The emergence of BioMEMS fabrication technologies such as soft lithography, micromolding and assembly of 3D structures, and biodegradable microfluidics, are already making significant contributions to the field of regenerative medicine. Over the past decade, BioMEMS have evolved from early silicon laboratory devices to polymer-based structures and even biodegradable constructs suitable for a range of ex vivo and in vivo applications. These systems are still in the early stages of development, but the long-term potential of the technology promises to enable breakthroughs in health care challenges ranging from the systemic toxicity of drugs to the organ shortage. Ex vivo systems for organ assist applications are emerging for the liver, kidney and lung, and the precision and scalability of BioMEMS fabrication techniques offer the promise of dramatic improvements in device performance and patient outcomes.

Ultimately, the greatest benefit from BioMEMS technologies will be realized in applications for implantable devices and systems. Principal advantages include the extreme levels of achievable miniaturization, integration of multiple functions such as delivery, sensing and closed loop control, and the ability of precision microscale and nanoscale features to reproduce the cellular microenvironment to sustain long-term functionality of engineered tissues. Drug delivery systems based on BioMEMS technologies are enabling local, programmable control over drug concentrations and pharmacokinetics for a broad spectrum of conditions and target organs. BioMEMS fabrication methods are also being applied to the development of engineered tissues for applications such as wound healing, microvascular networks and bioartificial organs. Here we review recent progress in BioMEMS-based drug delivery systems, engineered tissue constructs and organ assist devices for a range of ex vivo and in vivo applications in regenerative medicine.

Electromagnetic enhancement arising from plasmon resonance excitation plays a major role in surface-enhanced Raman spectroscopy (SERS), and as a result nanoparticle morphology can significantly affect SERS intensities. In this paper we have calculated these enhancements as well as extinction spectra using the discrete dipole approximation for a system consisting of a dimer of gold disks that is made using on-wire lithography.Including surface roughness in the calculations leads to SERS enhancements for the disks whose dependence on disk spacing and thickness is in agreement with experimental measurements, with a maximum enhancement when the thickness of the disk and the disk-disk gap are 100 nm and 32 nm, respectively. These results are in better agreement with experiments than earlier estimates based on flat surfaces.

The micro-mechanical properties of 5 μm thick histological sections of ferret aorta and vena cava were mapped as a function of distance from the outer adventitial layer using nanoindentation. In order to decouple the effect of the glass substrate on the elastic modulus of these thin sections, the nanoindentation data were analyzed using the extended Oliver and Pharr method which is readily accessible for coatings and layered materials with the software package, FilmDoctor®. In the aorta, the elastic modulus was found to decrease progressively from 35 MPa at the adventitia (outermost layer) to 8 MPa at the intima (innermost layer). This decrease in modulus was inversely correlated with elastic fibre density. In contrast, in the vena cava, the stiffest regions were found to be the adventitial (outer) and intimal (innermost) sections of the vessel cross-section. Both these regions were enriched in ECM components. The central region, thought to be largely cellular, had a relatively constant modulus of around 20 MPa. This study demonstrates that with this methodology it is possible to distinguish micro-mechanically between large arteries and veins, and therefore the same approach should allow age or disease related changes in the mechanical properties within a tissue to be quantified.

Transparent organic-inorganic hybrid aerogels and aerogel-like xerogels have been prepared from methyltrimethoxysilane (MTMS) respectively by supercritical drying (SCD) and ambient pressure drying (APD). The new aerogels and xerogels significantly deform without collapsing on uniaxial compression and almost fully relax when unloaded. This elastic behavior, termed as “gspring-back”, allows APD without noticeable shrinkage and cracking. The flexible network composed of lower cross-linking density (up to three bonds per every silicon atom) compared to silica gels (up to four bonds) and repulsion between hydrophobic methyl groups bonded to every silicon atom largely contributes to the pronounced deformability and relaxing, respectively. Lower surface silanol group density also plays a crucial role for the “gspring-back” behavior.

In April 2007, the Office of Basic Energy Science, United States Department of Energy organized and conducted a Basic Energy Sciences Workshop for Electrical Energy Storage at which basic research needs for capacitive energy storage were considered in detail. This paper is intended to highlight the materials research findings/needs of the workshop and to relate them to the development of high energy density capacitors that can have an energy density approaching that of lead acid batteries, a power density greater than that of lithium ion batteries, and cycle life approaching that of carbon/carbon double-layer capacitors. Capacitors inherently have long cycle life and high power capability so the key issue is how to increase their energy density with minimum sacrifice of their inherent cycle life and power advantages. This requires the development of electrode charge storage materials with an effective high specific capacitance (F/g) and high electronic conductivity. The most promising electrode materials appear to be optimized activated carbons, graphitic carbons, nanotube carbons, and metal oxides. Cells can be assembled that utilize one of these materials in the one electrode and another of the material in the other electrode. Such hybrid cells can operate at 3-4V using organic electrolytes and potentially can have energy densities of 15-25 Wh/kg. Initial research is also underway on solid-state, high energy density devices utilizing high dielectric materials (K>15000) which would operate at very high cell voltage. If such dielectric materials can be developed, these devices may have energy densities approaching those of lithium batteries.

We present an experimental study of asymmetric wafer deformation for 3C-SiC layers grown on deliberately misorientated silicon substrates. An asymmetric curvature has been observed both on (100) and (111) oriented layers. In this work we focus on the (100) oriented samples. The curvature of the wafers is studied as a function of wafer thickness and offcut angle. We look for the correlations between the observed asymmetric strain relaxation and the layer morphology and microstructure. We claim that different defect pattern, measured along [110] and [1-10] direction can be at the origin of almost complete relaxation of mismatch strain along the offcut direction.

Epitaxaially-grown KNbO3 thick films over 8 μm in thickness were successfully grown at 220 °C for 6 h on (100)cSrRuO3//SrTiO3 substrates by a hydrothermal method. Epitaxial SrRuO3 layers grown on (100)cSrTiO3 substrates by sputter method were used as bottom electrode layers. Relative dielectric constant and the dielectric loss were 530 and 0.11, respectively. Clear hysteresis loops originated to the ferreoelectricity were observed and a remanent polarization was 25 μC/cm2 at a maximum applied electric field of 540 kV/cm. In addition, the hydrothermal KNbO3 thick film was able to transmitting and receiving of ultrasonic waves over 50MHz.

Refractory materials such as carbon possess properties that make joining them difficult. In this work, bonding of a carbon–carbon composite is achieved by employing self-sustained, oxygen-free, high-temperature combustion reactions. The effects of several parameters, such as the composition of the reaction media, and the values of the applied current and pressure, on the mechanical strength of the joint were investigated. It was found that the C–C composite possesses a high activity with the reactive media layer, the level of electrical current used to initiate the reaction and the applied pressure do not need to be excessive to obtain a strong joint. Some aspects of the joining mechanism are discussed in detail.

Chalcogenides, in particular germanium-antimony-tellurium (GeSbTe) and antimony-rich tellurium (R-SbTe) based alloys, are the most technologically significant alloys currently being applied to recordable optical storage as typified by rewritable digital versatile discs (DVD-RW), DVD random access memory, (DVD-RAM). The same alloys are also being applied to nonvolatile random access memory electrical memory in the form of phase change random access memory (PCRAM). In 2004, the phase transition mechanism of GeSbTe was first revealed, demonstrating that the amorphous state is not a random configurational network but is locally well-ordered with the crystalline to amorphous switching process being based upon Ge atoms moving between octahedral and tetrahedral symmetry positions. The kinetic barrier between these two states gives rise to the non-volatile nature of GeSbTe as a storage medium. In contrast, no theoretical analysis has been proposed for SbTe alloys because a Ge-free system. In this paper, the Sb2Te structure has been investigated using the local density approximation (LDA) using a plane-wave basis and compared with experimental results. The effect of external stress on the structure was also investigated. It was found that Sb2Te undergoes two phase-transitions at around 18 GPa (compressive) and −3 GPa (tensile). In the case of negative stress, the c-axis was found to expanded more than the other axes, giving rise a large refractive index change. We report on coherent (uniaxial) melting induced by the breaking a sigma bond between Sb2Te3 and Sb superlattices. We believe this to be the origin of the phase transition that induces a large change in physical properties.

Tin-dioxide (SnO2) ultra-small nanorods (UNR) have been successfully synthesized using the novel micellar technique. From transmission electron microscopy, the average diameter and length of the UNRs are estimated to be 1.3 nm and 5.0 nm, respectively. The crystal structure of the SnO2 UNRs was found to be tetragonal from the glazing incidence x-ray diffraction. The optical band gap estimated from the absorption spectrum is blue-shifted by 1 eV from that of bulk (3.64 eV). The photoluminescence spectrum shows two groups of peaks each with several fine peaks, one in the wavelength range of 270 – 370 nm and the other in the range of 380 – 500 nm which are due to the strong quantum confinement effect.

We report herein the results of density functional theory calculations of the geometric and electronic structure for a series of fused heterocyclic compounds.These molecules were compared with the corresponding carbocyclic oligoacenes, which are currently being experimentally investigated for use as organic semiconductors.The impact of various structural modifications on this class of compounds on the calculated structures is examined.The results of our calculations reveal that such materials hold exceptional promise as organic semiconductors.

The molecular conformation-dependent write-once read-many-times (WORM) memory based on an acrylate polymer containing pendant carbazole (donor) groups is transformed into a flash (rewritable) memory when acrylate units containing pendant oxadiazole (acceptor) groups are incorporated to form a copolymer. The as-fabricated device based on the acrylate copolymer containing carbazole-oxadiazole donor-acceptor pendant groups is in its low conductivity state and can be written to a high conductivity state at a threshold voltage of -1.8 V. The high conductivity state can be switched (erased) to the low conductivity state with a positive bias of 3.6 V. The device exhibits a high ON/OFF current ratio of 103 at a read voltage of -1 V. This rewritable polymer memory can be programmed and erased repeatedly with good accuracy. The copolymer is potentially useful for application in flash memory devices.

The morphology and organic field effect transistor (OFETs) properties of two component blends of semicrystalline 6,13-bis(triisopropylsilylethinyl)pentacene (TIPS-pentacene) with selected amorphous and semi-crystalline low permittivity side chain aromatic insulating binders deposited at room temperature under vacuum from a good solvent are reported. When blended with an amorphous binder there is evidence from XPSfor strong interaction between TIPS-pentacene and binder in the solidified film giving rise to twisted TIPS-pentacene crystals containing dislocations. Due to this strong interaction we see no evidence of segregation of TIPS-pentacene towards the active interface and hence we observe a rapid fall off in saturated hole mobility at a active concentration less than 50 wt-%. When blended with a crystalline binder there is no evidence from XPS of any interaction between TIPS-pentacene and binder in the solidified film. We propose that when a crystalline binder is used, which crystallizes more slowly from solution than TIPS-pentacene, we observe stratification of the active material to both interfaces and as a result an increase of saturated hole mobility to 0.4 cm2/Vs at 20 wt-% in isotactic poly(vinylbisphenyl). The potential application of the approach are in the formulation of low cost organic semiconductors whose solution and solid state properties can be fine tuned by careful binder selection.

The design and development of prototype cold crucible melters for waste vitrification are based on models of the basic physical phenomena, including electromagnetic induction and the thermal and hydraulic properties in natural or forced convection. The complexity of new nuclearized facilities results in significant errors on the results of predictive models based on 2D axisymmetric geometry that can only be resolved by modeling the device in 3D geometry. This document discusses the specification and electromagnetic design of a melter carried out using electromagnetic computation software, FLU3D, developed in 3D geometry by Cedrat. The principles and results of this study are directly applicable to nuclear facilities with allowance for the particular requirements of a nuclearized environment.

Using a model cathode-electrolyte system composed of epitaxial thin-films of La1-xSrxMnO3-δ (LSM) on single crystal yttria-stabilized zirconia (YSZ), we investigated changes in the cation concentration profile in the LSM during heating and under applied potential using grazing incidence x-rays. Pulsed laser deposition (PLD) was used to grow epitaxial LSM(011) on YSZ(111). At room temperature, we find that Sr segregates to form Sr enriched nanoparticles and upon heating the sample to 700°C, Sr is slowly reincorporated into the film. We also find different amounts of Sr segregation as the X-ray beam is moved across the sample. The variation in the amount of Sr segregation is greater on the sample that has been subject to 72 hours of applied potential, suggesting that the electrochemistry plays a role in the Sr segregation.

Hydrogenated nanocrystalline silicon (nc-Si:H) has strong potential to replace the hydrogenated amorphous silicon (a-Si:H) in thin film transistors (TFTs) due to its compatibility with the current industrial a-Si:H processes, and its better threshold voltage stability [1]. In this paper, we present an experimental TFT array backplane for direct conversion X-ray detector, using inverted staggered bottom gate nc-Si:H TFT as switching element. The TFTs employed a nc-Si:H/a-Si:H bilayer as the channel layer and hydrogenated amorphous silicon nitride (a-SiNx) as the gate dielectric; both layers deposited by plasma enhanced chemical vapor deposition (PECVD) at 280°C. Each pixel consists of a switching TFT, a charge storage capacitor (Cpx ), and a mushroom electrode which serves as the bottom contact for X-ray detector such as amorphous selenium photoconductor. The chemical composition of the a-SiNx was studied by Fourier transform infrared spectroscopy. Current-voltage measurements of the a-SiNx film demonstrate that a breakdown field of 4.3 MV/cm.. TFTs in the array exhibits a field effect mobility (μEF ) of 0.15 cm2/V·s, a threshold voltage (VTh ) of 5.71 V, and a subthreshold leakage current (Isub ) of 10−10 A. The fabrication sequence and TFT characteristics will be discussed in details.

After an introduction to the rare earth – hydrogen phase diagram, stressing the often broad existence range of the solid solution (α), dihydride (β) and trihydride (γ) phases, we are describing in detail the fluorite-type dihydride and its superstoichiometric composition, RH2+x, where the x atoms occupy the available octahedral interstitial sites. It is shown how these additional x atoms interact with each other to form ordered H superlattices (sometimes distorting the cubic CaF2 structure) and how the latter influences the electronic structure of the systems modifying the magnetic properties and/or leading to metal-semiconductor transitions.

We have investigated coaxial electrospinning to produce core-sheath fibers for tissue engineering. We have successfully produced core-sheath structured fibers of poly(ε-caprolactone) (PCL) and gelatin using the coaxial electrospinning technique. The core-sheath scaffold exhibits better mechanical properties compared to gelatin scaffold. We have characterized the resulting core and core-sheath fiber diameters and the scaffold porosity, etc.

A new method to fabricate superhydrophobic hard films is described. Surface texture of lotus leaf was replicated on an acetate film, on which a nanocrystalline (NC) Ni coating with a grain size of 30 ± 4 nm and a hardness of 4.42 GPa was electrodeposited. The surface texture consisted of conical protuberances with a height of 10.0 ± 2.0 0m and a tip radius of 2.5 ± 0.5 0m. An additional electrodeposition for 120 s and 300 s was used to locally modify the surface structure by depositing ‘Ni crowns' on the protuberances that increased their height to 14.0 ± 2.0 0m and their tip radius to 6.0 ± 0.5 0m. The modified structures were then treated with a perfluoropolyether (PFPE) solution, which provided a high water contact angle of 156°, i.e., comparable to the naturally superhydrophobic lotus leaf. The increased hydrophobicity as a result of surface structure and chemistry modifications was evident compared to a smooth NC Ni sample, which had a contact angle of 64°.

Commercial scandium oxide doped thermionic cathodes have demonstrated current densities over 100 A/cm2. In order to understand the effect of Sc- and Ba- oxides on the emissivity of these cathodes we have imaged thin films of scandium oxide and barium oxide on tungsten foils using photoelectron emission microscopy and thermionic emission microscopy. Arrays of 100 um × 100 um squares of scandium and 25 um × 25 um squares of barium, 200 nm thick, were sputter deposited onto 50 um thick sheets of tungsten foil.Imaging squares of different sizes gives an unequivocal identification of each material and a completely consistent comparison of each material and cathode structure under identical conditions in one image.

The metal squares oxidize in air before imaging. Each sample was heated in situ in a Bauer-Telieps style LEEM/PEEM used primarily in the ThEEM mode. The barium oxide squares emit below 875 K, and diffuse over the scandium below 875 K. Thermionic emission from scandium oxide squares is observed at temperatures significantly larger than 875 K. Failure of the barium oxide film cathode is through barium desorption. AES spectra show that the Sc does not desorb.

While the origin of reduced emission temperature is commonly believed to be a result of a low work function monolayer of Ba and Sc oxides, in our study, the benefits of a combined Ba/Sc cathode are present in a thick (multi-layer), layered structure of barium oxide on top of a thick scandium oxide layer.