High-resolution direct-writing of metallic electrodes on flexible substrates for high performance organic field effect transistors

We report on organic field-effect transistors (OFETs) with sub-micrometer channels fabricated on plastic substrates with fully direct-written electrical contacts. In order to pattern source and drain electrodes with high resolution and reliability, we adopted a combination of two digital, direct writing techniques: ink-jet printing and femtosecond laser ablation. First silver lines are deposited by inkjet printing and sintered at low temperature and then sub-micrometer channels are produced by highly selective femtosecond laser ablation, strongly improving the lateral patterning resolution achievable with inkjet printing only. These direct-written electrodes are adopted in top gate OFETs, based on high-mobility holes and electrons transporting semiconductors, with field-effect mobilities up to 0.2 cm²/V s. Arrays of tens of devices have been fabricated with high process yield and good uniformity, demonstrating the robustness of the proposed direct-writing approach for the patterning of downscaled electrodes for high performance OFETs, compatibly with cost-effective manufacturing of large-area circuits.     

Microlayer and nanolayer tubing and piping via layer multiplication coextrusion. I. Validation

Layered annular structures produced with layer multiplication coextrusion, utilizing both a standard in-line “spider” die, and a custom annular die, are compared in structures up to 129 layers. One multilayered system, of a Dow LDPE 5004I was utilized in generating experimental results to validate the custom die design performance. It was found that the custom design demonstrates successful extrusion of high layer number annular structures with substantial benefits over the standard spider die. Moreover, a design method incorporating angular rotation was implemented within the custom die to eliminate weld lines and attain concentric layer structures to further enhance commercial viability and mechanical integrity. Results indicate angular rotation may be utilized to generate idealized annular products with concentric layer structures. Additionally, exploration of flow through the annular die land was conducted with ANSYS Polyflow in under several conditions of angular rotation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48683.     

A robust authentication scheme for telecare medical information systems

Multimedia Tools and Applications - With the speedy progress in technology, the Internet has become a non-separable part of human life. It is obvious to use the Internet in all fields and medical...     

3D Printing of Micrometer-Sized Transparent Ceramics with On-Demand Optical-Gain Properties

Transparent ceramics are usually polycrystalline materials, which are wildly used in many optical applications, such as lasers. As of today, the fabrication of transparent ceramic structures is still limited to conventional fabrication methods, which do not enable the formation of complex structures. A new approach for 3D printing of micrometer-size, transparent ceramic structures is presented. By using a solution of metal salts that can undergo a sol–gel process and photopolymerization by two-photon printing, micrometer-sized yttrium aluminum garnet (YAG) structures doped with neodymium (Nd) are fabricated. The resulting structures are not only transparent in the visible spectrum but can also emit light at 1064 nm due to the doping with Nd. By using solution-based precursors, without any particles, the sintering can be performed under air at ambient pressure and at a relatively low temperature, compared to conventional processes for YAG. The crystalline structure is imaged at atomic resolution by ultrahigh-resolution scanning transmission electron microscopy (STEM), indicating that the doped Nd atoms are located at the yttrium positions. Such miniaturized structures can be used for diverse applications, e.g., optical components in high-intensity laser systems, which require heat resistance, or as light sources in optical circuits.     

Exploring for 3D photonic bandgap structures in the 11 f.c.c. space groups

The promise of photonic crystals and their potential applications has attracted considerable attention towards the establishment of periodic dielectric structures that in addition to possessing robust complete bandgaps, can be easily fabricated with current techniques. A number of theoretical structures have been proposed. To date, the best complete photonic bandgap structure is that of diamond networks having Fd3m symmetry (2-3 gap). The only other known complete bandgap in a face-centred-cubic (f.c.c.) lattice structure is that of air spheres in a dielectric matrix (8-9 gap; the so called 'inverse-opal' structure). Importantly, there is no systematic approach to discovering champion photonic crystal structures. Here we propose a level-set approach based on crystallography to systematically examine for photonic bandgap structures and illustrate this approach by applying it to the 11 f.c.c. groups. This approach gives us an insight into the effects of symmetry and connectivity. We classify the F-space groups into four fundamental geometries on the basis of the connectivity of high-symmetry Wyckoff sites. Three of the fundamental geometries studied display complete bandgaps--including two: the F-RD structure with Fm3m symmetry and a group 216 structure with F43m symmetry that have not been reported previously. By using this systematic approach we were able to open gaps between the 2-3, 5-6 and 8-9 bands in the f.c.c. systems.     

Effect of anisotropic thermal conductivity of the GDL and current collector rib width on two-phase transport in a PEM fuel cell

A two-dimensional two-phase model based on the classical two-fluid model is used to analyze electrochemical and thermal transport in a PEMFC. The model is extended to account for the dependence of interfacial area density on liquid volume fraction. At a given fixed voltage, the fuel cell generates maximum current density for low through-plane and high in-plane thermal conductivities at high humidity operating conditions. It is also predicted that for low humidity operating conditions, the fuel cell generates maximum current density if the GDL is tailored to have high through-plane thermal conductivity near the inlet and progressively decreasing through-plane thermal conductivity at distances away from the inlet. At fully humidified cathode inlet conditions, narrower current collector ribs generate higher current densities at all voltages by reducing the resistance to diffusion of reactants and products through the GDL. In order to maximize the current density at low humidities, ribs must be wider near the inlet and narrower away from the inlet. The proposed methodology for tailoring GDL through-plane thermal conductivities and rib widths reduces the risk of membrane dehydration near inlet and also reduces the possibility of excessive liquid accumulation in the region away form the inlet.     

The wide band gap of highly oriented nanocrystalline Al doped ZnO thin films from sol–gel dip coating

Undoped and Al doped ZnO thin films were prepared on glass substrate by sol–gel dip coating from PVP-modified zinc acetate dihydrate and aluminium chloride hexahydrate solutions. The XRD patterns of all thin films indexed a highly preferential orientation along c-axis. The AFM images showed the average grain size of undoped ZnO thin film was about 101 nm whereas the smallest average grain size at 8 mol% Al was about 49 nm. The values of direct optical band gap of thin films varied in the range of 3.70–3.87 eV.     

Evolution of reproductive strategies in incipient multicellularity

Multicellular organisms potentially show a large degree of diversity in reproductive strategies, producing offspring with varying sizes and compositions compared to their unicellular ancestors. In reality, only a few of these reproductive strategies are prevalent. To understand why this could be the case, we develop a stage-structured population model to probe the evolutionary growth advantages of reproductive strategies in incipient multicellular organisms. The performance of reproductive strategies is evaluated by the growth rates of the corresponding populations. We identify the optimal reproductive strategy, leading to the largest growth rate for a population. Considering the effects of organism size and cellular interaction, we found that distinct reproductive strategies could perform uniquely or equally well under different conditions. If a single reproductive strategy is optimal, it is binary splitting, dividing into two parts. Our results show that organism size and cellular interaction can play crucial roles in shaping reproductive strategies in nascent multicellularity. Our model sheds light on understanding the mechanism driving the evolution of reproductive strategies in incipient multicellularity. Beyond multicellularity, our results imply that a crucial factor in the evolution of unicellular species’ reproductive strategies is organism size.     

Fortification of soy sauce using various iron sources: sensory acceptability and shelf stability

BACKGROUND: Soy sauces are available in different types and grades, which allows them to reach consumers of all socioeconomic groups. Ferric sodium ethylenediaminetetraacetic acid (NaFeEDTA) has been used for iron fortification of soy sauces in some countries, however, its high cost may make it unattractive to policymakers and industry. OBJECTIVE: We evaluated the feasibility of using more economical iron sources for iron fortification, with soy sauce of various types and grades used as a vehicle. METHODS: Seven iron sources were tested for their feasibility for fortification of four types of soy sauce: naturally fermented in the traditional style, naturally fermented according to large-scale industrial formulas 1 and 5, and chemically hydrolyzed at 5 mg per serving (15 mL, per Thailand's food labeling regulations). Either citric acid or sodium citrate was added at 0.1% as a chelator. RESULTS: Five iron sources--ferrous sulfate, NaFeEDTA, ferric ammonium citrate, ferrous lactate, and ferrous gluconate--did not significantly affect the sensory qualities of the product over a period of 3 months (p > .05). Ferrous fumarate and ferrous bisglycinate caused unacceptable precipitation. Less than 3% of 260 and 306 commonly cooked foods out of 871 and 772 preparations using soy sauces fortified with NaFeEDTA and ferrous sulfate, respectively, were found to be different from normal with regard to sensory qualities. The cost of fortification was US 0.22 cents to US 3.28 cents per bottle (700 mL). CONCLUSIONS: Both naturally fermented and chemically hydrolyzed soy sauces could be fortified with all five iron sources. Ferrous sulfate is the most appropriate source because of its low cost and acceptable sensory characteristics. Soy sauce is a promising vehicle for iron fortification, however, the bioavailability of iron in the products examined here needs to be evaluated under normal use conditions.