Surface Microtopography Research Articles

Theoretical and experimental investigation on surface generation and subsurface damage in fixed abrasive lapping of optical glass

Fixed abrasive lapping (FAL) is a promising technology increasingly used for finishing optical mirrors and molds in a number of materials due to its high finishing efficiency, environmental friendliness, and relatively better surface and subsurface quality. A theoretical model for fixed-abrasive lapping of optical glass was developed in this paper by using indentation fracture mechanics, contact mechanics, mathematical statistics, lapping kinematics, and convolution iterative principle to provide an enhanced scientific understanding of the surface microtopography generation and subsurface damage (SSD) control mechanisms. In the modeling, the influence of the shape, size, and spatial distribution of abrasive particles and the ductile and brittle removal mechanisms of the material were considered. A series of lapping experiments on fused silica glass was carried out to quantitatively analyze the feasibility and accuracy of the model and study the influence mechanism of process parameters on the surface and subsurface state. Results indicated that the models could well predict the surface micromorphology and the SSD depth, and the range of sharpness angle of abrasive particles and tool load affected the predicted SSD range. In addition, the material removal mechanism and lapping tool wear characteristics were revealed by the surface structure and element component analysis. Finally, the FAL process was optimized by the evaluation indices of material removal rate (MRR), surface roughness, and SSD.

Presenting in-situ AFM investigations for the evolution of micro-surface topography and elastic modulus of rock under variable loads

Understanding the micro and nano-scale surface deformation and mechanical properties of rock under load possess enormous significance for underground engineering research and provides strong basis for comprehending rock failure as well. According to the documented research, the in-situ observation of micro-surface under dynamic load has not been yet reported. With this motive, a novel approach is presented in this work that takes advantages of combined Atomic Force Microscope (AFM) and customized micro-loading device for in-situ characterization of the the micro-surface topography and elastic modulus of rocks under different load strength. The in-situ comparison of micro-surface properties is carried out using interactive tools of AFM image post-processing software including crop and split, and section analysis. Taking the typical observation results of igneous rock and shale as an example, the results show that the micro-surface topography undulations of rock can reach up to tens of nanometers. Although no apparent fracture occurred, the local fluctuation of the rock samples’ micro-surface changed with the increasing load strength at nanometer level, and in the measurement area of 5 × 5 μm2, the topographies of different pixel points are various, showing significant local difference. With the increasing load strength, the elastic modulus distribution of the rock’s micro-surface shows heterogenity, and the local elastic modulus also increases or decreases, while the variation difference at different pixel points reaches hundreds of MPa. Additionally, the macroscopic fracture characteristics of rock under load, especially the non-uniform crack propagation and its mechanism are discussed. The analysis indicates that the heterogeneous distribution of the rock’s micro-surface elastic modulus and its local complex change with load are accounting for the complexity of the macroscopic crack path and the numerous crack branches. This study provides a novel insight into micro-surface behavior in rock and presents a new method for the investigation of the fracture mechanism of rock.

Leaf surface microtopography shaping the bacterial community in the phyllosphere: evidence from 11 tree species

Phyllosphere bacteria are an important component of environmental microbial communities and are closely related to plant health and ecosystem stability. However, the relationships between the inhabitation and assembly of phyllosphere bacteria and leaf microtopography are still obscure. In this study, the phyllosphere bacterial communities and leaf microtopographic features (vein density, stomatal length, and density) of eleven tree species were fully examined. Both the absolute abundance and diversity of phyllosphere bacterial communities were significantly different among the tree species, and leaf vein density dominated the variation. TITAN analysis showed that leaf vein density also played more important roles in regulating the relative abundance of bacteria than stomatal features, and 6 phyla and 62 genera of phyllosphere bacteria showed significant positive responses to leaf vein density. Moreover, LEfSe analysis showed that the leaves with higher vein density had more bacterial biomarkers. Leaf vein density also changed the co-occurrence pattern of phyllosphere bacteria, and the co-occurrence network demonstrated more negative correlations and more nodes on the leaves with larger leaf vein density, indicating that higher densities of leaf veins improved the stability of the phyllosphere bacterial community. Phylogenetic analysis showed that deterministic processes (especially homogeneous selection) dominated the assembly process of phyllosphere bacterial communities. The leaf vein density increased the degree of bacterial clustering at the phylogenetic level. Therefore, the inhabitation and assembly of the phyllosphere bacterial community are related to leaf microtopography, which provides deeper insight into the interaction between plants and bacteria.

Temporal and spatial variability of corrosion of high-strength steel wires within a bridge stay cable

The temporal and spatial corrosion variability of high-strength steel wires has a significant influence on the service performance deterioration behaviors of bridge stay cable. To proposed quantitative descriptions of the temporal and spatial variability, three different kinds of specimens are manufactured by Galvanized steel wires, and the accelerated corrosion experiments are conducted. For the single-wire specimens, the uniform corrosion process, the variation of surface microtopography and the time-dependent pitting corrosion model are investigated. In addition, the spatial corrosion variability of wires within a cable cross section is investigated by considering different damage conditions of sheath. It is found that the uniform corrosion process of the single-wire specimen can be divided into two stages, which correspond to the corrosion of Galvanized coating and substrate, respectively. The variability of uniform corrosion depth decreases firstly and then tends to be steady. The microtopography of corroded wire surface tends from compact spherical structure to be porous, hollow and loose. In the second corrosion stage, the corrosion products seem to be small clumps fluffy or flowery floccule, and then tend to be lamellar cross form and sand granular. The block maximum pitting factor of a single wire can be described by Gumbel distribution, and in the developed time-dependent model, both the location parameter and scale parameter decrease exponentially in the first corrosion stage and linearly in the second corrosion stage. The corrosion process difference factor of wires in adjacent layers of stay cable can be described by Normal distribution when the sheath is globally aging, and the mean value and coefficient of variation are 0.6758 and 0.2543, respectively. The spatial corrosion variability of cable wires is significantly affected by the broken shape of sheath. The difference of global corrosion degree of wires in different layers decreases with the extension of the exposure period. The sheath with rectangular broken shape and quadrate broken shape will lead to stronger spatial corrosion variability in cable wires than that with semi-annular broken shape.

An Innovative Movement Mode of Friction and Wear Tester Worktable and Its Application in CMP

To improve the reliability of chemical mechanical polishing (CMP) simulation on friction and wear tester, an innovative movement mode of worktable was proposed and optimized. MATLAB was used to simulate the relative movement trajectory under various movement modes. The impact of the worktable movement modes on the evolution of pad surface micro-texture was investigated through friction and wear test. High resolution white light interferometry was used to analyze the pad samples for their surface micro-topography. Finite element analysis was performed to understand the friction process under different movement conditions. The results reveal that with the increase of relative movement trajectory density, the average height and porosity of pad surface decreased, the concentration degree of surface height distribution increased, and the uniformity of pad surface wear was improved gradually. But the porosity of pad surface increased unexpectedly, and surface average height declined rapidly while the period ratio of rectangular cyclic mode to rotational mode raised up to 8:1. The coefficient of friction (COF) was impacted by both material compliance and pad surface flatness. Meanwhile, innovative movement modes of worktable can efficiently reduce the degree of pad deformation and stress concentration while improve the distribution uniformity of friction heat on wafer surface.

Degradation of Arable Soils in Central Yakutia: Negative Consequences of Global Warming for Yedoma Landscapes

Global warming, which is especially intensive (up to 0.08°C yr−1) in permafrost area of Central Yakutia, has dramatic consequences for scarce arable land resources in this region. In Yedoma landscapes, intense permafrost thawing on arable fields unprotected by forest vegetation transforms the surface microtopography with the formation of residual thermokarst mounds (byllars) of 6–10 m in diameter surrounded by a polygonal network of hollows of 0.3–1.5 m in depth above melting ice wedges. This process also takes place on former croplands abandoned in the recent decades because of socioeconomic reasons. It is accompanied by a significant transformation of the previously highly likely homogeneous soil cover composed of Cambic Turbic Cryosols (Sodic) into differentiated complexes of permafrost-affected Stagnic Cambisols or Calcic Solonetzes (Turbic) on the mounds and Calcic Stagnic Solonetzes (Turbic) in the microlows. Surface soil horizons on the mounds have a strongly to very strongly alkaline reaction (pH 8.5–9.5) and low (<2%) organic carbon content; a wavy line of effervescence is found at a depth of 15–30 cm. Soils in the microlows have a close to neutral reaction in the upper horizons (pH 6.2–7.5); higher organic carbon content (2–3%); more pronounced textural differentiation of the profile with the formation of typical natric Btn and, in some cases, overlying eluvial E horizons; deeper (50–60 cm) line of effervescence; and clear stagnic features in the lower part of the profile. In the case of shallow embedding by ice wedge, the lowermost part of the soil in the microlow is characterized by the low bulk density (1.04 g cm−3) because of the appearance of hollows after thawing of the ice-rich transient layer and melting of the top of ice wedges. This may be indicative of the further soil subsidence in the future and the appearance of initial thermokarst lakes (dyuedya) within the Yedoma terrain with its transformation into the alas type of landscape. Rapid thermokarst-driven development of microtopography followed by differentiation of the soil cover with increasing soil alkalinity on the microhighs and soil textural differentiation and overmoistening of deep layers in the microlows prevents the return of abandoned arable land to agriculture in Yedoma landscapes.

Anti-corrosive superhydrophobic coatings fabricated by a simple dipping method

ABSTRACT The two-step dipping technique was used to fabricate anti-corrosive fluorocarbon paint (FP)/SiO2 superhydrophobic coatings on the surfaces of aluminium alloy substrates. In order to characterise the surface microtopography, chemical element and groups, hydrophobicity, and corrosion performance of these prepared coatings, we employed a scanning electron microscope (SEM) and X-ray photoelectron spectrometer (XPS) as well as performing electrochemical experiments. Coating adhesion was reflected by the scotch-tape test. The coatings had a micron–nanometre hierarchical structure, and their surface morphologies were strongly dependent on the silica nanoparticle concentration. The superhydrophobicity of the coating was correlated with its microstructure and composition. The electrochemical experiments revealed that the obtained coating could enhance the corrosion performance of the underlying Al alloy substrates.

Determination of Vapor and Momentum Roughness Lengths Above an Undulating Soil Surface Based on PIV‐Measured Velocity Profiles

AbstractAccurately predicting bare‐soil evaporation requires the proper characterization of the near‐surface atmospheric conditions. These conditions, dependent on factors such as surface microtopography and wind velocity, vary greatly and therefore require high‐resolution datasets to be fully incorporated into evaporation models. These factors are oftentimes parameterized in models through the aerodynamic resistance (ra), in which the vapor roughness length (z0v) and the momentum roughness length (z0m) are two crucial parameters that describe the transport near the soil‐atmosphere interface. Typically, when evaluating bare‐soil evaporation, these two characteristic lengths are assumed equal, although differences are likely to occur especially in turbulent flows over undulating surfaces. Thus, this study aims to investigate the relationship between z0v and z0m above undulating surfaces to ultimately improve accuracy in estimating evaporation rate. To achieve this goal, four uniquely designed wind tunnel—soil tank experiments were conducted considering different wind speeds and undulation spacings. Particle image velocimetry (PIV) was used to measure the velocity field above the undulating surface in high resolution. Using the high‐fidelity data set, the logarithmic ratio of z0v to z0m is determined and used to estimate ra. Results confirm that these lengths differ significantly, with the logarithmic ratio roughly ranging from −15 to −5 under the conditions tested. PIV‐measured results demonstrate this ratio is closely tied to the mass and momentum transport behaviors influenced by surface undulations. Using the data‐integrated formulation of ra, predictions of evaporation rate were prepared for both the laboratory and lysimeter experiments, demonstrating the efficacy of the proposed approach in this study.

Turning Parameters Optimization for Diffraction Effect Suppression of Diamond-Turned Surface Combining Surface Micro-Topography Model and Scattering Theory

Abstract The diamond-turning process is a mean optical surface generation technique with high figure accuracy and surface finish. The diamond-turned surface has a significant diffraction effect introduced by the tool marks remaining on the surface, which heavily degrade the optical performance in the visible wavelength spectrum. The traditional approach that was used to eliminate this effect was polishing. In this paper, we present a method to find turning parameters that can generate an optical surface without diffraction effect directly by coupling a surface micro-topography model of a turned surface via the scattering theory. The surface micro-topography model of the turned surface reveals the relationship between tool marks and the diamond-turning parameters (DTPs). The scattering theory reveals the relationship between diffraction intensity distributions (DIDs) and surface micro-topography of the turned surface. Therefore, we obtained the relationship between DIDs and DTPs. The diffraction effect is considered to be eliminated when the first-order diffraction intensity is less than 0.01% of incidence intensity. The criterion of turning parameters for diffraction elimination is then obtained. Finally, turning experiments are performed to confirm the effectiveness of this method, and the diffraction-free surface finish is achieved.

Dissolution and sorption mechanisms at the aluminosilicate and carbonate mineral-AMD (Acid Mine Drainage) interface

Aluminosilicate/silicate and carbonate materials (pure and industrial) interacted with natural Acid Mine Drainage (AMD) under ambient conditions for different time periods in order to elucidate the chemical processes at the aluminosilicate and carbonate mineral-AMD interface. More precisely, powdered materials were subjected to macroscopic neutralization experiments (using on-line pH-measurements, Inductively Coupled Plasma Optical Emission Spectroscopy, Powder X-ray Diffraction and Scanning Electron Microscopy with Energy Dispersive Spectroscopy), whereas interacted mm-sized single crystals were examined by means of nanoscale microscopic (in-situ Atomic Force Microscopy) and surface & bulk spectroscopic techniques (X-ray Photoelectron Spectroscopy, 12C-Rutherford Backscattering Spectroscopy, Solid-State 29Si and 27Al Magic-Angle-Spinning Nuclear Magnetic Resonance). The carbonates were proven to be more effective for neutralization of AMD, related to adequate removal of metals from the contaminated aqueous medium, but they are readily dissolved. The application of aluminosilicate/silicates showed that the removal of metals is considerably lower, and the pH stabilized at lower values, but they are more resistant. The investigation of interacted zeolite and calcite crystals revealed changes to the macrotopography, microtopography and nanotopography of surfaces. It was indicated that coupled dissolution and sorption (surface precipitation/co-precipitation, nucleation/crystal growth, adsorption or even absorption-including solid-state diffusion) phenomena occur simultaneously. Based on the experimental results, two generalized models -in nano(molecular)-scale- can be suggested regarding interaction of AMD with aluminosilicate and carbonate mineral surfaces.

The effects of tillage induced surface roughness, slope and discharge rate on soil detachment by concentrated flow: An experimental study

AbstractSoil erosion in sloping cropland is a key water and soil conservation issue in the Loess Plateau region, China. How surface roughness influences soil detachment remains unclear due to the inconsistent results obtained from existing studies. The objectives of the present study were to evaluate the effects of tillage practices on soil detachment rate in sloping cropland and establish an accurate empirical model for the prediction of soil detachment rates. A series of movable bed experiments were conducted on sloping surfaces under three different tillage practices (manual dibbling, manual hoeing, and contour drilling), with a smooth surface (non‐tillage) as a control. The research indicated that soil detachment rate significantly increased with roughness (p < 0.05) since the average soil detachment rate was the highest under the contour drilling treatment (6.762 g m−2 s−1), followed by manual hoeing (4.180 g m−2 s−1), and manual dibbling (3.334 g m−2 s−1); the lowest detachment rate was observed under the non‐tillage treatment (3.214 g m−2 s−1). Slope gradient and unit discharge rate were positively correlated with soil detachment rate and proved to be more influential than soil surface roughness. Four composite hydraulic parameters were introduced to estimate soil detachment rate on tilled surfaces. Regression analyses revealed that stream power was the most effective predictor of soil detachment rate compared with unit length shear force, shear stress, and unit stream power. By integrating surface roughness as a variable, the detachment rate could be accurately described as a nonlinear function of stream power and surface roughness. The results of the present study indicate that tillage practice could influence soil loss on sloping cropland, considering the higher soil detachment rates under all tillage practices tested compared with non‐tillage. The results are attributed mainly to concentrated flow caused by the high water storage levels on tilled surfaces, which could damage surface microtopography and, subsequently, the development of headcuts.

A High Precision Modeling Technology of Material Surface Microtopography and Its Influence on Interface Mechanical Properties.

In order to accurately and effectively obtain the contact performance of the mating surface under the material surface topography characteristics, a numerical simulation method of rough surface based on the real topography characteristics and a multi-scale hierarchical algorithm of contact performance is studied in this paper. Firstly, the surface topography information of materials processed by different methods was obtained and characterized by a measuring equipment; Secondly, a non-Gaussian model considering kurtosis and skewness was established by Johnson transform based on Gaussian theory, and a rough surface digital simulation method based on real surface topography was formed; Thirdly, a multi-scale hierarchical algorithm is given to calculate the contact performance of different mating surfaces; Finally, taking the aeroengine rotor as the object, the non-Gaussian simulation method was used to simulate the mating surfaces with different topographies, and the multi-scale hierarchical algorithm was used to calculate the contact performance of different mating surfaces. Analysis results showed that the normal contact stiffness and elastic–plastic contact area between the mating surfaces of assembly 1 and assembly 2 are quite different, which further verifies the feasibility of the method. The contents of this paper allow to perform the fast and effective calculation of the mechanical properties of the mating surface, and provide a certain analysis basis for improving the surface microtopography characteristics of materials and the product performance.

Klebsiella aerogenes and Comamonas testosteroni as bioremoval agents on graffiti-coated concrete and granite: Impact assessment through surface analysis

Klebsiella aerogenes ATCC 13048 and Comamonas sp. ATCC 700440 (here identified as Comamonas testosteroni) have previously been shown to be good candidates for graffiti bioremoval, demonstrating in both immersion and subaerial strategies high levels of tolerance to the presence of the graffiti paint and some ability to degrade the graffiti material. To explore further the graffiti bioremoval capacity by these two newly found suitable bacteria, an experiment was carried out encompassing an improved assay protocol (protocol time was reduced from 20 to 14 days). The formation of pinholes - noticeably higher on concrete than on granite - was already observable by naked eye and further proved by digital image analysis, novel to this experiment, which showed holes greater in number due to K. aerogenes and greater in size due to C. testosteroni. Complementarily, surface microtopography - also novel for bioremoval studies with bacteria - offered detailed information on surface irregularities that allows better understanding of the performance of the bacteria. In contrast, non-mapping techniques, such as wetting by droplet, specular gloss and roughness measured in line transects provided less information for the study. Infrared (ATR-FTIR) spectroscopy and colour change assessment – mainly in the achromatic parameter L* – showed more intense changes by Comamonas testosteroni.

Effects of Underlay on Hill-Slope Surface Runoff Process of Cupressus funebris Endl. Plantations in Southwestern China

Clarifying the impact of underlay (i.e., the combination of near-surface vegetation and surface micro-topography) on the surface runoff process would provide a significant theoretical basis for the adjustment of vegetation patterns and the control of soil erosion on steep slopes in mountainous areas of southwestern China. In the current study, the runoff process under different rainfall characteristics was observed based on 10 natural runoff plots, and the correlation between the spatial pattern of cypress (Cupressus funebris), micro-topography, and runoff characteristic parameters was tested using the Pearson correlation coefficient method. The coupling effects of the spatial pattern of cypress and micro-topography on surface runoff also were analyzed using the Response Surface Method (RSM). The results showed that (1) under the conditions of long-duration moderate rainfall or long-duration rainstorm, topographic relief, surface roughness, runoff path density, contagion index of cypress, and stand density of cypress were the main reasons for the difference in the peak flow of each runoff plot, while under the condition of the short-duration rainstorm, the factors previously mentioned were no longer the dominant factors; (2) under the conditions of long-duration heavy rainfall or long-duration rainstorm, the common laws reflected by the response of the peak flow to the composite index of the spatial pattern of cypress and micro-topography were that (1) when the composite index of the spatial pattern of cypress (V) was below 21 and the composite index of micro-topography (U) was below 10.5, the peak flow would not be significantly affected; (2) when U > 10.5, increasing the composite index of the spatial pattern of cypress within a certain range would promote peak flow; (3) when U < 7.5 and V > 18, the increase of V value could significantly reduce the peak flow, and on this basis, adjusting the V value to 41, the reduction rate of peak flow could reach 84%.

Influence of fly ash or slag on nucleation and growth of early hydration of cement

In this study, isothermal calorimetry and the boundary nucleation and growth model (BNG model) were adopted to investigate the influence of fly ash (FA) and slag (SL) on the nucleation and growth of cement hydrates at early-stage. Afterwards, the mechanism was discussed by analyses of instantaneous activation energy and microtopography. The results show that the hinderance of FA on the early hydration at 20℃ is possibly contributed by the inhibition of nucleation, while SL promotes nucleation at both 20℃ and 60℃. Moreover, it is found that the paste containing FA has the lowest activation energy at early-stage, while the paste containing SL has the highest activation energy, which further indicate that the nucleation of the paste containing FA is more difficult. Besides, the surface microtopography analysis of particles confirm that SL has higher reactivity than FA in paste to generates more additional C-S-H gel to provide stronger seeding effect for producing C-S-H.

Research on Three-Dimensional Interpolation Modeling Method of Micro - and Nanometer Controllable Surface

The fundamental cause of friction and wear is the effect of force, resulting in material heating, deformation, fatigue, adhesion and furrow effect, which is closely related to the micro-topography of the contact surface of friction pair. How to establish the real three-dimensional (3D) rough surface, using inter-polation surface reconstruction based on real data, especially in the three dimensional precision measurement data processing, etc, also the lack of research and practice, so in this paper, fractal interpolation and spline interpolation, Fourier interpolation surface modeling interpolation algorithm of three methods for modeling, a detailed analysis and expounds the advantages and disadvantages of the three ways of modeling with surface, and finally to the surface of the atomic force microscope to measure the actual extraction of a small number of sampling points are simulated.

Development of multifunctional Si-Ca-PEG-nAg sol–gel implant coatings from calcium-2-ethoxyethoxide

Titanium implant success is compromised by microbial biofilms and aseptic loosening. This research aimed to develop robust multifunctional class II organic-inorganic hybrid coatings for implants with osteoconductive and antibacterial properties. 3-Glycidoxypropyltrimethoxysilane was coupled with organic polymer poly(ethylene) glycol-diamine (PEG-NH2) for integration into an inorganic sol backbone composed of tetraethoxysilane and calcium, which was sourced from newly synthesized calcium-2-ethoxyethoxide. Nuclear magnetic resonance and attenuated total reflectance Fourier transform infrared spectroscopy confirmed synthesis of precursors and the structure of coating constituents. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS) demonstrated homogenous coatings, micro-topographical surface features, and apatite-like ex vivo mineralization in simulated body fluid. Tensile adhesion testing demonstrated robust and highly adherent (15.1 ± 3.3 MPa) coatings on titanium substrates. Hybrid coatings imbedded with silver nanoparticles (nAg) significantly inhibited (P < 0.05) Staphylococcus aureus and Escherichia coli planktonic cultures and biofilm formation. These Si-Ca-PEG-nAg hybrid coatings for titanium implants offer robust multifunctional features.

Aggregation of Zoospores on Sharklet Microtopographic Surfaces

Surfaces with engineered microtopographies are potential candidate against biofouling to replace the use of biocides in the marine environment. Understanding the antifouling mechanism of microtopographic surfaces against marine microorganisms, however, has been limited. In this work, we theoretically studied the aggregation of Ulva linza zoospores on the Sharklet topographic surfaces by employing the extended Surface Energetic Attachment (SEA) model proposedin a previous work. The energy parameters of the model were obtained by matching theoretical results with experimental data for one type of Sharklet surface. Monte Carlo simulations were then carried out for a series of Sharklet surfaces with various numbers of distinct features. Inagreement with prior experimental results, our simulations indicate that engineered topographies promote smaller aggregates than those on a smooth surface. Furthermore, we show that the maximum effect of the Sharklet topography on the aggregate size of U. linza can be obtained with just 3 distinct features.

A free-form patterning method enabling endothelialization under dynamic flow

Endothelialization strategies aim at protecting the surface of cardiovascular devices upon their interaction with blood by the generation and maintenance of a mature monolayer of endothelial cells. Rational engineering of the surface micro-topography at the luminal interface provides a powerful access point to support the survival of a living endothelium under the challenging hemodynamic conditions created by the implant deployment and function. Surface structuring protocols must however be adapted to the complex, non-planar architecture of the target device precluding the use of standard lithographic approaches. Here, a novel patterning method, harnessing the condensation and evaporation of water droplets on a curing liquid elastomer, is developed to introduce arrays of microscale wells on the surface of a biocompatible silicon layer. The resulting topographies support the in vitro generation of mature human endothelia and their maintenance under dynamic changes of flow direction or magnitude, greatly outperforming identical, but flat substrates. The structuring approach is additionally demonstrated on non-planar interfaces yielding comparable topographies. The intrinsically free-form patterning is therefore compatible with a complete and stable endothelialization of complex luminal interfaces in cardiovascular implants.

Inferring Sediment Transport Capacity from Soil Microtopography Changes on a Laboratory Hillslope

In hillslope erosion modeling, the Transport Capacity (Tc) concept describes an upper limit to the flux of sediment transportable by a flow of given hydraulic characteristics. This widely used concept in process-based erosion modeling faces challenges due to scarcity of experimental data to strengthen its validity. In this paper, we test a methodology that infers the exceedance of transport capacity by concentrated flow from changes to soil surface microtopography sustained during rainfall-runoff events. Digital Elevation Models (DEMs) corresponding to pre- and post-rainfall events were used to compute elevation change maps and estimate spatially-varying flow hydraulics ω taken as the product of flow accumulation and local slope. These spatial data were used to calculate a probability of erosion PE at regular flow hydraulics intervals. The exceedance of Tc was inferred from the crossing of the PE = 0.5 line. The proposed methodology was applied to experimental data collected to study the impact of soil subsurface hydrology on soil erosion and sediment transport processes. Sustained net deposition occurred under drainage condition while PE for seepage conditions mostly stayed in the net erosion regime. Results from this study suggest pulsating erosion patterns along concentrated flow networks with intermittent increases in PE to local maxima followed by declines to local minima. These short-range erosion patterns could not be explained by current Tc-based erosion models. Nevertheless, Tc-based erosion models adequately capture observed decline in local PE maxima as ω increased. Applying the proposed approach suggests a dependence of Tc on subsurface hydrology with net deposition more likely under drainage conditions compared to seepage conditions.