In back injection molding, a polymer film (most commonly a decorative label) is inserted into the mold and fused with the polymer product by injection of the polymer melt from behind. By placing a bendable film into a mold cavity and by injection of polymer melt, the film conforms to the outlines of the cavity, thus enabling the decoration of elements with non-planar surfaces. This technique allows for pre-patterning of films by a planar process, and then convert these into the surface skin of a non-planar molded part. In this research we demonstrate the integration of silver wires onto the surface of a curved polymer part. As an example, we used poly (methyl methacrylate) films of different thicknesses that were pre-structured with micrometer-sized V-grooves, filled with silver nanoparticle ink and placed into the cavity of a commercial injection molding tool. The effect of the back injection molding process on unfilled and filled V-grooves was evaluated for different process parameters. In most cases, the silver wires remained undamaged and their electrical conductivities remained essentially similar to those in planar films. The resulting surface-integrated silver wires were characterized by scanning electron microscopy and electrical resistivity measurements.

Monolithic integration of integrated circuits onto macroscopic polymer parts can be done by adding individual electronic elements after the polymer part has been molded or by adding a film with the entire circuit prepared in advance. In the first case, the patterning of non-flat surfaces requires a patterning method with tools that can follow the outline of a 3D topography, in the second case a flexible film that needs to be deformed. This approach has been used for thermoforming and is now also favored for printed electronics [1,2]. This way, fabrication methods for low-cost flexible electronics can be used to prepare the polymer films. We placed a 175 μm-thick polymeric film into the crowned mold of an injection-molding tool that constitutes a concave cylinder lens with a radius of 30 mm and a depth of 10 mm, with a convex cylinder at the opposite side. The film (PMMA: Evonik Plexiglas film 99524, Tg 113°C) was patterned by thermal nanoimprint (T-NIL) at 180°C and was pressed into this crowned surface by the viscous polymer (Evonik Plexiglas 7N, Tg 110°C) injected onto the backside of the film. The tool temperature (40°C) was low enough that the 260°C hot melt was cooled down to ~100°C when it reaches the film upon entering the mold cavity, thus it was able to deform the thermoplastic film without erasing its topography. The resulting back-injected cylinder-like element consists of the film that is covering the top of a 3 mm thick convex polymer body. Two cases were implemented: When the film is patterned towards the mold surface, the resulting cylinder has a surface topography constituted by the film. When it is patterned towards the injecting polymer, the surface structures are embedded. The latter is an interesting alternative if not only surface structures are used, but films that are already processed, e.g., covered with electrodes. We used both cases for the fabrication of components covered with a metal wire array (Fig. 1). Our process has, in comparison to inkjet printing used for printed electronics, resolutions down to sub-μm and relies on nanoparticle self-confinement in V-grooves [3]. Similarly, films with open microchannels were back-injection molded (Fig. 2). The shape of the 3.1 μm wide Vgrooves is slightly flattened by the process, thus enabling capillary filling in an open microfluidic approach [4]. In both cases, the wires are electrically conducting. Combining nanoimprint lithography and additive patterning techniques may be a viable strategy to create low-cost devices on large areas or even free-form components. Such strategies can be applied to various designs of electrical circuits that enable to build complex devices as planned within the SFA project FOXIP [5]. Applications would be LEDs and sensors embedded in polymer components.

The study in the transmission electron microscopy (TEM) of the irradiation-induced microstructure of tungsten, a material promising for its applications at high temperatures in harsh radiation environments, is rendered difficult by the high level of radioactivity. To circumvent this problem, it is nowadays a routine to reduce the TEM sample size with the focused ion beam (FIB) technique. In this way, one extracts an electron transparent thin lamella that is only a few microns in size. However, FIB induces additional radiation damage in the surface layer, which has to be removed by the so-called flash polishing technique in order to detect the initial damage structure in an irradiated sample. In this study, we evaluate the technique of flash electropolishing in an aqueous solution of NaOH as a method to remove this surface damage from tungsten lamella samples. The conditions of flash electropolishing are optimized as a function of temperature, voltage, FIB grid and weld material. Anisotropic etching dependence on the crystallographic direction was evaluated, with the highest polishing resistance in the region between (5 2 1) and (1 1 0).

Essential oils (EOs) are commonly applied in mouth care products like mouthwashes, mostly as an ethanolic solution or by usage of surfactants as solubilising agents. In this study, we present a formulation for preparation of Pickering nano-emulsions (PnE) of EOs as a novel form for application of EOs in mouth care. For the preparation of PnE, we have synthesised surface-modified silica nanoparticles with a mean diameter of 20 nm, as well as we have examined the effect of EOs concentration on PnE droplet size and stability. In vitro study of their effect on the Streptococcus mutans biofilm as the main pathogen of dental health problems has been performed. We have found that EOs in the PnE form has the highest effectiveness against biofilm formation. Diffusion through the biofilm model membrane was studied to explain this observation. We have found that PnEs have a better performance in the transportation of EOs trough model membrane than the ethanolic solutions and conventional emulsions (CEs).

In this paper the fabrication of UV-sensors based on an interdigitated electrode array with a 70 nm sputtered ZnO coating is demonstrated. The electrodes were fabricated using polymer substrates prepatterned with nanoimprint lithography, imprinted with mu m-sized grooves and reservoirs at two sides. The V-shaped capillaries were filled with nanoparticle based silver ink either by capillary action in an open-fluidics approach or with spin coating. This enables the use of low-resolution additive methods to fabricate high precision wires for low cost flexible electronics. The 1 x 1 mm(2) sensor area contained 100 wires in alternating directions that were electrically insulated from each other, and were attached to contact pads. Characterization of UV sensor devices was carried out experimentally by performing electrical measurements under 355 and 385 nm UV light illumination.

Low-cost additive methods such as inkjet and gravure printing are favored fabrication processes for printed electronics, however, with resolutions often in the range much larger than 10 μm [1]. They are not suitable for large area electrode applications where sub-μm or even sub-wavelength resolutions are needed. Here, the deposition of nanoparticle inks on prepatterned substrates is a solution [2,3]. If polymer substrates are imprinted with μm-sized grooves and reservoirs attached to them, then they can be filled from the side in an open-fluidics approach (Fig. 1). As has been shown with 2 and 5 μm wide grooves, convective effects enable to fill the grooves to a higher extend than would be predicted by the solid content of nanoparticle based silver ink. A much simpler approach is the spincoating of entire substrates of highly diluted inks (Fig. 2). While deposition on flat areas does not lead to dense coatings, within the grooves the nanoparticles form electrically conducting wires. With μm-sized Vgrooves it was possible to confine spincoated silver particle-based inks down to 130 nm width from accumulated metal ink nanoparticles forming at the bottom of the grooves [1]. This is in the range of the nanoparticle size of ~50 nm that grow during sintering. The two methods, capillary filling and spincoating, can both be used for the fabrication of extended electrodes and wires. Using this, we demonstrate the fabrication of UV-sensors based on an interdigitated electrode array (IDEA) with a 70 nm sputtered ZnO coating. The 1×1 mm2 sensor area contained 100 wires in alternating directions that were electrically insulated from each other, and were attached to contact pads. Characterization of UV sensor devices was carried out experimentally by performing electrical measurements under UV light illumination (Fig. 3). As substrates, we used replicas from V-grooves obtained by anisotropic etching of <100> silicon substrates in a potassium hydroxide (KOH)-based etchant. For the final replication the stamps were imprinted (T-NIL) into 175 μm thick films (PMMA: Evonik Plexiglas film 99524, Tg 113°C) at 180°C. Genes’Ink dispersions with silver nanoparticles with particle sizes <50 nm were used and further thinned down with different solvents. As UV-source, an unmounted LED was used with 355 nm (Lumex SSLLXTO46355C) and 385 nm (Thorlabs M385F1) wavelength, and with an intensity of 0.080 and 0.087 mW/cm2, respectively, at the distance of 10 mm. Combining nanoimprint lithography and additive patterning techniques may be a viable strategy to create low-cost devices on large areas. Such strategies can be applied to various designs of electrical circuits that enable to build complex devices as planned within the SFA project FOXIP [4].

Here, the fabrication of sub‐200 nm metal wires from commercial silver inks with 50 nm particle size, 100 times narrower than with typical low‐resolution ink‐jet and screen printing in flexible electronics, is demonstrated. Using a combination of spincoating on prepatterned polymer substrates and flash lamp annealing, nanoparticles merge to wires featuring good electrical conductivity. With this method less than 150 nm thin wires can be generated from 2 µm wide or smaller V‐grooves due to adapted dilution of particle content, self‐confinement in V‐grooves, shrinkage of line width during solvent evaporation, and sintering. After nanoimprinting, grooves made from PMMA are smoothened out by thermal reflow without affecting the wires. The resistivity of 300 µm long, 400 nm wires is similar to more conventional ink‐jet printed wires with 10–50 µm widths.

Essential oils (EOs) are becoming increasingly popular in medical applications because of their antimicrobial effect. Direct bioautography (DB) combined with thin layer chromatography (TLC) is a screening method for the detection of antimicrobial compounds in plant extracts, for example, in EOs. Due to their lipophilic character, the common microbiological assays (etc. disk diffusion) could not provide reliable results. The aim of this study was the evaluation of antibacterial and anti-biofilm properties of the EO of cinnamon bark, clove, peppermint, thyme, and their main components against Haemophilus influenzae and H. parainfluenzae. Oil in water (O/W) type Pickering nano-emulsions stabilized with silica nanoparticles from each oil were prepared to increase their water-solubility. Samples with Tween80 surfactant and absolute ethanol were also used. Results showed that H. influenzae was more sensitive to the EOs than H. parainfluenzae (except for cinnamon bark oil). In thin layer chromatography-direct bioautography (TLC-DB) the ethanolic solutions of thyme oil presented the best activity against H. influenzae, while cinnamon oil was the most active against H. parainfluenzae. Pickering nano-emulsion of cinnamon oil inhibited the biofilm formation of H. parainfluenzae (76.35%) more efficiently than samples with Tween80 surfactant or absolute ethanol. In conclusion, Pickering nano-emulsion of EOs could inhibit the biofilm production effectively.

We demonstrate the use of prepatterned polymer substrates with mu m-sized grooves to enhance the low resolution of additive methods such as inkjet and gravure printing by a factor of 10. This enables their use for low cost flexible electronics. Droplets of ink dispersions with < 50 nm Ag nanoparticles with volumes in the nanoliter range were deposited on imprinted receiver pads and drawn into grooves by capillary action in an open-fluidics approach. Using this method, up to 2mm long, 2 to 5 mu m wide wires were created in U- and V-groove capillaries. The characterization of wire thickness before and after sintering revealed that ink supply of the already filled grooves continues from the reservoir during evaporation. By this, higher thickness is achieved than expected from the initial nanoparticle loading, and thus wires with sufficient electrical conductivity are formed.

In the field of essential oil research, the low water solubility of essential oils (EOs) causes several problems, not only in pharmaceutical applications, but also in microbiological experiments. The aim of our work was to prepare Pickering emulsions with tea tree, thyme, and anise EOs stabilized with silica nanoparticles, in order to enhance their availability for microbiological tests. We have examined the influence of surface properties and concentration of silica nanoparticles and dispergation energy on emulsion stability and droplet size. In vitro diffusion experiments have been performed on model agar gel membranes, with the stable Pickering emulsions and conventional emulsions of EOs stabilized with Tween80 surfactant. We have examined the influence of surface modifying group type, surface coverage of silica nanoparticles, and droplet size of the emulsions on the diffusion properties of the EOs. Our results show that highly stable Pickering emulsions can be prepared with silica nanoparticles of 20 nm diameter and 20% of surface covered with ethyl groups, in a wide EO concentration range. The cumulative amount of the EO was more effective in Pickering emulsions than in conventional emulsions for tea tree and thyme EOs, whereas the opposite case was true for anise EO. As the droplet size of the Pickering emulsion decreases, the cumulative concentration of the EO increases. In this work, we have shown that the Pickering emulsions of EOs are a suitable form for EO transport through complex membranes, and hopefully can be effectively applied in microbiological and pharmaceutical experiments.

A fahéjkéreg-illóolaj alkalmazhatósága légúti betegségek esetén – pécsi tapasztalatok Horváth Györgyi1,*, Ács Kamilla1, Balázs Viktória Lilla1, Csikós Eszter1, Ashraf Amir Reza1, Kocsis Béla2, Böszörményi Andrea3, Horváth Barbara4, Széchenyi Aleksandar4, Kereskai László5, Csekő Kata6, Kemény Ágnes6, Helyes Zsuzsanna6,7 1 PTE GYTK Farmakognóziai Intézet, 7624 Pécs, Rókus u. 2. 2 PTE ÁOK Orvosi Mikrobiológiai és Immunitástani Intézet, 7624 Pécs, Szigeti út 12. 3 SE GYTK Farmakognóziai Intézet, 1085 Budapest, Üllői út 26. 4 PTE GYTK Gyógyszertechnológiai és Biofarmáciai Intézet, 7624 Pécs, Rókus u. 2. 5 PTE ÁOK Pathologiai Intézet, 7624 Pécs, Szigeti út 12. 6 PTE ÁOK Farmakológiai és Farmakoterápiai Intézet, 7624 Pécs, Szigeti út 12. 7 PTE Szentágothai János Kutatóközpont, 7624 Pécs, Ifjúság útja 20. *e-mail: horvath.gyorgyi@gytk.pte.hu

Purpose The aim of this paper is to present a review of the tin whisker growth phenomena. The study focuses mainly on whisker growth in a corrosive climate when the main inducing factor of the whisker growth is oxidation. The tin whisker phenomenon is still a big challenge in lead-free reflow soldering technology. Modern lead-free alloys and surface finishes with high tin content are considered to be possible sources of whisker development, also the evolution of electronic devices towards further complexity and miniaturization points to an escalation of the reliability risks. Design/methodology/approach The present work was based on a worldwide literature review of the substantial previous works in the past decade, as well as on the results and experience of the authors in this field. Findings The effect of corrosion on tin whisker growth has been under-represented in reports of mainstream research; however, in the past five years, significant results were obtained in the field which raised the corrosion phenomena from being a side effect category into one of the main inducing factors. This paper summarizes the most important findings of this field. Practical implications This literature review provides engineers and researchers with a better understanding of the role of corrosion in tin whisker growth and the current challenges in tin whisker mitigation. Originality/value The unique challenges and future research directions about the tin whisker phenomenon were shown to highlight rarely discussed risks and problems in lead-free soldering reliability.

In this work, the microstructure of pure tungsten irradiated in a target of the Swiss spallation neutron source is studied. The tested tungsten specimens were irradiated to two doses of 1.4 and 3.5 ddpa with 37 and 140 appm He at 80 and 110 degrees C, respectively. The specimen of 1.4 dpa was consecutively annealed at temperatures of 500 degrees C, 600 degrees C, 800 degrees C and 900 degrees C, for 1 h, and the post-irradiation annealing effect on the microstructure was investigated. Microstructural features such as dislocations, defect clusters, dislocation loops and bubbles were observed by means of transmission electron microscopy (TEM). TEM images were obtained in different areas of the samples, to obtain quantitative information of the dislocations and defect clusters. There was a significant change in the microstructure of the tungsten after irradiation and post-irradiation annealing. The average dislocation density and defect cluster density were evaluated. (C) 2017 Elsevier B.V. All rights reserved.

Different types of Sn coatings are widely used in the electronics industry. However, they are susceptible to spontaneous whisker formation which can cause reliability issues. In this paper, whisker growth from submicron Sn thin films was studied at room temperature for 150days. For this purpose, 99.99% pure Sn was vacuum evaporated onto 1.5mm thick Cu and ceramic substrates, with an average thickness of 400nm. It was found that the submicron thick Sn layers on a Cu substrate can generate intense whiskering directly after layer deposition. The microstructure, composition and grain orientation of the whiskers and the areas underneath were studied with a Scanning Ion Microscope (SIM) and a Transmission Electron Microscope (TEM). It was proven that the whisker growth was induced by Cu6Sn5 intermetallic layer growth between the Cu substrate and the Sn thin film which resulted in large stress within the film. We found the first evidence in a tin-copper layer system that the high stress due to the intermetallic formation itself can initiate the interfacial flow mechanism (without a direct mechanical load) between the Sn layer and the intermetallic layer. This phenomenon can explain the intense whisker growth from submicron Sn thin films.