A hand operated benchtop stamping press was developed to conduct research on microscale hole fabrication in polymer membranes for applications as scaffolds in tissue engineering. A biocompatible and biodegradable polymer, poly(ε-caprolactone), was selected for micropunching. Membranes between 30 μm and 50 μm thick were fabricated by hot melt extrusion, but could not be stamped with a 200 μm circular punch at room temperature, regardless of die clearance due to excessive strain to fracture. This problem was overcome by cooling the membrane and die sets with liquid nitrogen to take advantage of induced brittle behavior below the polymer’s glass transition temperature. While cooled, 203 μm hole patterns were successfully punched in 33 μm thick poly(ε-caprolactone) membranes with 11% die clearance, achieving 71% porosity.

The current gold-standard therapeutic strategies for bone grafts in the patient population are to use either allograft or autograft bone. Although these approaches have a long track record of utilization, neither is without risk to the patient, and there remains a desire in the field to improve treatment options. While there have been treatments approved by the FDA for full length growth factors and calcium salt-laden collagen sponges, these are not available for the entire population of potential bone graft patients. One viable strategy to focus on these concerns is to design an implantable bone graft substitute that can address all the negative drawbacks of autograft bone, allograft bone, and full length proteins. The work provides a preliminary investigation of synthetic, nanofiber-permeated, composite polymer/ceramic scaffold for bone repair using thermally induced phase separation, PLLA microspheres, and hydroxyapatite. The scaffolds as described have fiber diameters that mimic natural collagen ECM networks in bone as determined by scanning electron microscopy and will serve as the basis for future studies in substrate-guided bone tissue regeneration.

The formation of misfit dislocations is an important issue for the performance of heteroepitaxial micro- and optoelectronic devices. We analyze three approaches that quantify the stability of misfit dislocations in axial-heteroepitaxial nanowires with respect to applicability and predictions of critical nanowire dimensions. The “nanoheteroepitaxy” approach of Zubia and Hersee proves suitable for determination of strain partitioning in the presence of an elastic mismatch. Concerning the critical thickness and diameter however the descriptions of Ertekin et al. and Glas respectively yield more reliable results, owing to the consideration of the total coherent and dislocation related energies plus the residual strain energy. In contrast to the model of Ertekin et al., which refers to infinitely long nanowires, the other two mentioned approaches allow predictions of the critical thickness of mismatched deposits on the nanowire axial face.

4H-SiC p+n photodiodes based on ultrathin-junctions have been fabricated with distinct processes for the p+-region creation: either with Aluminium conventional ion implantation, or with Boron Plasma Ion Immersion Implantation. Spectral sensitivity measurements were performed at several temperatures from room temperature up to 340°C, with incident wavelengths ranging from 200 to 400 nm. Both responses are characterized by a stability between 200 and 270 nm, and a important increase with temperature between 270 and 380 nm. This fact has to be related to the two different kinds of optical absorption phenomena in SiC with respect to the wavelength, which are direct and indirect (phonon assisted) transitions. When decreasing the temperature, we noticed a hysteresis effect, which could be due to charge trapping by temperature activated defects. After strong proton and electron irradiations, the diodes showed a stability of the response below 270 nm, making them suitable for use in harsh environments. Simulation was performed at room temperature, with a good correlation between simulated and experimental room temperature curves.

Silver nanoparticle inks are increasingly applied for the manufacture of inkjet-printed electrically conductive patterns. In order to obtain high conductivity, the printed liquid patterns have to be functionalized by an appropriate post- treatment step. Modern post-treatment methods using e.g. microwaves, intense pulsed light or adopted infrared radiation, are nevertheless the basis of the thermal process. The thermal treatment e.g. in furnaces or on heating plates, is applicable for a great variety of inks and ensures an efficient sintering without major technical efforts. It has been studied intensively wherein the reports mainly focus on reduction of the resistivity by controlling the parameters of the thermal treatment. Our researches exceed these comparative studies by investigating multi-layered patterns, their manufacturing and post-treatment.

Two silver nanoparticle inks were inkjet printed on a rigid and a flexible substrate. The geometry of the patterns was varied. The different drying behaviors of the inks were investigated. In addition, the number of layers which were printed on top of each other was varied. The sintering temperatures and time durations were varied.

The morphology of the patterns is investigated by profilometry and optical microscopy. The microstructure is analyzed by scanning electron microscope and X-ray diffraction. Furthermore, the electrical characteristics were determined by the measurement of the resistance. The results indicate the relation between the manufacture and the resulting microstructure and functionality of the patterns. The knowledge of these parameters enables us to control the industrial manufacturing of similar conductive patterns.

We report magneto-dielectric anomaly of the multiferroic (Bi0.95Nd0.05)(Fe0.97Mn0.03)O3 (BNFM) ceramic near Néel temperature. The ceramic pellets were synthesized by conventional solid state reaction route. X-ray diffraction patterns revealed that most of the peaks shifted slightly towards higher Bragg’s angle compared to those of pure BiFeO3 and also confirmed the formation of rhombohedral phase. It also suggests that the small chemical substitution of Nd and Mn atoms at Bi and Fe sites of BiFeO3 (BFO) perovskite respectively does not alter the crystal structure. Temperature and frequency dependent dielectric response indicate large dielectric anomaly at 620 K, slightly below the known Néel temperature of BFO. The enhancement in dielectric properties of BNFM ceramic was observed as compared to BFO due to suppression of oxygen vacancies by the doping. Temperature dependent dielectric response in conjunction with Raman and thermo-analytical data show that the BNFM sample presents significant magneto-dielectric response around Néel temperture TN ∼ 620 K.

We review an optofluidic waveguiding lab-on-a-chip used to sense bioparticles. The sensor uses a liquid filled Anti-Resonant Reflecting Optical Waveguide (ARROW) that is interfaced with standard ridge waveguides. The ridge waveguides are coupled to off-chip lasers and detectors via optical fiber. A perpendicular intersection between the ARROW and a ridge waveguide is especially useful for detecting fluorescently tagged particles. Light coupled into the ridge waveguide can fluorescently excite these particles within a very small volume. Fluorescent signal can then be guided within the ARROW and subsequently off chip to a detector.

We also discuss how such devices are fabricated. Both the ARROW and ridge waveguides are made using alternating thin films of tantalum oxide and silicon dioxide on silicon substrates. These thin films are deposited by either sputtering or plasma enhanced chemical vapor deposition (PECVD). The waveguides are patterned using a combination of standard photolithographic processes, reactive ion etching, and sacrificial etching. Low-loss optical guiding is very dependent on both the waveguide structure and the materials used. The latest processes for maximizing detection sensitivity are reviewed.

We also present results using the optofluidic waveguiding sensor for detecting a variety of different types of particles such as fluorescently labeled nanobeads, viruses, ribosomes, and RNA.

B-type carbonate apatite (B-CAp) powders were prepared by a wet method using Ca(OH)2 suspension and H3PO4 solution including NaHCO3 as a carbonate source, and porous B-CAp ceramics with two different amounts of carbonate contents were fabricated by sintering freeze-dried mixtures of the powders and gelatin composite. The porous B-CAp ceramics prepared had three-dimensionally interconnected pores. The sinterability of B-CAp ceramics was dependent on the chemical composition, especially sodium content and vacancy of OH site, and the carbonate contents did not directly influence the dissolution rate of porous B-CAp ceramics.

Our recent efforts using primarily nanodiamonds as lubricant additives are discussed. For traditional high performance engine oils, our results show a reduction in friction for steel surfaces for both laboratory experiments under controlled conditions and in a pilot study of passenger cars under typical driving conditions. Examination of the surfaces suggests that surface polishing at the sub-micron scale may be responsible for these results. A separate set of experiments using a quartz crystal microbalance to measure dissipation and drag due to friction has shown that when added to water the charge of the nanodiamond acquired from surface functionalization can have a large influence on uptake and friction at the water-metal interface. More importantly, these results suggest the possibility of creating nanodiamonds with controllable frictional drag at the solid-liquid interface through surface processing. Companion simulation results for nanodiamonds in water sliding between diamond surfaces are also presented. Future possibilities for further understanding and tuning the properties of nanodiamonds as lubricant additives through synergistic experiments and modeling are also discussed.

Two types of TiN/HfOx/TiN devices have been fabricated where the top 200nm TiN electrode has been deposited by two different sputtering methods; reactive, using a titanium target in a nitrogen environment, and non-reactive, using a titanium nitride target. Characterization of the materials shows that the reactive TiN is single-phase stoichiometric TiN with a sheet resistance of 7Ω/square. The non-reactive TiN has a sheet resistance of 300Ω/square and was found to contain significant amounts of oxygen. The resistive switching behavior differs for both devices. The reactive stoichiometric TiN device results in bipolar switching with a Roff/Ron ratio of 50. The non-reactive TiN results in unipolar switching with a Roff/Ron ratio of more than 103, however this device shows poor reproducibility. These results show that an oxygen rich layer between the top electrode and insulator affects the Roff value. It supports the theory of oxygen vacancies leading to the formation of conductive filaments.

Scanning electronic microscopy (SEM), X ray diffraction (XRD) and photoluminescence (PL) have been applied to the study of structural and optical properties of ZnO nanocrystals prepared by the ultrasonic spray pyrolysis (USP) at different temperatures. The variation of temperatures and times at the growth of ZnO films permits modifying the ZnO phase from the amorphous to crystalline, to change the size of ZnO nanocrystals (NCs), as well as to vary their photoluminescence spectra. The study has revealed three types of PL bands in ZnO NCs: defect related emission, the near-band-edge (NBE) PL, related to the LO phonon replica of free exciton (FE) recombination, and its second-order diffraction peaks. The PL bands, related to the LO phonon replica of FE, and its second-order diffraction in the room temperature Pl spectrum testify on the high quality of ZnO films prepared by the USP technology.

A new route to producing microcrystalline silicon (µc-Si) thin films by re-crystallizing Si nanoparticle films by flash lamp method is presented. High quality Si nanoparticle films with high uniformity and high particle packing density were obtained using a stable non-aqueous Si nanoparticle suspension and the electrophoretic deposition (EPD) method. Morphology and crystallinity of as-deposited and flash lamp re-crystallized Si nanoparticle films were studied.

The surface passivation of Si wafer by AlOx thin films grown by mist CVD in an open-air atmosphere was studied with a view to improving the effect of high-performance c-Si solar cells. In AlOx thin film grown at a temperature above 400°C by mist CVD, the OH bonding did not remain in the film and the breakdown field (E BD) was over 6 MV/cm. In Si wafers passivated by AlOx thin films grown by mist CVD at growth temperature above 400°C, the negative fixed charge density (Q f) at the interface was higher than 1012 cm-2 and the surface recombination velocity (S eff) was 44.4 cm/s. These results show that mist CVD, which is fundamentally an environmentally friendly technique, may be suitable for the fabrication of a passivation film on Si surfaces designed to improve the effect of high-performance c-Si solar cells.

Optical pump-probe studies of cubic crystalline Ge2Sb2Te5/GaSb(001) have previously shown that the amplitude of a coherent optical phonon (COP) with frequency of 3.4 THz observed in the anisotropic reflectance (AR) signal exhibits a four-fold dependence upon the polarization of the probe beam. The appearance of the mode in the AR signal but not the reflectance (R) signal, and the dependence upon probe polarization, both suggest a three-dimensional mode character. Confirmation that this mode indeed has three-dimensional character, similar to the Raman inactive T 2 mode in the pristine rock salt structure, is highly important in understanding the structure of the crystalline phase of Ge2Sb2Te5 that has important applications within data storage technology. A phonon of the same frequency has been observed in an epitaxial Ge2Sb2Te5/InAs(111) structure, suggesting that this phonon is indeed characteristic of epitaxial cubic GST. A theory, which considers the symmetry of the Raman tensor for a particular phonon mode, is used to predict the dependence of R and AR signal amplitude upon pump and probe polarization for the T 2 mode of a (111) facet of the putative rock-salt structure.

Obstructing commercialization of Proton Exchange Membrane Fuel Cells (PEMFC) is the soaring cost of platinum and other catalysts used to increase membrane efficiency. The goal of this investigation is to find a relatively inexpensive catalyst for coating the membrane and enhancing the efficiency of the PEMFC. Graphene oxide was reduced using NaBH4 in the presence of metal salts, primarily KAuCl4 and K2PtCl4, to synthesize metal-nanoparticle/reduced graphene oxide (RGO). FTIR indicated the successful synthesis of RGO, while Transmission Electron Microscopy displayed the presence of nanoparticles on RGO sheets. Nafion® membranes were coated with metal-nanoparticle/RGO and tested in an experimental PEMFC alongside bare Nafion®, Gold (Au) nanoparticles, and RGO. The metal-nanoparticle/RGO composites enhanced the PEMFC compared to bare Nafion®. Au-RGO, the best catalyst composite, increased the efficiency up to 150% better than nanoparticles or RGO alone while using only 1% of the concentration of Au nanoparticles. Theoretical power output of the Au-RGO synergy could increase fuel cell efficiency up to 18 times more than the Au-nanoparticles themselves by altering concentrations of Au nanoparticles in Au-RGO. The Au nanoparticles changed the structure and catalytic ability of graphene in the Au-RGO, offering a promising future for PEM fuel cell technology.

In this paper we report on the 532 nm Nd:YAG laser-induced crystallization of 10 nm thick boron-doped hydrogenated amorphous silicon thin films deposited on flexible polyimide and on rigid oxidized silicon wafers by hot-wire or by plasma-enhanced chemical vapor deposition. The dark conductivity increased from ∼10-7 Ω-1cm-1, in the as-deposited films, to ∼10 and 50 Ω-1cm-1 after laser irradiation, on rigid and flexible substrates, respectively. Depending on type of substrate, laser power and fluence, a Raman crystalline fraction between 55 and 90 % was measured in HWCVD films, which was higher than observed in rf-PECVD films (35-55 %). Crystallite size remained small in all cases, in the range 6-8 nm. Due to a very high conductivity contrast (>7 orders of magnitude) between amorphous and crystallized regions, it was possible to define conductive paths in the a-Si:H matrix, by mounting the sample on a X-Y software-controlled movable stage under the laser beam, with no need for the usual lithography steps. The resistors scribed by direct laser writing had piezoresistive properties, with positive gauge factor ∼1. The details of the laser interaction process with the Si film were revealed by scanning electron microscopy imaging.

Novel hyperbranched molecules containing pyrrole units were obtained from ortho-, meta- and para-diaminodiphenyldiacetylenes, as AB2 type monomers by one-step polymerization. Diacetylenic fragments reacted with terminal amino groups in the presence of copper chloride to give pyrrole units. Diaminodiphenyldiacetylene monomers have been synthesized from ethynilanilines in three steps. The novel monomers and hyperbranched molecules were characterized by NMR, IR and thermal analysis. Some conductivity proofs were also carried out and this behavior was assessed.

The electronic behavior of some of these molecules was studied by means of theoretical methods. DFT optimization processes were carried out for three structures derived from the generation growing. There are at least two conformational isomers of the structure (meta- and para-) which show conductivity properties, the meta-isomer shows semiconductor nature but this species is hard to modeling because the steric hindrances cause optimization problems and indeed the third generation species was not achieved. In other context, the para-isomer allows the calculation of three generations and shows clearly a tendency to narrow the energy gap between the frontier orbitals but besides the behavior of the HOMO-1 seems reinforce the conductivity phenomenon.

1/f noise in semiconductor devices and circuits provides important information regarding quality of the interface as well as the transport mechanism. In 1D and 2D channel materials, 1/f noise also provides information on stability under ambient conditions, including effects of contaminants adsorbed on the surface. In addition, noise levels are important in evaluating suitability of the device for analog and digital applications. In this work, we have fabricated back-gated field-effect transistors (FETs) using various thicknesses of mechanically exfoliated MoS2 flakes (bilayer and 15 layer flakes) and studied the 1/f noise under ambient conditions. The on-current of the devices scales with the number of layers. The Hooge parameters inferred from the measured noise amplitudes and calculated carrier densities are comparable to prior reports on devices such as CNTs and graphene FETs, even when measured under ambient conditions. The effect of channel and contacts on both the conductance and noise can be inferred from bias-dependent current and noise measurements.

We demonstrate one-dimensional (1D) and two-dimensional (2D) resonant nanoelectromechanical systems (NEMS) derived from nano carbon materials, where the resonance frequency and the quality (Q) factor of the devices are measured experimentally using ultrasensitive optical interferometry. The 1D nano carbon resonators are formed using carbon nanofibers (CNFs) which are synthesized using a plasma-enhanced chemical vapor deposition (PECVD) process, while the 2D nanocarbon resonators are based on CVD grown graphene. The CNFs are prototyped into few-μm-long cantilever-shaped 1D resonators, where the resonance frequency and Qs are extracted from measurements of the undriven thermomechanical noise spectrum. The thermomechanical noise measurements yield resonances in the ∼3–15 MHz range, with Q of ∼200–800. Significant changes in resonance characteristics are observed due to electron beam induced amorphous carbon deposition on the CNFs, which suggests that 1D CNF resonators have strong prospects for ultrasensitive mass detection. We also present NEMS resonators based on 2D graphene nanomembranes, which exhibit robust undriven thermomechanical resonances for the extraction of ultrasmall strain levels.