Preparation And Tribology Studies of Alkyl Carboxylic Acid Monolayer Films on Pei-Coated Glass Substrate

首次在涂敷PEI的玻璃表面上制备了癸酸及全氟癸酸的单分子层膜。研究了成膜机理及摩擦特性。结果表明。脱水剂DCCD促进了癸酸或全氟癸酸与PEI酞胺化的反应。导致两种羧酸在PEI表面产生了靠化学键（酞胺键）连接的稳定的单分子层膜,摩擦、磨损实验表明。单分子层有机膜的摩擦特性受膜的组成、表面能及有序性和堆积密度的重要影响。表面能越低,有序性和堆积密度越高。摩擦系数越低。与碳氢化合物相比。碳氟化合物形成的有序膜具有更高的强度和抗磨性能。

Correct biological timing in Arabidopsis requires multiple light-signaling pathways.

Circadian oscillators provide rhythmic temporal cues for a range of biological processes in plants and animals, enabling anticipation of the day/night cycle and enhancing fitness-associated traits. We have used engineering models to understand the control principles of a plant's response to seasonal variation. We show that the seasonal changes in the timing of circadian outputs require light regulation via feed-forward loops, combining rapid light-signaling pathways with entrained circadian oscillators. Linear time-invariant models of circadian rhythms were computed for 3,503 circadian-regulated genes and for the concentration of cytosolic-free calcium to quantify the magnitude and timing of regulation by circadian oscillators and light-signaling pathways. Bioinformatic and experimental analysis show that rapid light-induced regulation of circadian outputs is associated with seasonal rephasing of the output rhythm. We identify that external coincidence is required for rephasing of multiple output rhythms, and is therefore important in general phase control in addition to specific photoperiod-dependent processes such as flowering and hypocotyl elongation. Our findings uncover a fundamental design principle of circadian regulation, and identify the importance of rapid light-signaling pathways in temporal control.

Characterization of a Laser-Discrete Quenched Steel Substrate/Chromium System by Dissolving Coatings

A laser-discrete quenched steel (LDQS) substrate/as-deposited chromium (top high-contraction (HC) and underlying low-contraction (LC) chromium) system was investigated by dissolving coatings in order to reveal the mechanism that the service life of the coated parts is largely improved using the hybrid technique of laser pre-quenching plus chromium post-depositing. It was found that the surface characteristics of the substrate, LC and HC chromium layer can be simultaneously revealed owing to the dissolution edge effect of chromium coatings. Moreover, the periodical gradient morphologies of the LDQS substrate are clearly shown: the surfaces of laser transformation-hardened regions are rather smooth; a lot of fine micro-holes exist in the transition zones; there are many micro-dimples in the original substrate. Furthermore, the novel method of dissolving coatings with sharp interfaces may be used to reveal the structural features of a substrate/coating system, explore the effect of the substrate on the initial microstructure and morphologies of coatings, and check the quality of the coated-parts.

Evidence of quantum lateral confinement in side-gated resonant tunnelling diodes formed by patterned substrate regrowth

MBE regrowth on patterned np-GaAs wafers has been used to fabricate GaAs/AlGaAs double barrier resonant tunnel diodes with a side-gate in the plane of the quantum well. The physical diameters vary from 1 to 20 μm. For a nominally 1 μm diameter diode the peak current is reduced by more than 95% at a side-gate voltage of -2 V at 1.5 K, which we estimate corresponds to an active tunnel region diameter of 75 nm ± 10 nm. At high gate biases additional structure appears in the conductance data. Differential I-V measurements show a linear dependence of the spacing of subsidiary peaks on gate bias indicating lateral quantum confinement. © 1996 American Institute of Physics.

Substrate Effects on the Micro/Nanomechanical Properties of TiN Coatings

Nanoindentation and nanoscratch tests were performed for titanium nitride (TiN) coatings on different tool steel substrates to investigate the indentation/scratch induced deformation behavior of the coatings and the adhesion of the coating–substrate interfaces and their tribological property. In this work, TiN coatings with a thickness of about 500 nm were grown on GT35, 9Cr18 and 40CrNiMo steels using vacuum magnetic-filtering arc plasma deposition. In the nanoindentation tests, the hardness and modulus curves for TiN/GT35 reduced the slowest around the film thickness 500 nm with the increase of indentation depth, followed by TiN/9Cr18 and TiN/40CrNiMo. Improving adhesion properties of coating and substrate can decrease the differences of internal stress field. The scratch tests showed that the scratch response was controlled by plastic deformation in the substrate. The substrate plays an important role in determining the mechanical properties and wear resistance of such coatings. TiN/GT35 exhibited the best load-carrying capacity and scratch/wear resistance. As a consequence, GT35 is the best substrate for TiN coatings of the substrate materials tested.

Influence of ion energy and substrate temperature on the optical and electronic properties of tetrahedral amorphous carbon (ta-C) films

The properties of amorphous carbon (a-C) deposited using a filtered cathodic vacuum arc as a function of the ion energy and substrate temperature are reported. The sp3 fraction was found to strongly depend on the ion energy, giving a highly sp3 bonded a-C denoted as tetrahedral amorphous carbon (ta-C) at ion energies around 100 eV. The optical band gap was found to follow similar trends to other diamondlike carbon films, varying almost linearly with sp2 fraction. The dependence of the electronic properties are discussed in terms of models of the electronic structure of a-C. The structure of ta-C was also strongly dependent on the deposition temperature, changing sharply to sp2 above a transition temperature, T1, of ≈200°C. Furthermore, T1 was found to decrease with increasing ion energy. Most film properties, such as compressive stress and plasmon energy, were correlated to the sp3 fraction. However, the optical and electrical properties were found to undergo a more gradual transition with the deposition temperature which we attribute to the medium range order of sp2 sites. We attribute the variation in film properties with the deposition temperature to diffusion of interstitials to the surface above T1 due to thermal activation, leading to the relaxation of density in context of a growth model. © 1997 American Institute of Physics.

Characterisation of cell adhesion to substrate materials and the resistance to enzymatic and mechanical cell-removal

Cell-implant adhesive strength is important for prostheses. In this paper, an investigation is described into the adhesion of bovine chondrocytes to Ti6Al4V-based substrates with different surface roughnesses and compositions. Cells were cultured for 2 or 5 days, to promote adhesion. The ease of cell removal was characterised, using both biochemical (trypsin) and mechanical (accelerated buoyancy and liquid flow) methods. Computational fluid dynamics (CFD) modelling has been used to estimate the shear forces applied to the cells by the liquid flow. A comparison is presented between the ease of cell detachment indicated using these methods, for the three surfaces investigated. © 2008 Materials Research Society.

Spark plasma sintering of TiNi nano-powders for biological application

Nano-sized TiNi powder with an average size of 50nm was consolidated using spark plasma sintering (SPS) at 800 °C for 5min. A layer of anatase TiO 2 coating was formed on the sintered TiNi by chemical reaction with a hydrogen peroxide (H2O2) solution at 60 °C followed by heat treatment at 400 °C to enhance the bioactivity of the metal surface. Cell culture using osteoblast cells and a biomimetic test in simulated body fluid proved the biocompatibility of the chemically treated SPS TiNi. © IOP Publishing Ltd.

Generalized Maugis-Dugdale Model of an Elastic Cylinder in Non-Slipping Adhesive Contact with a Stretched Substrate

We have recently developed a generalized JKR model for non-slipping adhesive contact between an elastic cylinder and a stretched substrate where both tangential and normal tractions are transmitted across the contact interface. Here we extend this model to a generalized Maugis-Dugdale model by adopting a Dugdale-type adhesive interaction law to eliminate the stress singularity near the edge of the contact zone. The non-slipping Maugis-Dugdale model is expected to have a broader range of validity in comparison with the non-slipping JKR model. The solution shares a number of common features with experimentally observed behaviors of cell reorientation on a cyclically stretched substrate.

Size Dependent Nanoindentation of a Soft Film on a Hard Substrate

Nanoindentation experiments on Al/glass systems show that, as the indentation depth increases, the hardness decreases during a shallow indentation, and increases when the indenter tip approaches the film–substrate interface. We associate the rise in hardness during two stages with the strong strain gradient effects, the first stage is related with the small scale effects and the second stage with the strain gradient between the indenter and the hard substrate. Using the strain gradient theory proposed by Chen and Wang and the classical plasticity theory, the observed nanoindentation behavior is modeled and analyzed by means of the finite element method, and it is found that the classical plasticity cannot explain the experiment results but the strain gradient theory can describe the experiment data at both shallow and deep indentation depths very well. The results prove that both the strain gradient effects and substrate effects exist in the nanoindentation of the film–substrate system.

A Label-Free Protein Microfluidic Array for Parallel Immunoassays

A label-free protein microfluidic array for immunoassays based on the combination of imaging ellipsometry and an integrated microfluidic system is presented. Proteins can be patterned homogeneously on substrate in array format by the microfluidic system simultaneously. After preparation, the protein array can be packed in the microfluidic system which is full of buffer so that proteins are not exposed to denaturing conditions. With simple microfluidic channel junction, the protein microfluidic array can be used in serial or parallel format to analyze single or multiple samples simultaneously. Imaging ellipsometry is used for the protein array reading with a label-free format. The biological and medical applications of the label-free protein microfluidic array are demonstrated by screening for antibody–antigen interactions, measuring the concentration of the protein solution and detecting five markers of hepatitis B.

On the Formation of Periodic Segmentation Cracks in a Coating Plated on a Substrate with Periodic Subsurface Inclusions

The mechanism of the formation of periodic segmentation cracks of a coating plated on a substrate with periodic subsurface inclusions (PSI) is investigated. The internal stress in coating and subsequently the strain energy release rate (SERR) of the segmentation cracks are computed with finite element method (FEM). And the effect of the geometrical parameters of the PSI is studied. The results indicate that the ratio of the width of the inclusion to the period of the repeated structure has an optimum value, at which the maximum internal tensile stress and SERR arise. On the other hand, the ratio of the max-thickness of the inclusion to the thickness of the coating has a threshold value, above which the further increase of this ratio should seldom influence the internal stress or the SERR.

Evaluation of the Interfacial Adhesion between Brittle Coating and Ductile Substrate by Cross-Secitional Indention

The cross-sectional indentation method is extended to evaluate the interfacial adhesion between brittle coating and ductile substrate. The experimental results on electroplated chromium coating/steel substrate show that the interfacial separation occurs due to the edge chipping of brittle coating. The corresponding models are established to elucidate interfacial separation processes. This work further highlights the advantages and potential of this novel indentation method.