Giant stretchability of thin gold films on rough elastomeric substrates

Stretching metallic conductors to large deformations while maintaining a low and constant electrical resistance is one of the main challenges in stretchable electronics technologies. Here, we report the conservation of conductivity for deformations of up to 100% in 80 and 500 nm thick gold films deposited on rough polydimethylsiloxane (PDMS) substrates. The roughness is produced by curing PDMS on sand-blasted or surface-etched masters. Under stretching, roughness creates a fine-scale inhomogeneous stress state within the film and a non-percolating crack pattern develops, preserving the conductivity. Compared to smooth surfaces, the strain corresponding to electrical failure is increased by a factor >50. By combining the roughness effect with prestretching of the substrate during deposition, a fine-scale random wrinkling morphology develops and the stretchability is enhanced even further. The stretchability is finally improved by increasing the thickness of the film. These synergistic effects can be explained based on fracture mechanics arguments. Finally, a high number of large deformation cycles can be accommodated without electrical failure.     

Preparation and elastic moduli of germanate glass containing lead and bismuth

This paper reports the rapid melt quenching technique preparation for the new family of bismuth-lead germanate glass (BPG) systems in the form of (GeO₂)₆₀–(PbO)_40−x–(½Bi₂O₃)_x where x = 0 to 40 mol%. Their densities with respect of Bi₂O₃ concentration were determined using Archimedes’ method with acetone as a floatation medium. The current experimental data are compared with those of bismuth lead borate (B₂O₃)₂₀–(PbO)_80−x–(Bi₂O₃)_x. The elastic properties of BPG were studied using the ultrasonic pulse-echo technique where both longitudinal and transverse sound wave velocities have been measured in each glass samples at a frequency of 15 MHz and at room temperature. Experimental data shows that all the physical parameters of BPG including density and molar volume, both longitudinal and transverse velocities increase linearly with increasing of Bi₂O₃ content in the germanate glass network. Their elastic moduli such as longitudinal, shear and Young’s also increase linearly with addition of Bi₂O₃ but the bulk modulus did not. The Poisson’s ratio and fractal dimensionality are also found to vary linearly with the Bi₂O₃ concentration.     

Performance measurements of mammographic systems

Performance measurements of 30 mammographic installations were carried out in order to see the current level of image quality and breast doses.The half of the systems tested in this survey indicated automatic exposure control and beam collimation problems. Film processing and dark room conditions were not optimum for the majority of the installations. Image quality phantoms were exposed by the user and team of the survey at each visited center. Lower breast doses were obtained at equal image qualities for the radiographs of the team indicating the importance of adequate handling of some exposure parameters. Corrective actions were suggested to each installation and necessary guidance was advised for the implementation of routine quality control activities.     

The function of lactic acid bacteria and brine solutions on biogenic amine formation by foodborne pathogens in trout fillets

The influences of lactic acid bacteria and brine solutions on the biogenic amine formation by Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Enterococus faecalis, Pseudomonas aeruginosa, Listeria monocytogenes, Aeromonas hydrophila and Salmonella paratyphi A in fermented trout fillets were investigated. Fish fillets were divided into four groups, group 1 without any lactic acid bacteria inoculation, group 2 and group 3 with different salt concentration inoculated with lactic acid bacteria and food-borne pathogens, and group 4 inoculated with lactic acid bacteria and food-borne pathogens without a salt solution. The histamine content in trout fillets in group 4 was found to be more than 10 mg/100 g, while the other groups contained less than 7.5 mg/100 g. The highest tyramine production was found for group 1 and group 3, ranging from 3 to 18 mg/100 g. Lactic acid bacteria did not seem to play an important role on biogenic amine production by food borne pathogens, while adding brine solution on fillets has inhibitory effects on some of the biogenic amines.     

Graphene Nanoplatelets as Novel Reinforcement Filler in Poly(lactic acid)/Epoxidized Palm Oil Green Nanocomposites: Mechanical Properties

Graphene nanoplatelet (xGnP) was investigated as a novel reinforcement filler in mechanical properties for poly(lactic acid) (PLA)/epoxidized palm oil (EPO) blend. PLA/EPO/xGnP green nanocomposites were successfully prepared by melt blending method. PLA/EPO reinforced with xGnP resulted in an increase of up to 26.5% and 60.6% in the tensile strength and elongation at break of the nanocomposites respectively, compared to PLA/EPO blend. XRD pattern showed the presence of peak around 26.5° in PLA/EPO nanocomposites which corresponds to characteristic peak of graphene nanoplatelets. However, incorporation of xGnP has no effect on the flexural strength and modulus. Impact strength of PLA/5 wt% EPO improved by 73.6% with the presence of 0.5 wt% xGnP loading. Mechanical properties of PLA were greatly improved by the addition of a small amount of graphene nanoplatelets (<1 wt%).     

Stretchable Gold Tracks on Flat Polydimethylsiloxane (PDMS) Rubber Substrate

A process to fabricate stretchable gold tracks on silicone rubber substrates is studied by XPS, static water contact angle measurement, AFM, and SEM. The process involves several steps: removing uncured oligomers by hexane Soxhlet extraction; pre-stretching the substrate; activating the strained silicone surface by an oxygen plasma treatment; coating the strained substrate with 5 nm titanium and 80 nm gold layers; and finally releasing the sample. The plasma treatment creates a thin brittle silica-like layer that temporarily increases the substrate's surface energy. Indeed, the plasma treatment is followed by a hydrophobic recovery. As a consequence, the delay between plasma treatment and metal deposition has to be reduced as much as possible. The silica-like layer can be nicely observed after release. The entire process allows us to obtain stretchable metallized samples that remain conductive even after an excessive deformation leading to electrical failure.     

Synthesis of Biodiesel through Catalytic Transesterification of Various Feedstocks using Fast Solvothermal Technology: A Critical Review

The fossil fuel reserves are depleting at a more rapid rate as a result of the population growth and the ensuing energy utilization. Biodiesel is a mixture of fatty acid methyl esters produced from the transesterification of plant oils or animal fats. Moreover, the source of raw materials and manufacturing costs have become the major hurdle in the commercialization of biodiesel; thus, alternative sources such as the use of waste oils and non-edible oils together with biodiesel production techniques have long been considered. Selecting an appropriate feedstock and increasing production yield are two important approaches to decrease the costs of biodiesel production. Typically, biodiesel, which operates with electrical or conventional heating to generate high efficiency of the product, consumes a huge amount of power in a long reaction time. In contrast, chemical reactions speed up by microwave irradiation which results in producing high yields of product in a shorter chemical reaction time. In this extensive article, an effort has been made to review the use of microwave technology including multi-feedstock and recent studies on microwave-assisted heterogeneously catalyzed processes for biodiesel production. The heterogeneous catalyst performance has also been covered, including the measurement of their pysico-chemical properties. The microwave irradiation used for the synthesis of biodiesel is also included. In addition, the reaction variables impacting the transesterification process, such as heating system, microwave power, type and amount of heterogeneous catalyst, oil/methanol molar ratio, reaction time, temperature and mixing intensity, are covered. The final part of this article will cover the details of previously performed work on heterogeneous catalysts. Finally, energy balances for the traditional and microwave-based processes, conclusions, and recommendation on the topic are presented. The aim this article is to focus on recent studies on microwave-assisted heterogeneously catalyzed processes.     

Effect of different cell disruption methods on lipid yield of Schizochytrium sp.

In this study, it was investigated to increase the lipid yield of the microalgae Schizochytrium sp., by applying different cell disruption methods; acid treatment with HCl, osmotic shock, enzyme applications and ultrasonic homogenizer were combined with the Bligh and Dyer or Soxhlet methods. In the Soxhlet method, the lipid and fatty acid yields decreased due to the inability of the method to break down the lipid cells sufficiently and the high temperature application. Enzyme application (hemicellulase treatment at 55°C for 2 days) prior to Bligh and Dyer method (BDE) was found more efficient in terms of lipid and DHA yield compared to other methods. BDE process increased the lipid yield to 21.72 ± 0.74% and DHA content to 19.25 ± 0.09% from lipid yield of 18.87 ± 0.4% and DHA content of 18.41 ± 0.20% by the Bligh and Dyer control (BDC). Major saturated fatty acids were 14:0, 16:0, 18:0, 24:0 and the highest saturated fatty acid was 16:0 (palmitic acid). Lipid health indices such as n-6/n-3, PUFA/SFA, atherogenicity index, thrombogenicity index and hypocholesterolemic/hypercholesterolemic ratios were almost favorable. With this study, appropriate lipid extraction methods were studied to provide an economical and environmental friendly suggestion for future studies to be used in areas such as food, feed and cosmetics grade. It was concluded that the most convenient method among the cell disruption methods was BDE owing to lipid and fatty acid yield.     

An iterated greedy algorithm for the planning of yarn-dyeing boilers

Yarn dyeing is a critical link in the textile production chain that consumes the most time and energy. Today's dyeing shops receive hundreds of demands with thousands of different colors, different due dates, and different production requirements. This situation has made it very difficult for the human brain to create a minimum-cost production plan by complying with the due dates. In this study, a real-life problem of a company operating in the textile industry is discussed and a solution has been developed for the planning of yarn-dyeing boilers. The application was held in Bursalı Textile, which is the major towel manufacturer operating in Turkey. The problem dealt with is basically in the nature of the variable-size bin-packing problem (VSBPP). The limited availability of bins (boilers) of different sizes and the packing of the items (yarn work orders) with due date constraints are the original aspects of this study. Multi-objective mixed integer programming model is developed to minimize two objectives. For the solution, the preemptive method called the lexicographic approach, in which the objectives are solved in order, is preferred. As the first objective, the overcapacity usage is minimized and then the second objective, which is the boiler usage cost, is minimized. Given that the VSBPP is strongly NP-hard, an iterated greedy algorithm with two different decoding approaches is proposed. Computational experiments were conducted on 20 randomly generated benchmark instances and a real-world industrial dataset. The numerical results show that good solutions can be obtained in seconds using the proposed approaches.