Effect Of Substrate Geometry Research Articles

3D Co-Printing and Substrate Geometry Influence the Differentiation of C2C12 Skeletal Myoblasts.

Cells are influenced by several biomechanical aspects of their microenvironment, such as substrate geometry. According to the literature, substrate geometry influences the behavior of muscle cells; in particular, the curvature feature improves cell proliferation. However, the effect of substrate geometry on the myogenic differentiation process is not clear and needs to be further investigated. Here, we show that the 3D co-printing technique allows the realization of substrates. To test the influence of the co-printing technique on cellular behavior, we realized linear polycaprolactone substrates with channels in which a fibrinogen-based hydrogel loaded with C2C12 cells was deposited. Cell viability and differentiation were investigated up to 21 days in culture. The results suggest that this technology significantly improves the differentiation at 14 days. Therefore, we investigate the substrate geometry influence by comparing three different co-printed geometries-linear, circular, and hybrid structures (linear and circular features combined). Based on our results, all structures exhibit optimal cell viability (>94%), but the linear pattern allows to increase the in vitro cell differentiation, in particular after 14 days of culture. This study proposes an endorsed approach for creating artificial muscles for future skeletal muscle tissue engineering applications.

Effect of substrate geometry and flow condition on the turbulence generation after a monolith

AbstractThis paper reports a study of turbulence generation after a monolith honeycomb. Large eddy simulation is used to analyze the turbulence generated when steady, turbulent, or pulsating flow leaves a monolith channel. Substrates with different cell densities, wall thicknesses, and channel cross‐sectional shapes are investigated. The results show that the magnitude of the turbulence generated depends on the wall thickness and monolith void fraction, though not much on the cell density. For pulsating flow, different frequency of the pulsations produced only slightly different results, however, the amplitude of the pulsations is proportional to the magnitude of the turbulence generated. The outflow of the channels can act as a jet and trigger turbulence along a distance from 10 to 30 channel diameters, significantly affecting the total pressure drop and the inlet conditions for elements in series downstream, such as particulate filters or other substrates.

Thermal modelling for conformal polishing in inductively coupled atmospheric pressure plasma processing

Inductively coupled atmospheric pressure plasma processing (IC-APPP) is a novel polishing technique for silica-based optics to quickly mitigate the surface or subsurface damage due to its high efficiency and low cost. However, theoretically uniform removal of materials is difficult to achieve because of complex thermal effect. In this paper, numerical modelling and experimental study of global temperature field in IC-APPP is presented. First, a transient heat transfer model is established using finite element analysis to study the characteristics of temperature field distribution during the process. Then, the effects of substrate geometry and processing parameters are systematically analyzed. Finally, conformal polishing experiments are carried out to illustrate the correlation between the effectiveness of uniform removal and the temperature field. The surface shape can be maintained well with optimal processing parameters in IC-APPP.

Influence of metal support in-plane symmetry on the corrugation of hexagonal boron nitride and graphene monolayers

Predicting the properties of two-dimensional (2D) materials as graphene and hexagonal boron nitride (h-BN) monolayers after their growth on any given substrate is a major challenge. While the influence of the electron configuration of the atoms of the underlying surface is well-understood, the effect of substrate geometry still remains unclear. The structural properties of h-BN monolayers grown on a rectangularly packed Rh(110) surface were characterized in situ by ultrahigh vacuum scanning tunneling microscopy and were compared to those that this material exhibits when grown on substrates showing different crystallographic orientations. Although the h-BN monolayer grown on Rh(110) was dominated by a unique quasiunidimensional moire pattern, suggesting considerable interface interaction, the moire corrugation was unexpectedly smaller than those reported for strongly interacting interfaces with hexagonal-terminated substrates, owing to differences in the possible binding landscapes at interfaces with differently oriented substrates. Moreover, a rule was derived for predicting how interface corrugation and the existence and extent of subregions within moire supercells containing favorable sites for orbital mixing between h-BN monolayers and their supports depend on substrate symmetry. These general symmetry considerations can be applied to numerous 2D materials, including graphene, thereby enabling the prediction of how substrate choice determines the properties of these materials. Furthermore, they could also provide new routes for tuning 2D material properties and for developing nanotemplates showing different geometries for growing adsorbate superlattices.

Li-insertion/extraction properties of three-dimensional Sn electrode prepared by facile electrodeposition method

Toward the realization of reliable Li-ion batteries with high performance and safety, component materials such as those of the current collector and negative electrode require further innovation. Sn, one of the most promising negative-electrode materials, can be electrochemically fixed on a substrate without any binder or conductive additive. However, the pulverization of Sn-plated films on substrates caused by large volume changes during Li–Sn reactions is the main reason hindering the practical application of Sn-plated electrodes. In the present study, we developed an electrodeposited three-dimensional (3D) Cu substrate applied to underlayer of the electrode. The effect of substrate geometry on the charge–discharge performance of the Sn electrode was investigated. The 3D-Cu/Sn electrode exhibited superior cycling performance with a reversible capacity of 470 mA h g−1 even at the 300th cycle, whereas the Sn-plated electrode prepared on a typical flat Cu substrate showed a capacity of only 20 mA h g−1. The results demonstrated that the 3D structure played a key role in accommodating volumetric changes in the Sn to suppress electrode disintegration. The developed 3D-Cu substrate will be significantly useful as a current collector for alloy-based active materials.

The effect of substrate geometry and surface orientation on the film structure of DLC deposited using PECVD

Potential applications of diamond-like carbon (DLC) coatings range from precision tools and biomedical implants to micro mechanical devices and engine components. Where uniform coatings are required on substrates with complex geometries, plasma enhanced chemical vapour deposition (PECVD) is often a preferred deposition method. As a non-line of sight process, the geometry of the substrate is often considered negligible. For this reason analysis of PECVD coatings, such as amorphous carbon, has mostly been concerned with reactor deposition variables, such as bias voltage, pressure and gas ratios. Samples are therefore usually prepared and positioned to minimise the influence of other variables. By depositing nominally similar DLC films on silicon samples positioned horizontally and vertically on the reactor cathode plate it was possible to examine the variations in the coating characteristics and mechanical properties that occur due to the geometry of the substrate being coated. Topographic measurements and analysis of bonding structures revealed significant heterogeneity in the coatings. Electron microscopy showed variation in surface structure as well as thickness disparities of up to 50% in the vertical sample. Atomic force microscopy showed roughness, Ra, varied from 0.37nm to 15.4nm between samples. Raman spectroscopy highlighted variations in the sp2/sp3 bonding ratios whilst micro wear tests demonstrated how these variations reduce the critical load performance. These effects are explained in terms of the deposition mechanisms involved and are related to variation in deposition species and geometrical field enhancements within the deposition chamber. Improved understanding of these local variations will aid in the optimisation of coatings for complex substrate geometries.

Effects of ACF Bonding Parameters on ACF Joint Characteristics for High-Speed Bonding Using Ultrasonic Bonding Method

As the use of anisotropic conductive films (ACFs) in flex-on-board bonding has increased recently, the need for high-speed bonding for higher productivity has developed. For high-speed bonding, a fast-curable acrylic resin has been used instead of an epoxy resin, and ultrasonic (US) bonding is introduced to allow for short bonding time at high bonding temperatures. However, it is possible for fast curable acrylic ACFs at 250°C to be fully cured before the resins flow out sufficiently between the electrodes. In such cases, the ACF joints could show poor electrical characteristics due to there being no conductive particle capture. Therefore, in this paper, in order to understand important factors for high-speed bonding, the effects of the bonding parameters, substrate geometry, and ACF material property on the ACF joint characteristics, such as resin flow and joint resistance, are investigated using acrylic-based ACFs and US bonding. The fast-curable acrylic resin is fully cured at a bonding temperature of 250°C within 1 s. However, the ACF joints bonded at 250°C show joint gaps larger than the diameter of conductive particles, i.e., 8 μm, due to insufficient resin flow and open failure due to no particle capture. As the bonding pressure increases from 2 to 4 MPa, the ACF joint gap at 250°C is smaller than the conductive particle size, and the joint resistance reaches about 20 mΩ within 7 s when using 3-mm-long electrodes and a high-viscosity resin. However, in order to use a shorter bonding time and the common bonding pressure of 3 MPa, the effects of substrate geometry and resin property on ACF joint characteristics are investigated. As the electrode length of the substrates are decreased from 3 to 1 mm, the ACF joints show stable ACF joint gaps and joint resistance at 3 MPa despite the bonding temperature of 250°C applied within 1 s. In terms of the ACF resin properties, when a resin with low minimum viscosity is used, the ACF joint gaps are smaller than the diameter of the conductive particles. Furthermore, the joint resistance of low-minimum-viscosity ACF is more stable than that of the ACF joints bonded with the high-minimum-viscosity resin at 250°C within 1 s, even though a 3-mm-long electrode is used. These results indicate that the substrate geometry of the printed circuit board and the ACF resin viscosity are significant factors for high-speed bonding to obtain stable ACF joints at a high bonding temperature of 250°C within 1 s.

Effects of Substrate Geometry on Active Site Engagement Govern the Preferential Action of Prothrombinase on One of the Two Cleavage Sites in Prothrombin.

Prothrombin activation by prothrombinase is a paradigm for proteolytic activation reactions wherein product is produced following cleavage at more than one site in the substrate. Prothrombin is tethered to prothrombinase through exosite binding and is preferentially cleaved at R320. Subsequent cleavage at R271, in the resulting intermediate, yields thrombin. Selective presentation of the R320 site for active site docking and cleavage likely arises from the combined constraints of exosite-dependent tethering and the position of the cleavage site within the polypeptide sequence of prothrombin. A series of recombinant variants with substitutions in residues at and preceding the R320 cleavage site have been employed to investigate the role of geometric effects in enforcing the selective action of prothrombinase on this site in prothrombin. Replacement of the sequence D-G-R320 in wild type prothrombin (IIWT) with D-R-R320 (IIRR) or R-G-R320 (IIRGR) yielded substrate species that were indistinguishable from IIWT in their conversion to thrombin by prothrombinase. Equivalent progress curves for bands produced following initial cleavage at R320 followed by cleavage at R271 were established by SDS-PAGE for all three substrate species. Specific and quantitative cleavage at R320 rather than at R319 or R318 in the initial cleavage reaction was established by N-terminal sequencing. Substitution of R320 in IIWT with Q (IIQ320) rendered this site uncleavable and led to very slow cleavage only at the R271 site. These findings support a role for geometric constraints in precisely positioning R320 in II for preferential cleavage. Surprisingly, substitution of flanking sequences in IIQ320 to yield R-G-R-Q320 (II-1Shift) and R-G-R-G-Q320 (II-2Shift) yielded variants that were cleaved in a manner similar to IIWT. For either variant, the rate of prothrombin consumption was within 2-fold that observed with IIWT and could be quantitatively explained by cleavage at R319 (II-1Shift) or R318 (II-2Shift) determined by N-terminal sequencing. Thus, provided position 320 cannot be cleaved, geometric effects are not absolute and flexibility can be tolerated in the position of the scissile bond presented for preferential active site engagement. Variants containing RGR substitutions further shifted to the -3 and -4 positions were instead cleaved ~30-fold slower but at R271 similar to IIQ320. Dramatic loss of cleavage seen with these further N-terminal shifts establishes the limits of possible flexibility in substrate presentation to the active site. Further insights were provided by binding studies examining the ability of these variants to engage and displace 4-aminobenzamidine from the active site of the catalyst within prothrombinase assembled with XaA195. R320 in prothrombin engaged the active site with an equilibrium constant that was ~600-fold more favorable than R271. The register shift variants showed systematic decreases in their affinities for engaging the active site. Loss of cleavage at R316 in II-4Shift correlated with a markedly reduced affinity for active site docking. Thus, geometric constraints, arising from exosite binding, play an essential role in affecting the thermodynamics of active docking by prothrombin. However, very significant decreases in the equilibrium constant for active site docking of an otherwise highly favorable interaction are evident as only minor changes in rate. Large changes in rate and qualitative differences in cleavage pathway result when the equilibrium constant for cleavage at R316 in II-4Shift approaches that for R271. Our findings provide an explanation for how the action of prothrombinase on prothrombin is regulated by both precise substrate geometry and competition for active site docking between different sites within the substrate. The unexpected relationship between thermodynamics and rate reveals new mechanistic insights into the ability of prothrombinase to discriminate between sites within prothrombin and how thrombin formation is regulated.

Effect of substrate geometry on liquid-crystal-mediated nanocylinder-substrate interactions

Using classical density functional theory, the liquid crystal (LC)-mediated interaction between a cylindrical nanoparticle and a structured substrate is studied. The surface is structured by cutting a rectangular groove into the surface. In the absence of the nanoparticle, a range of defect structures is formed in the vicinity of the groove. By varying the groove width and depth, the LC-mediated interaction changes from repulsive to attractive. This interaction is strongest when the groove is of comparable size to the nanoparticle. For narrow grooves the nanoparticle is attracted to the center of the groove, while for wider grooves there is a free energy minimum near the sidewalls.

Effect of Substrate Geometry on Polymer Molecular Weight and Polydispersity during Surface-Initiated Polymerization

Poly(methyl methacrylate) (PMMA) anchored chains were grown on porous silicon (p-Si) and anodically etched aluminum oxide (AAO) substrates via surface-initiated atom transfer radical polymerization (ATRP). Using hydrogen fluoride, the chains could be cleaved from the substrates, as evidenced by infrared spectroscopy. The molecular weights and molecular weight distributions of PMMA could be analyzed directly on these substrates (after cleaving the chains from the support) using direct ionization mass spectrometry (DIOS-MS) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). Two principal conclusions were drawn from the study. First, matrix-free DIOS-MS was effective at direct analysis of the polymers up to a molecular weight of ≈6 kDa; the signal-to-noise ratio for heavier polymer chains diminished rapidly. Second, under the same polymerization conditions, PMMA grown on both p-Si and AAO substrates had a much lower molecular weight and a broader molecular weight distribution than that grown in solution. Confinement effects imposed by the pores during the polymerization are proposed as the likely mechanism for the reduced growth rates and more polydisperse chains.

Effect of substrate geometry on the deposition rate in chemical vapor deposition

Advances in technology demand high volume production of semiconductors. Chemical vapor deposition (CVD) is a standard technique for producing semiconductors when quality and cost matter the most. The substrate geometry has a large effect on the deposition rate, which in turn plays a critical role in assessing the performance of the CVD reactor. Unfortunately, in the open literature, not much attention has been paid to the substrate geometry. Instead, standard geometries and those produced via heuristics have been employed. This paper proposes a deposition model with a flexible substrate geometry. Using this model, the effect of various substrate geometries on the deposition rate of zinc sulfide is assessed. The results indicate that certain substrate geometries change the flow patterns, create recirculation, and increase the deposition rate.

Effects of substrate geometry on growth cone behavior and axon branching

At the leading edge of a growing axon, the growth cone determines the path the axon takes and also plays a role in the formation of branches, decisions that are regulated by a complex array of chemical signals. Here, we used microfabrication technology to determine whether differences in substrate geometry, independent of changes in substrate chemistry, can modulate growth cone motility and branching, by patterning a polylysine grid of narrow (2 or 5 microm wide) intersecting lines. The shape of the intersections varied from circular nodes 15 microm in diameter to simple crossed lines (nodeless intersections). Time-lapse recordings of cultured hippocampal neurons showed that simple variations in substrate geometry changed growth cone shape, and altered the rate of growth and the probability of branching. When crossing onto a node intersection the growth cone paused, often for hours, and microtubules appeared to defasciculate. Once beyond the node, filopodia and lamellipodia persisted at that site, sometimes forming a collateral branch. At nodeless intersections, the growth cone passed through with minimal hesitation, often becoming divided into separate areas of motility that led to the growth of separate branches. When several lines intersected at a common point, growth cones sometimes split into several subdivisions, resulting in the emergence of as many as five branches. Such experiments revealed an intrinsic preference for branches to form at angles less than 90 degrees . These data show that simple changes in the geometry of a chemically homogeneous substrate are detected by the growth cone and can regulate axonal growth and the formation of branches.

Substrate porosity enhances chondrocyte attachment, spreading, and cartilage tissue formation in vitro

Tissue engineering is being explored as a new approach to treat damaged cartilage. As the biomaterial used may influence tissue formation, the effects of substrate geometry on chondrocyte behavior in vitro were examined. Articular chondrocytes were isolated and cultured on the surface of smooth, rough, porous-coated, and fully porous Ti-6Al-4V substrates. The percentage of chondrocytes that attached to each substrate at 24 h was determined. After 24 and 72 h, chondrocytes were visualized by scanning electron microscopy and cell areas were measured. Collagen and proteoglycan accumulation within the first 24 h was determined by incorporation with [3H]-proline and [35S]-SO4, respectively. Chondrocyte attachment as well as matrix accumulation was enhanced as substrate surface area increased. Cell areas on the fully porous substrate were over four times greater than on any other substrate by 72 h in culture. After 8 weeks in culture, a continuous layer of cartilaginous tissue formed only on the surface of the fully porous substrate. This suggests that fully porous Ti-6Al-4V substrates provide the conditions that favor cartilage tissue formation by influencing cell attachment and extent of cell spreading. Understanding how substrate porosity influences chondrocyte behavior may help identify methods to further enhance cartilage tissue formation in vitro.

Micromachined wide-band lithium-niobate electrooptic Modulators

We present our detailed study of a micromachined substrate approach for a wide-band lithium-niobate modulator and other ultra-wideband RF interconnection applications. Resonant substrate mode coupling often results in large RF loss that affects the frequency performance in LiNbO/sub 3/ modulators. Using the micromachining approach, we demonstrated significantly reduced resonant mode coupling loss in LiNbO/sub 3/ modulator electrodes. In this paper, the effects of substrate geometry and material combination on microwave transmission are experimentally investigated. Our investigation showed that the RF launch of the coplanar-waveguide circuit is a major contributor to the resonant mode coupling. Micromachining the launch area allows us not only to suppress resonant couplings, but also to retain substrate mechanical strength for high-yield production. Two micromachined modulator die configurations were proposed and experimentally demonstrated.

Enantioselective Hydrogenation of (E)‐ and (Z)‐Isomeric Ethyl 3‐Acetamidobutenoates with Rh‐Bisphosphine Complexes: Effects of Substrate Geometry and Solvents on Reaction Rates and Catalyst Reusability.

Enantiopure β-amino acids are crucial structural features of numerous biologically active natural products as well as important building blocks for the synthesis of β-peptides and β-lactam antibiotics. Numbers of stoichiometric chiral auxilaries and catalytic methods have been developed to make chiral β-amino acids. One of the most promising processes for the convenient preparation of chiral β-amino acids on large scale is the asymmetric hydrogenation of suitable unsaturated precursors such as β-acetamido acrylates with Rh(I) catalysts bearing chiral phosphine ligands. The requisite prochiral substrates are easily available by treatment of β-keto carboxylates with NH4OAc and subsequent acylation. However, while literally thousands of reports are concerned with the Rh-catalyzed enantioselective hydrogenation of related prochiral α-acetamido acrylates, only a few devoted to the hydrogenation of β-analogues as substrates exist. The main reason for this is probably different behavior in the asymmetric hydrogenation, which had for a long time been attributed to particular substrates such as the isomeric ethyl 3-acetoamido butenoates (E)-1 and (Z)-1.

Enantioselective Hydrogenation of (E)-and (Z)-Isomeric Ethyl 3-Acetamidobutenoates with Rh-Bisphosphine Complexes: Effects of Substrate Geometry and Solvents on Reaction Rates and Catalyst Reusability

Enantiopure β-amino acids are crucial structural features of numerous biologically active natural products as well as important building blocks for the synthesis of β-peptides and β-lactam antibiotics. Numbers of stoichiometric chiral auxilaries and catalytic methods have been developed to make chiral β-amino acids. One of the most promising processes for the convenient preparation of chiral β-amino acids on large scale is the asymmetric hydrogenation of suitable unsaturated precursors such as β-acetamido acrylates with Rh(I) catalysts bearing chiral phosphine ligands. The requisite prochiral substrates are easily available by treatment of β-keto carboxylates with NH4OAc and subsequent acylation. However, while literally thousands of reports are concerned with the Rh-catalyzed enantioselective hydrogenation of related prochiral α-acetamido acrylates, only a few devoted to the hydrogenation of β-analogues as substrates exist. The main reason for this is probably different behavior in the asymmetric hydrogenation, which had for a long time been attributed to particular substrates such as the isomeric ethyl 3-acetoamido butenoates (E)-1 and (Z)-1.

Monte Carlo simulations on the effect of substrate geometry on adsorption and compression.

Canonical Monte Carlo simulations were used to study the adsorption and compression of fluid layers on model substrates with cubic, (111) fcc, and graphite geometries. The effect of the relative size of the fluid and substrate molecules on adsorption was considered for strong molecule-surface interactions. In the case of monolayer formation, it was found that the surface geometry and the size of the adsorbate molecules had a significant effect on the structure of the adsorbed layer. These structures varied from well-ordered, commensurate layers to liquid-like structures. Lateral compression was observed for certain fluid to substrate molecule sizes. For the interactions studied in this work, it was found that maximum lateral compression occurred on the cubic surface when adsorbate molecules had a diameter approximately 15% larger than the substrate diameter. In the case of multilayer formation, it was found that second and higher adsorbed layers could compress into the adsorbed layers below them. For cubic substrates, the interlayer compression was predicted analytically with reasonable accuracy, with maximum interlayer compression found for fluid diameters approximately 90% the size of substrate molecule diameters.

Static SIMS studies of adsorbate structure III. CO on Pd(100)

The relationship between secondary ion emission and adsorbate structure is further investigated by an in-situ comparison of experimental static SIMS and High Resolution Electron Energy Loss Spectroscopy (HREELS) data for CO adsorption on Pd(100). The study permits a clarification of the SSIMS fragmentation pattern for a doubly-bridged CO overlayer at low coverages. Coverage dependent changes in the relative amounts of linear and bridged CO bands from HREELS correlate closely with the proportion of PdCO + and Pd 2CO + ions from SSIMS. The consistency of these results with earlier SSIMS studies on a variety of metal surfaces is discussed along with the effects of substrate geometry, adsorbate binding energy and adsorbate-adsorbate interactions on secondary ion emission.