Non-coated Films Research Articles

Effects of Different Processing Techniques and Sol-Gel Coating on Physical Properties of Starch and Clay-Based Biocomposite Material

This study investigated the effects of different processing techniques and sol-gel coating on the physical properties of biocomposite material. Two dispersion series from corn starch, clay, and sorbitol were prepared by conventional and microwave-assisted processing, and casting technique. One film from each series was sol-gel coated by immersion. All the samples were subjected to moisture content (MC), water solubility (WS), water absorption (WA), FT-IR, DSC, and SEM/digital microscopy tests. The results showed that the coated films contained higher MC (11.5±0.5%) than the non-coated films (5.3±0.6%) and absorbed less water (44.7±12.4%), compared to the non-coated ones (166.3±2.5%). Non-coated films exhibited less solubility in water (26.1±0.2%) than the coated ones (51.0±0.7%). FT-IR test detected cross-linking (1723 cm-1 ester) in the microwave-assisted coated film. The sol-gel coating increased the latent heat of melting and specific heat values by 14.9% and 19.4% for conventionally fabricated samples, and 22.3% and 25.3% for microwaved films, respectively, whereas it reduced the temperature of melting by 23.1% for conventionally fabricated ones, and 6.6% for microwaved ones. Microscopic tests revealed that microwaved compact morphology indicated better gelatinization of starch. Overall, microwaving and sol-gel coating need further investigation to improve the physical properties of biocomposite materials for food packaging.

Field Emission Characteristics of Metal-Coated Nanocrystalline Diamond Films

Effect of thin metal coatings in nanoscale on field emission characteristics of nitrogen-incorporated nanocrystalline diamond films is examined with different metal species and thicknesses. The films show minimal change in surface morphology by coating a thin layer of Ag, Au, and In and consist of fine grains with sizes ranging from 10 to 20 nm depending upon the metal species and thickness. While the emission turn-on field is increased slightly to 3.6 Vμm−1 with very small thicknesses of the metals, it is decreased toward 2.5 Vμm−1 typical of a non-coated film with increasing thickness of the metals up to a few nm. The field enhancement factor related to the surface morphology of the films gives stronger effects on emission performance than the effective barrier height related to the work function of the metals. The Ag-coated film shows higher emission current stability than the non-coated film for duration up to 13 h.

Orientation Direction Control in Liquid Crystalline Photoalignable Polymeric Films by Adjusting the Free-Surface Condition.

Adjusting the free-surface condition facilely controls the in-plane and out-of-plane orientations in liquid crystalline polymer (LCP) films. Top coating with aromatic molecules onto LC polymethacrylate films with N-benzylideneaniline (NBA) or 4-methoxybiphenyl (MB) side groups (PNBAM or PMBM) and subsequent annealing generate a random planar orientation while simultaneously removing the coated aromatic molecules, whereas annealing noncoated films induces a homeotropic orientation of the mesogenic side groups. Additionally, irradiating a top-coated PNBAM film with linearly polarized (LP) 365 nm light induces an in-plane molecular reorientation of the NBA side groups without changing the orientation in the homeotropically oriented region. Changes in the surface topology of the LCP films due to the reorientation processes are investigated in detail. Inkjet coating with aromatic molecules and LP 365 nm light exposure precisely controls the in-plane and out-of-plane alignment pattern in a PNBAM film.

Time-dependent mussel-inspired functionalization of poly(l-lactide-co-ɛ-caprolactone) substrates for tunable cell behaviors

Surface properties of biomaterials, such as hydrophobic/hydrophilic balance, chemical group distribution, and topography play important roles in regulation of many cellular behaviors. In this study, we present a bio-inspired coating of synthetic biodegradable poly(L-lactide-co-ɛ-caprolactone) (PLCL) films by using polydopamine for tunable cell behaviors such as adhesion and proliferation. Polydopamine coating decreased the water contact angles of the PLCL film from 75° to 40°, while the amount of coated polydopamine increased from 0.6 μg/cm(2) to 177.9 μg/cm(2). During the process, dopamine could be directly polymerized on the surface of the PLCL film to form a thin layer or nanosized particles of self-aggregates, which resulted in increase of overall roughness in a time-dependent manner. Characterization of surface atomic composition revealed an increase in signals from nitrogen and the C-N bond, both suggesting homogeneous polydopamine coating with prolonged coating time. The mechanical properties were similar following reaction with polydopamine for a time shorter than 30 min, while alterations in elongation and Young's modulus were observed when the coating time exceeded 240 min. Cell adhesion and proliferation on the polydopamine-coated films were significantly greater than those on the non-coated films. Interestingly, these cell behaviors were significantly improved even under the minimal coating time (5 min). In summary, the bio-inspired coating is of use to generate modular surface of biomaterial based on synthetic poly(α-hydroxy ester)s for tunable cell behaviors with optimization of coating time within the range in which their mechanical properties are not compromised.

Collagen‐Coated Poly(l‐lactide‐co‐ɛ‐caprolactone) Film: A Promising Scaffold for Cultured Periosteal Sheets

We previously demonstrated that human periosteal sheets prepared on culture dishes function as an osteogenic "graft material" applicable to periodontal regenerative therapy. However, a lower level of initial adhesion of the excised periosteum tissue segments to culture dishes was a critical point that compromised the successful preparation of functional periosteal sheets. To improve on this weakness, we developed a transparent, biodegradable poly(L-lactide-co-ɛ-caprolactone) (LCL) film and tested its function as a scaffold and carrier of periosteal sheets. Human periosteum tissue segments excised from alveolar bone of healthy donors were cultured on type I atelocollagen-coated LCL films. Initial adhesion was examined by simple agitation. Cell outgrowth and in vitro mineralization were cytohistochemically examined. Osteogenic activity was histochemically examined in an animal implantation model using nude mice. Surface collagen-coating modified the hydrophobic nature of LCL and substantially improved the initial adhesion. Compared to cultures in plastic dishes, the growth rate was delayed in non-coated films, but not in collagen-coated films. In the trimming process for animal implantation, periosteal sheets were frequently detached from non-coated films, but not from collagen-coated films. Regardless of collagen-coating, LCL films did not cause any significant infiltration of inflammatory cells, or negatively impact mineralized tissue formation. Collagen-coating improved the initial adhesion of periosteum segments, which facilitated cell outgrowth and also handling efficiency on implantation. Therefore, we believe that once evaluated in human studies, our collagen-coated LCL film will contribute to improving the periodontal regenerative methodology with the application of cultured autologous periosteal sheets.

The improvement of fibroblast growth on hydrophobic biopolyesters by coating with polyhydroxyalkanoate granule binding protein PhaP fused with cell adhesion motif RGD

Polyhydroxyalkanoates (PHA), a family of biopolyesters, have been studied as tissue engineering biomaterials due to their adjustable mechanical properties, biodegradability and tissue compatibility. Amphiphilic PHA granule binding protein PhaP has been shown to be able to bind to hydrophobic surfaces of polymers, especially PHA, via strong hydrophobic interaction. Genes of PhaP and RGD peptides, which are a cell adhesion motif recognized by many cell surface receptors, were successfully expressed and obtained as a pure fusion protein PhaP-RGD in Escherichia coli DH5α. When films of poly(3-hydroxybutyrate- co-3-hydroxy- hexanoate) (PHBHHx), poly(3-hydroxybutyrate- co-3-hydroxyvalerate) (PHBV) and polylactic acid (PLA) were coated with PhaP-RGD, their surface hydrophilicities were all increased compared with their corresponding naked (non-coated) films, respectively. Among the three biopolyesters, PHBHHx demonstrated the strongest affinity to PhaP. In vitro study showed that mouse fibroblasts L929 and mouse embryonic fibroblasts NIH/3T3 attached better and grew faster on all three PhaP-RGD coated films compared with their related behaviors on PhaP coated and non-coated films, respectively. Both fibroblasts attached and grew very well on PhaP-RGD coated PHBHHx, PHBV and PLA, even in their serum-free medium, while the non-coated and PhaP coated biopolyesters poorly supported the cell growth if the two fibroblasts were incubated in their serum free medium. These results indicated that PhaP-RGD could be used as a coating material to improve cell growth on hydrophobic biopolyesters for implant tissue engineering purposes.

Cell attachment to PET films coated with a thermo-sensitive block co-polymer with different chemical composition

This objective of this study is to characterize the surface of poly(ethylene terephthalate) (PET) films coated with the thermo-sensitive di-block co-polymers of 2-ethoxyethyl vinyl ether and 2-phenoxyethyl vinyl ether segments (EOVE-b-PhOVE) with a high polydispersity and evaluate the behavior of cell attachment on them at different temperatures. The EOVE segment possessed a low critical solution temperature at 20°C while the hydrophobic PhOVE segment functioned as the site to allow the co-polymer to adsorb onto the PET films. X-ray photoelectron spectroscopy and contact angle measurements revealed that the PET film was coated with the EOVE-b-PhOVE co-polymers. The density of co-polymers coated increased with the concentration of co-polymers used for coating. Irrespective of the co-polymer type, 3T3L1 cells attached on the surface of coated films at 37°C, while the cells showed a spread shape, which is similar to that of cells attached on the original non-coated film. However, when the temperature decreased from 37 to 4°C, the cell shape changed to be round, in contrast to that of the original PET film. The percent increase of round cells depended on the coating density and the polymerization degree of EOVE segment.

A study of moisture diffusion in plastic packaging

The absorption and desorption processes of moisture in plastic material were studied with experimental measurement and finite element (FE) simulation. The diffusion coefficient and the saturate concentration were determined by experiment and simulation results with Fick's law. The water molecules inside the plastic material were chemically bonded with polymers by hydrogen bonds in the microholes formed by the polymer molecule chains. On the saturate concentration, the moisture density in the effective volumes was 100 times larger than the vapor density in standard state. However. it is only 8% of liquid water. The water inside the plastic material was in a liquid situation. The delamination and the delamination recovery of flip-chip packaging inspected by C-mode scanning acoustic microscropy (C-SAM) during a high-temperature and high-humidity accelerating test could be explained with the state change of the water in plastic material space. The delamination recovery resulted from the increase in content of liquid water. The bonding of water molecules and polymers reduced the adhesive strength at the interface between epoxy material and die, and the delamination on the interface was initiated. A comparison of three cases with noncoated film, top-side SiCx coated, and both-sides SiCx coated indicated that the delamination would occur when the moisture concentration was between 50% and 95% of the saturate concentration. During the reflow process, the low interface-adhesive strength and the high vapor pressure of the wet sample might cause popcorning of the plastic packaging. Popcorning could be predicted by simulation of the moisture concentration at the interface.