Biodegradation of Poly(Lactic Acid) Biocomposites under Controlled Composting Conditions and Freshwater Biotope

The influence of additives such as natural-based plasticiser acetyl tributyl citrate (ATBC), CaCO3 and lignin-coated cellulose nanocrystals (L-CNC) on the biodegradation of polylactic acid (PLA) biocomposites was studied by monitoring microbial metabolic activity through respirometry. Ternary biocomposites and control samples were processed by a twin-screw extruder equipped with a flat film die. Commonly available compost was used for the determination of the ultimate aerobic biodegradability of PLA biocomposites under controlled composting conditions (ISO 14855-1). In addition, the hydro-degradability of prepared films in a freshwater biotope was analysed. To determine the efficiency of hydro-degradation, qualitative analyses (SEM, DSC, TGA and FTIR) were conducted. The results showed obvious differences in the degradation rate of PLA biocomposites. The application of ATBC at 10 wt.% loading increased the biodegradation rate of PLA. The addition of 10 wt.% of CaCO3 into the plasticised PLA matrix ensured an even higher degradation rate at aerobic thermophilic composting conditions. In such samples (PLA/ATBC/CaCO3), 94% biodegradation in 60 days was observed. In contrast, neat PLA exposed to the same conditions achieved only 16% biodegradation. Slightly inhibited microorganism activity was also observed for ternary PLA biocomposites containing L-CNC (1 wt.% loading). The results of qualitative analyses of degradation in a freshwater biotope confirmed increased biodegradation potential of ternary biocomposites containing both CaCO3 and ATBC. Significant differences in the chemical and structural compositions of PLA biocomposites were found in the evaluated period of three months.

Nanostructure ITO and Get More of It. Better Performance at Lower Cost

In this paper, we investigated how different growth conditions (i.e., temperature, growth time, and composition) allows for trading off cost (i.e., In content) and performance of nanostructured indium tin oxide (ITO) for biosensing applications. Next, we compared the behavior of these functionalized nanostructured surfaces obtained in different growth conditions between each other and with a standard thin film as a reference, observing improvements in effective detection area up to two orders of magnitude. This enhanced the biosensor’s sensitivity, with higher detection level, better accuracy and higher reproducibility. Results show that below 150 °C, the growth of ITO over the substrate forms a homogenous layer without any kind of nanostructuration. In contrast, at temperatures higher than 150 °C, a two-phase temperature-dependent growth was observed. We concluded that (i) nanowire length grows exponentially with temperature (activation energy 356 meV) and leads to optimal conditions in terms of both electroactive surface area and sensitivity at around 300 °C, (ii) longer times of growth than 30 min lead to larger active areas and (iii) the In content in a nanostructured film can be reduced by 10%, obtaining performances equivalent to those found in commercial flat-film ITO electrodes. In summary, this work shows how to produce appropriate materials with optimized cost and performances for different applications in biosensing.

Hybrid organic-inorganic perovskite metamaterial for light trapping and photon-to-electron conversion

Dielectric metamaterials with high refractive indices may have an incredible capability to manipulate the phase, amplitude, and polarization of the incident light. Combining the high refractive index and the excellent electrical characteristics of the hybrid organic-inorganic perovskites (HOIPs), for the first time we experimentally demonstrate that metamaterial made of HOIPs can trap visible light and realize effective photon-to-electron conversion. The HOIP metamaterials are fabricated by focused ion beam milling on a solution-grown single-crystalline HOIP film. The optical absorption is significantly enhanced at the visible regime compared to that of the flat HOIP film, which originates from the excited Mie resonances and transverse cavity modes with inhibited interface reflection. Furthermore, compared to the flat film, the HOIP metamaterial shows increased photocurrent of up to ~40%, where the effective photocarrier generation efficiency increases by ~40% and the related internal efficiency by ~20%. Our data point to the potential application of HOIP metamaterials for high-efficiency light trapping and photon-to-electron conversion.

3D FEM Study of the Flow Uniformity of Flat Polypropylene Film/Sheet Extrusion Dies

Coat-hanger dies are widely used in the extrusion of polymer sheets and films. However, when designing the flat film/sheet extrusion dies manufacturing companies still facing difficulties in achieving the flow uniformity of the polymer melt. This affects the product quality and tool life. This study examines the existing extrusion die design which is used in in the industry in Kazakhstan for polypropylene sheet production and proposes better geometry of a die. These die geometries will be tested for flow uniformity in terms of velocity and pressure at the outlet.

Investigating Neurogenic Differentiation of Dental Pulp Stem Cells Using PLA and Graphene Thin-Film and Electrospun Fiber Scaffolds in Vitro

ABSTRACTDental pulp derived cells are pluripotent stem cells which can be differentiated along odontogenic, osteogenic, adipogenic, or neurogenic lineages. Odontogenic and osteogenic differentiation, in the absence of dexamethasone, have been shown to be highly dependent on substrate morphology and mechanics. Here we focus on neurogenic differentiation, using the protocol described by A. Arthur et al., and its dependence on substrate nature. DPSCs were cultured on PLA, a biodegradable polymer approved for internal use. The upregulation of genetic markers was compared with that of cells plated on standard TCP. The role of substrate morphology was investigated by plating on electrospun fibers approximately 2.0 ± 1.0 μm in diameter and on spin-cast thin films. The influence of graphene was investigated through the addition of 3% and 10% graphene nanoparticles to the films and fibers respectively.The aspect ratio of the cells was measured using confocal microscopy. Cells grown on graphene containing substrates had larger aspect ratios than their non-graphene counterparts, and cells grown on microfibers were longer than their counterparts on the flat films. But the cell aspect ratio did not necessarily correlate with genetic differentiation. The results after 21 days of incubation indicated that early markers (TBP, β-III tubulin), decreased uniformly on all substrates relative to day 0, with the largest decrease occurring on the PLA flat film with graphene. The late stage marker, NEFM, which indicates differentiation, was upregulated to a significantly larger extent on all PLA substrates. No difference was observed between the fibers and the flat film in the absence of graphene, thus morphology did not play a significant role on this polymer. Addition of graphene did not affect the outcome on the fibers, but significantly suppressed the gene expression on the flat films. These results indicate that PLA is a promising scaffold material for neurogenic differentiation.

Combining Thermal Spraying and Magnetron Sputtering for the Development of Ni/Ni-20Cr Thin Film Thermocouples for Plastic Flat Film Extrusion Processes

In the digitalization of production, temperature determination is playing an increasingly important role. Thermal spraying and magnetron sputtering were combined for the development of Ni/Ni-20Cr thin film thermocouples for plastic flat film extrusion processes. On the thermally sprayed insulation layer, AlN and BCN thin films were deposited and analyzed regarding their structural properties and the interaction between the plastic melt and the surfaces using Ball-on-Disc experiments and High-Pressure Capillary Rheometer. A modular tool, containing the deposited Ni/Ni-20Cr thin film thermocouple, was developed and analyzed in a real flat film extrusion process. When calibrating the thin film thermocouple, an accurate temperature determination of the flowing melt was achieved. Industrial type K sensors were used as reference. In addition, PP foils were produced without affecting the surface quality by using thin film thermocouples.

Epitaxial Growth of Orthorhombic GaFeO3 Thin Films on SrTiO3 (111) Substrates by Simple Sol-Gel Method

A Sol-gel method assisted with spin-coating has been successfully used to grow orthorhombic GaFeO3 epitaxial films on SrTiO3 (111) substrates for the first time. The film with Pna21 crystal structure has been grown along the c-axis. The rocking curve of (004) reflection shows that the Full-Width at Half-Maximum (FWHM) value could be determined to be 0.230°, indicating good single crystallinity and high quality. X-ray Φ scan reveals a three-fold symmetry of the substrate and a six-fold symmetry of the film, respectively. The in-plane domains rotate 60° from each other in the film. Uniform film with dense structure, columnar grains with similar grain size was obtained. The thickness of the film was evaluated to be ~170 nm. The roughness value (RMS) measured by AFM was 4.5 nm, revealing a flat film. The in-plane Magnetization versus Magnetic field (M-H) curve at 5 K performs a typical ferri- or ferromagnetic hysteresis loop with a saturated magnetization (Ms) value of 136 emu/cm3. The Curie temperature could be determined to be 174 K. Compared to Pulsed Laser Deposition (PLD), the sol-gel method can prepare large area films with low cost. These new films show promising applications in multiferroic devices.

Flat Film: Strategies of Depthlessness in Pleasantville and La Haine

In this essay I consider the device of depthlessness in film. I am interested in particular in the ways in which this device can determine, or at least raise questions about, the nature of the fictional world. Taking my cue from two films from the turn of the century – Gary Ross' 1998 film Pleasantville and Matthieu Kassovitz' 1995 La Haine – as well as, more broadly, arts historical and cultural theoretical debates, where rather more attention has been devoted to the issue of depthlessness, I focus on moments in which depth, that is, in Andre Bazin's oft-cited words, the “continuity” of the fictional realm, is flattened so as to trace the correlation between depthlessness and the ontology of the fictional world. The two strategies I look at are shallow focus and the dolly zoom. What I intend, here, is to offer some first, superficial (no pun intended), reflections that may allow us to begin thinking about this cinematic notion of the depthless as a device and concept in its own right, with its own rationales and implications, just as art historians and cultural theorists have found it an interesting concept by which to study and categorize artistic and cultural developments. There is so much discussion in film studies about depth – from Bazin's discourse about neorealism's “decisive step forward” re-introducing deep focus, to Gilles Deleuze's talk about Orson Welles' “freeing” of depth, it might be helpful to consider its supposedly backwards, “restrictive” antithesis as well.