Electrical discharge machining (EDM) is a method capable of modifying the microstructure of metal surfaces. Here, we present a predictive computer supported model of the roughness generated on the surface by this process. EDM is a stochastic process, in which charge generated between a metallic substrate and an electrode creates impacts, and thus is suitable for modeling through iterative simulations. The resulting virtual, modified surface structures were evaluated for roughness. Curvatures were analyzed using Abbott-Firestone curves. Three radii of impacts (10, 20, 30 μm) and two values for the depth to radius ratio (0.1, 0.3) were used as input parameters to compute a total of six simulations. It was found that the roughness parameters followed an inverse exponential trend as a function of impact number, and that the strongly concave curvatures reached equilibrium at an earlier impact number for lower depth to radius ratios.

In the search for chemically stable two-dimensional (2D) materials with high in-plane mobility, proper bandgap, and compatibility with vapor-based fabrication, van der Waals semiconductor SiP has become a potential candidate as a robust variation of black phosphorous. While bulk SiP crystals were synthesized in the 1970s, the vapor-based synthesis of SiP nanostructures or thin films is still absent. We here report the first chemical vapor growth of SiP nanostructures on SiO2/Si substrate. SiP islands with lateral size up to 20 μm and showing well-defined Raman signals were grown on SiO2/Si substrate or on SiP-containing concentric rings. The presence of SiP phase is confirmed by XRD. The formation of rings and islands is explained by a multiple coffee ring growth model where a dynamic fluctuation of droplet growth front induces the topography of concentric ring surfaces. This new growth method might shed light on the controlled growth of group IV-III high-mobility 2D semiconductors.

Superporous Carboxy Methyl Cellulose (CMC) cryogels were synthesized by chemical crosslinking of linear CMC with divinyl sulfone (DVS) with different mole ratios of CMC repeating unit down to 2.5%. The morphology of macroporous CMC cryogels was visualized by optic microscope and scanning electron microscope (SEM) images. The swelling capacity and pore volume of CMC cryogels were found to increase with the decrease in the ratio of crosslinker to CMC, and the highest swelling capacity and pore volume values were 10825±1799% and 22.1±0.4 mL/g for 2.5% mole ratio of crosslinked CMC cryogels. The blood compatibility of CMC cryogels revealed that blood cells were destroyed with very low hemolysis ratio of 1.09±1% and also showed less thrombogenic activity with 80.2±5.1% blood clotting indexes.

Calcium ions impact nearly every aspect of cellular life, playing crucial roles as secondary messengers in regulation of neurotransmission, cell proliferation, migration and differentiation processes, intracellular homeostasis, long-distance signal propagation and stimuli physiological response. Despite its key-role, available techniques to study and selectively regulate Ca2+ signalling largely rely on chemical and electrical approaches, which often cannot ensure the necessary spatial and temporal resolution, specificity, modulation and reversal capability. In this context, Ca2+ modulation based on physical stimuli, such as magnetic, mechanical and optical tools, are emerging ass promising innovative solutions. Here, we focus our attention on a subclass of these approaches, namely wireless-activated techniques, and on functional materials able to act as non-invasive transduction elements. We present an overview of most recent outcomes in the field, and we critically evaluate their advantages and drawbacks. This work is mainly directed to the material science community, but hopefully it will provide a useful perspective also to the broader readership of biotechnologists, physiologists and clinicians.

The present study investigates the adsorption of fluorides (F) by a hydrotalcite MgFe (HT MgFe) and an iron-based metal oxide (MgFe oxide). Both materials were synthesized by the coprecipitation method and were calcined at the same temperature HT MgFe, HTC MgFe, oxide MgFe and oxide MgFeC. Both solids were characterized by the XRD technique. Materials showed typical crystalline forms; in the case of HT MgFe, an octahedral crystalline form and for the oxide MgFe cubic crystalline form, the analysis of the BET method classifies the materials as mesoporous. In the adsorption study, it was determined that the optimal pH for adsorption is 7. Regarding the adsorption kinetics, the HTC MgFe and oxide MgFeC samples were adjusted to the pseudo-second order model, which describes the process as chemiadsorption; meanwhile, for the samples, isotherms were adjusted to the Langmuir model, which describes the material as homogeneous with a strong interaction between the sorbate and the sorbent.

Several photocatalysts, based on titanium dioxide, were synthesized by spark anodization techniques and anodic spark oxidation. Photocatalytic activity was determined by methylene blue oxidation and the catalytic activities of the catalysts were evaluated after 70 hours of reaction. Scanning Electron Microscopy and X Ray Diffraction analysis were used to characterize the catalysts. The photocatalyst prepared with a solution of sulfuric acid and 100 V presented the best performance in terms of oxidation of the dye (62%). The electric potential during the synthesis (10 V, low potential; 100 V, high potential) affected the surface characteristics: under low potential, catalyst presented smooth and homogeneous surfaces with spots (high TiO2 concentration) of amorphous solids; under low potential, catalyst presented porous surfaces with crystalline solids homogeneously distributed.

X-ray Absorption Spectroscopy is a technique of fundamental importance in nuclear waste management, as an element specific probe of speciation, which governs radionuclide solubility, immobilisation and migration. Here, we exploit recent developments in laboratory instrumentation for X-ray Absorption Spectroscopy, based on a Rowland circle geometry with a spherically bent crystal analyser, to demonstrate speciation in prototype ceramic and glass-ceramic waste forms. Laboratory and synchrotron XANES data acquired from the same materials, at the Ce and U L3 edges, were found to be in excellent quantitative agreement. We establish that analysable laboratory XANES data may be acquired, and interpreted for speciation, even from quite dilute absorber concentrations of a few mol%, albeit with data acquisition times of several hours. For materials with suitable absorber concentrations, this approach will enable routine element specific speciation studies to support rapid optimisation of radioactive waste forms and analysis of radiological materials in a purpose designed laboratory, without the risk associated with transport and manipulation at a synchrotron radiation facility.

Hollow microcapsules prepared via layer-by-layer (LbL) self-assembled polyelectrolytes are prevalent biomaterials in the synthesis of biocompatible delivery systems for drugs, imaging probes, and other macromolecules to control biodistribution and lower toxicity in vivo. The use of LbL self-assembly for the synthesis of these capsules provides several benefits including ease of fabrication, abundance in choice of substrates and coating material, as well as application-specific tunability. This study explores the development of hollow microcapsules by LbL assembly of chitosan and alginate onto live E. coli cells, and also provides a proof-of-concept of this capsule as a delivery platform through the encapsulation of quantum dots as a cargo. The study found that robust bilayers of chitosan/alginate can be formed onto the core substrate (E. coli) containing quantum dots as demonstrated with zeta potential analysis. Confocal microscopy was used to verify cell viability and the internalization of quantum dots into the cells as well as confirmation of the coating using fluorescein-labelled chitosan. Furthermore, transmission electron microscopy (TEM) was used to analyse cells coated with four-bilayers and showed a uniform coating morphology with a capsule thickness of 10-20 nm, which increased to 20-50 nm for hollow capsules after cell lysis. Quantum dot retention in the capsules was demonstrated using fluorescence measurements. Overall, the study shows promising results of a novel fabrication method for hollow microcapsules that uses biocompatible polymers and mild core dissolution conditions using cell templates with applications in sustained release of therapeutics and imaging probes.

We demonstrate the fabrication, by exclusive means of inkjet-printing, of capacitive relative humidity sensors on flexible, plastic substrate. These sensors can be successfully used for the measurement of relative-humidity in both air and common soil. We also show that the same technique may be used for the fabrication of the same type of sensors on the surface of the leaves of Elægnus Ebbingei (silverberry).Our results demonstrate the suitability of leaves as substrate for printed electronics and pave the way to the next generation of sensors to be used in fields such as agriculture and flower farming.

In the last years, perovskite solar cells have attracted great interest in photovoltaic (PV) research due to their possibility to become a highly efficient and low-cost alternative to silicon solar cells. Cells based on the widely used Pb-containing perovskites have reached power conversion efficiencies (PCE) of more than 20 %. One of the major hurdles for the rapid commercialization of perovskite photovoltaics is the lack of deposition tools and processes for large areas. Chemical vapor deposition (CVD) is an appealing technique because it is scalable and furthermore features superior process control and reproducibility in depositing high-purity films. In this work, we present a novel showerhead-based CVD tool to fabricate perovskite films by simultaneous delivery of precursors from the gas phase. We highlight the control of the perovskite film composition and properties by adjusting the individual precursor deposition rates. Providing the optimal supply of precursors results in stoichiometric perovskite films without any detectable residues.

Functional polymers were previously employed to minimize the susceptibility of metallic nanoparticles (MNPs) for aggregation. Herein, we intended to conjugate catechol moiety into the polymer chain end considering its anchoring ability to virtually most surfaces. Accordingly, catechol end-functionalized polysarcosine (cat-PSar) was successfully prepared from the ring-opening polymerization (ROP) of sarcosine N-carboxyanhydrides (Sar-NCA) using dopamine hydrochloride initiator. ROP of Sar-NCA was carried out at different monomer to initiator feed ratios. The molecular structure of cat-PSar was confirmed by 1H NMR and MALDITOF. Afterward, the obtained catechol functionalized polymer was used for in-situ synthesis and stabilization of silver nanoparticles (Ag-NPs) in aqueous solution. The observed characteristic absorption peak at λmax of 415 nm indicates the formation of Ag-NPs. Scanning electron microscope (SEM) images also elucidate the formation of Ag-NPs with the relatively small sizes of the nanocomposite at a high concentration of silver nitrate. Hence, biomimetic polymers could play a dual role as reducing and stabilizing agents in the preparation of monodispersed MNPs.

Quantum Dots (QDs) like Cadmium Sulphide have exciting applications, consequent to their size-dependent optical properties. This compound is used as a pigment in papers, paint, and it can also be found in solar cells. Due to the high use of nanoparticles in society, there is a significant concern in the scientific community about the potential toxicity of these nanomaterials in aquatic environments. According to this main problem, we have a theoretical assumption that Cadmium Sulphide (CdS) particles at nanoscale are more toxic than those in macroscale (bulk), and a higher concentration means higher toxicity. To verify its toxicity in the aquatic environment, first, we need to make sure the nanoparticles are soluble in water. Based in the mentioned before, the objectives of this research were: (i) synthesize Cadmium Sulphide QDs in aqueous phase in presence of biocompatible molecules like L-Glutathione and N-Acetyl-L-cysteine, (ii) characterize the quantum dots optically, structurally and morphologically and; (iii) evaluate the toxicity of Cadmium Sulphide in biological systems. CdS, L-Glutathione-covered CdS and N-Acetyl-L-Cysteine-covered CdS evidenced shoulder peaks at 473 nm (2.40 eV), 450 nm (2.62 eV) and, 381 (3.03 eV) nm, respectively. A broad and high emission peak centered at 545 nm was observed for CdS Nps covered with N-acetyl-L cysteine; whereas as QDs without cover and those covered with L-glutathione showed weak peaks in the visible range (470 nm-650 nm). The presence of L-Glutathione or N-Acetyl-L-cysteine on the quantum dots surface was verified by Infrared Spectroscopy. Energy Dispersive X-Ray Spectroscopy (EDX) assays evidenced the chemical composition of produced nanostructures having 57.91% of S and 42.09% of Cd. The morphology and the size were carried out by High-Resolution Transmission Electron Microscopy (HR-TEM). In this way, nanoparticles were spherical and with a size of ~3 nm. Toxicity results evidence that nanoparticles covered with N-Acetyl-L-Cysteine had a negative interaction in marine organisms at concentrations higher than 700 ppm, after 24 or 48 hours of contact. Also, CdS bulk showed absence of toxicity to marine crustaceans.

In this study, biological hydroxyapatite (HAp) was synthesized from catfish (Pangasius hypophthalmus) bones. First, the as-received catfish bones were de-proteinized in open air, and then converted to HAp by a solid state heat treatment method at a temperature of 900 °C for a holding time of 2 h in a muffle furnace. X-ray diffraction (XRD) analysis confirmed that HAp with high crystallinity of 99.9% was formed matching the structural properties of flouro-apatite with crystallite sizes of approximately 37.1 nm. The morphology of the HAp prepared showed irregularly shaped particles and revealed the appearance of open pores with a less agglomerated structure and a Ca/P ratio of about 1.58. The specific mechanical properties: hardness, compressive strength and fracture toughness of the catfish derived scaffolds were recorded as 480 MPa, 1.92 MPa, and 5.72 Mpa.m1/2, respectively. The fracture toughness of the HAp derived scaffolds suggests that the produced biomaterial is promising for biomedical applications. These findings are useful for the production and application of the HAp powders prepared from catfish bones, and further suggests a possible low-cost route for producing inexpensive ceramics using natural catfish bones.

This article contextualizes how the antimicrobial properties and antipathogenic contact killing/inactivating performance of copper cold spray surfaces and coatings and can be extended to the COVID-19 pandemic as a preventative measure. Specifically, literature is reviewed in terms of how copper cold spray coatings can be applied to high-touch surfaces in biomedical as well as healthcare settings to prevent fomite transmission of SARS-CoV-2 through rapidly inactivating SARS-CoV-2 virions after contaminating a surface. The relevant literature on copper-based antipathogenic coatings and surfaces are then detailed. Particular attention is then given to the unique microstructurally-mediated pathway of copper ion diffusion associated with copper cold spray coatings that enable fomite inactivation.

We examined a working hypothesis of sticky thermoelectric (TE) materials, which is inversely designed to mass-produce flexible TE sheets with lamination or roll-to-roll processes without electric conductive adhesives. Herein, we prepared p-type and n-type sticky TE materials via mixing antimony and bismuth powders with low-volatilizable organic solvents to achieve a low thermal conductivity. Since the sticky TE materials are additionally injected into punched polymer sheets to contact with the upper and bottom electrodes in the fabrication process, the sticky TE modules of ca. 2.4 mm in thickness maintained temperature differences of ca. 10°C and 40°C on a hot plate of 40 °C and 120°C under a natural-air cooling condition with a fin. In the single-cell resistance analysis, we found that 75∼150-µm bismuth powder shows lower resistance than the smaller-sized one due to the fewer number of particle-particle interfaces in the electric pass between the upper and bottom electrodes. After adjusting the printed wiring pattern for the upper and bottom electrodes, we achieved 42 mV on a hot plate (120°C) with the 6 x 6 module having 212 Ω in the total resistance. In addition to the possibility of mass production at a reasonable cost, the sticky TE materials provide a low thermal conductivity for flexible TE modules to capture low-temperature waste heat under natural-air cooling conditions with fins for the purpose of energy harvesting.

We investigate whether first-principles calculations with an improved description of electronic correlations can explain the large magnetic moments and the strong magnetocrystalline anisotropy in the ferromagnetic compound UGa2. The correlations are treated within a static mean-field approximation DFT+U combining the density functional theory (DFT) with an onsite Hubbard interaction U. We find that DFT+U improves the agreement of the magnetic moments with the experiment compared to DFT but worsens the theoretical description of the magnetocrystalline anisotropy.

The low-level nuclear wastes such as decontamination waste from Fukushima are disposed in near-surface underground, where the intermittent recharge of rain and groundwater causes spatial distribution of water content. Therefore, pores of soils are not filled with water, that is, an unsaturated zone will be formed. In such a condition, since the water flow path are detoured by clogged gas in pores of soil in the unsaturated zone, the migration path of radionuclide would be different from the saturated zone. So far, the one-dimensional advection-dispersion equation (ADE) model has been widely used in order to explain experimental results under an unsaturated condition. However, the detouring of local flow-paths remarkably affects the mass transfer. The one-dimensional ADE evaluates such a detouring effect by using Peclet number and retardation coefficient as fitting parameters. In other words, the one-dimensional ADE model is difficult to explain mass transfer under an unsaturated condition. Therefore, the purpose of this study is explaining such complicated transport of radionuclides using a multi-path model based on phenomena in underground. The proposed multi-path model considering both water saturation and permeability distributions showed good agreement with the experimental data under an unsaturated condition.

Hot carrier based methods constitute a valuable approach for efficient and silicon compatible sub-bandgap photodetection. Although, hot electron excitation and transfer have been studied extensively on traditional materials such as Au and Ti, reports on alternative materials such as titanium nitride (TiN) are rare. Here, we perform hot hole photodetection measurements on a p-Si/metal thin film junction using Ti, Au and TiN. This material is of interest as it constitutes a refractory alternative to Au which is an important property for plasmonic applications where high field intensities can occur. In contrast to Au, a TiN/Si junction does not suffer from metal diffusion into the Si, which eases the integration with current Si-fabrication techniques. This work shows that a backside illuminated p-Si/TiN system can be used for efficient hot hole extraction in the IR, allowing for a responsivity of 1 mA/W at an excitation wavelength of 1250 nm and at zero bias. Via a comparison between TiN and other commonly used materials such as Au, the origin of this comparably high photoresponse can be traced back to be directly linked to a thin TiO2-x interfacial layer allowing for a distinct hot-hole transfer mechanism. Moreover, the fabrication of TiN nanodisk arrays is demonstrated which bears great promise to further boost the device efficiency.

This paper presents a numerical approach to predict the thermal residual stresses in polymer nanocomposites reinforced with a periodic array of wavy carbon nanotubes. A three dimensional unit cell model is established to accurately account for the waviness of the nanotube. Periodic boundary conditions are determined for the unit cell with a pair of curved surfaces. Appropriate methods to evaluate the macroscopic stresses and strains are also determined for the unit cell model in which the interior pores of the nanotubes are explicitly included. It is demonstrated that the macroscopic behavior of the nanocomposites is orthotropic due to the symmetries manifested. By employing material properties of the two constituents, the thermal residual stresses and strains induced by high temperature curing and cooling-down are predicted for an epoxy/wavy-nanotube composite. It is also demonstrated that the curing process tends to increase the waviness of the nanotube and the waviness has a significant influence on the distribution of the microscopic residual stresses.

For high switching speed HV Schottky diodes, with very high work function metal and extremely lightly doped epi, the built-in potential may be too high for thermionic emission to occur, when the applied external voltage is quite low (near VF = 0.07V). If the epi is lightly doped p type, the built-in potential (VBuilt-in: potential difference between the metal and silicon Fermi levels) is 1.0V (measured with CV). If the external bias is 0.1V, near the measured VF, it is not enough to overcome the built-in potential for thermionic emission as illustrated. It is likely that in addition to thermionic emission, tunnelling and diffusion currents also contribute to the total HV Schottky diode forward current. TCAD simulation of HV Schottky diodes with N+ guard bands suggests the potential barrier and electric fields at the Schottky junction are relatively high for thermionic emission to occur, when external bias V ≈ VF. In this paper we report HV Schottky diodes fabricated with various metals, metal alloys and epitaxial films. Metal work functions and epi doping profiles are extracted with high frequency Capacitance-Voltage (CV) technique. 150V of breakdown voltage and very low forward voltage (VF = 0.07V) are demonstrated. The measured data indicate very high work function metal or metal alloy is needed to achieve high switching speed and low forward voltage.