Intrinsic Surface Properties Research Articles

APPROXIMATELY ISOMETRIC SHAPE CORRESPONDENCE BY MATCHING POINTWISE SPECTRAL FEATURES AND GLOBAL GEODESIC STRUCTURES

A practical method for finding correspondences between nonrigid isometric shapes is presented. It utilizes both pointwise surface descriptors, and metric structures defined on the shapes to perform the matching task, which is formulated as a quadratic minimization problem. Further, the paper explores the correspondence ambiguity problem arising when matching intrinsically symmetric shapes using only intrinsic surface properties. It is shown that when using isometry invariant surface descriptors based on eigendecomposition of the Laplace–Beltrami operator, it is possible to construct distinctive sets of surface descriptors for different possible correspondences. When used in a proper minimization problem, those descriptors allow us to explore number of possible correspondences between two given shapes.

Measurement and characterization of ultra-precision freeform surfaces using an intrinsic surface feature-based method

Ultra-precision freeform surfaces are complex surfaces that possess non-rotational symmetry and are widely used in advanced optics applications. Due to the geometrical complexity of optical freeform surfaces, there is, as yet, a lack of generalized surface characterization methods which measure various types of ultra-precision freeform surfaces with sub-micrometer form accuracy and surface finish in the nanometer range. To make good this deficiency, a generalized approach for the measurement and characterization of ultra-precision freeform surfaces, named the intrinsic surface feature-based method (ISFM), is presented in this paper. The ISFM makes use of intrinsic surface properties (e.g. curvatures, normal vectors, torsion and intrinsic frames) to conduct data matching or uses some algorithms to search for correspondences such as correlation functions. The method is experimentally verified through a series of measurement experiments. The results show that the proposed ISFM is capable of addressing the deficiencies and limitations of traditional freeform surface characterization methods which are susceptible to outliers and to uncertainty due to the geometry of the freeform surfaces. ISFM is a generalized methodology which is not dependent on the type of freeform surface being characterized.

Wettability of ceramic surfaces -A wide range control of surface wettability from super hydrophilicity to super hydrophobicity, from static wettability to dynamic wettability

Surface wettability is dependent to surface energy of the material. Therefore the surface wettability basically reflects its intrinsic surface property and it has been thought that it is hard to be controlled arbitrarily. For example, inorganic materials such like metal oxides usually exhibit relatively hydrophilic property as compared with organic materials. However recent series of studies by our group revealed that photo-induced surface reaction, nanometer scale roughness, nanometer scale physical and chemical heterogeneity affect wettability greatly. This fact clearly shows that the surface wettability of a metal oxide can be controlled from superhydrophilic state to superhydrophobic state. The target of control includes not only static wettability but also dynamic wetttability. Oxide surface with high dynamic hydrophobicity can be obtained by optimizing these factors. Water repellency of developed hydrophobic ceramic surface turned out to be like a polymer surface. The novel technology to control wettability of ceramic surfaces is expected to contribute to various applications.

Study of O 2 and OH adsorption energies on Pd–Cu alloys surface with a quantum chemistry approach

Variation of the intrinsic metal surface properties (lattice parameter, binding energy, work function ( W f), d-band filling and d-band center ɛ d) and O 2 and OH adsorption energies of on (1 1 1) Pd–Cu surface alloys were determined using ab initio program. Calculations of these parameters were based on plane waves approach on slab system with density functional theory (DFT) using the Vienna ab initio simulation program (VASP). It was shown that insertion of Cu atoms in Pd lattice affects geometric and electronic properties of Pd. These changes influence significantly O 2 and OH adsorption. Indeed, the highest OH adsorption energy and the lowest O 2 adsorption energy were found with 30 at.% in Cu. The volcano shape of the O 2 and OH adsorption with composition in Cu was explained, respectively, by firstly the highest bond distance that reduces adsorption energy of oxygen and the compromise between low DOS(E f) and secondly, low band width ( W) reach for Pd 3Cu which leads to the highest OH adsorption energy. O 2 and OH adsorption energies tendency could explain effect of the transition metal (TM) on kinetic current of the oxygen reduction reaction.

Superhydrophobic Properties of Nanostructured–Microstructured Porous Silicon for Improved Surface-Based Bioanalysis

Wettability is a fundamental property of a solid surface, which plays important roles in many industrial applications. The possibility to create well-controlled nonwetting states on silicon surfaces without photolithography-based processing can bring many advantages in the biotechnology and microfluidics areas. In this paper, superhydrophobic properties of macroporous–nanoporous structured silicon are reported. The superhydrophobic porous silicon layers are prepared by electrochemical etching of bulk crystalline silicon wafers. Altered anodization conditions provide surfaces with varying pore morphologies, yielding different wetting properties, ranging from highly wetting (nanoporous morphologies) to water-repellent surfaces (macroporous morphologies). Subsequent surface modification with a fluorocarbon coupling agent can further improve nonwetting properties and stabilize the surface for a long term. Contact angles as high as 176° were achieved on macroporous silicon and superhydrophobicity was maintained for several months without degradation. The porous surfaces have proven to be a very attractive substrate for protein microarrays. Fluorescence-based assay of immunoglobulin G in plasma is reported with a limit of detection of 1 pM, a spot size of 50 μm, and an array density of 15,625 spots per square centimeter. Macroporous surfaces have also been developed for matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) applications, where the intrinsic hydrophobic surface properties confine the deposited sample to MALDI spots of less than 200 μm with well-defined MALDI crystals, providing a high-sensitivity readout. Furthermore, a superhydrophobic MALDI-TOF MS target anchor chip composed of nonporous anchor points surrounded by superhydrophobic porous areas for sample deposition and on anchor point confinement is reported. Such anchor chips allowed localized crystallization of large sample volumes (5 μL) improving the hydrophobic spot confinement strategy in terms of final MALDI crystal localization and readout sensitivity.

Rosensweig instability of ferrogel thin films or membranes

We derive the dispersion relation of surface waves for magnetic gel membranes or thin films at the interface between two fluids in the presence of an external magnetic field normal to the free surface. Above a critical field strength surface waves become linearly unstable with respect to a stationary pattern of surface protuberances. This linear stability criterion generalizes that of the Rosensweig instability for ferrofluid and ferrogel free surfaces to take into account bending elasticity and intrinsic elastic and magnetic surface properties of the film or membrane, additionally. The latter is of interest for uniaxial ferrogel film or membranes, which show a locked-in permanent magnetization.

Surface complexation modeling of uranium(VI) sorbed onto zirconium oxophosphate versus temperature: Thermodynamic and structural approaches

This work presents an investigation of the interaction mechanisms between uranyl ions and a solid phosphate, the zirconium oxophosphate: Zr 2O(PO 4) 2. Both thermodynamic and structural points of view are developed. Indeed, prior to any simulation of the retention data, it is necessary to precisely characterize the system under study in order to gain information at a molecular scale. First, the intrinsic surface properties of this synthetic compound have been investigated for different temperatures ranging from 25 to 90 °C. Mass and potentiometric titrations show that the surface site density remains constant between 25 and 90 °C, while the experimental point of zero charge slightly decreases from 4.8 to 4.5 with an increasing temperature. The potentiometric titration data are simulated, for each temperature, using the constant capacitance model and taking into account two surface sites ( Zr O and P O) with a total surface site density equal to 7.0 sites nm −2. For both reactive sites, the intrinsic protonation constants do not change with the temperature, while the deprotonation ones increase. These results led to the determination of the associated enthalpy and entropy changes according to the van't Hoff relation. Second, the speciation of U(VI) at the solid/solution interface has been studied using two complementary spectroscopic techniques probing the sorbed uranyl ions: time-resolved laser-induced fluorescence spectroscopy (TRLFS) and X-ray absorption spectroscopy (EXAFS). The substrate presents two different reactive surface sites against uranium retention, which are constituted by the oxygen atoms of the surface PO 4 groups and the oxygen atoms linked to the zirconium atoms. Two inner-sphere complexes are thus present on the substrate, their relative proportion depending on the pH value of the suspension. The effects of the temperature (25–90 °C) on the surrounding uranium were checked using the TRLFS technique. The uranyl sorption constants onto the Zr 2O(PO 4) 2 substrate were determined taking into account the structural investigation. The surface complexation modeling was performed using the constant capacitance model included in the FITEQLv4.0 code. The four adsorption edges obtained at 25, 50, 75, and 90 °C were simulated. The modeling of these experimental data was realized considering two surface complexes (( ZrOH) 2UO 2+ 2, ( PO) 2UO 2) according to the structural investigation. The constant value associated with the ZrO site does not change with the temperature, while the one corresponding to the PO site increases. Finally, the enthalpy and entropy changes associated with the uranyl sorption constants have been determined using the van't Hoff relation.

High-performance poly(3-hexylthiophene) transistors with thermally cured and photo-cured PVP gate dielectrics

We have fabricated poly(3-hexylthiophene) organic field-effect transistors (P3HT-OFETs) with either high-temperature (200 °C) thermally cured PVP gate dielectrics or low-temperature (120 °C) photo-cured PVP gate dielectrics. We prepared the thermally cured PVP dielectric layer from a blend of poly(4-vinylphenol) (PVP) and poly(melamine-co-formaldehyde) (PMF); the photo-cured PVP dielectric formulation contained an additional photo-acid generator (PAG), which allowed the temperature for the cross-linking reaction to be reduced. We examined the intrinsic dielectric properties (e.g., the dielectric constant, the electrical insulating properties) and surface properties (e.g., morphology, surface energy) of the formulations loaded with various amounts of PAG (from 0 to 2.4 wt%). The P3HT-OFETs with the thermally cured PVP gate dielectrics exhibited an excellent carrier mobility of ca. 0.1 cm2V−1 s−1, a sub-threshold swing of 2.0 V decade−1, and an on/off ratio of 1.2 × 104. For comparison, the P3HT-OFET devices with the photo-cured PVP gate dielectrics also exhibited good electrical characteristics, including carrier mobilities as high as 0.06 cm2V−1 s−1, sub-threshold swings as low as 1.4 V decade−1, and on/off ratios as large as 3.0 × 104. To take advantage of the photo-cured PVP films, we also fabricated OFETs on a flexible, cheap ITO/PET substrate.

Using Ferroelectric Poling to Change Adsorption on Oxide Surfaces

Adsorption has been invoked to explain many phenomena in ferroelectric materials including the unanticipated stability of ultrathin ferroelectric films; however, the intrinsic surface properties of ferroelectric oxides have been largely unexplored. Therefore, the effect of ferroelectric poling on the adsorption/desorption of two polar molecules, acetic acid and 2-propanol, and one nonpolar molecule, dodecane, on LiNbO3(0001) was compared. The two polar molecules were found to adsorb significantly more strongly on the positive surface. Temperature-programmed desorption (TPD) data yielded desorption pre-exponentials of the two polar molecules more than 11 orders of magnitude lower than expected. Ferroelectric materials are also intrinsically pyroelectric, and it is shown that the unusually low desorption pre-exponentials can be explained by temperature dependent heats of adsorption that result from changes in the surface dipole as the samples are heated. This conclusion was supported by dodecane adsorption/desorption, which was independent of polarity with normal desorption pre-exponentials. The differences between the polar and nonpolar molecules indicate that interactions between polar molecules and ferroelectric surfaces are dominated by electrostatics. It is shown that adsorption energy differences between positive and negative surfaces are large enough to switch the polarity of ferroelectric thin films.

Color Subspaces as Photometric Invariants

Complex reflectance phenomena such as specular reflections confound many vision problems since they produce image ‘features’ that do not correspond directly to intrinsic surface properties such as shape and spectral reflectance. A common approach to mitigate these effects is to explore functions of an image that are invariant to these photometric events. In this paper we describe a class of such invariants that result from exploiting color information in images of dichromatic surfaces. These invariants are derived from illuminant-dependent ‘subspaces’ of RGB color space, and they enable the application of Lambertian-based vision techniques to a broad class of specular, non-Lambertian scenes. Using implementations of recent algorithms taken from the literature, we demonstrate the practical utility of these invariants for a wide variety of applications, including stereo, shape from shading, photometric stereo, material-based segmentation, and motion estimation.

Temperature effects on the surface acidity properties of zirconium diphosphate

As part of the temperature effects study on the sorption of metallic cations onto zirconium diphosphate, we have first investigated the intrinsic surface properties of this synthetic compound for different temperatures (25, 50, 75 and 90 °C). A physico-chemical study (IR, XRD) assessed its purity, and the measured N 2-BET specific area was 13.4 ± 0.2 m 2 g −1 . Mass and potentiometric titrations showed that the experimental point of zero charge ( pH pzc = 2.6 ± 0.2 ) and the surface site density remained constant between 25 and 90 °C. The potentiometric titration data were simulated with the constant capacitance model, considering two reactive surface sites, with a total surface site density equal to 7.2 sites nm −2 . The intrinsic protonation and deprotonation constants were found to increase with the temperature, as well as the calculated apparent constants. The simulation results showed that the capacitance increased with the temperature. The proportions of the neutral, protonated and deprotonated forms for each site type were quantified thermodynamically by application of the Van't Hoff relation.

Intrinsic structure of the free liquid surface of an alkali metal

An operational procedure to obtain the intrinsic properties of free liquid surfaces, and which had been previously applied to computer simulations of dielectric liquid models, is used here to sample the intrinsic surface properties of liquid lithium, sodium, and potassium, with an ab initio orbital free description of the electrons. When properly scaled, the intrinsic profiles of the three alkali fluids turn to be virtually identical. As in simple fluid models these intrinsic density profiles show a strong layering structure, similar to that of the bulk liquid pair distribution function, but with specific surface aspects like the density of the first liquid layer, and the interlayering spacing. The capillary wave fluctuations of the surface partially damp the intrinsic layering and produce density profiles which depend strongly on the transverse sampled area, but which still show an oscillating structure. The assumptions of the capillary wave theory, which is used in the interpretation of x-ray reflectivity data, may be directly checked, and a direct comparison with the experimental data presented, with very good agreement between our results and the measured electronic surface structure factor for potassium.

Construction of Lagrangian surfaces in complex Euclidean plane with Legendre curves

An important problem in the theory of Lagrangian submanifolds is to find non-trivial examples of Lagrangian submanifolds in complex Euclidean spaces with some given special geometric properties. In this article, we provide a new method to construct Lagrangian surfaces in the complex Euclidean plane C2 by using Legendre curves in S3(1) $\subset$ C2. We also investigate intrinsic and extrinsic geometric properties of the Lagrangian surfaces in C2 obtained by applying our construction method. As an application we provide some new families of Hamiltonian minimal Lagrangian surfaces in C2 via our construction method.

Illumination Color and Intrinsic Surface Properties —Physics-based Color Analyses from a Single Image

Illumination Color and Intrinsic Surface Properties —Physics-based Color Analyses from a Single Image

Grating formation in step flow heterogeneous growth and wavelength selection induced by confinement

Based on kinetic Monte Carlo simulations, we show that modulated wires and island gratings can be formed at vicinal surfaces. The modulation (grating) wavelength along the steps can be tailored by external conditions (coverage and temperature) and intrinsic surface properties (diffusion, terrace width) via a scaling law. Above 220 K a thermodynamic saturation value for the wavelength occurs, which depends only on the terrace width. This morphological behavior can be understood in terms of nucleation arguments applied to heteroepitaxial growth of Ag on stepped Pt(1 1 1) surfaces.

Special Issue on Solid Modeling Theory and Engineering Applications

Special Issue on Solid Modeling Theory and Engineering Applications

Dispersion of Single-Walled Carbon Nanotubes in Aqueous Solutions of the Anionic Surfactant NaDDBS

The insolubility of single-walled carbon nanotubes (SWNT) in either water or organic solvents has been a limitation for the practical application of this unique material. Recent studies have demonstrated that the suspendability of SWNT can be greatly enhanced by employing appropriate surfactants. Although the efficiency of anionic, cationic, and nonionic surfactants has been demonstrated to different extents, the exact mechanism by which carbon nanotubes and the different surfactants interact is still uncertain. To deepen the understanding of this interfacial phenomenon, we have investigated the effects of chemical modifications of the surface on the extent of nanotube−surfactant interaction. Such changes in the surface chemistry of the SWNT can be achieved by simply varying the pretreatment method, which can be acidic or basic. We have found that intrinsic surface properties such as the PZC (point of zero charge) are greatly affected by the purification method. That is, the electrical charge of the SWNT surface varies with the pH of the surrounding media. However, it has been found that during the adsorption of the anionic surfactant sodium dodecylbenzenesulfonate (NaDDBS) on SWNT Coulombic forces do not play a central role, but are overcome by the hydrophobic interactions between the surfactant tail and the nanotube walls. Only at pH values far from the PZC do the Coulombic forces become important. The hydrophobic forces between the surfactant tail and the nanotube determine the structure of the surfactant-stabilized nanotubes. In such a structure, each nanotube is covered by a monolayer of surfactant molecules in which the heads form a compact outer surface while the tails remain in contact with the nanotube walls. It is important to note that although the final configuration can be described as a cylindrical micelle with a nanotube in the center, the mechanism of formation of this structure does not proceed by incorporation of a nanotube into a micelle, but rather by a two-step adsorption that ends up in the formation of a surfactant monolayer.

An algorithm for optimal free-form object matching

A novel method of matching for 3-D free-form objects (points vs. surface and surface vs. surface) is proposed. The method formulates the problem in terms of solution of a non-linear polynomial equation system, which can be solved robustly by the Interval Projected Polyhedron (IPP) algorithm. Two intrinsic surface properties, the Gaussian and the mean curvatures, are used as object features for matching. The related iso-curvature lines are used to establish the correspondence between two objects. The intersection points of these iso-curvature lines are calculated and sorted out to satisfy the Euclidean constraints from which the translation and rotation transformations are estimated. The performance of the proposed algorithm is also analyzed. This approach can cover global and partial matching, and be applied to automated inspection, copyright protection of NURBS models, and object recognition. Examples illustrate our technique.

Definition and invariance properties of structured surface BRDF

The bidirectional reflectance distribution function (BRDF) is used to characterize the directional properties of surface reflectance, but the most recent standardized definition fails to address some important aspects for the structured and varying surfaces encountered in remote sensing. This paper proposes an updated definition of BRDF that is applicable for such surfaces. The updated definition then motivates an examination of the resulting measurement requirements and invariance properties. The conclusion is that structured surface BRDF can be defined in a consistent manner that is an intrinsic surface property, and it does exhibit the usual invariance properties associated with BRDF, such as reciprocity.

Simple generic method for predicting the effect of strain on surface diffusion

We show, by first-principles calculations, that the effect of external strain on surface diffusion is inherently correlated with the intrinsic surface stress induced by the adatom along its diffusion pathways. We demonstrate a simple generic method for a priori predicting quantitatively how an external strain will change surface diffusion on any given surface, based on calculations of surface-stress tensors of the unstrained surface. diffusion. Our understanding of the fundamental physical mechanisms underlying the relationship between strain and diffusion is still very limited. In this paper, we present a comprehensive first-principles investigation of the effect of strain on diffusion on a semiconductor surface. We show that the effect of strain on surface diffusion is inherently corre- lated with the intrinsic surface stress induced by an adatom along its diffusion pathways. We demonstrate a simple ge- neric theoretical method to a priori predict quantitatively how an external strain changes surface diffusion on any given surface. The effect of strain on surface diffusion is not only of general scientific interest but also of technological impor- tance. For example, the strain-affected surface diffusion can alter the transition of growth mode 2,5 from two-dimensional ~2D! to 3D growth. Surface diffusion directed by a nonuni- form surface strain field is a key ingredient in driving self- organized growth of nanostructures, such as formation of 2D island arrays, 7 coarsening of 2D islands, 8 and growth of 3D island superlattices in multilayer films. 9 Recently, both experiment 5 and theory 6 show that on a metal surface @such as Ag~111!#, a biaxial compressive strain increases surface diffusion, while a biaxial tensile strain decreases it. The first- principles calculations 6 further show that the diffusion bar- rier scales linearly with the external strain. A natural question is whether these observations are also true on a semiconduc- tor surface where more complex diffusion processes are gen- erally involved with multiple diffusion pathways and with diffusion anisotropy. And a more fundamental question is what are the underlying physical mechanisms that define the dependence of surface diffusion on strain and whether it is possible to a priori predict the change of surface diffusion under an external strain from the intrinsic surface properties of the unstrained surface.