Characterization and conformal analysis of ultrawideband cognitive radio antenna using polyvinyl alcohol and graphite composite substrate

The accuracy of spatiotemporal control cargo delivery and release are primordial to enhance the therapeutic efficiency and decrease the undesirable effects, in this context a novel prodrug were developed based on biocompatible polyvinyl alcohol (PVA) substrate. PVA was conjugated to doxorubicin (PVA-DOX) via an acid-labile hydrazone linkage. PVA was first functionalized with acidic groups, then reacted with hydrazine hydrate to form an amide bond. The amine group of PVA hydrazide was linked to carbonyl group (C = O) of DOX to form a pH sensitive hydrazone bond. The molecular structure of the PVA-DOX was confirmed by FTIR, XPS, and 1H-NMR analysis methods. The degree of grafting were evaluated by TGA and confirmed by XPS, which reveals the successful bond attachment of DOX to PVA. Our findings confirm pH dependent DOX release from PVA-DOX prodrug with faster release rate in acidic environment (pH 5.0, pH 6.0) and slower release rate in neutral pH environment (pH 7.4). Compared to the primary DOX, our synthesized PVA-DOX conjugates could exhibit a promising therapeutic effect, high biocompatibility and zero premature release. The results prove the successful synthesis of PVA-DOX conjugates with high efficiency.

Behavior of embryonic rat cerebral cortical stem cells on the PVA and EVAL substrates

Culture substrates display profound influence on biological and developmental characteristic of cells cultured in vitro. This study investigates the influence of polyvinyl alcohol (PVA) substrates blended with different concentration of collagen or/and gelatin on the cell adhesion, proliferation, shape, spreading, and differentiation of stem cells. The collagen/gelatin blended PVA substrates were prepared by air drying. During drying, blended collagen or/and gelatin can self-assemble into macro-scale nucleated particles or branched fibrils in the PVA substrates that can be observed under the optical microscope. These collagen/gelatin blended substrates revealed different surface topography, z-average, roughness, surface adhesion and Young's modulus as examined by the atomic force microscope (AFM). The results of Fourier transform infrared spectroscopy (FTIR) analysis indicated that the absorption of amide I (1,600-1,700cm-1) and amide II (1,500-1,600cm-1) groups increased with increasing collagen and gelatin concentration blended and the potential of fibril formation. These collagen or/and gelatin blended PVA substrates showed enhanced NIH-3T3 fibroblast adhesion as comparing with the pure PVA, control tissue culture polystyrene, conventional collagen-coated and gelatin-coated wells. These highly adhesive PVA substrates also exhibit inhibited cell spreading and proliferation. It is also found that the shape of NIH-3T3 fibroblasts can be switched between oval, spindle and flattened shapes depending on the concentration of collagen or/and gelatin blended. For inductive differentiation of stem cells, it is found that number and ration of neural differentiation of rat cerebral cortical neural stem cells increase with the decreasing collagen concentration in the collagen-blended PVA substrates. Moreover, the PVA substrates blended with collagen or collagen and gelatin can efficiently support and conduct human pluripotent stem cells to differentiate into Oil-Red-O- and UCP-1-positive brown-adipocyte-like cells via ectodermal lineage without the addition of mitogenic factors. These results provide a useful and alternative platform for controlling cell behavior in vitro and may be helpful for future application in the field of regenerative medicine and tissue engineering.

In this research, preparation of Au films on poly vinyl alcohol (PVA) substrates by using plasma direct current glow discharge sputtering (FT-IR)results for poly vinyl alcohol showed matching the sites of the active groups of the polymer with its chemical composition X-ray diffraction (XRD) showed that the thin films had a polycrystalline while the surface roughness was diagnosed using an atomic force microscopy (AFM)the where the results showed that the roughness increased from (30.099-55.221)nm with increasing the thickness from (90-195)nm. Scanning electron microscope(SEM)showed that nanoparticles with a spherical shape the particles aggregates to form larger clusters with increased film thickness.

An easy and sensitive method for the determination of serotonin (5-HT), tryptamine (Try) and gramine (Gra) was developed by using solid-substrate room-temperature phosphorimetry on a poly (vinyl alcohol) substrate. The method did not require a dry gas flush during the measurement of phosphorescence. The phosphorescence intensities of the compounds were enhanced by using a NaOH solution {water-ethanol, 50:50 (v/v)} as the solvent, and potassium iodide and sodium dodecyl sulfate as enhancers. The order of spotting phosphor and enhancers onto the substrate also affected the phosphorescence intensity. The analytical figures of merit for these three compounds were as follows. The linear dynamic ranges of 5-HT, Try and Gra were 5500, 2.5250 and 2.5250 pmol/spot (5 μl), respectively. The correlation coefficients of the calibration curves were over 0.991 and the relative standard deviations at 50 pmol/spot (5 μl) varied from 5.0 to 6.5%, showing a good precision of the proposed method.

To prepare a water vapor barrier membrane, organic/silica nanocomposites were used with perhydropolysilazane (PHPS) and poly(tert‐butyl acrylate) (P(tBA)) or poly(tert‐butyl acrylate‐co‐2‐hydroxyethyl methacrylate) (TBAH) on a poly(vinyl alcohol) (PVA) substrate. Water vapor permeability coefficient, Q, of the coated PVA substrates was measured. To prevent crack formation in the organic/silica nanocomposite layer, P(tBA) or TBAH with lower Tg than that of PVA was inserted as a stress relaxation layer between the PVA substrate and the composite layer. The insertion of the stress relaxation layer drastically decreased the Q value. The lowest Q value was observed especially when TBAH was inserted between TBAH/silica nanocomposite layer and the PVA substrate. Observation with a scanning electron microscope (SEM) did not show any crack both in the composite layer and near the interface between layers. It would be due to the good compatibility of the TBAH stress relaxation layer to the TBAH/silica nanocomposite layer and to the PVA substrate. Copyright © 2008 John Wiley & Sons, Ltd.

Determination of p-aminobenzoic acid in the presence of bovine serum albumin by room-temperature phosphorimetry on a poly(vinyl alcohol) substrate

Electronics that degrade after stable operation for a desired operating time, called transient electronics, are of great interest in many fields, including biomedical implants, secure memory devices, and environmental sensors. Thus, the development of transient materials is critical for the advancement of transient electronics and their applications. However, previous reports have mostly relied on achieving transience in aqueous solutions, where the transience time is largely predetermined based on the materials initially selected at the beginning of the fabrication. Therefore, accurate control of the transience time is difficult, thereby limiting their application. In this work, we demonstrate transient electronics based on a water-soluble poly(vinyl alcohol) (PVA) substrate on which carbon nanotube (CNT)-based field-effect transistors were fabricated. We regulated the structural parameters of the PVA substrate using a three-dimensional (3D) printer to accurately control and program the transience time of the PVA substrate in water. The 3D printing technology can produce complex objects directly, thus enabling the efficient fabrication of a transient substrate with a prescribed and controlled transience time. In addition, the 3D printer was used to develop a facile method for the selective and partial destruction of electronics.

A flexible, scalable, and self-powered mid-infrared detector based on transparent PEDOT: PSS/graphene composite

Properties enhancement of graphene and chemical reduction silver nanoparticles conductive inks printed on polyvinyl alcohol (PVA) substrate

Electrochemical Performance of Binary Ni-Co Particles Deposited on Graphene Oxide/Polyvinyl alcohol Substrate in Alkaline Medium

Recently, there have been considerable interests in strain sensors that are flexible and stretchable, due to their potential for use in wearable electronics applications. Herein, a facile approach has been employed to produce synergistic strain sensor, taking advantage of the salient properties of hybrid conductive inks produced from graphene and silver nanoparticles (AgNPs). The hybrid ink was inkjet-printed on a polyvinyl alcohol (PVA) substrate. The effect of factors such as amount of graphene, annealing time and printing cycle on the performance of the hybrid conductive ink was investigated. The results showed that an increase in the amount of graphene from 0.1 to 0.5 wt% produced about 90% enhancement in the electrical conductivity of the hybrid ink. However, the change in electrical conductivity values of the hybrid ink at 0.5 wt% and 0.7 wt% graphene content is negligible. On the other hand, it was observed that the electrical conductivity was notably influenced by the number of printing cycle, as well as the annealing time. Significantly, the sensitivity performance of the printed hybrid graphene/AgNPs strain sensor is higher than that of individual graphene and AgNPs printed strain sensors under the strain range up to 20%.

A transparent flexible volatile memory with ultrahigh ON/OFF ratio and ultralow switching voltage

Epidermal electronics play increasingly important roles in human-machine interfaces. However, their efficient fabrication while maintaining device stability and reliability remains an unresolved challenge. Here, a facile in situ Joule heating method is proposed for fabricating stable epidermal electronics on a polyvinyl alcohol (PVA) substrate. Benefitting from the precise control of heating locations, the crystallization and enhanced rigidity of PVA are restricted to desired areas, leading to strain isolation of the active regions. As a result, the electronic device can be conformably attached to skin while showing negligible degradation in device performance during deformation. Based on this method, a flexible surface electromyography (sEMG) sensor with outstanding stability and highly comfortable wearability is demonstrated, showing high accuracy (91.83%) for human hand gesture recognition. These results imply that the fabrication method proposed in this research is a facile and reliable approach for the fabrication of epidermal electronics.

Unveil self-plasticized polyvinyl alcohol derived customizable patterned photosensitive resin films