T lymphocytes are a key regulatory component of the adaptive immune system. Understanding how the micro- and nano-scale details of the extracellular environment influence T cell activation may have wide impact on the use of T cells for therapeutic purposes. In this article, we examine how the micro- and nano-scale presentation of ligands to cell surface receptors, including microscale organization and nanoscale mobility, influences the activation of T cells. We extend these studies to include the role of cell-generated forces, and the rigidity of the microenvironment, on T cell activation. These approaches enable delivery of defined signals to T cells, a step toward understanding the cell-cell communication in the immune system, and developing micro/nano- and material- engineered systems for tailoring immune responses for adoptive T cell therapies.

Light management and enhanced photon harvesting is a critical area for improving efficiency of thin film solar cells. Red and near infrared photons with energies just above the band edge have large absorption lengths in amorphous silicon and can not be efficiently collected. We previously demonstrated that a photonic crystal back reflector involving a periodically patterned ZnO layer can enhance absorption of band edge photons. We propose and design alternative new plasmonic crystal structures that enhance absorption in thin film solar cell structures. These plasmonic crystals consist of a periodically patterned metal back reflector with a periodic array of holes An amorphous/nanocrystalline silicon layer resides on top of this plasmonic crystal followed by a standard anti-reflecting coating. We have found plasmonic crystal structures enhance average photon absorption by more than 10%, and by more than a factor of 10 at wavelengths just above the band edge, and should lead to improved cell efficiency. The plasmonic crystal diffracts band edge photons within the absorber layer, increasing their path length and dwell time. In addition there is concentration of light within the plasmonic crystal. Design simulations are performed with rigorous scattering matrix simulations where both polarizations of light are accounted for.

The present investigation deals with a two-junction device having GaAs as the top cell and Ge for the bottom cell on a Ge substrate. Compared with the conventional two-terminal device configuration, three terminals avoid the loss due to current mismatching between the cells, and the resistance loss originating from the tunnel junction between the cells. Device structures were investigated and optimized with regard to the thicknesses and doping levels of both top and bottom active junctions that lead to the highest device performance. Due to the split of the incident solar spectrum between GaAs and Ge cells, the latter only receives the light to which the former is transparent (mainly in the near infrared) and therefore behaves differently from a single-junction Ge cell. Optimal current-voltage and power-voltage characteristics were generated for individual cells together with the corresponding device PV parameters. The predictions show that an extended spectral coverage is achieved leading to an enhanced overall power output from the devices. The potential applications of these devices in conventional as well as concentrator PV were assessed and discussed as a function of the simulated concentration ratio of the incident light under AM1.5 illumination conditions. We have shown that a relatively thin double-junction GaAs/Ge device can achieve a remarkably high power output.

We report the evidence that the oxygen defects induced by focusing an intense infrared femtosecond laser pulse in fused silica can be self-organized by the interference pattern between photon and electron plasma wave. Self-organized nanostructure with a sub-wavelength modulation in refractive index exhibits form birefringence which is rewritable and directionally-controllable. Intriguingly, such optical anisotropy, which indicates a remarkable non-reciprocity, has initially evolved from residual birefringence originated from internal stress distribution due to local heating followed by structural change, regardless of interpulse time. This anisotropic light-matter interaction could be interpreted in terms of an asymmetric relation between light polarization and pulse front tilt. Apart from fundamental understanding of self-organization mechanism, the direction of encoded birefringence can introduce an entirely new concept for rewritable optical storage beyond the diffraction limit of light.

The defect structure in B12As2 epitaxial layers grown at two different temperatures on (0001) 6H-SiC by chemical vapor deposition (CVD) was studied using synchrotron white beam x-ray topography (SWBXT) and high resolution transmission electron microscopy (HRTEM). The observed differences in microstructures were correlated with the differences in nucleation at the two growth temperatures. The effect of the difference in microstructure on macroscopic properties of the B12As2 was illustrated using the example of thermal conductivity which was measured using the 3-ω technique. The relationship between the measured thermal conductivity and observed microstructures is discussed.

We studied the effects of multiwalled carbon nanotubes (MWCNTs) on the Freedericksz transition of a liquid crystal (LC) and calibrated the altitudinal angle of CNTs as a function of the electric field. In addition, we directed the azimuthal angle which gave us complete control of the 3D orientation of the CNTs. We constructed anti-parallel electro-optic cells using a nanocomposite at a concentration of 0.01% CNTs with 4-Cyano-4'-pentylbiphenyl (5CB) liquid crystal. This low concentration was necessary to achieve maximum transmission of electromagnetic radiation through the cell and to minimize the Van der Waals attraction between the CNTs responsible for their aggregation. We chose two dimensional microscopic transmission ellipsometry (2D-MTE) to measure the phaseshift of the polarized electromagnetic radiation through the cell and to derive from it the altitudinal angle of the CNTs. Our results show that in the presence of CNTs the Freedericksz transition occurs at 55% of the transitional electric field as compared to the control electro-optic cell without CNTs. The width of the Freedericksz transition narrows by a similar factor. The switching time of the cell decreased in the presence CNTs by 18.5%.

The effect of Ag substituting Cu on the structural features of the Cu55Zr45, Cu45Zr45Ag10, and Cu35Zr45Ag20 glassy alloys was studied using the real-space pair distribution and radial distribution functions. The experimental x-ray diffraction data obtained in a synchrotron beam were used to derive pair and radial distribution functions through Fourier transformation processing. These results suggest that a certain degree of medium-range order in this alloy is maintained up to about 2.5 nm distance. It is suggested that the addition of Ag causes formation of a more homogeneous local atomic structure compared with that of a binary Cu–Zr alloy, which could be considered as a reason for the improved glass-forming ability of this alloy.

A recent theoretical study suggested that the substitution of Cd in PbTe can result in a distortion in the electronic density of states (DOS) near the bottom of the conduction band in PbTe. In this study we explored the effect of Cd doping on the thermoelectric properties of PbTe in an effort to test the theoretical prediction that DOS distortion can increase the Seebeck coefficient. We present detailed investigation of structural and spectroscopic data, transmission electron microscopy, as well as transport properties of samples of PbI2 doped PbTe-x% CdTe (x = 1, 3, 5, 7, 10). All samples follow the Pisarenko relationship and no enhancement of the Seebeck coefficient was observed due to DOS distortions. A low lattice thermal conductivity was achieved by nanostructuring observed via high resolution transmission electron microscopy. A maximum ZT of ˜1.2 at ˜720 K was achieved for the 1% CdTe sample.

For several years there have been many efforts to employ ink jet technologies in the fabrication of consumer electronics. The potential of displacing large and expensive pieces of electronic fabrication equipment and processes with seemingly appropriately scaled inexpensive alternatives is attractive. However, of course, the devil is in the details. Feature size, accuracy, registration and materials all have sever impacts on design rules, processing, performance and the types of devices appropriate to the technology. Here we present a look at some of the materials and deposition challenges along with solutions developed at PARC. The discussion will include the defining of printed features >5μm with ±1.5μm drop placement and layer to layer alignment accuracy, the materials characteristics of the generally complex functional fluids of interest required for reliable jetting and device performance. Examples of ink jet fabricated integrated circuits, working displays, imagers and RGB color filters for LCD displays will be shared.

Single crystals and polycrystalline samples of durable actinide host phases such as garnet, zircon, and Ti-pyrochlore doped with varying amounts of U, Pu, Np and Am, were studied by cathodoluminescence (CL) spectroscopy. The following characteristic bands were identified: uranyl-ion [UO2]2+– 495 nm in garnet and pyrochlore; [UO4]2− – 710 nm in garnet; and Am3+ – in garnet and zircon at 550 nm, 614 nm, 740÷750 nm.

The growth of of metallic copper by atomic layer deposition (ALD) using copper(I) di-sec-butylacetamidinate ([Cu(sBu-amd)]2) and molecular hydrogen (H2) on SiO2/Si surfaces has been studied. The mechanisms for the initial surface reaction and chemical bonding evolutions with each ALD cycle are inferred from in situ Fourier transform infrared spectroscopy (FTIR) data. Spectroscopic evidence for Cu agglomeration on SiO2 is presented involving the intensity variations of the SiO2 LO/TO phonon modes after chemical reaction with the Cu precursor and after the H2 precursor cycle. These intensity variations are observed over the first 20 ALD cycles at 185°C.

Degradation of current gain for ion implanted 4H-SiC bipolar junction transistor is described. The influence of bandgap-narrowing to the collector and base currents of the transistor was investigated using ISE-TCAD simulator. Simulated results show good agreement with the measured results, which show that the common emitter current gain of 3.9 is obtained at a maximum base concentration of 2×1017/cm3 and a maximum emitter concentration of 4×1019/cm3 for ion implanted 4H-SiC BJTs.

Sufficiently dense films of cerium oxide nanocrystals modified with decanoic acid, with sizes of ˜9 nm, were fabricated on the surface by modifying a silicon substrate with 3,4-dihydroxyhydrocinnamic acid, where catechol group lied at the top. By doing this, no further pretreatment for the modified cerium oxide nanocrystals is required to fix them chemically on the substrate. Selective adhesion between nanocyrstals and the substrate for the two-dimensional assembly can be attributed to the chemical bonding formed by on-site ligand exchange between carboxyl and catechol groups.

Zinc peroxide (ZnO2) nanocrystals were directly produced by hydrothermal process. The nanocrystals were synthesized using zinc acetate as precursor and hydrogen peroxide as oxidant agent. The ZnO2 powders were characterized by X-ray powder diffraction and transmission electron microscopy. The results of transmission electron microscopy indicated that the ZnO2powders consisted of nanocrystals with diameters below to 20 nm and a faceted morphology. High resolution electron microscopy observations have been used in order to the structural characterization. ZnO2 nanocrystals exhibit a well-crystallized structure.

ZnO nanostructured films were deposited at room temperature on glass substrates and cotton fabrics by activated reactive evaporation in a single step without using metal catalyst or templates. Morphological observation has shown that the nanostructured film contains seaurchin-like structures, and this seaurchin containing large number of randomly grown ZnO nanoneedles. Microstructural analysis revealed the single crystalline nature of the grown nanoneedles and their growth direction was indentified to be along [0002]. PL spectrum of nanostructured films has shown a relatively weak near-band-edge emission peak at 380 nm, and a significant broad peak at 557 nm due to the oxygen vacancy-related emission. ZnO nanostructured films grown on glass substrates and cotton fabrics have shown good photocatalytic activity against rhodamine B.

We have grown tree-like vertically-aligned carbon nanotubes (CNTs) on silicon substrate, suitable for highly sensitive interdigital capacitive sensors. As an application, we present a sensitive pressure sensor with branched CNTs as its capacitance plates.

After realization of the interdigital structure, the growth of CNTs has been achieved through direct-current plasma enhanced chemical vapor deposition (DC-PECVD) method. A sequential growth and hydrogenation has led to the formation of multiple branched structures of nanotubes. The growth of tree-like CNTs on the interdigitally patterned substrate results in a high overlap between adjacent fingers and consequently a significant response to mechanical variations of the membrane as a result of the applied pressure.

The idea that nanotechnologies have the potential to transform different industry sectors and impact on various market segments is receiving large support and contributions from international economic organisations’ reports, research institutions’ newsletters, academics’ and management scholars’ papers and consulting firms’ articles.The patent landscape, with its burgeoning number of patent filings, and the patent offices worldwide reporting on the increasing number of patent applications in the nanotechnology field, appear as complementary indicators of this trend. As nanosciences research and engineering efforts made feasible the attractive promise of closing the gap between research and industrialization, research outcomes and applications were protected for exclusive exploitation via patent filing and patent portfolio building.

We report the synthesis of Zn-doped TiO2 nanowires by a solution-based process. The synthesis takes place at 200°C in an alkali solution and results in both nanowire and nanoparticle precipitates. Several transmission electron microscopy techniques were used to characterize the resulting precipitates: diffraction patterns and high resolution phase contrast images provided identification of the crystalline phase of the material as well as insights into the resulting lattice parameters, energy dispersive x-ray spectroscopy allowed identification of constituent elements, and electron energy loss spectroscopy permitted quantification of relative concentrations of hydroxyl and lattice-type oxygen bonding. In addition, scanning electron microscope images provide overall perspective of the growth uniformity and morphology.

A novel immobilized metal affinity chromatography (IMAC) bead, Zr(IV)-immobilized resin, was prepared by surface template polymerization to enrich phosphorylated proteins and peptides from complex peptides mixtures. In order to enhance both the kinetics and the efficiency, large pathways for the proteins and peptides in the resin were formed, and the Zr(IV)-phosphate complexes were immobilized on the polymer surface. The morphology of the Zr(IV)-immobilized resin was evaluated the by measuring the specific surface area, pore volume, and pore distribution. The resin possessed large amount of the large-macro pores around 300 nm. The separation performance of β-casein from bovine serum albumin (BSA) solution was evaluated by phosphopeptide enrichment and MALDI-TOF MS analysis. The Zr(IV)-immobilized resin showed the high selectivity of the phosphopeptide.

The present paper outlines the energetic and kinetic effect by substitutional N, or by coadsorbed NHx (x =1, 2), on one of the key growth steps in the CVD growth mechanism of diamond (100); H abstraction by gaseous H radical species from the (100) surface plane. Theoretical calculations were performed based on Density Functional Theory under periodic boundary conditions. Substitutionally positioned N was shown to have a large effect on the H abstraction process. The H abstraction energy from the diamond surface was greatly improved with N positioned in C layer 2. In order to outline the effect by N on the growth rate, the barriers of energies were calculated. The barrier of abstraction was shown to substantially decrease with N substitutionally positioned in the second C layer, leading to an improvement of the abstraction reaction rate by approximately a factor of 3.