Effects Of Surface Geometry Research Articles

Microfabricated dynamic brain organoid cocultures to assess the effects of surface geometry on assembloid formation.

Organoids have emerged as valuable tools for the study of development and disease. Assembloids are formed by integrating multiple organoid types to create more complex models. However, the process by which organoids integrate to form assembloids remains unclear and may play an important role in the resulting organoid structure. Here, a microfluidic platform is developed that allows separate culture of distinct organoid types and provides the capacity to partially control the geometry of the resulting organoid surfaces. Removal of a microfabricated barrier then allows the shaped and positioned organoids to interact and form an assembloid. When midbrain and unguided brain organoids were allowed to assemble with a defined spacing between them, axonal projections from midbrain organoids and cell migration out of unguided organoids were observed and quantitatively measured as the two types of organoids fused together. Axonal projection directions were statistically biased toward other midbrain organoids, and unguided organoid surface geometry was found to affect cell invasion. This platform provides a tool to observe cellular interactions between organoid surfaces that are spaced apart in a controlled manner, and may ultimately have value in exploring neuronal migration, axon targeting, and assembloid formation mechanisms.

Effects of surface geometry on light exposure, photoacclimation and photosynthetic energy acquisition in zooxanthellate corals.

Symbiotic corals display a great array of morphologies, each of which has unique effects on light interception and the photosynthetic performance of in hospite zooxanthellae. Changes in light availability elicit photoacclimation responses to optimize the energy balances in primary producers, extensively documented for corals exposed to contrasting light regimes along depth gradients. Yet, response variation driven by coral colony geometry and its energetic implications on colonies with contrasting morphologies remain largely unknown. In this study, we assessed the effect of the inclination angle of coral surface on light availability, short- and long-term photoacclimation responses, and potential photosynthetic usable energy. Increasing surface inclination angle resulted in an order of magnitude reduction of light availability, following a linear relationship explained by the cosine law and relative changes in the direct and diffuse components of irradiance. The light gradient induced by surface geometry triggered photoacclimation responses comparable to those observed along depth gradients: changes in the quantum yield of photosystem II, photosynthetic parameters, and optical properties and pigmentation of the coral tissue. Differences in light availability and photoacclimation driven by surface inclination led to contrasting energetic performance. Horizontally and vertically oriented coral surfaces experienced the largest reductions in photosynthetic usable energy as a result of excessive irradiance and light-limiting conditions, respectively. This pattern is predicted to change with depth or local water optical properties. Our study concludes that colony geometry plays an essential role in shaping the energy balance and determining the light niche of zooxanthellate corals.

Surface phase diagrams from nested sampling.

Studies in atomic-scale modeling of surface phase equilibria often focus on temperatures near zero Kelvin due to the challenges in calculating the free energy of surfaces at finite temperatures. The Bayesian-inference-based nested sampling (NS) algorithm allows for modeling phase equilibria at arbitrary temperatures by directly and efficiently calculating the partition function, whose relationship with free energy is well known. This work extends NS to calculate adsorbate phase diagrams, incorporating all relevant configurational contributions to the free energy. We apply NS to the adsorption of Lennard-Jones (LJ) gas particles on low-index and vicinal LJ solid surfaces and construct the canonical partition function from these recorded energies to calculate ensemble averages of thermodynamic properties, such as the constant-volume heat capacity and order parameters that characterize the structure of adsorbate phases. Key results include determining the nature of phase transitions of adsorbed LJ particles on flat and stepped LJ surfaces, which typically feature an enthalpy-driven condensation at higher temperatures and an entropy-driven reordering process at lower temperatures, and the effect of surface geometry on the presence of triple points in the phase diagrams. Overall, we demonstrate the ability and potential of NS for surface modeling.

The effect of surface geometry on the aerodynamic behaviour of a football

Several studies have investigated the effect of surface features on the aerodynamic behaviour of a sphere or a football. Research on footballs typically compare real footballs with highly complex seam geometry and surface texture, making it difficult to identify which features influence the aerodynamic behaviour. This study commissioned many 3D printed footballs with regularly increasing seam length and surface texture to undertake a designed experiment to study these changes in a controlled fashion. Each ball was tested in a wind tunnel in non-spinning cases, or spinning about a vertical axis, at a range of speeds and key aerodynamic parameters were extracted from the data. Several methods were employed to characterise the roughness of each ball, and these roughness metrics were statistically tested for correlations with selected aerodynamic parameters. Using these relationships provides design guidance to football manufacturers to understand how modifying their surface geometry would influence the ball’s aerodynamic behaviour. In general, increasing the volume of roughness of the ball, measured as the change in volume of the ball introduced through seams or texture compared to a smooth sphere, decreased the critical Reynolds number. Balls with larger texture elements, particularly those with protrusive texture, had a much lower critical Reynolds number than other balls with the same absolute volumes of roughness. The post-critical drag coefficient did not significantly correlate with any of the roughness features of the balls. In a spinning case, the balls with high roughness generated a higher side force, this relationship plateaued at a certain level of roughness. The reverse Magnus behaviour changed significantly with the surface roughness; as the overall roughness volume of the ball increased, the Reynolds number at which the reverse Magnus changed to a conventional Magnus effect decreased. The large protrusive texture elements were effective at preventing a reverse Magnus effect from occurring at all in the tested Reynolds number range.

Inverse determine the interfacial strength and surface geometry effects concerning carbon fiber reinforced epoxy composites by experiment aided FFT‐based spectral analysis

AbstractThe interfacial strength of carbon fiber reinforced epoxy composites is determined inversely by the combination of the transverse fiber bundle tensile experiment and fast Fourier transforms based spectral method. A representative volume element with transverse random fiber distribution is established to predict the strength of the composites, where the nanoscale interphase region between fiber and matrix is discretized by multi‐layer pixels. The interfacial stiffness is described by an exponential function, while the interfacial strength is a variable input. By using the spectral method, the interfacial strength of composites with different fiber types is analyzed rapidly. The effects of fiber modulus and interfacial geometric features (including interface topology and interphase thickness) on the mechanical behaviors and interfacial strength inversion are investigated to reveal the interface enhancement mechanisms. This study can be greatly helpful for interface design and performance evaluation of new‐type carbon fiber reinforced composites in engineering application.

Transient boiling heat transfer mechanism of droplet impacting heated cylinder

The spray on the heated cylindrical surface for boiling widely exists in the industrial application. In order to discover the transient boiling heat transfer mechanism, the cases of droplet impacting on the cylindrical surface were experimentally carried out. In this experiment, the droplet hydrodynamics were captured by high-speed camera. The effects of impact velocity and wall temperature on the hydrodynamics and boiling heat transfer performance were studied in detail. The results show that, for the droplet impacting on the heated cylindrical surface, four types of phase change heat transfer regimes, i.e., film evaporation regime, nucleate boiling regime, transition boiling regime and film boiling regime are found. From the built map of relationship between wall temperature and Weber number, it is demonstrated that when the wall superheat is low, increasing the droplet impact velocity enlarges the solid-liquid contact area, boosting the heat transfer performance in the film evaporation and nucleate boiling regimes. However, when the wall superheat is high, increasing the droplet impact velocity or Weber number makes the Leidenfrost point be lower and is unfavorable for heat transfer due to the easy generation of vapor layer, which strongly differs from the conclusion of droplet impacting on the heated flat surface according to others’ investigations. The underlying mechanism can be revealed from two aspects, i.e., the formation mechanism of Leidenfrost state and the effect of surface geometry. Finally, the quantitative relationship between Leidenfrost point and Weber number is given.

The Effect of Surface Geometry of Solid Wall on the Collapse of a Cavitation Bubble

Abstract The objective of this paper is to reveal the influence of different surface geometric conditions on the dynamic behavior characteristics of a laser-induced bubble collapse. A high-speed camera system was used to record the oscillation process of the laser-induced bubble on plane solid walls with different roughness and a wall containing reentrant cavities full of water or gas. The focus is on the quantitative analysis of the morphological characteristics of the cavitation bubble near the solid wall under different surface forms during the first two oscillation periods. The results show that the dimensionless ratio γ, defined as the distance from the center of the bubble to the wall divided by the maximum radius of the bubble, has a great influence on the change of the cavitation shape in the direction of the vertical wall. Different surface geometries without gas in our cases have no significant effect on the collapse time of cavitation bubbles. While for the surface containing gas, the direction of movement of the bubble accompanying the microjet will greatly change during the collapse of the cavitation bubble, and the collapse time seems to be independent of the dimensionless ratio γ. These achievements shed the light for engineering to avoid the damage of the microjet caused by designing suitable surface geometry.

Effect of surface geometry on laser powder bed fusion defects

Laser Powder Bed Fusion (L-PBF) is an additive manufacturing (AM) technology which has enabled the fabrication of highly complex structures and components. A major challenge in producing these high complexity structures is predicting where defects are likely to occur, and how severe those defects will be. In this study build geometry is linked to manufacturability, using quantifiable AM defects and metrics. This was achieved by fabricating a variety of unsupported, thin-walled samples with different curvatures using Al-10Si-Mg alloy. A combination of X-Ray computed tomographic (XCT) and digital stereomicroscopy were used to capturing positional data about the total geometric error, surface quality and roughness metrics (Ra and Rz). This dataset was used to create empirical model which predicts geometric error based on the local curvature, orientation and thickness of the computer-aided-design (CAD) geometry. Local inclination angle was observed to have the strongest effect on manufacturability, heavily impacting the geometric error and surface quality metrics. Sample shape defined by curvature was observed to be a secondary factor, which became important in areas of low inclination angle. The empirical model was applied in a case study of a cellular structure, the double gyroid, which successfully identified problematic regions of the structure. The approach of linking fundamental geometry features to defects shown in this study provides additional guidance in design for AM, with potential applications in topology optimisation, optimising part orientation to reduce support, and for design of other intricate components such as the internal conduits of heat exchange devices, where supports are not feasible to use.

Numerical Investigation of the Effect of Surface Geometry on Bullet Aerodynamic Behaviours

Gelişen silah sistemleri, sistemlerde kullanılan sarf malzeme niteliğindeki mermilerin üzerinde de çalışılması ve geliştirilmesi ihtiyacını gerektirmektedir. Malzeme ve geometri alanında gerçekleştirilen iyileştirme çalışmaları ile tahrip güçleri, menzilleri, hareket ve hedefe ulaşım stabilizasyonları iyileştirilmiş mermilerin üretimi çalışılmaktadır. Bu çalışmada, 9 mm parabellum tip hafif mermi çekirdeği yüzeyine oluşturulan kanal yapı ve çukur yapının mermi etrafında oluşan aerodinamik akış davranışı üzerine etkisinin incelenmesi konu edinilmiştir. Mermi çekirdeği etrafında oluşan hava akışı hesaplamalı akışkanlar dinamiği tabanlı Fluent yazılımı ile incelenmiştir. Sıkıştırılabilir hava akışı, Sutherland’s kanununa bağlı viskoz etkiler dikkate alınarak Spalart Allmaras türbülans akış modeli ile analiz edilmiştir. Çalışmada mermi geometrisi üzerine oluşturulan kanal veya çukur yüzey formunun mermi hızında artışa, kayma gerilimi ve sürükleme kuvvetinde ise azalışa sebep olabildiği sonucuna ulaşılmıştır. Mermi yüzey formunda meydana getirilecek çukur veya kanal yapının mermi hareketinde stabilizasyon yanında menziline de olumlu katkılar sağlayacağı değerlendirilmiştir.

Effects of surface geometry on advection–diffusion process in rough fractures

The surface geometry of a natural fracture may feature self-affine properties, which affects the advection–diffusion process significantly. A good understanding of the underlying mechanisms of controlling such a process is of fundamental importance for a clear description of complex hydrodynamic problems. However, the effects of hydraulic tortuosity, surface roughness, scale-invariance properties, and size effect on self-affine fractures have not been fully verified. In this work, we clarify the presence of triple effects of surface geometries on the advection–diffusion process by analytical derivations, quantify their physical implications based on Poiseuille flow and Fick’s law, establish a triple-effect advection–diffusion model for rough fractures by taking into consideration the joint effect of hydraulic tortuosity (τ), surface tortuosity (τs), and stationary roughness (fσ), and then reformulate the triple-effect model into a scaling form as per the size effect in self-affine fractures. For validation, we propose a novel Weierstrass–Mandelbrot function to model self-affine fractures according to the fractal topography theory, simulate the advection–diffusion process at the pore scale by the lattice Boltzmann method, and verify the triple-effect model and its scaling form systematically. The results indicate that the advection–diffusion process is composed of effective molecular diffusion and advection-induced dispersion, with the former inversely proportional to τ2 and the latter inversely proportional to τ2τs6fσ. Moreover, τs and τ are both scaled by H−1 (H is the Hurst exponent) with the mean aperture in self-affine fractures. Theoretical analysis and numerical simulations demonstrate that our model enables the generalization of several conventional models reported in the literature.

Numerical Simulation for Rock Fracture Viscoelastic Creep under Dry Conditions

In many rock engineering projects such as hydrocarbon extraction and geothermal energy utilization, the hydraulic and mechanical behavior of rock fractures significantly affects the safety and profitability of the project. In field conditions, the hydraulic and mechanical behavior of rock fractures changes with time (the rock fractures creep), and this creep is not negligible even under dry conditions. In addition, creep is strongly affected by the rock fracture surface geometry. However, there is not much literature systematically studying the effect of surface geometry on rock fracture creep under dry conditions. This paper presents the results of a numerical study considering the effect of surface geometry on rough fracture viscoelastic deformations. An in-house numerical code has been developed to simulate the viscoelastic deformation of rough fractures. In addition, another numerical code has been developed to generate synthetic rough fracture surfaces by systematically changing the surface roughness parameters: the Hurst exponent, mismatch length, and root mean square roughness. The results indicate that by increasing the Hurst exponent or decreasing the mismatch length or decreasing the root mean square roughness, the fracture mean aperture decreases, and the contact ratio (number of contacting cells/total number of cells) increases faster with time.

Cell Theranostics on Mesoporous Silicon Substrates.

The adhesion, proliferation, and migration of cells over nanomaterials is regulated by a cascade of biochemical signals that originate at the interface of a cell with a substrate and propagate through the cytoplasm to the nucleus. The topography of the substrate plays a major role in this process. Cell adhesion molecules (CAMs) have a characteristic size of some nanometers and a range of action of some tens of nanometers. Controlling details of a surface at the nanoscale—the same dimensional over which CAMs operate—offers ways to govern the behavior of cells and create organoids or tissues with heretofore unattainable precision. Here, using electrochemical procedures, we generated mesoporous silicon surfaces with different values of pore size (PS ≈ 11 nm and PS ≈ 21 nm), roughness (Ra ≈ 7 nm and Ra ≈ 13 nm), and fractal dimension (Df ≈ 2.48 and Df ≈ 2.15). Using electroless deposition, we deposited over these substrates thin layers of gold nanoparticles. Resulting devices feature (i) nanoscale details for the stimulation and control of cell assembly, (ii) arrays of pores for drug loading/release, (iii) layers of nanostructured gold for the enhancement of the electromagnetic signal in Raman spectroscopy (SERS). We then used these devices as cell culturing substrates. Upon loading with the anti-tumor drug PtCl (O,O′-acac)(DMSO) we examined the rate of adhesion and growth of breast cancer MCF-7 cells under the coincidental effects of surface geometry and drug release. Using confocal imaging and SERS spectroscopy we determined the relative importance of nano-topography and delivery of therapeutics on cell growth—and how an unbalance between these competing agents can accelerate the development of tumor cells.

Simulation Effects of Surface Geometry and Water Optical Properties on Hydrographic Lidar Returns

. Water LiDAR model was applied to simulate the returned waveforms of hydrographic LiDAR considering the effects of surface geometry and water optical properties. The signal to noise ratio(SNR) of bottom returned peak was considered as a criterion for performance of hydrographic LiDAR. The behavior of LiDAR was sensitive to water optical properties and it was insensitive to water surface roughness.

Material composition evaluation of historical Cu alloy aquamanilia by complementary XRF and LIBS measurements

The material composition of seven historical aquamanilia from museum collections in Krakow and Gdansk were examined using X-ray fluorescence (XRF) spectrometry and micro-ablation sampling by means of laser-induced breakdown spectroscopy (LIBS) to better understand the materials found in these objects as well as for providing information that can be used towards authentication and dating studies. An additional set of Cu-alloy objects and also a late medieval XV century bronze aquamanile served for reference and comparison. It was found that four of the figures were casted using quaternary and ternary Cu alloys characterized by a Zn content in the range 17.5-23%, admixtures of Sn and Pb below 7%, and presence of impurities like Fe, Ni, Ag, Si, Ba, and Ca. The observed composition similarities were confirmed by statistically processed data. This indicated that the animal figures (lions) are most probably brass replicas of the medieval ones and were produced during the XVIII-XX centuries. In situ measurements were adequate despite inaccuracies associated with signal intensity fluctuations due to surface geometry effects, the presence of patinas, corrosion or contamination, and systematic errors originating from calibration. The proposed complementary approach that uses portable XRF and LIBS instruments ensures consistent data for compositional studies on historical alloys.

New theoretical model for effects of Reynolds number on laminar boundary layer along ribbed surfaces

By utilizing a simplified asymptotic model, researchers calculate the effects of surface geometry on laminar boundary layer flows for ribbed surfaces.

Manipulation of the first stop band in periodically corrugated elastic layers via different profiles

We demonstrate the manipulation of the first frequency bands by changing the periodic corrugations on the surfaces of elastic plates. Based on the Fourier analysis and Floquet theorem, we have derived the dispersion relations for elastic waves propagating in periodically corrugated plates with different geometric profiles, which can always lead to the creation of forbidden bands. The effects of corrugation profiles on the forbidden bands have been quantified by the introduced shape factor, which has been proved to be proportional to the bandwidth. The simulations have confirmed the effects of surface geometries on the bandwidth, which is linearly dependent on the shape factor and corrugation amplitude. The calculated shape factor from the simulated data is very close to its theoretical value, verifying the applicability of the proposed band manipulation mechanism. The theoretical and numerical results indicate that the desired forbidden band could be obtained by selecting the corrugation geometries with the optimal shape factor and corrugation amplitude, which provides an efficient way to realize elastic wave filters and band gap materials in vibration control engineering.

Surface tracking of diffusion bonding void closure and its application to titanium alloys

Diffusion bonding is a process by which two flat, usually metallic, surfaces are welded together at a high temperature and moderate pressure. Bonding occurs due to a combination of diffusion and power law creep that close the voids formed by microscopic differences between the mating surfaces. While the different process parameters are well understood the effects of surface condition and void shapes during bonding has not been thoroughly researched. In this paper we use measured surface profiles, discretize them, and apply the diffusion and creep equations numerically to the profiles in order to provide insight into the effects of surface geometry on bonding. Using this method the voids can interact with each other and the effects of nearby voids can be computed. Experimental tests are performed to confirm the model and theoretical tests were created to determine what the effects of different surface geometries are on bonding performance. While in most cases the bonding was dominated by power law creep the most optimal void shape was one where the voids had completed the creep stage and were controlled by diffusive processes. It was also found that concentrating the overlap area also increases bonding performance.

Asymmetric electrolytes near structured dielectric interfaces.

The ion distribution of electrolytes near interfaces with dielectric contrast has important consequences for electrochemical processes and many other applications. To date, most studies of such systems have focused on geometrically simple interfaces, for which dielectric effects are analytically solvable or computationally tractable. However, all real surfaces display nontrivial structure at the nanoscale and have, in particular, a nonuniform local curvature. Using a recently developed, highly efficient computational method, we investigate the effect of surface geometry on ion distribution and interface polarization. We consider an asymmetric 2:1 electrolyte bounded by a sinusoidally deformed solid surface. We demonstrate that even when the surface is neutral, the electrolyte acquires a nonuniform ion density profile near the surface. This profile is asymmetric and leads to an effective charging of the surface. We furthermore show that the induced charge is modulated by the local curvature. The effective charge is opposite in sign to the multivalent ions and is larger in concave regions of the surface.

Investigation of impingement surface geometry effects on heat transfer in a laminar confined impinging slot jet

We investigated the laminar heat transfer characteristics of a milli-scale confined slot jet impinging on concave and convex surfaces at a uniform wall temperature. The flow at the nozzle exit had a fully developed velocity profile. The effects of Reynolds number, dimensionless nozzle-to-surface distance, and target surface geometry on heat transfer were investigated. The results revealed that the axial distributions of local Nusselt numbers exhibited a peak at the stagnation point and decreased monotonically in the wall jet region for all values of Re and H/B tested. The local Nusselt numbers for the concave surface were, at maximum, 47% larger than those for the convex surface in the region corresponding to x/B≤2.0. This is due to the larger unsteady lateral distortions and earlier flapping motion of the jet column for the convex surface than for the concave surface, resulting in a larger heat transfer reduction for the convex surface.

Effects of Surface Geometry on the Wenzel‐to‐Cassie Transition of a Water Droplet

The Wenzel (WZ) to Cassie‐Baxter (CB) transition of a water droplet on a periodic array of pillars was investigated theoretically. Treating the WZ to CB transition as a phase transition, an analytical theory was developed previously for the threshold value of the inter‐pillar spacing, ST, below which the WZ to CB transition occurs. Herein, the theory of ST was applied to the square array of rectangular, cylindrical, or ellipsoidal pillars with a range of experimental sizes. The behavior of ST was examined by varying the height and width of the pillars. The theory is shown to agree well with previous experiments. The present analytic expressions of ST can provide guidelines for designing the surface structure forming the CB states of water droplets.