 4 × 4 patch arrays fabricated on various substrates including RO 4003C, polyimide, and polyethylene naphthalate. For comparison purposes, conventional approaches using printed circuit boards are also implemented and tested. The results indicate the generality and capability of the proposed technique.

Inkjet-Printed Three-Electrode System on Flexible Substrate for Low-Cost Electrochemical Analysis

Inkjet printing (IJP) has emerged as a promising additive manufacturing technique for fabrication of electrodes and sensors due to its cost-effectiveness compared to the traditional techniques, such as screen-printing. In this work, we present a planar, three-electrode system fabricated by inkjet printing on a polyethylene naphthalate (PEN) flexible substrate for rapid voltametric electrochemical analysis. An in-house formulation of aqueous-based gold ink with low temperature-sintering was used in printing the working and counter electrodes. The reference electrode was also inkjet-printed using a commercial silver ink and chlorinated to form an AgCl layer. Cyclic voltammetry studies using the ferri/ferrocyanide redox couple showed that the inkjet-printed electrode system has a comparable electrochemical performance to a commercial screen-printed electrode. Fabrication of a single inkjet-printed electrochemical 3-electrode platform consumes only about 0.5 mg Au and 0.2 mg Ag loading of ink with minimal waste during fabrication because of the additive nature of the printing technique. The 3-electrode platform operates with a microliter sample volume for analysis and can be used in aqueous media without delamination.

Inkjet Printing of UHF RFID Antennas Using Silver and Gold Inks

Compared with current methods, additive manufacturing processes could offer a more environment-friendly and cost-effective solution in producing long lasting RFID tags for identification and sensing applications. In this work we report the fabrication of UHF RFID antennas by inkjet printing on a flexible substrate. Silver and gold were chosen as ink materials since they are more resistant to weathering than other metals, particularly for applications that require long-term reusability. We compared the print performance of a commercial silver ink and our lab-developed gold nanoparticle (AuNP) ink on polyethylene naphthalate. The printing process for each ink is described using an adopted loop antenna design optimized for 866-868 MHz frequency range. Assembled passive and battery-assisted RFID tags using single-and double-layer sintered, printed antennas coupled with a readable UHF RFID chip showed tolerable detection distances using a commercial compact reader (with short read range specifications). Additionally, we observed a more consistent print behavior and quality, and consequently longer read ranges for the gold antennas (up to 40 cm with battery). Furthermore, the silver antennas oxidized over time resulting in decreased read ranges. Overall, our results show the viability of a printable gold RFID antenna with a tag working range that may be fit for close range non-contact reading.

Hybrid confinement mechanism of large-small rupture strain FRP on concrete cylinder

This study aims to investigate the hybrid mechanism of concrete cylinders confined with different types of fiber reinforced polymer (FRP). The adoptive FRP sheets include three types of low rupture strain FRPs (carbon fiber polymer (CFRP), glass fiber polymer (GFRP) and basalt fiber polymer (BFRP)) and two types of high rupture strain FRPs (polyethylene terephthalate fiber polymer (PET-FRP) and polyethylene naphthalate fiber polymer (PEN-FRP)). More hybrid gradients are designed to exposit the hybrid mechanism of large-small rupture strain FRPs. A total of 39 FRP-confined concrete cylinders are conducted under axial compression. The tested parameters are FRP types and the number of FRP layers. The failure modes, stress-strain responses, lateral confined pressures under different axial stresses, the apparent Poisson's ratio variation and energy-dissipating capacities are analyzed to reveal the mechanical mechanism of the specimens. The results show that the hybridization of the FRP sheets with rather different elongation capacities brings a pseudo ductility behaviour of concrete cylinders. That definitely improves the strain capacity, but the strength improvement relies on the adequate axial stiffness discrepancy between higher elongation FRP and lower elongation FRP sheets. By the hybridization, the utilization of lower elongation FRP sheets is markedly improved. The concrete cylinders confined by hybrid FRP sheets with similar elongation capacities behave like to the single FRP confined ones. Moreover, the predicted formulas are proposed and capture well the ultimate state of hybrid FRP confined concrete cylinders.

Usage of PEN as self-vetoing structural material in the LEGEND experiment

Polyethylene naphthalate (PEN) is an industrial plastic which is interesting to the physics community as a wavelength-shifting scintillator. Recently, PEN structures with excellent radiopurity have been successfully produced using injection compression molding technology. This opens the possibility for the usage of optically active structural components with wavelength shifting capabilities in low-background experiments. Thus, PEN holders will be used to mount the germanium detectors in the LEGEND-200 experiment. In this contribution the ongoing R&D on PEN is outlined with a focus on the evaluation of its optical properties. In addition, the ongoing efforts for further application of PEN in the LEGEND-1000 experiment are presented.

High-power impulse magnetron sputter deposition for enhanced optical transmittance and electrical conductivity of flexible coating

A transparent conductive material, mostly transparent conductive oxide (TCO), is essential and indispensable for flexible electronics. Different from the conventional, single-layered TCO, multilayered oxide/metal/oxide (OMO) structures have been investigated as a promising alternative. The metal layer serves to reduce the electrical resistance of the oxides and the transparency is enhanced by suppressing the reflection from middle metal layer and substrate. Meanwhile, due to the limited temperature tolerance of the flexible polymeric substances, high-power impulse magnetron sputtering technique has been used to deposit the OMO structures at a substrate temperature lower than 70 °C. Two different OMO multilayered structures, including ZnO/Ag/ZnO and ZnO/Cu/ZnO, are deposited on polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), and soda lime glass. The effects of layer thickness and metal type on the transmission and resistivity of the obtained OMO structures are investigated. The correlation between OMO structure characteristics and the resulting photoelectric properties are also studied. A 35-nm ZnO/20-nm Ag/30-nm ZnO having excellent resistivity of 6.2 × 10−5 Ωcm (7.2 Ωsq−1) and transmittance of 87.7% is demonstrated. Furthermore, after 3000 bending cycles, the multilayered OMOs on PET and PEN retain their superior electrical properties, exhibiting resistivity of 3.8 × 10−4 and 1.3 × 10−4 Ωcm, respectively.

Durability assessment of PEN/PET FRP composites based on accelerated aging in alkaline solution/seawater with different temperatures

Large rupture strain (LRS) fiber-reinforced polymer (FRP) composites, including polyethylene naphthalate (PEN) FRP and polyethylene terephthalate (PET) FRP composites, have become increasing popular in civil construction. PET FRP and PEN FRP can be recyclable and thus they are environmentally friendly. However, the durability of LRS FRP composites under extreme environmental conditions (e.g., marine environment and high temperature) has not been understood. To this end, durability tests on 282 LRS FRP sheets after aging in alkaline/seawater solution with different temperatures (25℃, 40℃, 60℃) were conducted in this study. The microstructure of PEN FRP sheets was also analyzed using scanning electron microscope (SEM). The results show that the changes of the elastic modulus of the first linear portion and the elastic modulus of the second linear portion of PEN FRP sheets after aging in different aging temperatures are slight. For PEN FRP sheets with an aging period of 365 days in 60 °C solutions, the degradation rate of the tensile strength is around 10% for both alkaline (pH = 13.2) and seawater solutions, and the degradation rate of the tensile rupture strain is around 12.5%. Additionally, under a higher exposure temperature, there is a significant decrease in the tensile strength of LRS FRP composites. Furthermore, it shows that the durability of PEN FRP sheets was significantly affected in the alkaline environment compared to that in the seawater environment, and the alkaline resistance of PEN FRP composites is better than that of PET FRP composites.

Gate‐Deterministic Remote Doping Enables Highly Retentive Graphene‐MXene Hybrid Memory Devices on Plastic

AbstractIn this work, a highly retentive and synaptic‐functional transistor memory device architecture based on the gate‐deterministic remote doping of graphene via surface‐oxidized Ti3C2TX MXene nano‐floating‐gates (NFG) is presented. By using solution‐phase size‐sorting followed by controlled surface oxidation process, a regulated distribution of MXene nanoflakes comprising metallic Ti3C2TX as the core surrounded by TiO2‐a high dielectric constant insulator‐as the shell is achieved. The size‐sorted core/shell‐like MXene nanoflakes show a self‐sustainable charge trapping/detrapping behavior, which is highly feasible for realizing non‐embed NFGs for transistor memory devices. Interestingly, unlike the conventional NFG‐embedded architecture, the introduction of core/shell‐like MXene under an electrolyte‐gated graphene field‐effect transistor (GFET) architecture induces a cooperative evolution of the hysteresis loop associated with ionic motion in the electrolyte gates and charge trapping/detrapping in the nanoflakes, resulting in a deterministic remote doping of the graphene layer. The resulting device exhibited a highly retentive memory behavior, which can be optimized by the nanoflake size distribution. In addition, synaptic functions having mechanical flexibility can be successfully emulated using MXene‐based GFETs fabricated on a flexible polyethylene naphthalate substrate.

Investigation of polyesters as daytime radiative cooling materials

We discovered that polyesters, particularly polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), are potential candidates for daytime radiative cooling (RC). A significant temperature drop was observed in both PET and PEN films when they were exposed to liquid nitrogen. In addition, their RC efficiency was compatible with previously reported RC materials such as polydimethylsiloxane and soda-lime glass. Polyesters have advantages over other RC materials in terms of chemical stability, moldability, and impact resistance. In particular, PET can be utilized for daytime RC of solar cells due to its transparency in the visible region.

Conductive Polymer PEDOT:PSS-Based Platform for Embryonic Stem-Cell Differentiation.

Organic semiconductors are constantly gaining interest in regenerative medicine. Their tunable physico-chemical properties, including electrical conductivity, are very promising for the control of stem-cell differentiation. However, their use for combined material-based and electrical stimulation remains largely underexplored. Therefore, we carried out a study on whether a platform based on the conductive polymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) can be beneficial to the differentiation of mouse embryonic stem cells (mESCs). The platform was prepared using the layout of a standard 24-well cell-culture plate. Polyethylene naphthalate foil served as the substrate for the preparation of interdigitated gold electrodes by physical vapor deposition. The PEDOT:PSS pattern was fabricated by precise screen printing over the gold electrodes. The PEDOT:PSS platform was able to produce higher electrical current with the pulsed-direct-current (DC) electrostimulation mode (1 Hz, 200 mV/mm, 100 ms pulse duration) compared to plain gold electrodes. There was a dominant capacitive component. In proof-of-concept experiments, mESCs were able to respond to such electrostimulation by membrane depolarization and elevation of cytosolic calcium. Further, the PEDOT:PSS platform was able to upregulate cardiomyogenesis and potentially inhibit early neurogenesis per se with minor contribution of electrostimulation. Hence, the present work highlights the large potential of PEDOT:PSS in regenerative medicine.

Production and validation of scintillating structural components from low-background Poly(ethylene naphthalate)

Poly Ethylene Naphthalate (PEN) is an industrial polymer plastic which is investigated as a low background, transparent, scintillating and wavelength shifting structural material. PEN scintillates in the blue region and has excellent mechanical properties both at room and cryogenic temperatures. Thus, it is an ideal candidate for active structural components in experiments for the search of rare events like neutrinoless double-beta decay or dark matter recoils. Such optically active structures improve the identification and rejection efficiency of backgrounds events, like this improving the sensitivity of experiments. This paper reports on the production of radiopure and transparent PEN plates These structures can be used to mount germanium detectors operating in cryogenic liquids (LAr, LN). Thus, as first application PEN holders will be used to mount the Ge detectors in the Legend-200 experiment. The whole process from cleaning the raw material to testing the PEN active components under final operational conditions is reported.