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Purpose: To evaluate the effect of applied power on dental ceramic bonding of composite resin using nonthermal atmospheric pressure plasma (APP). Materials and Methods: A pencil-type APP torch was used to modify the surface chemical composition and hydrophilicity of dental ceramic and to improve the adhesion of composite resin to the surface. The effect of the applied power on chemical changes of the plasma polymer on a ceramic surface and the adhesive strength between the composite resin and feldspathic porcelain were examined. Adhesion was evaluated by comparing shear bond strengths (SBS) using the iris method. The chemical composition of the plasma polymer deposited on the ceramic surface was evaluated using x-ray photoelectron spectroscopy (XPS). Hydrophilicity was evaluated by contact angle measurements. The fracture mode at the interface was also evaluated. Results: The APP treatment was effective and the SBS of the experimental groups were significantly higher than those of the negative control group (p < 0.05). Moreover, the SBS obtained with the APP treatment at the highest input voltage was statistically similar to the gold standard of HF etching and silane coupling-agent coating. Two-thirds of the fractures observed in the specimens bonded with application of APP were mixed and cohesive fractures. Conclusion: Application of APP enhanced adhesion by producing carboxyl groups on the ceramic surface and as a result by improving surface hydrophilicity. The carboxyl group contents in the plasma polymer on the ceramic surface increased as the applied power increased. [ABSTRACT FROM AUTHOR]

If plasma technology can come out of the vacuum chamber and plasma can be extruded through a small pencil-type torch, it can be applied widely to dental practices. For this study, we designed a small pencil-type non-thermal atmospheric-pressure glow discharge plasma torch. The purpose of this study was to determine the effect of plasma polymer coating on the adhesion of composite resin to feldspathic porcelain. The effect of plasma polymer coating was evaluated using shear bond strength (SBS) test. Contact angle measurements and fracture mode analysis were also performed. Among the groups treated with plasma polymer coating, the SBS of the adhesive (Adper Scotchbond Multi-Purpose, 3M ESPE) to the ceramic surface pre-treated sequentially with water plasma and triethyleneglycol dimethacrylate (TEGDMA) plasma in helium gas was significantly higher than that of the adhesive to the untreated surface ( p < 0.05). In this group, the predominant fracture mode was mixed fracture, where small cohesively fractured fragments of ceramic were dispersed on the adhesively fractured flat adhesive surface. However, the SBS values of all the plasma polymer-coated groups were lower than those obtained through a routine porcelain bonding procedure with HF acid and silane coupling agent ( p < 0.05). The non-thermal atmospheric-pressure plasma polymer coating technique was found to have a potential promoting adhesion to dental materials. [ABSTRACT FROM AUTHOR]

This paper examines the mechanics of ball shear testing with the objective of understanding the mechanism by which the maximum shear force and the rate of crack growth is dependent on the solder bump size. For this, Pb-Sn solder bumps with diameters between 460 μm and 760 μm are soldered to 400 μm-diameter Cu pads and subjected to ball shear testing. In spite of the constant interface area, the bump size significantly impacts the measured shear fracture force and the crack growth rate. Both the fracture force and the crack growth rate increase with bump size, and in the case of the fracture force, the increase is almost linear. Our analysis finds that the linear increase in the fracture force is a result of the bump deformation force, which increases with bump size. A simple model that accounts for the deformation force component is developed and used to extract the true interface fracture force. The estimated true interface fracture force is found to vary little with bump size, tightly converging to the 40 MPa to 48 MPa range. On the other hand, the dependence of crack growth rate on bump size is found to result from the higher degree of rotational moment associated with larger bumps. [ABSTRACT FROM AUTHOR]

Finite element micromagnetic studies on the magnetic behaviors of granular structures are performed to investigate the magnetostatic contributions of the curved surfaces of grains with various film thicknesses. From the result, it is found that the magnetization reversal process in one grain is much faster when the grains have convex surfaces. The magnetization vectors of all convex models are stabilized in shorter time by factor of 10 compared to those of flat models. And, the reversals of each grain are carried out by nucleation and domain wall propagation in the entire granular structure, whereas the grains in flat model are individually reversed. Moreover, the magnetization behaviors of the convex models are closer to the experimental results. Since the geometric and magnetic conditions are same for the two models, the only origin of the more realistic magnetic behavior is the magnetostatic interaction between the grains, enhanced by introducing the convex surfaces. From the further analysis, it is found that the convex surface induces pinning field that suppress other parts' reversal. [ABSTRACT FROM AUTHOR]

A stiff skin forms on surface areas of a flat polydimethylsiloxane (PDMS) upon exposure to focused ion beam (FIB) leading to ordered surface wrinkles. By controlling the FIB fluence and area of exposure of the PDMS, one can create a variety of patterns in the wavelengths in the micrometer to submicrometer range, from simple one-dimensional wrinkles to peculiar and complex hierarchical nested wrinkles. Examination of the chemical composition of the exposed PDMS reveals that the stiff skin resembles amorphous silica. Moreover, upon formation, the stiff skin tends to expand in the direction perpendicular to the direction of ion beam irradiation. The consequent mismatch strain between the stiff skin and the PDMS substrate buckles the skin, forming the wrinkle patterns. The induced strains in the stiff skin are estimated by measuring the surface length in the buckled state. Estimates of the thickness and stiffness of the stiffened surface layer are estimated by using the theory for buckled films on compliant substrates. The method provides an effective and inexpensive technique to create wrinkled hard skin patterns on surfaces of polymers for various applications. [ABSTRACT FROM AUTHOR]

Stepwise cross-sectional crystallographic measurement was performed on the stress-induced void (SIV) of copper interconnect and it was possible to investigate the three-dimensional crystallographic structures near the submicron scale void. The void mainly happened at a triple junction of grain boundaries and there were at least two grains with high biaxial elastic modulus near the triple junction. The preferred site for the SIV could well be understood by considering the elastic anisotropy of each grain and the grain boundary type. [ABSTRACT FROM AUTHOR]

The grain growth which occurs during the self-annealing in copper electrodeposits was investigated by in situ observation with an electron backscattered diffraction technique. From these observations, it was found that a newly created twin was initiated on the front interface of growing twin and that the transverse direction for the growth was <110>. Most of the twins had the Σ3 twin boundary of {111}<110>. The formation of the twin and its peculiar growth direction could be explained quite well based on the hypothesis that the growth front interface is one of the {111} planes. [ABSTRACT FROM AUTHOR]

Micromagnetic simulations are performed to study the difference between fully discretized finite element simulations and macro spin simulations, where each grain is described with a uniform magnetization. Two exchange coupled grains with an edge length of 10 nm are used as test system. The magnetization of one grain is fixed with a large anisotropy. The switching time of the free grain shows that the difference between macro spin calculations and finite element simulations increases with larger intergrain exchange and smaller Gilbert damping constant. The deviation can be compensated by increasing the Gilbert-damping. [ABSTRACT FROM AUTHOR]

For a flexible electronic device integrating inorganic materials on a polymer substrate, the polymer can deform substantially, but the inorganic materials usually fracture at small strains. This paper describes an approach to make such a device highly stretchable. A polyimide substrate is first coated with a thin layer of an elastomer, on top of which SiNx islands are fabricated. When the substrate is stretched to a large strain, the SiNx islands remain intact. Calculations confirm that the elastomer reduces the strain in the SiNx islands by orders of magnitude. [ABSTRACT FROM AUTHOR]