Macroscopic assembling of responsive hydrogels has been used to construct soft actuators that transform their shape upon external stimuli. It remains a challenge to establish a robust assembling interface between gels. Here, we demonstrate a fabrication of bilayered hydrogel actuators assembled by host-guest recognition at the interface. The supramolecular recognition enabled efficient, rapid, and robust macroscopic assembling of hydrogels, which was utilized to create gel bilayers that were actuated upon unbalanced swelling/deswelling.

In this article, we report low-temperature electron spin resonance (ESR) investigations carried out on solution processed three-layer inverted solar cell structures: PC61BM/CH3NH3PbI3/PEDOT:PSS/Glass, where PC61BM and PEDOT:PSS act as electron and hole transport layers, respectively. ESR measurements were conducted on ex-situ light (1 Sun) illuminated samples. We find two distinct ESR spectra. First ESR spectra resembles a typical powder pattern, associated with gx = gy = 4.2; gz = 9.2, found to be originated from Fe3+ extrinsic impurity located in the glass substrate. Second ESR spectra contains a broad (peak-to-peak line width ∼ 10 G) and intense ESR signal appearing at g = 2.008; and a weak, partly overlapped, but much narrower (peak-to-peak line width ∼ 4 G) ESR signal at g = 2.0022. Both sets of ESR spectra degrade in intensity upon light illumination. The latter two signals were found to stem from light-induced silicon dangling bonds and oxygen vacancies, respectively. Our controlled measurements confirm that these centers were generated during UV-ozone treatment of the glass substrate –a necessary step to be performed before PEDOT:PSS is spin coated. This work forms a significant step in understanding the light-induced- as well as extrinsic defects in perovskite solar cell materials.

Multi-pass compression tests were carried out on the Gleeble-1500D® and Gleeble-3800TM® thermo-mechanical simulators to investigate the effect of temperature, strain rate and inter-pass time on the development of the texture in ferritic stainless steels (FSS) AISI 430 and 433, the latter an Al-containing variant. Orientation Distribution Functions (ODFs) through the electron backscattered diffraction (EBSD) technique was employed to characterise and study the texture present in the steels after hot working. The mean flow stress analysis showed that, the dynamic recrystallization to dynamic recovery transition temperature decreases with an increase in strain rate in both grades of stainless steels possibly allowing texture optimisation at lower hot rolling temperatures. Higher finishing rolling temperatures, lower strain rates and longer inter-pass times led to improvement in the formation of the desired γ-fibre texture which contributes to ductility or drawability in these steels. Dynamic recrystallization which promotes the formation of the desired γ-fibre texture was found to occur in both AISI 430 and 433 at temperatures above 1000 °C and strain rates less than 5 s-1. Generally AISI 433 develops a stronger gamma texture than the AISI 430 when hot rolled under similar conditions.

Lithium sulfide (Li2S) is one of the most attractive cathode materials for high energy density lithium batteries as it has a high theoretical capacity of 1166 mA h g-1. However, Li2S suffers from poor rate performance and short cycle life due to its insulating nature and polysulfide shuttle during cycling. In this work, we report a facile and viable approach to address these issues. We propose a method to synthesize a Li2S based nanocomposite cathode material by dissolving Li2S as the active material, polyvinylpyrrolidone (PVP) as the carbon precursor, and graphene oxide (GO) as a matrix to enhance the conductivity, followed by a co-precipitation and high-temperature carbonization process. The Li2S/rGO cathode yields an exceptionally high initial capacity of 817 mAh g-1 based on Li2S mass at C/20 rate and also shows a good cycling performance. The carbon-coated Li2S/rGO cathode demonstrates the capability of robust core-shell nanostructures for different rates and improved capacity retention, revealing carbon coated Li2S/rGO composites as an outstanding system for high-performance lithium-sulfur batteries.

Underwater welding using reactive materials pre-deposited at the junction surfaces as a self-contained, in-situ ignitable heat source mitigates external power and gas supply requirements. Consequently, lending itself to robotic implementation eliminating the cost along with health and safety hazards of human welder-divers. This project reports on lap joining of aluminum sheets with sandwiched commercial reactive Ni-Al multilayers that are perforated to allow for melt fusion under compression upon ignition, in saline and deionized water as well as air for comparison. Finite-element thermal simulations are employed to study the resulting welding temperature field and melt conditions. Infrared pyrometry and thermocouple measurements during welding were used to validate the computational simulations. The lap joints are subjected to standard shear testing, and comparable compliance, strength and toughness values of the welds are assessed for underwater and dry joints. Scanning electron (SEM) of the weld sections reveal rapidly melting and solidifying microstructures of the parent metal, with minimal melt flow and perfusion of nickel aluminide aggregates from the reacted multilayers, and no signs of cavitation.

Indium oxide (InOx) and indium tin oxide (ITO) thin films were deposited on glass substrates by plasma enhanced reactive thermal evaporation (PERTE) at different substrate temperatures. The films were then submitted to two etching solutions with different chemical reactivity: i) HNO3 (6%), at room temperature; ii) HCl (35%): (40 °Bé) FeCl3 (1:1), at 40 °C. The dependence of the etchability of the films on the structural and deposition conditions is discussed. Previously to etching, structural characterization was made. X-ray diffraction showed the appearance of a peak around 2θ=31° as the deposition temperature increases from room temperature to 190 °C, both for ITO and InOx. AFM surface topography and SEM micrographs of the deposited films are consistent with the structural properties suggested by X-ray spectra: as the deposition temperature increases, the surface changes from a finely grained structure to a material with a larger-sized grain or/and agglomerate structure of the order of 250-300 nm. The roughness Rq varies from 0.74 nm for the amorphous tissue to a maximum of 10.83 nm for the sample with the biggest crystalline grains. Raman spectra are also presented.

Current FDA-approved permanent female sterilization procedures are invasive and/or require the implantation of non-biodegradable materials. These techniques pose risks and complications, such as device migration, fracture, and tubal perforation. We propose a safe, non-invasive biodegradable tissue scaffold to effectively occlude the Fallopian tubes within 30 days of implantation. Specifically, the Fallopian tubes are mechanically de-epithelialized, and a tissue scaffold is placed into each tube. It is anticipated that this procedure can be performed in less than 30 minutes by an experienced obstetrics and gynaecology practitioner. Advantages of this method include the use of a fully bio-resorbable polymer, low costs, lower risks, and the lack of general anaesthesia. The scaffold devices are freeze-cast allowing for the custom-design of structural, mechanical, and chemical cues through material composition, processing parameters, and functionalization. The performance of the biomaterial and de-epithelialization procedure was tested in an in vivo rat uterine horn model. The scaffold response and tissue-biomaterial interactions were characterized microscopically post-implantation. Overall, the study resulted in the successful fabrication of resilient, easy-to-handle devices with an anisotropic scaffold architecture that encouraged rapid bio-integration through notable angiogenesis, cell infiltration, and native collagen deposition. Successful tubal occlusion was demonstrated at 30 days, revealing the great promise of a sterilization biomaterial.

Structural analysis on interfaces between ionic liquids (ILs) and solid substrates is an important study for not only the basic fundamental aspects but also many technological processes. In the present work, we utilized frequency modulation atomic force microscopy (FM-AFM) based on a quartz tuning fork sensor to elucidate the structure of interface between 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6) IL and highly ordered pyrolytic graphite (HOPG) surface. It was observed that this IL form solvation layers at their interface, with ∼0.5-0.57 nm thickness of each layer. We have compared our experimental results with previously reported results from molecular dynamics simulation study, and combination of classical molecular dynamics and density functional theory calculations in order to understand the IL/HOPG interface.

A solar thermoelectric generator (STEG) system composed of an optical concentrator system (OPS), a Bismuth Telluride thermoelectric module (TEG), and a cold plate-based cooling system (CPCS) was numerically simulated, to measure the efficiency of electric generation of a commercial thermoelectric module under controlled temperatures. The OPS is composed by a Fresnel lens that allows a temperature of around 200 °C, the OPS works with a solar irradiance of 1000 W/m2 (AM 1.5 Reference) and an optical concentration of 60. The OPS is coupled to the hot side of the TEG that consists of a commercially available thermoelectric module. The CPCS maintains a temperature of around 50 °C on the cold side of the TEG. To evaluate the configuration, a computational fluid dynamic (CFD) analysis was carried out to evaluated the thermal performance of the CPCS and the temperature achieved on the upper surface of the cooling device. Based on the numerical results generated by the CFD analysis, an analytical TEG efficiency of around 5% was achieved when a temperature difference, between the hot and cold sides of the commercial TE module, of 150 °C was maintained. We perform an analysis using the Hogan and Shih model that uses the thermoelectric material properties exposed by Chen et al.

During decomposition of copper formate, a volatile intermediate is formed, that can be utilized to fabricate conductive copper lines for electrical interconnections. By the method called Reactive Transfer Printing (RTP), a pattern of copper (II) formate was printed, and placed adjacent to a second surface; decomposition of the printed pattern led to a transfer of copper to the second substrate. It was found that the yield of the transfer process improved due to presence of several carboxylic acids which are liquid with a high boiling point. Furthermore we found that the transport of copper starts at a lower temperature than previously reported, indicating that the first decomposition step of copper formate is related to the catalytic decomposition of formic acid on a copper surface. The findings enable printing of conductive copper patterns onto the interior surface of a glass vessel.

Among energy storage devices, the redox flow batteries are important for variety of applications such as for grid storage. In this class of batteries a large number of redox couples have been examined in the past. The vanadium redox couple, although is attractive for this application, suffers from a) poor charge transfer characteristics b) electrode degradation and c) deteriorating performance. We wish to report here that all these deficiencies have been overcome by using a graphene quantum dot electrodes. This electrode has the advantage of large surface area, high electrical and thermal conductivity. The cell voltage of 1.5 V and power density of about 120 mW/cm2 and coulombic efficiency of 90% can be achieved as the redox couples, V(IV)/V(V) and V(III)/V(II) undergo fast electron transfer at the interface of the quantum dots and solution resulting in higher reversibility. The cyclic voltammetric experiments carried out with quantum dots in the solutions during the oxidation of V(IV) show enhanced currents, due to the movements of the dots which is conducive for power gain in the battery operation. The electrochemical degradation is absent with the quantum dot electrode. The charge/discharge cycles have been reproducible.

Single crystal Au microspheres, of 3 μm diameter, with sputter-deposited Ni surface layers, of 40 or 80 nm thickness, were tested in compression at three loading rates to investigate the role of thin passive layers on the mechanisms of plastic deformation of small-volume FCC ductile metal samples. The Ni layer resulted in an increase in the incipient yield force by about 10%. Micro-cracking of the Ni layer was observed to occur with incipient yielding. The estimated apparent activation volume of the incipient plastic deformation process was found to be nearly identical for the Ni-coated and the uncoated Au microspheres. This suggests that, while the stress required to initiate incipient plastic deformation was increased by the constraint imposed by the Ni layer, the subsequent plastic flow occurred by a dislocation nucleation and glide mechanism that is essentially the same as that occurring in an unconstrained Au microsphere.

Organic light-emitting diodes (OLEDs) have progressively attracted generous attention because of their versatile applications in solid state lighting and full color displays. High-efficiency is crucial for OLED devices being energy saving and to have a longer lifespan. Numerous approaches have been attempted to attain high-efficiency OLEDs via newly synthesized organic materials, light-extraction structure design and energy-efficient device architectures. The organic materials used in optoelectronic devices have inherently low dielectric constant. In this work, we demonstrate a comprehensive model to quantitatively investigate the role of dielectric constant of the electron transporting material on the electric field distribution, charge drift and exciton recombination probability across the emissive layer (EML) and electron transport layer (ETL) in organic light-emitting diode via commercialized electrical simulation package SETFOS.

Using dissipative particle dynamics approach, we model phase separation in a ternary system encompassing cross-linked polyacrylamide (PAM) gel, oil and water. PAM gels are widely used in many applications, from food and cosmetic applications to enhanced oil recovery approaches. We show that the PAM nanogel adsorbs at the oil-water interface and spreads out over this interface for the case of a loosely cross-linked polymer network. Tailoring PAM behavior at the oil-water interfaces by controlling gel’s properties could allow one to alter the properties of oil-water emulsions.

Vanadium Oxide has application to infrared bolometers due to high temperature coefficient of resistivity (TCR). It has attracted interest for switchable plasmonic devices due to its metal to insulator transition near room temperature. We report here the properties of vanadium oxide deposited by an aqueous spray process. The films have a ropy surface morphology with ∼70 nm surface roughness. The polycrystalline phase depends on annealing conditions. The films have TCR of ∼2%/deg, which compares well with sputtered films. Only weak evidence is found for an insulator-metal phase transition in these films.

This study provides detailed information on the manufacture of III-V metal organic vapor phase epitaxy precursors through extensive literature and patent research. This data informed a cradle-to-gate life cycle assessment of these chemicals. Reported impacts include cumulative energy demand and greenhouse gas emissions. The results were interpreted to identify sources of environmental burden within the life cycle and were compared to energy demand reported in previous studies.

Here, we present a numerical study of the far field optical response of a monolayer composed by an hexagonal closed packed array of SiO2 spheres with a single Au NP at each interstitial position. The Optical Efficiencies, Reflection, Transmission and Absorption at normal incidence, were calculated using Discrete Dipole Approximation model extended to periodic targets. In order to consider different amounts of loads of Au NPs per unit of area in the monolayer, we have fixed the diameter of Au NPs (9 nm) and varied the diameter of the SiO2 spheres. The numerical calculations indicate that Au-SiO2 composite monolayers can absorb and scatter the incident electromagnetic wave, as the load of Au NPs increases the monolayer becomes less transparent to light and the spectra are red-shifted. The profile of the absorption spectrum of the Au-SiO2 composite monolayer is very similar to that of a Au NPs monolayer (composite monolayer without the Silica spheres) but less intense, presumably because the Silica spheres screen the coupling of the Localized Surface Plasmons of Au NPs.

Chitosan is a polymeric compound with functional groups which enable surface binding to nanoparticles and antibacterial activity. The antimicrobial activity was studied using silver nanoparticles with varied concentrations of chitosan. The nanoparticles were synthesized through a simple and environmentally friendly method at room temperature. Spherical particles with average sizes between 2 and 6 nm were obtained and their crystallinity showed a face-centered cubic phase. The evidence of chitosan presence on the nanoparticle surface was confirmed by the characteristic diffraction peak of chitosan and by FTIR spectra where the bonding of amine group could be depicted. The chitosan-capped silver nanoparticles showed good antibacterial and antifungal activities with MIC values between 0.20 and 1.5 mg.mL-1 compared to those obtained from most of references (up to 6.25 mg.mL-1) on the selected gram-positive (Staphylococcus aureus, Enterococcus faecalis), gram-negative (Klebsiella pneumoniae, Pseudomonas aeruginosa ) bacteria and fungi (Candida albicans, Cryptococcus neoformans).

Although Pb-based perovskite solar cells already achieve power conversion efficiencies (PCE) beyond 20 %, the use of toxic Pb is causing considerable environmental concern. As a consequence, a variety of alternative cations have been investigated to replace Pb2+ in the perovskite structure. Methylammonium bismuth iodide (MA3Bi2I9, MBI) has shown promising results for environmentally benign and chemically stable devices. While the PCE of MBI-based solar cells are still comparably low, structural improvements have been made by using chemical vapor deposition (CVD). CVD allows for the well-controlled formation of coherent and dense MBI layers in contrast to solution-processing. In this work, CVD as a possible MBI fabrication method for efficient and size-scalable solar cells is discussed. The precursors MA iodide (MAI) and Bi iodide (BiI3) are deposited in an alternating deposition process forming the desired MBI perovskite on the heated substrate. Substrate temperatures as well as deposition times of each precursor are varied with the aim of forming coherent and dense MBI layers. Optimized films are further processed to solar cell prototypes and compared with solution-processed reference devices. The results reveal that CVD possesses great potential to enable the manufacture of MBI photovoltaic (PV) devices processed in a solvent-free environment.

MnO2-multiwalled carbon nanotube (MWCNT) supercapacitor electrodes with active mass loading of 30-45 mg cm-2 were prepared. In method 1, MnO2 and MWCNT were dispersed using 3,4-dihydroxybenzaldehyde (DHB) and toluidine blue (TD), respectively. The Schiff base formation between amino group of TD and aldehyde group of DHB facilitated improved mixing of MnO2 and MWCNT. In method 2, gallocyanine (GC) was used as a co-dispersant for MnO2 and MWCNT. The catecholate type bonding of DHB and GC allowed for adsorption of the dispersant molecules on MnO2 nanoparticles. The electrodes, prepared by method 1 showed higher capacitance, compared to the electrode, prepared by method 2. The highest capacitance of 7.8 F cm-2 (173 F g-1, 139 F cm-3) was obtained at a scan rate of 2 mV s-1 and active mass loading of 45 mg cm-2.