bluuebunny/crossref_metadata_2025_split huggingface dataset:
NanoLiterBioReactor: Monitoring of Long-Term Mammalian Cell Physiology at Nanofabricated Scale
Authors: Prokop Ales , Prokop Zdenka , Schaffer David , Kozlov Eugene , Wikswo John , Cliffel David , Baudenbacher Franz 
Published: April 2011

AbstractThere is a need for microminiaturized cell-culture environments, i.e., NanoLiter BioReactors (NBRs), for growing and maintaining populations of up to several hundred cultured mammalian cells in volumes three orders of magnitude smaller than those contained in standard multi-well screening plates. Reduced NBR volumes would not only shorten the time required for diffusive mixing, for achieving thermal equilibrium, and for cells to grow to confluence, but also simplify accurate cell counting, minimize required volumes of expensive analytical pharmaceuticals or toxins, and allow for thousands of culture chambers on a single instrumented chip. These devices would enable the development of a new class of miniature, automated cell-based bioanalysis arrays for monitoring the immediate environment of multiple cell lines and assessing the effects of drug or toxin exposure. The challenge, beyond that of optimizing the NBR physically, is to detect cellular response, provide appropriate control signals, and, eventually, facilitate closed-loop adjustments of the environment--e.g., to control temperature, pH, ionic concentration, etc., to maintain homeostasis, or to apply drugs or toxins followed by the adaptive administration of a selective toxin antidote. To characterize in a nonspecific manner the metabolic activity of cells, the biosensor elements of the NBR might include planar pH, dissolved oxygen, and redox potential sensors, or even an isothermal picocalorimeter (pC) to monitor thermodynamic response. Equipped with such sensors, the NBR could be used to perform short- and long-term cultivation of several mammalian cell lines in a perfused system, and to monitor their response to analytes in a massively parallel format. This approach will enable automated, parallel, and multiphasic monitoring of multiple cell lines for drug and toxicology screening. An added bonus is the possibility of studying cell populations with low cell counts whose constituents are completely detached from typical tissue environment, or populations in controlled physical and chemical gradients.
Implanted 3D Micro/Nano-Structure Fabrication: New Processing Techniques for the Creation of Nanoscale Opto-Mechanical Machines in Silicon Dioxide on a Silicon wafer
Authors: Abraham Meg 
Published: April 2011

AbstractA novel method of making nanoscale devices in silicon dioxide on a silicon wafer has been developed in our laboratory. The method is both inexpensive and can be fully integrated with existing VLSI type electronic processing technology. The devices are defined using conventional micronscale photolithography and then reduced in scale during the processing sequence to form nanoscale structures. Further, since the structures are defined using lithography, they can be made to span the range of scales from macro to nano in one processing step. Finally, we have found that by using laser assisted chemical etches, we can “release” these very fine structures without the damage associated with wet processes such as stiction.
Fabrication of 2-D and 3-D Photonic Bandgap Structures Using Laser-assisted Imprinting of Self-assembled Particles
Authors: Lu Y.F. , Li L.P. , Mendu K.K. , Shi J. , Doerr D.W. , Alexander D.R. 
Published: April 2011

AbstractFabrication of 2-D and 3-D photonic bandgap (PBG) structures on silicon substrates using laser-assisted nanoimprinting of silica particles has been investigated. Monolayers of silica particles, with different diameters ranging from 160 nm to 5 νm, were deposited on silicon substrates by self-assembly. A quartz plate, which is transparent to the laser wavelength of 248 nm, was tightly placed on the substrate surface. A KrF excimer laser beam with the wavelength of 248 nm was vertically irradiated on the quartz/nanoparticle/silicon structure. The silica particles were imprinted into silicon substrates by the quartz to form a 2-D PBG structure due to the transient Si surface melting during the laser pulse. 3-D PBG structures can be fabricated by directly imprinting multilayer self-assembled silica particles into Si substrates. They can also be fabricated by repeating a process cycle of silica nanoparticles self-assembly, amorphous Si layer deposition, and simultaneous laser melting, imprinting and recrystallization.
Synthesis and Self-Assembly of Metal-Coated Nanoparticles
Authors: Park W. , Borsa T. 
Published: April 2011

AbstractWe report theoretical and experimental studies on the metal-dielectric photonic crystal structure, which is constructed by the self-assembly of metal-coated nanoparticles. The finite- difference time-domain (FDTD) simulations were carried out to predict the width and position of the 3D photonic bandgap. For fabrication, we first prepared gold-embedded silica nanoparticles containing extremely small gold nanoparticles. The core particles are then immersed in a gold- containing solution in which the gold shells were formed by subsequent reduction. Formation of continuous shells was confirmed by scanning electron microscope (SEM) and the optical response due to the surface plasmons. We also performed self-assembly of both the gold- embedded core particles and metal-coated particles. SEM micrographs showed the formation highly ordered structures. The optical reflectance spectra exhibited shifts of the Bragg reflection peak due to the change in refractive index produced by gold nanoparticles.
Anatase Inverse Opal: Preparation and Electrochemical Properties
Authors: Zukalova Marketa , Kalbac Martin , Kavan Ladislav , Heyrovsky J. 
Published: April 2011

AbstractAnatase inverse opal was synthesized both in the powder form and in the thin layer by means of templating with latex spheres. The voids between close-packed latex particles were filled via deposition from the titanium (IV) isopropoxide solution, electrochemical deposition from the solution of TiCl3, and liquid phase deposition from the (NH4)2TiF6 solution. The resulting material exhibited a regular fcc ordering of macropores surrounded with the framework consisting of the anatase nanocrystallites of 20 nm in size. Electrochemical performance for lithium insertion of anatase inverse opal was sluggish compared to that of non-templated anatase with more dense packing of nanocrystals.
Investigation of the Layer-by-Layer Assembly of Colloid Crystals on a Templated Substrate
Authors: Grego Sonia , Jarvis Thomas , Stoner Brian , Lewis Jay 
Published: April 2011

AbstractWe investigated the fabrication of a 3D colloid crystal assembled in a layer-by-layer fashion on a template substrate. This method of assembling an ordered structure offers flexibility in the choice of crystal orientation, because of the template, and the capability to insert a “defect” layer to introduce defect modes in the stop bands of the crystal. The assembly of layers of 4.4 νm polystyrene microspheres on the patterned (100) substrates was studied using a combination of evaporation and chemical binding. It was observed that the ordering process depends on the physical parameters of the template such as well size and depth. A good adhesion of the beads to the template required chemical functionalization of the substrate.
Constrained Grain Boundary Diffusion In Thin Copper Films
Authors: Buehler Markus J. , Hartmaier Alexander , Gao Huajian 
Published: April 2011

AbstractIn a recent study of diffusional creep in polycrystalline thin films deposited on substrates, we have discovered a new class of defects called the grain boundary diffusion wedges (Gao et al., Acta Mat. 47, pp. 2865-2878, 1999). These diffusion wedges are formed by stress driven mass transport between the free surface of the film and the grain boundaries during the process of substrate-constrained grain boundary diffusion. The mathematical modeling involves solution of integro-differential equations representing a strong coupling between elasticity and diffusion. The solution can be decomposed into diffusional eigenmodes reminiscent of crack-like opening displacement along the grain boundary which leads to a singular stress field at the root of the grain boundary. We find that the theoretical analysis successfully explains the difference between the mechanical behaviors of passivated and unpassivated copper films during thermal cycling on a silicon substrate. An important implication of our theoretical analysis is that dislocations with Burgers vector parallel to the interface can be nucleated at the root of the grain boundary. This is a new dislocation mechanism in thin films which contrasts to the well known Mathews-Freund-Nix mechanism of threading dislocation propagation. Recent TEM experiments at the Max Planck Institute for Metals Research have shown that, while threading dislocations dominate in passivated metal films, parallel glide dislocations begin to dominate in unpassivated copper films with thickness below 400 nm. This is consistent with our theoretical predictions. We have developed large scale molecular dynamics simulations of grain boundary diffusion wedges to clarify the nucleation mechanisms of parallel glide in thin films. Such atomic scale simulations of thin film diffusion not only show results which are consistent with both continuum theoretical and experimental studies, but also revealed the atomic processes of dislocation nucleation, climb, glide and storage in grain boundaries. The study should have far reaching implications for modeling deformation and diffusion in micro- and nanostructured materials.
Modeling the Elastic Fields in Epitaxially Grown Multilayers
Authors: Vanamu Ganesh , Khraishi Tariq A. , Datye Abhaya K. , Zaidi Saleem H. 
Published: April 2011

AbstractA model was developed to calculate the elastic fields, including strain energy density, in multilayers grown epitaxially on a planar substrate. This model works well for compliant and non-compliant substrates. In particular we illustrate the model for four layer heterostructure and apply it for graded Ge (SixGe1−x) grown on a planar silicon substrate. Using the equations for static equilibrium and Hooke's law for isotropic materials under a plane stress condition, the elastic fields associated with each layer were calculated. The strain partitioning in this model reduces to the limiting case of a two- layer structure available in the literature. As it turns out here, strain partitioning is a function of the bulk unstrained lattice parameters, elastic constants and thicknesses of the layers. The model was qualitatively verified by comparing the strain energy density with the dislocation density away from a relatively thick substrate. This model helps shed some light on the factors important in achieving defect free multilayers for optoelectronic devices.
Elevated Temperature Mechanical Properties of Devitrified Metallic Glass
Authors: Mara Nathan A. , Sergueeva Alla V. , Mukherjee A.K. 
Published: April 2011

AbstractElevated temperature tensile tests of different microstructures arising from different heat treatments of the Fe-based metallic glass Vitroperm (Fe73.5Cu1Nb3Si15.5B7) are presented. An anneal at 600°C for 1h yields a single phase μ-Fe microstructure with equiaxed, randomly oriented 15 nm grains, which is an ideal candidate for study of material properties at diminishing length scale. This microstructure has good stability during tensile testing at 600°C, showing a strain rate exponent correlating to grain boundary sliding (m=0.5), but little ductility, and strengths to 1250 MPa. The brittle behavior could be attributed to the lack of dislocation activity at such length scales. At temperatures up to 725°C, grain growth occurs, leading to elongations as large as 65% at flow stresses of 250 MPa. Precipitation of a second Nb-rich phase accompanies the grain growth. This investigation is supported by NSF, Division of Materials Research, grant NSF-DMR-0240144.
Thermomechanical properties and fatigue of nanocrystalline Ni/Cu electrodeposits
Authors: Arnould Olivier , Hubert Olivier , Hild François 
Published: April 2011

AbstractThis study deals with the long-term reliability of a high precision pressure sensor using bellows mainly made of electroplated Ni. Thermomechanical properties of this deposit are obtained by several experiments and compared to theoretical models, computations and other authors' results. Bellows are expected to stay in service for many decades, thus their high cycle fatigue behavior has to be known. Stress-life fatigue curve for crack initiation and fatigue crack growth in the electroplated Ni are measured and identified using numerical computations. Results are compared with other results obtained on similar Ni electrodeposits. Normalized stress-life fatigue curve shows no specific nanosize effects.
Deformation and Failure of Nanostructured Materials with Bimodal Grains
Authors: Ye R.Q. , Han B.Q. , Lavernia E.J. 
Published: April 2011

AbstractThe low ductility of nanostructured materials is attributed to the deficit of dislocation activity in the nanometer range. Recent scientific interest in nanostructured materials stems from reports of alterative combinations of mechanical properties, although a low ductility is typically reported. One promising approach based on the concept of multiple length scales is illustrated by a “bimodal” microstructure, i.e. containing a mixture of nanostructured and coarse grains. The present work reports a numerical study of the tensile deformation and fracture of a nanostructured Al alloy with a bimodal microstructure. In the theoretical framework used in the present study, the elastic-plastic behavior and deformation processes are approximated by Ramberg-Osgood formula and finite element method, respectively. The numerical results are found to be in a good agreement with the experimental behavior.
Stress Distribution in Ultra Thin SiO2 Film/Si Substrate System Measured by a Low Level Birefringence Detection Technique
Authors: Liu X. H. , Peng H. J. , Wong S.P. , Zhao Shounan 
Published: April 2011

AbstractIn this work, a low level birefringence detection system was employed to study the stress distribution in Si substrate induced by thermally grown ultra-thin SiO2 film. According to traditional bi-metallic strip theory, it is expected that the stress should show a linear dependence on depth with the zero stress plane located at the position of two third of the thickness of the substrate from the SiO2/Si interface. The linear dependence of stress on depth in accordance with the bi-metallic strip theory was observed only in part of the substrate. For the region below the SiO2/Si interface extending to a depth of about 1/5 of the thickness of the substrate, the magnitude of the stress was found to be significantly smaller than expected. The position of the zero stress plane was found to depend on the thickness of the SiO2 film and the oxidation conditions. The zero stress plane seemed to move towards the bottom of the Si substrate as the thickness of the SiO2 film became thinner and no zero stress plane was observed in the Si substrate when the SiO2 films became sufficiently thin.
Microstructural Refinement in Steels by Machining
Authors: Swaminathan S. , Swanson C. , Brown T. L. , Kezar R. F. , Chandrasekar S. , Compton W. D. , Trumble K. P. 
Published: April 2011

AbstractA study has been made of microstructure and hardness of machining chips created from commercially pure iron and carbon steels. Large shear strains imposed during chip formation in machining are found to produce significant microstructure refinement in the chips, resulting in higher hardness compared to the bulk. Transmission electron and scanning electron microscopy have shown the chips to consist entirely of ultra-fine grain structures with ferrite grain sizes in the range of 100-800 nm. With high carbon steels, the microstructure of the bulk material prior to machining is also seen to have a significant influence on the characteristics of the chip.
Preparation of A New Carbon Nano-particle by Arc Discharge
Authors: Li Bean-Jon , Kung Sheng-Chin , Hsu Chih-Ming , Gao Jhy-Yeong , Lai Hong-Jen 
Published: April 2011

AbstractSynthesis and characterization of a new carbon particle are investigated in this study. The carbon particle, which possesses a very high surface area (682 cm2/g), is suitable for catalysts loading in application of fuel cell. As well known, carbon materials are used to be a support of Pt catalyst to achieve high dispersion to enhance the activity of Pt. The synthesis was performed by conventional arc discharge process between two graphite electrodes in vacuum. A high-current range from 100∼ 300 ampere was utilized to evaporate the cathode electrode in order to produce carbon soot onto the wall of chamber, and further high production rate of 10 g/hr was achieved. The morphology and microstructure of the materials were investigated by SEM, HRTEM, XRD and Raman spectroscopy.Observations of the soot by SEM and HRTEM have shown that it consists agglomerations of carbon particles linked each other to form a chain-like structure. Most carbon particles are approximate 30 ∼ 60 nm in diameter. HRTEM observation reveals that a carbon particle is comprised of several defective onions with different diameters and extremely curled graphene sheets, which appear as double-sheet layers.
Assemblies of Semiconductor and Metal Nanoparticles for Renewable Energy
Authors: Markarian Marie Zabel , El-Harakeh Maysaa , Makki Rabieh , Halaoui Lara I. 
Published: April 2011

AbstractNanostructured electrodes were assembled layer-by-layer from polyacrylate-capped Pt nanoparticles (<d>=2.5 ± 0.6 nm) in a cationic polyelectrolyte. Cyclic voltammetry revealed hydrogen adsorption peaks at the modified nanoparticles characteristic of an activated polycrystalline Pt surface, with a negative shift in the peak potentials indicating a less facile electro-adsorption relative to the polycrystalline electrode, possibly due to nanoparticle surface modification. Current-voltage measurements at multilayers of Pt nanoparticles in polyelectrolytes indicated the feasibility of charge hopping between the particles embedded in the insulating matrix. Such feasibility was also evidenced in photoluminescence quenching of Q-CdS dots (<d>=3.6 ± 0.5 nm) assembled in polyelectrolytes upon inserting Pt nanoparticles in the architecture.
Primary osteoblasts adhesion onto RGD-functionalized and cross-linked polyelectrolyte multilayer films
Authors: Picart Catherine , Richert Ludovic , Elkaim René , Schaaf Pierre , Voegel Jean-Claude , Frisch Benoît 
Published: April 2011

AbstractThe adhesion of primary osteoblastic cells on top of biocompatible polyelectrolyte multilayer (PEM) films was investigated for native films and after changing the films properties either with a chemical stimulus (film functionalization), with a mechanical stimulus (film cross-linking), or with both stimuli combined. For the functionalization, a 15 amino acid peptide containing a –RGD- (-Arg-Gly-Asp) sequence was grafted to poly(L-glutamic) acid and deposited on top of poly(L-lysine)/poly(L-glutamic) (PLL/PGA), PLL/Poly(alginic), and PLL/Poly(galacturonic) films. The film buildup and the adsorption of the PGA-RGD was followed by Optical Waveguide Lightmode Spectroscopy and by Atomic Force Microscopy. The mechanical stimulus was achieved by crosslinking the films with a water soluble carbodiimide (EDC) in combination with N-hydroxysulfo-succinimide (sulfo-NHS) to induce amide formation. Fourier Transform Infrared Spectroscopy evidenced the conversion of amine and carboxylic groups into amide groups.The alkaline phosphatase (ALP) activity test was used to assess osteoblast adhesion and proliferation on top of the different films over a period of eight days in culture. Whereas the native films are poorly adherent, the RGD-functionalized films exhibit an increased short time adhesion. The native films could also be successfully cross-linked thereby dramatically enhancing cell proliferation. The cells did not react similarly on the different types of films investigated : the cross-linked (PLL/Palg) and (PLL/Pgal) films were much more efficient than the native or functionalized films in terms of proliferation. On the other hand, for the (PLL/PGA) films, functionalization and film cross-linking had a similar long term effect. Very interestingly, for these latter films, both stimuli could be combined.
Surface Engineering of Nano-fibrous Biodegradable Poly(L-lactic acid) Scaffolds for Tissue Engineering
Authors: Liu Xiaohua , Won Youngjun , Ma Peter X. 
Published: April 2011

AbstractThe architectural design and surface properties of scaffolds are important aspects in tissue engineering. The porous scaffolds accommodate cells and guide their growth, while the surface nature of the scaffolds can directly affect cell attachment, proliferation, and ultimately neo tissue regeneration. In this work, a highly porous poly(L-lactic acid) (PLLA) scaffold with nano-fibrous pore wall architecture has been fabricated by mimicking the structure of natural collagen using a novel thermally induced phase separation method developed in our group. A universally effective surface modification method was developed, and gelatin was successfully grafted onto the surface of nano-fibrous PLLA scaffolds by entrapment procedure. The surface composition, morphology, and properties were examined using ATR-FTIR, XPS and SEM. The surface coverage of gelatin on the PLLA surface was as high as 39.4%. MC3T3-E1 osteoprogenitor cells were cultured for 6 weeks in solid-walled PLLA scaffolds, nano-fibrous PLLA scaffolds, and surface-modified nano-fibrous PLLA scaffolds, respectively. The osteoblasts proliferated in all three types of scaffolds, but the cell numbers were always significantly higher in the surface-modified nano-fibrous scaffolds than in the other two types of scaffolds, and the cell numbers in nano-fibrous scaffolds were higher than that in the solid-walled scaffolds. These results demonstrate that the surface-modified nano-fibrous architecture could serve as a superior scaffold for tissue engineering.