Thin Polyethylene Terephthalate Films Research Articles

Transparent and broadband switchable absorber/reflector based on structured water medium

A reconfigurable absorber/reflector, which has optical transparency and broadband switching function, is developed based on structured water medium. The conductive indium tin oxide coating is deposited on a thin polyethylene terephthalate film to act as the reflective backplane. Pure water is encapsulated by polydimethylsiloxane materials to construct structured water. The average optical transmittance is about 61.88%/56.44% in the visible spectrum of 380–760 nm with/without pure water. Based on the combination of the stacking technique and the super-element configuration, an obvious switching function from broadband absorption (12.47–28.43 GHz) to broadband reflection (12–30 GHz) can be attained under normal incidence through the injection and discharge of pure water. Besides, the broadband switchable characteristics of the proposed structure remain effective for transverse electric (TE) and transverse magnetic (TM) modes when illuminated by oblique incident waves up to 45°. Moreover, the proposed switchable absorber/reflector shows good temperature stability and can work under different liquid temperatures. Furthermore, the excellent performance of the proposed design is demonstrated by both simulated and experimental results, exhibiting great potential as transparent smart windows in large-scale ground-based stealth systems.

MEMS Piezoresistive Pressure Sensor Based on Flexible PET Thin-Film for Applications in Gaseous-Environments

This experimental study presents the operation of pressure sensors made from low-temperature flexible substrates. Design, simulation, fabrication, and characterization are carried out with a number of fabricated flexible pressure devices. Simulations are used to optimize the sensor parameters such as the geometrical shape, electrical potential output, sensitivity and working-range of the sensor, thus predicting the sensing behavior before fabrication. The behaviour of the devices are simulated by using COMSOL Multiphysics. The pressure structure consists of a substrate of polyethylene terephthalate (PET) thin-film used as a diaphragm. A thin layer of indium tin oxide (ITO) on the PET substrate is obtained and used as a first conductive metallic track. Subsequently, nichrome (NiCr 80/20 wt%) alloy material was deposited by electron beaming to generate four piezoresistors with thickness of 50 nm that can be used to detect resistance change using a Wheatstone bridge when the sensor is exposed to different working pressures. Aluminum metallic tracks of 200 nm in thickness are deposited by sputtering in order to connect the four piezoresistors. A working range of pressure is applied from 0 kPa to 130 kPa. Resistivity and sensitivity measured values were <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.37 \times 10^{-3}\, {\Omega }$ </tex-math></inline-formula> -cm and 6.365 mV/kPa respectively. All simulations and experimental results showed that the sensor characteristics are favorable for applications where the pressure is below 130 kPa.

Induced gyrotropy in thin PET films before and after swift heavy ion irradiation evidenced from analysis of optical interference fringes

We present here experimental studies of the UV/vis/near IR transmission spectra of polyethylene terephthalate (PET) films before and after irradiation with Kr+15 ions of energy 1.75 MeV/a.u. and fluence of 1.9 × 10 10 cm−2. Our data show small variations (∼0.5%) in transmission between individual pristine PET film samples in the IR region of the spectrum, as would be expected for films produced to certain manufacturing tolerances. Swift heavy ion (SHI) irradiation of a sample reduces transmission in this region, but by less than the observed variation in transmission between individual pristine samples, and does not affect local transmission variations in the spectrum, indicating that SHI irradiation has not destroyed the molecular structure of the PET film responsible for these variations. We use established methods to separate our experimental spectra into interference-free transmission spectra and isolated interference fringes and estimate the absorption coefficient and dispersion of the refractive index for pristine and irradiated PET films. We show that the observed amplitude modulation of the interference fringes is due to the optical activity of our PET samples and is a signature of induced gyrotropy. In some spectral regions, we observe a refractive index that is negative relative to the Cauchy approximation. We provide evidence that this is due to the ordering/texture of chiral molecules in PET films, suggesting that very highly textured PET films may exhibit a greater degree of negativity.

Fabrication of Flexible Electrode with Sub-Tenth Micron Thickness Using Heat-Induced Peelable Pressure-Sensitive Adhesive Containing Amide Groups.

In response to the increasing demand for flexible devices, there is increasing effort to manufacture flexible electrodes. However, the difficulty of handling a thin film is an obstacle to the production of flexible electrodes. In this study, a heat-induced peelable pressure-sensitive adhesive (h-PSA) was fabricated and used to manufacture a flexible electrode with sub-tenth micron thickness. Unlike the control PSA, the incorporation of amide groups made the h-PSA fail through adhesive failure at temperatures ranging from 20 to 80 °C. Compared to the peeling adhesion (1719 gf/in) of h-PSA measured at 20 °C, the value (171 gf/in) measured at 80 °C was decreased by one order of magnitude. Next, the 8 μm thick polyethylene terephthalate (PET) film was attached on a thick substrate (50 μm) via h-PSA, and Mo/Al/Mol patterns were fabricated on the PET film through sputtering, photolithography, and wet-etching processes. The thick substrate alleviated the difficulty of handling the thin PET film during the electrode fabrication process. Thanks to the low peel force and clean separation of the h-PSA at 80 °C, the flexible electrode of metal patterns on the PET (8 μm) film was isolated from the substrate with little change (<1%) in electrical conductivity. Finally, the mechanical durability of the flexible electrode was evaluated by a U-shape folding test, and no cracking or delamination was observed after 10,000 test cycles.

Ultrawideband inkjet‐printed monopole antennas for energy harvesting application

AbstractMultiple communication and identification systems are taking advantage of inkjet‐printing techniques for the production of flexible, low‐cost, and lightweight printed radiating elements. In this paper, we bring the advantages of inkjet printing to the design of efficient and low‐cost wideband radio‐frequency (RF) energy harvesters. We present the design, manufacturing, and measurement of two inkjet‐printed ultrawideband monopole antennas. Both elliptical and circular monopoles are printed with a silver conductive ink on a thin polyethylene terephthalate film that lays on a foam substrate. Measurements show that the antennas operate efficiently from 0.6 to 8 GHz, covering the most relevant power contributions coming from the radio spectrum. In addition, the antennas show omnidirectional characteristics, highly desirable for broad spatial coverage in RF energy harvesting.

A disposable smart microfluidic platform integrated with on-chip flow sensors

Microfluidic devices are powerful tools for biological, biomedical, chemical, and pharmaceutical applications, but their commercialization is still hindered by the lack of methods to automatically control fluid flow in a low-cost, simple, accurate, and safe manner. This study introduces a disposable smart microfluidic platform (DIS-μChip), which can be fully automated and utilized for a wide range of applications. On-chip microfluidic flow sensors are integrated with the platform and placed at all inlet and outlet channels, thereby allowing the DIS-μChip to be fully automated with a pressure control system. Furthermore, these confer a self-diagnosis function through monitoring of all the input and output flow rates. The DIS-μChip consists of a disposable polymeric microchannel superstrate and a permanent multifunctional substrate, which could be assembled and disassembled using only vacuum pressure. The superstrate was fabricated by combining a polydimethylsiloxane microchannel structure with a polyethylene terephthalate (PET) thin film. The substrate contains sense electrodes for the on-chip-integrated flow sensors and functional components for creating an energy field, which can penetrate the PET thin film and manipulate the fluid in the microchannels of the superstrate. Owing to the film-chip technique, the superstrate was disposable and could prevent biological cross-contamination, which cannot be realized with conventional flow sensors. The usefulness of the DIS-μChip was demonstrated by using it to isolate circulating tumor cells from the blood of patients with pancreatic cancer and to obtain cancer-specific genetic information from them with droplet digital PCR.

Flexible Out-of-Plane Wind Sensors with a Self-Powered Feature Inspired by Fine Hairs of the Spider.

The quest for out-of-plane and self-powered wind sensors has motivated the field of outdoor sports, exploration, space perception, and positioning. Fine hairs of spiders act as hundreds of individual wind sensors, allowing them to feel the nearby wind change caused by the predators or the prey. Inspired by this natural teacher, here, we demonstrate the fabrication of bioinspired self-powered out-of-plane wind sensors based on flexible magnetoelectric material systems. The shape of flexible sensors, by patterning silver nanoparticles on a thin polyethylene terephthalate film through a screen printing technique, mimics fine hairs of the spiders, allowing for out-of-plane tactile perceptual monitoring caused by the wind. Owing to the employment of flexible magnetoelectric materials, the sensors can distinguish forward/backward winds and are totally self-powered. The working mechanism for sensors has been explained by the Maxwell numerical simulation, allowing for further improvement of their performance by tuning diverse factors. Furthermore, the wind sensor can detect the wind with a velocity down to 1.2 m/s and distinguish multidegree wind by their arrays. It is expected that, in the near future, our design can provide new findings for out-of-plane wind sensors with superior self-powered properties toward new flexible electronics.

Ion track etching in polyethylene-terephthalate studied by charge particle transmission technique

ABSTRACTIn the paper, thin films of polyethylene-terephthalate, pristine or irradiated with 170 MeV Xe+ ions to the fluence of 105 cm−2, were etched in the mild 1 M NaOH medium at 60°C for different times. The main aspects of the etching process (i.e. development of the pores, dependence of the foil thickness and transparency on the time of etching) were studied by the ion transmission technique (ion energy loss spectroscopy) that was previously introduced by the author’s team. It has been shown that the transmission method makes it possible to closely monitor the development of the polymeric porosity and to determine the important parameters of the etching process (e.g. etching rate along the latent tracks, bulk etching rate, radial etching rate, breakthrough, foil transparency). The measurement was carried out at the NPI Rez using the alpha particle microprobe on the Tandetron accelerator.

Impact of hydrolytic degradation on mechanical properties of PET - Towards an understanding of microplastics formation

Ocean pollution by microplastics, i.e. small pieces of plastic of less than 5 mm, is one of the major concerns for the future of our planet. Secondary microplastics formation is due to fragmentation of macroplastic waste. This fragmentation can be attributed to environmental loadings such as waves, winds and tides, coupled with a change in mechanical properties of polymers induced by UV and seawater ageing. This study aims to characterize and understand changes in the mechanical behaviour of Polyethylene Terephthalate (PET) induced by hydrolysis, especially for high degradation levels. Thin films (200 μm) of PET were aged in water at temperatures from 110 °C to 80 °C for up to 150 days. Embrittlement occurs with chain scission during hydrolysis when molar mass of the polymer falls below 17 kg/mol. When the polymer is brittle, i.e. for high levels of degradation, the stress at break decreases linearly with the molar mass, and can be described by a simple mathematical expression.

Tunable graphene/dielectric laminate for adaptive low-gigahertz shielding and absorbing screens

Shielding and absorbing screens made of tunable graphene/ dielectric laminate (GL) doped by an electrostatic field bias are designed applying simple modelling procedures in the low-gigahertz frequency range. The adaptive response of both types of screens is achieved through the control of the effective sheet resistance of the GL, consisting of a proper number of doped graphene layers separated by thin films of polyethylene terephthalate (PET). The performances of the shielding screen are predicted in the frequency range up to 1 THz, using simple approximate expressions and rigorous simulation models. The multilayer absorber is a twoperiod dielectric Salisbury screen, in which the outer lossy sheet is made of a single-layer graphene and the inner one is a GL with two electrically doped graphene layers. The reflection coefficient is minimized at each frequency through the proper setting of the electrostatic field bias. The optimal absorbing performances of the screen are predicted in the frequency range between 2 GHz and 25 GHz.

Effect of polybutylene adipate-co-terephthalate on properties of polyethylene terephthalate thin films

The aim of this research is to study the mechanical, thermal properties and morphology of polybutylene adipate-co-terephthalate (PBAT) blended with polyethylene terephthalate (PET) thin films. Effect of TiO2 and ZnO is also investigated on mechanical and thermal properties of PBAT/PET thin films. PBAT and PET are blended by a twin screw extruder and film is casted by film extruder. Mechanical, thermal properties and morphology are studied by using universal testing machine, differential scanning calorimeter, thermogravimetric analyzer and scanning electron microscope. From the results, higher PBAT content led to the increment of elongation at break with the sacrifice of modulus of PET thin films. In addition, thermal stability of PBAT/PET thin films is lower than neat PET films. Moreover, modulus and tensile strength could be improved by adding 1-2 wt% ZnO into PET/PBAT film. However, the addition of TiO2 has no significant effect on tensile properties of PET/PBAT film.

Influence of SHI upon nanohole free volume and micro scale level surface modifications of polyethyleneterephthalate polymer films

Topographic micro scale and in-depth nano scale level modifications of polymeric materials play an important role in engineering their physical and chemical properties. Polyethylene terephthalate (PET) is an important class of semi-crystalline polymers used for gas separation properties. The gas diffusion and permeability parameters are directly related to the free volume fractions and the hole distributions. The controlled and precise ion beam irradiation can be used to induce surface and in-depth modifications in the properties of the polymers which help in modifying free volume holes and their distributions. In the present study, the investigation of free volume (nano scale level) and surface (micro scale level) properties of PET polymeric thin films after SHI treatment were employed by means of positron annihilation lifetime spectroscopy (PALS) and atomic force microscopy (AFM), respectively. The PET thin films were irradiated by 50MeV lithium ions as a function of ion fluence. The value of hole radius (R) and intensity (I3) of o-Ps were observed to be increased after ion beam treatment. The further analyses were employed to calculate the free volume and fractional free volume of holes from the obtained values of R and I3. The AFM studies reveal the surface modifications of the irradiated polymer films. The structural, optical and chemical properties were investigated by X-ray diffraction (XRD), UV–visible (UV–vis) and Fourier transform infrared (FTIR) spectrophotometry. Different parameters such as crystallite size and band gap energy were calculated from the obtained data of XRD and UV–vis, respectively.

A Triboelectric Generator Based on Checker‐Like Interdigital Electrodes with a Sandwiched PET Thin Film for Harvesting Sliding Energy in All Directions

A triboelectric generator based on checker‐like interdigital electrodes (TEGC) with a sandwiched polyethylene terephthalate (PET) thin film that can convert translation kinetic energy in all directions to electricity is reported. The design of the sandwiched PET thin film can effectively avoid direct wear between metal electrodes and sliding panel. The mechanism of the TEGC is described in detail. The performance of the TEGC in different sliding directions is studied, indicating a maximum output power density of 1.9 W m‐2 and open‐circuit voltage of 210 V achieved in the X or Y sliding direction. The TEGC is used to charge a 110 μF commercial capacitor to 5 V in 35 s and light up two light‐emitting diodes (LEDs) connected with the capacitor simultaneously. The TEGC based mouse pad and sliding panel are fabricated to harvest mouse operation energy to light up LEDs connected in antiparallel when the computer mouse operates a game. The TEGC has advantages of being flexible, light weight, durable, cost effective, and portable by folding or rolling into a small part. This work presents a significant progress toward the structure design of triboelectric generator for its practical applications.

Surface roughening of PET films through blend phase coarsening.

In this study, a novel method to increase the surface roughness of polyethylene terephthalate (PET) films is proposed. The mechanism of phase coarsening at the surface in extruded thin films of PET blended with low concentrations of polystyrene (PS) was investigated. A small amount of poly(hyroxyl ether) of bisphenol A (phenoxy resin, PKHH) was found to significantly increase the surface roughness due to its effect on the PS-PET interfacial tension. X-ray photoelectron spectroscopy (XPS) results indicated that in the presence of PKHH, PS droplets migrated spontaneously towards the surface of the polymer film. An increased local concentration of PS near the surface took the form of encapsulated droplets. Above the flow temperature of the blend, the local concentration of PS eventually reached a level where a co-continuous morphology occurred, resulting in the instabilities on the surface of the film. The adhesion properties of films with various roughnesses were determined using a pull-off test and found to be significantly increased, which suggested that co-continuous morphology and the coarsening process increased the adhesive properties of the film.

Precision patterning of conductive polymer nanocomposite using a laser-ablated thin film

We introduce a simple, reliable and low-cost microfabrication technique utilizing laser ablation of a thin polymer film to pattern polymer nanocomposite at a high resolution. A conductive composite of poly(dimethylsiloxane) (PDMS) and carbon nanotubes (CNTs) was selected due to their wide use in microelectromechanical systems (MEMS) and unique properties including flexibility and piezoresistivity. To pattern nanocomposite, an excimer laser ablated through a thin polyethylene terephthalate film creating mold patterns. PDMS-CNTs nanocomposite was then filled into the mold with excessive amount removed by a smooth-edged tool. Bulk PDMS was poured atop and cured. After debonding devices with relief patterns of polymer nanocomposite could be readily realized. Fabrication conditions were optimized which led to reliable patterning of various microstructures. Detailed surface profiling revealed excellent pattern authenticity and uniformity. Minimal feature size of patterns reached below 20 µm which indicated a significant improvement from prior reports. Moreover, the presented technique required only a software design to rapidly generate new patterns, thereby eliminating costly hardware such as lithography mask, stamp and clean room. Fabrication time and cost could be consequently reduced—ideal for lab prototyping purposes. Sensor examples are discussed to demonstrate versatile applications of polymer nanocomposite in MEMS.

Extraordinary mechanical flexibility in composite thin films composed of bimetallic AgPt nanoparticle-decorated multi-walled carbon nanotubes

Flexible, transparent, and conducting composite thin films, constructed from multi-walled carbon-nanotube-supported silver–platinum alloy nanoparticles (AgPt–MWCNT) on a flexible polyethylene terephthalate (PET) substrate through the combination of a two-step polyol process for synthesizing composites of carbon nanotubes (CNTs) and metallic nanoparticles (NPs) with an ultrasonic atomization-spin coating method for preparing thin films, have been fabricated. AgPt NPs with an average size of approximately 26nm were uniformly attached to the sidewalls of MWCNTs to form an effective and strongly mechanical conductive network. These composites were then exposed to microwave plasma irradiation, which can lower the contact resistance between the metallic NPs and CNTs and reinforce the network bridges. The resulting AgPt–MWCNT–PET thin films exhibit improved optoelectronic and mechanical properties, and they possess a sheet resistance of 154Ω/sq with a transmittance of 80% at 550nm. These values are competitive with those of most other CNT-based films. Most importantly, the corresponding sheet conductivity does not decrease even after 500 bending cycles. Therefore, the as-produced AgPt–MWCNT–PET films may be direct alternatives to indium tin oxide and other transparent conducting oxide films.

Molecular layer deposition of polyethylene terephthalate thin films

Thin films of polyethylene terephthalate (PET) have been grown using sequential surface chemical reactions on silicon substrates. The surface has been sequentially exposed to terephthaloyl chloride (TC) and ethylene glycol (EG) in an ASM F-120 atomic layer deposition reactor. Precursor pulses were alternated with 30 s of N2 purge. The process has been studied as a function of temperature, precursor pulsing time, and number of cycles. The films were deposited in the temperature range 145–175 °C and the precursors were held at 130 °C (TC) and 70 °C (EG). Before deposition the silicon surface was functionalized using 3-aminopropyltriethoxysilane to ensure nucleation of the film. The film growth exhibits self-limiting behavior and linear growth rate dependence that confirms its molecular layer deposition nature. The deposited films have been identified as PET by means of attenuated total reflectance FTIR which reveals the presence of characteristic carbonyl and aromatic groups. Film thickness was measured by spectroscopic ellipsometry. The maximum deposition rate of 3.3Å/cycle was obtained. Surface morphology was investigated using AFM showing average roughness (Ra) of 3.5 nm.

Optimization of SiO&lt;sub&gt;x&lt;/sub&gt;/PET Thin Films Prepared by RF Magnetron Sputtering Technology Based on Orthogonal Experiment

The SiOx thin films were deposited by RF magnetron sputtering physical vapor technology on the substrates of 20μm polyethylene terephthalate（PET）, using a pure SiO2 target. An L15 (33) orthogonal experiment was designed with three factors and three values including deposition time, sputtering power, sputtering pressure. Using OTR test the effect of process parameters were researched. The primary and secondary sequence of the design parameters were acquired by the quadratic multinomial. The result showed that deposition time affected more strongly the OTR of the films than the sputtering pressure, the sputtering power affected least between them. The best SiOx thin films were prepared at a deposition time of 27.9min，a sputtering power of 1825W，a sputtering pressure of 0.3455Pa. The calculated OTR was 0.8387 cc/(m2×day)，which was consistent with the test one.

Flexible inverted polymer solar cells containing an amorphous titanium oxide electron collection electrode

An inverted polymer solar cell was fabricated on a polyethylene terephthalate (PET) substrate. The cell structure was ITO/amorphous titanium oxide (TiO x )/[6,6]-phenyl C 61 butyric acid methyl ester (PCBM): regioregular poly(3-hexylthiophene) (P3HT)/poly(3,4-ethylenedioxylenethiophene):poly(4-styrene sulfonic acid) (PEDOT:PSS)/Au (TiO x cell). It was achieved using low boiling point diethyl amine (DEA) as a Ti 4+ complexing agent, and high boiling point 1,2,3,4-tetrahydronaphthalene (Tetralin) containing 2 vol.% 1,8-octanedithiol (ODT) as the solvent for PCBM:P3HT film preparation. With heat treatment at 100 °C, the use of DEA and Tetralin:ODT made it possible to prepare a TiO x electron collection layer and PCBM:P3HT photoactive layer, respectively. Fabricating the TiO x cell on the thin PET film was possible, as PET did not warp at 100 °C. The power conversion efficiency (PCE) of the TiO x cell fabricated on PET was 2.43%, under AM1.5G conditions. When fabricated on glass, the PCE was 2.76%. When [6,6] diphenyl C 62 bis(butyric acid methyl ester) (bis-PCBM) was instead used as the electron acceptor in the photoactive blend layer, the flexible air-stable cell provided a PCE of 2.81%.

Three-dimensional bulk metamaterials operating in the terahertz range

Three-dimensional bulk metamaterials that operate in the terahertz (THz) frequency range were fabricated by stacking 100 two-dimensional sheets containing metallic split-ring resonators (SRR) on thin polyethylene terephthalate film substrates. The THz magnetic resonance for the incident magnetic field perpendicular to the plane of the SRR structure was measured. We also investigated the dependence of the magnetic resonant strength on the metal thickness.