Bare Polyethylene Terephthalate Research Articles

Chondroitin sulfate coatings display low platelet but high endothelial cell adhesive properties favorable for vascular implants.

This study highlights the advantages of chondroitin sulfate (CS) as a sublayer combining selective low-fouling properties, low-platelet adhesion and pro-adhesive properties on endothelial cells, making CS promising for vascular graft applications. These properties were evaluated by comparing CS with well-known low-fouling coatings such as poly(ethylene glycol) (PEG) and carboxymethylated dextran (CMD), which were covalently grafted on primary amine-rich plasma polymerized (LP) films. Protein adsorption studies by quartz crystal microbalance with dissipation monitoring (QCM-D) and fluorescence measurements showed that CS is as effective as PEG in reducing fibrinogen adsorption (~90% reduction). CS also largely reduced adsorption of bovine serum albumin (BSA) as well as fetal bovine serum (FBS) but to a lower extent than PEG and CMD surfaces (72% vs 85% for BSA and 66% vs 89% for FBS). Whole blood perfusion assays indicated that, while LP surfaces were highly reactive with platelets, PEG, CMD, and CS grafted surfaces drastically decreased platelet adhesion and activation to levels significantly lower than polyethylene terephthalate (PET) surfaces. Finally, while human umbilical vein endothelial cell (HUVEC) adhesion and growth were found to be very limited on PEG and CMD, they were significantly increased on CS compared to that on bare PET and reached similar values as those for tissue culture polystyrene positive controls. Interestingly, HUVEC retention during perfusion with blood was found to be excellent on CS but poor on PET. Overall, our results suggest that the CS surface has the advantage of promoting HUVEC growth and resistance to flow-induced shear stress while preventing fibrinogen and platelet attachment. Such a nonthrombogenic but endothelial-cell adhesive surface is thus promising to limit vascular graft occlusion.

Transparent (NH4)xWO3 colloidal dispersion and solar control foils: Low temperature synthesis, oxygen deficiency regulation and NIR shielding ability

Highly-stable aqueous dispersion of (NH4)xWO3 crystallites (ac. 6–12nm in diameter and 20–100nm in length) with decent infrared shielding ability was synthesized at only 100°C. The effects of reducing agent (N2H4∙2HCl) dosage on the phase, morphology, zeta potential and composite of products have been systematically addressed. It was shown that the addition of N2H4∙2HCl in precursor solution introduced obvious oxygen deficiency into (NH4)xWO3 crystallites, resulting in a further improved NIR shielding ability. However, high dosages of N2H4∙2HCl were found to depress the zeta potentials and accelerate the growth of (NH4)xWO3 crystallites. A mechanism, which was reasonably supported by confirmatory experiments, was extracted to explain the result. To show potential application of our product, (NH4)xWO3-based flexible solar control foils were prepared by directly casting the dispersion onto polyethylene terephthalate (PET) substrates. The foils can selectively cut-off near infrared light (NIR) by 65.8% (transmittance depressed from 91.3% of a bare PET to 25.5% of the foils), while maintaining a high visible transmittance of 67.6%, showing promise as energy-efficient filter.

Characterization of local charge distribution of polyethylene terephthalate film and influence as a graphene substrate

We examine local electrostatic force distribution of polyethylene terephthalate (PET) film surface before and after transferring graphene in order to compare the influence of local electrostatic interaction between graphene and PET film in terms of the sheet resistance value of deposited graphene. By using the electrical modulation of amplitude in a tapping mode AFM tip, we can obtain the distinguished electrostatic force amplitude mapping of graphene. We determine that different electrostatic attractive interactions between Au-coated tip and bare PET are present and the observed difference can affect the graphene formation and electrical performance, which correlates with the sheet resistance difference.

Light induced hydrophilicity and osteoblast adhesion promotion on amorphous TiO2

We have studied the effect of the UV induced superhydrophilic wetting of TiO(2) thin films on the osteoblasts cell adhesion and cytoskeletal organization on its surface. To assess any effect of the photo-catalytic removal of adventitious carbon as a factor for the enhancement of the osteoblast development, 100 nm amorphous TiO(2) thin layers were deposited on polyethylene terephthalate (PET), a substrate well known for its poor adhesion and limited wettability and biocompatibility. The TiO(2) /PET materials were characterized by X-ray photoelectron spectroscopy, and atomic force microscopy and their wetting behavior under light illumination studied by the sessile drop method. The amorphous TiO(2) thin films showed a very poor photo-catalytic activity even if becoming superhydrophilic after illumination. The illuminated samples recovered partially its initial hydrophobic state only after their storage in the dark for more than 20 days. Osteoblasts (HOB) were seeded both on bare PET and on TiO(2) /PET samples immediately after illumination and also after four weeks storage in darkness. Cell attachment was much more efficient on the immediately illuminated TiO(2)/PET samples, with development of focal adhesions and cell traction forces. Although we cannot completely discard some photo-catalytic carbon removal as a factor contributing to this cell enhanced attachment, our photodegradation experiments on amorphous TiO(2) are conclusive to dismiss this effect as the major cause for this behavior.

Fabrication of a 60‐nm‐Diameter Perfectly Round Metal‐Dot Array over a Large Area on a Plastic Substrate Using Nanoimprint Lithography and Self‐Perfection by Liquefaction

Typically, nanopatterning on plastic substrates has poor fidelity, poor adhesion, and low yield. Here the proposal of and the first experiment using a new fabrication method that overcomes the above obstacles and has achieved arrays of 60-nm-diameter, perfectly round metal dots over a large area on a polyethylene terephthalate (PET) substrate with high fidelity and high yield is reported. This new method is based on the use of a thin hydrogen silsesquioxane (HSQ) layer on top of PET, nanoimprint lithography, and self-perfection by liquefaction (SPEL). The HSQ layer offers excellent thermal protection to the PET substrate during SPEL, as well as good surface adhesion and etching resistance. Nanoimprinting plus a lift off created a large-area array of Cr squares (100 nm x 130 nm) on HSQ and SPEL changed each Cr square into a perfectly round Cr dot with a diameter of 60 nm, reducing the Cr footprint area by 78%. Compared to bare PET, the use of HSQ also reduced the variation in the diameter of the Cr dots from 11.3 nm (standard deviation) to 1.7 nm, an improvement of over 660%. This new technology can be scaled to much larger areas (including roll-to-roll web processing) and thus potentially has applications in various fields.

Properties of indium tin oxide films deposited on unheated polymer substrates by ion beam assisted deposition

The optical, electrical and mechanical properties of indium tin oxide (ITO) films prepared on polyethylene terephthalate (PET) substrates by ion beam assisted deposition at room temperature were investigated. The properties of ITO films can be improved by introducing a buffer layer of silicon dioxide (SiO 2) between the ITO film and the PET substrate. ITO films deposited on SiO 2-coated PET have better crystallinity, lower electrical resistivity, and improved resistance stability under bending than those deposited on bare PET. The average transmittance and the resistivity of ITO films deposited on SiO 2-coated PET are 85% and 0.90 × 10 − 3 Ω cm, respectively, and when the films are bent, the resistance remains almost constant until a bending radius of 1 cm and it increases slowly under a given bending radius with an increase of the bending cycles. The improved resistance stability of ITO films deposited on SiO 2-coated PET is mainly attributed to the perfect adhesion of ITO films induced by the SiO 2 buffer layer.

Effects of parylene buffer layer on flexible substrate in organic light emitting diode

Parylene was deposited on a bare polyethylene terephthalate (PET) and poly carbonate (PC) film surface to enhance the oxygen and water barrier properties at room temperature. The deposition rate of the parylene was observed to have increased linearly as the working pressure was increased. The oxygen plasma pre-treatment of the PET for the adhesion between bare film and parylene was mostly effective to 5B, while the treatment of N-(2-Aminoethyl)-3-Aminopropylmethyldimethoxysilane solution at PC film resulted in 3B. Surface morphology and roughness were observed by atomic force microscopy and the barrier property was measured by oxygen transmission rate and water vapor permeation test equipments. The oxygen transmission rate (OTR) and water vapor transmission rate (WTR) of the PET film were reduced from 13.2 to 11.3 cc/m 2 day and from 4.6 to 2.0 g/m 2 day, respectively. When the parylene layer was coated onto the PC film, however, the barrier effects were significant from out of detection limit to 53.9 cc/m 2 day for the OTR, and from 24.7 to 3.5 g/m 2 day for the WTR. The real organic light emitting diode (OLED) device was fabricated with a parylene coated flexible substrate, which was subsequently deposited by transparent conducting layer and scratch-resistant layer. The initial brightness of the OLED device with a parylene buffer layer was 173 cd/cm 2, and 70% of its initial brightness was maintained after 40,000 s.

ITO films with enhanced electrical properties deposited on unheated ZnO-coated polymer substrates

Indium tin oxide (ITO) films were deposited by radio frequency (rf)-plasma enhanced reactive thermal evaporation (rf-PERTE) at room temperature on intrinsic ZnO/polymer substrates to enhance their electrical and structural properties. The polymer substrate used is polyethylene terephthalate (PET). The thickness of the ZnO films varied in the range 50–150 nm. The average thickness of the ITO films is of about 170 nm. Results show that ITO deposited on bare PET substrates exhibit: an average visible transmittance of about 85% and an electrical resistivity of 5.6 × 10 −2 Ω cm. ITO on ZnO/PET substrates show the optical quality practically preserved and the resistivity decreased to a minimum value of 1.9×10 −3 Ω cm for ZnO layers 125 nm thick. The electrical properties of ITO on ZnO/PET are largely improved by the increase in carrier mobility.

Surface analysis of the initial stages of Si film growth

Silicon films were deposited on gold-coated glass, copper-coated glass, bare polyethylene terephthalate (PET), and gold-coated PET substrates for times ranging from 10 s to 40 min at 130 °C for PET and 200 °C for the other substrates in order to study the chemistry of the initial stages of film growth. X-ray photoelectron spectroscopy (XPS) shows the formation of silicon oxide immediately upon commencement of the film growth. This oxide persists throughout the duration of the film growth. In PET films, the oxide is the dominant component of the Si 2p XPS peak, whereas it exists only as a minor, high-energy shoulder on the Si 2p peak for gold and copper-coated glass substrates and gold-coated PET substrates, indicating a less contaminated silicon film. X-ray diffraction (XRD) indicates that films grown on gold-coated glass for 40 min were polycrystalline with a (1 1 1) preferred orientation, and an average grain size of 95 ± 5 nm.

Influence of negative metal ion bombardment on the properties of ITO/PET films deposited by dc magnetron sputtering

Transparent conducting indium tin oxide (ITO) thin films were deposited on a polyethylene terephthalate (PET) substrate at a low substrate temperature by dc magnetron sputtering using a negative metal ion source and an ITO target. During separate deposition runs, the cesium partial pressure was varied from 1 × 10 −3 to 2.2 × 10 -3 Pa to investigate the effect of ion beam bombardment on the surface morphological, electrical and optical properties of the films. The resistivity of ITO films decreased with P Cs and reached as low as 6.2 × 10 −4 Ω cm at P Cs of 1.7 × 10 −3 Pa. Optical transmittance compared with bare PET substrate also varied significantly with P Cs and the highest optical transmittance of 87% (at λ=550 nm) was obtained at P Cs of 1.7 × 10 −3 Pa. According to a result obtained by AFM, surface roughness of the ITO/PET film showed remarkable change from 2.8 to 1.1 nm with P Cs. However, above optimal P Cs condition (>1.7 × 10 −3 Pa), the electrical, optical property and surface morphological properties deteriorated. From SEM, AFM, and Hall measurements, relatively low resistivity and high transmittance of ITO film deposited at P Cs=1.7×10 −3 Pa is caused by an increase in charge carrier concentration and flat surface morphology with secondary negative metal ion beam bombardment.