A new generation of cementitious materials is being engineered to selectively inhibit the growth of Acidithiobacillus, which are a key genera of acid-generating bacteria responsible for microbially induced concrete corrosion (MICC). In this context, the substitution of metal-laden granular activated carbon (GAC) particles and/or steel slag for a fraction of the fine aggregates traditionally used in concrete mixture has proven useful. While the antimicrobial properties of specific heavy metals (i.e. copper and cobalt) have been leveraged to inhibit acid-generating bacteria growth on sewer pipes, few studies have researched how biocidal aggregates may affect the microstructural and mechanical properties of cementitious materials. We report here on the effects that these biocidal aggregates substitutions can have on compressive strength, flowability, and setting times of cement-based formulations. Results showed that increases in compressive strength, regardless of the presence or absence of biocidal metals, resulted from the GAC incorporation where sand replacement was 3% by mass or lower, while flowability decreased when percentages higher than 3% of GAC was incorporated in a cement mix. When substituting fine aggregate with steel slag particles in mass ratios between 5% and 40%, compressive strength was not affected, regardless of the presence or absence of copper. Setting times were not affected by the inclusion of GAC or steel slag particles except when substituting GAC particles at 10% of the fine aggregate mass; under this condition both initial and final setting times were decreased. Results suggest that in order to have enhanced inhibition potential against acidophilic microorganisms and equal or improved mechanical properties, a combination of 1% metal-laden GAC and 40% copper-laden steel slag is an optimum fine aggregate substitution scenario.

The upcoming IoT society requires portable energy harvesters including thermoelectric generators around room temperature. Here we show a prototype, lightweight thermoelectric generator based on doped single-walled carbon nanotubes. The generator is fabricated by the standard printing and cut-and-paste techniques. The 12 cm-scale generator with a commercial DC-DC converter exhibits thermoelectric outputs high enough to drive small devices such as a light-emitting diode (LED). We believe such demonstration facilitates the studies not only of further improvements in the thermoelectric properties of carbon nanotube materials but also of the novel design for thermoelectric generators on the basis of thermal engineering.

Today, processing technologies have generated negative environmental impact as emission of toxic gases and degradation of the earth when certain products are placement in landfills leading to environmental pollution and several health risks, which damage societies to sustain the planet for future generations. As electronics waste, grain-oriented iron foils, graphite films and Mn-Zn ferrites have been identified as interesting candidates. Uncommon physical properties from such materials are available when these are converting technologically. A strategy such as Life-Cycle Assessment is employed here to taking into account all stages of the life cycle of electronics waste, including processing technology, manufacturing processes, use phase, and end-of-life routes to quantify the recycling performance as a function of the physical parameters that will characterize operability of a functional device. Hence, structure and conduction properties in waste materials are exploring by using Raman spectroscopy and electrical characterization techniques. Researching waste materials will provide theoretical basis for open-loop recycling, where trends related to green engineering must be attained with recyclable materials for practical adaptive structures using different performance principles compared to those used in silicon devices.

This paper reports a novel low power, fast nonvolatile memory utilizing high frequency phonons, atomic force dual quantum wells, ferromagnetism, coupled magnetic dipoles and random accessed magnetic devices. Very high-speed memories, such as SRAM and DRAM, are mostly volatile (data are lost when power is off). Nonvolatile memories, including FLASH and MRAM, are typically not as fast has DRAM or SRAM, and the voltages for WRITE/ERASE operations are relatively high. This paper describes a silicon nonvolatile memory that is compatible with advanced sub-7nm CMOS process. It consists of only one transistor (MOSFET) – small size, and more cost effective, compared with a 6-Transistor SRAM. There is no need to refresh, as required by DRAM. The access time can be less than 1ns – close to the speed level of relaxation time - much faster than traditional FLASH memories and comparable to volatile DRAM. The operating voltages for all memory functions can be as low as high speed CMOS.

Fracture of crystalline silicon (c-Si) solar cells in photovoltaic modules is a big concern to the photovoltaics (PV) industry. Cell cracks cause performance degradation and warranty issues to the manufacturers. The roots of cell fractures lie in the manufacturing and integration process of the cells and modules as they go through a series of elevated temperature and pressure processes, involving bonding of dissimilar materials, causing residual stresses. Evaluation of the exact physical mechanisms leading to these thermomechanical stresses is highly essential to quantify them and optimize the PV modules to address them. We present a novel synchrotron X-ray microdiffraction based techniques to characterize the stress and fracture in the crystalline silicon PV modules. We show the detailed stress state after soldering and lamination process, using the synchrotron X-ray microdiffraction experiments. We also calculate the maximum tolerable microcrack size in the c-Si cells to sustain the residual stress after lamination. We further demonstrate the effect of these residual stresses on the cell fractures using the widely accepted fracture (4-point bending) tests. These test results show that the soldering and lamination induced localized residual stresses indeed reduce the load-carrying capacity of the c-Si cells.

In this paper, we studied the temperature dependency effect of thermal coefficient of resistance (TCR) in amorphous silicon (a-Si) on the properties of uncooled microbolometer with a-Si as a resistance layer by simulation. The temperature of the microbolometer rises during the operation mainly due to the heat generated by Joule heating as well as IR radiation. Generally, the TCR of a-Si is treated as a constant for the simplicity but the absolute value of TCR has been reported to decrease as the temperature increases. Therefore, to improve the device characteristics, the effect of temperature dependency of TCR in a-Si should be considered carefully in the range of the operating temperature. The responsivities of microbolometer are simulated according to the width of the resistance layer (W) with TCR as a function of temperature, which shows that the optimal W condition is affected by the TCR value changed by the temperature.

Optimizing interfaces between photosynthetic natural photoconverters, like photosynthetic bacterial Reaction Centers (RCs) and electrode surfaces represents a challenge in the progress of bio-optoelectronic devices. The features of the surfaces may result detrimental for the tertiary and quaternary structures of the RC, even resulting in the denaturation of the enzyme. Functional surfaces possessing both confinement capability and conductive features able to preserve the conformation of the biomolecule and its bioelectronic behaviours are highly needed. In this work, the RC is adsorbed on diatomaceous silica and plasma treated hydrophobic silicon based materials. Both the materials are demonstrated to be able to preserve and enhance the RC photoconverting activity. In particular, we evaluate the functioning of isolated bacterial RC interacting with flat pSi electrode through two nanotextured interfaces designed to address the RC: a thin conductive silicon film nanotextured in pillars via plasma treatment, and a cast film of nanostructured dielectric biosilica obtained from diatomaceous earth. The characterization of these interfaces, together with the RC photocurrent production measurements, pave the way to new generation RC based bio-devices for photocurrent investigation.

The present work highlights the progress in the field of flexible thermoelectric generator (f-TEGs) fabricated by 3-D printing strategy on the typing paper substrate. In this study, printable thermoelectric paste was developed. The dimension of each planer thermoelectric element is 30mm*4mm with a thickness of 50 μm for P-type Bismuth Tellurium (Bi2Te3)-based/ poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) leg. A single thermoleg with this dimension can generate a voltage of 5.38 mV at a temperature difference of 70 K. The calculated Seebeck Coefficient of a single thermoleg is 76.86 μV/K. This work demonstrates that low-cost printing technology is promising for the fabrication of f-TEGs.

Developing functional, cleavable two-dimensional materials for use in next generation devices has recently become a topic of considerable interest due to their unique properties. Of particular interest, transition metal halides CrI3 and CrCl3 have shown to be good contenders for tunable and cleavable magnetic materials due to their unique magnetic properties in the monolayer. Here, electron spin resonance spectroscopy is used to pinpoint the atomic origins and underlying mechanisms of magnetic interactions as a function of temperature (5-500 K) and microwave frequency (9.43, 120 GHz) on CrI3 and CrCl3 bulk single crystals. ESR signals from CrI3 due to Cr3+ were observed to decay at 460 K, while ESR signals from CrCl3 remain up to 500 K. In the case of CrCl3, the temperature dependences of signal behavior, line width and g-value show characteristic signatures of ferromagnetic fluctuations at around 40 K, near to the antiferromagnetic phase transition at 17 K.

Optical reflectance (OR) and electro-reflectance (ER) spectroscopies were employed to study the resonant optical properties of GaAs/AlGaAs multiple quantum wells based Resonant Bragg Structures (RBS) at excited states. The RBS samples have 60 periods of GaAs/AlGaAs quantum well/barrier grown on semi-insulating GaAs substrates by molecular beam epitaxy with slightly different thicknesses of well/barrier. We observed enhanced OR and ER features when exciton energy coincides with the energy of the Bragg reflection peak, a double resonance condition. Bragg peak can significantly be tuned by changing the angle of incidence of the light. Exciton energies can be tuned by changing the temperature, external electric field and the thickness of the quantum wells. By tuning the Bragg peak for double resonance in the RBS samples of different thicknesses, we observed the electro-reflectance features related to the transitions of x(e2-hh2), x(e2-hh1), x(e2-lh1), x(e2-hh3) and x(e1-hh3) excitons along with the sharp features of x(e1-hh1) and x(e1-lh1) ground state exciton transitions from the ER experiments. The excitonic transitions x(e2-hh1), x(e2-lh1) and x(e2-hh3) which are prohibited at zero electric field, were also observed due to the increased overlap of the electron and hole wave functions caused by the electric field; built-in electric field or applied DC bias.

Thermoelectric (TE) thin films have promise for harvesting electrical energy from waste heat. We demonstrate TE materials and thermocouples deposited by aqueous spray deposition on glass. The n-type material was CdO doped with Mn and Sn. Two p-type materials were investigated, namely PbS with co-growth of CdS and doped with Na and Na2CoO4. Seebeck coefficients, resistivity, and power generation for thermocouples were characterized.

Sunlight is the most environmental friendly energy source available on Earth; many efforts devoted to design artificial photoconversion systems are ongoing, nevertheless they are still expensive and poorly efficient. Photoconversion devices made with organic-biological hybrids, or biohybrids, based on the photosynthetic reaction center (RC) have been introduced. In these systems, the photoenzyme is garnished with artificial antennas to enhance the photoactivity of the RC. Here we present a newly synthesized heptamethine cyanine dye that fulfills requisites to act as efficient RC light harvesting antenna.

The electrical reliability of multilayer high density interconnection printed circuit boards (HDI-PCBs) is mainly affected by the thermo-mechanical stability of stacked micro via interconnections. Here, a critical failure mode is the stress related crack between the electrolytically filled via and the target pad, commonly known as target pad separation. The junction includes two Cu-Cu-interfaces, one between the target Cu pad and the thin electroless Cu layer and the second between electroless Cu and electrolytic Cu. In this paper we will show that state-of-the-art electroless Cu plating processes are able to provide solid, completely recrystallized and highly reliable stacked via junctions. Defect free interfaces were achieved by using ionic Pd-activators and electroless Cu baths with a cyanide based stabilizer system. Cyanide free electroless Cu baths tend more to the formation of nanometer sized defects, discovered via Transmission Electron Microscopy (TEM). In this case a precise adjustment of single stabilizer components is mandatory to achieve defect free layers. The defects are hollow and were identified as “nano voids”. A critical density of these nano voids weakens the interface, predefines the crack path and reduces the overall reliability of the junction. A precise localization of the nano voids within the junction was enabled by detecting the Ni-containing electroless Cu layer via TEM-Ni mapping. Slower volume exchange of the electroless Cu solution within the blind micro via (BMV) substantially increases the nano void density. The ability of nano voids to migrate and coalesce at elevated temperatures was investigated as well.

The homo- and heteroepitaxial deposition of LGS (langasite, La3Ga5SiO14) thin films on LGS single crystals, Si and SiO2 substrates by pulsed laser deposition (PLD) is demonstrated. PLD is performed at substrate temperatures up to about 700 °C and results initially in Ga deficient films. Two strategies of counterbalancing the Ga deficit are realized. First, off-stoichiometric targets with an enhanced Ga content are applied. Secondly, an increased oxygen partial pressure up to about 6 Pa is used during deposition to suppress evaporation of Ga suboxides. Combining these adaptions results in the growth of stoichiometric LGS thin films. Films deposited on LGS substrates do not show any additional X-ray diffraction reflexes nor broadening of the peaks with respect to the single crystalline substrates. Therefore, the homoepitaxial approach can be considered successful. The deposition on Si and SiO2 substrates under the same conditions leads to the formation of polycrystalline films. However, post-annealing at 800 °C increases crystallinity. Stoichiometry and homogeneous distribution of La, Ga and Si cations are confirmed by secondary neutral mass spectrometry (SNMS). The composition remains constant within the film, implying stable process parameters.

Investigating the mechanical properties and dimensional accuracy of 3D printed parts is an important step towards achieving optimum printing conditions. This condition, which leads to the fabrication of parts with appropriate mechanical properties and accuracy, is achieved by studying the effect of different process parameters on the final structure. In this work, Response Surface Methodology (RSM) was employed to design specified experiments to investigate the effects of layer thickness, printing orientation and delay, on the compressive strength and dimensional error of the parts. The results show that an increase in the delay time in X orientation results in better binder spreading and uniformity followed by improvement in the compression strength. Furthermore, more binder spreads in the vertical direction leads to the higher dimensional error in the Z direction. The results proved that the RSM provides a time and cost-efficient design to print the prototypes with optimum strength and dimensional error.

Numerous fabrication protocols are known to yield transition metal oxides with structures related to layered double hydroxides, but the effect of fabrication protocol on the uniformity of mixed-metal compositions remain largely unexplored. We have analysed the apparent solubility limits and the structural implications of iron ions in nickel hydroxide lattices for materials prepared by four different fabrication protocols. Opposing shifts in the (100) and (001) reflection in powder X-ray diffraction results revealed a contraction of the nickel lattice upon successful incorporation of iron, with Ni-M distances exhibiting an apparently linear decrease with respect to iron content. This feature revealed the amount of iron incorporated into nickel-based materials to be dependent on fabrication protocol, varying from apparently negligible concentrations to over fifty atomic percent. The dependency of structure on fabrication protocols provides a handle to improve fundamental understanding of catalytically relevant coordination environments.

The electrical properties of Radio Frequency Sputtered NiFeO and NiO films deposited on n and p-type Silicon is investigated for two different oxygen flows. Rectifying properties for Ni0.8Fe0.2O1+ α on n-Si showed Iforward/Ireverse >10,000 for α>0 and Iforward/Ireverse >50 for α<0. Both types of devices have opposite forward biases. Results suggest that NiFeO sputtered at high oxygen flow is p-type. For NiO and NiFeO on p-Si no strong rectifying properties were observed. The specific contact resistivity of Pt/Ni0.9Fe0.1O1+ α (α>0) was estimated from the difference between the two and four-point probe resistances (0.0007 ± 0.0003 Ω cm2). Using density functional theory calculations, density of state and charge density plots were obtained for systems modelled after experiment, showing that states introduced by O vacancies in NiFeO are localized and prefer locations near Ni explaining the observed hysteresis effects in the IV curves of devices sputtered at low oxygen flow.

We summarize the advantages and disadvantages of some of the most commonly used bioinks. We have probed the mechanical and cytotoxicity properties of Cellink and designed our own bioink from gelatin and Xanthan gum.

Eggshell Membrane (ESM) is a naturally occurring proteinaceous microfibrous scaffold capable of mimicking the extracellular matrix (ECM). The extraction methodology deployed for its extraction process impedes its extensive application as a biomaterial in regenerative medicine. Herein, a unique route was deployed to decorate the surface of ESM with electrospun polycaprolactone (PCL) nanofiber in order to ameliorate the above problems and also fabricate a novel ECM mimicking bilayered scaffold for skin tissue engineering applications. Microstructural and surface topographic analysis confirms the formation of bilayered structure with smooth electrospun PCL nanofibers decorated on ESM. Carbodiimide chemistry was utilized to crosslink the two layers. Cytocompatibility evaluation of scaffolds was carried out with Human dermal fibroblast (HDF) cells. The biomimetic architecture and protein rich composition of as fabricated bilayered construct facilitated extensive cell adhesion, proliferation and migration in contrast the bare natural tissue led to impeded cell adhesion.

The search for nontoxic compositions in the thermoelectric field has motivated many researches to find alternatives to the toxic Pb-based systems, capable of reaching their high conversion efficiency. SnTe is gaining much attention during the past years due to its superior eco-friendly character, and its very similar crystal and band structure to that of PbTe. These makes SnTe a promising compound with great potential to answer the demand and use as a fair thermoelectric candidate. Most of the recently published studies mainly discuss the stoichiometric SnTe alloy. Only several focus on the effect of introducing excess tin/tellurium to the system. For that reason, this research aims to investigate in detail the nonstoichiometric SnxTe1-x co-doped by bismuth and indium/iodine, in an attempt to optimize the electronic properties.