Nanoscale Surface Research Articles

LFP via Nanoscale Surface Reforming with a Tiny Minimal Amount of Conductivity-Enhancing Material.

LiFePO4 (LFP) typically requires a conductive additive to improve its low ion and electron conductivity. In this study, we achieved significant enhancements in Li+ and electron mobility by applying a minimal amount of conductive material through a new coating process. The coin cell demonstrated an excellent capacity of 157.57 mA h g-1 at 0.1 C/25 °C, while the pouch cell exhibited excellent long-term cycling stability, maintaining 99.33% capacity after 150 cycles at 1 C/45 °C. Compared to pristine LFP, the rate capacities increased by 30%, reaching 130.9 mA h g-1 at 3 C. After 100 cycles, the RCT resistance value decreased by 10% compared to pristine. The uniform coating layer not only improved electronic conductivity but also enhanced the rate performance. DCIR testing of the pouch cell showed a 17.7% reduction in resistance values compared to that of pristine LFP with increasing cycles. This new coating method, using a very small amount of conductive material, forms a uniform coating layer that optimizes electrochemical performance while maintaining the economic benefits of the LFP cathode material.

A Concise Review on Magnetic Nanoparticles: Their Properties, Types, Synthetic Methods, and Current Trending Applications

: In recent years, there has been significant research on developing magnetic nanoparticles (MNPs) with multifunctional characteristics. This review focuses on the properties and various types of MNPs, methods of their synthesis, and biomedical, clinical, and other applications. These syntheses of MNPs were achieved by various methods, like precipitation, thermal, pyrolysis, vapor deposition, and sonochemical. MNPs are nano-sized materials with diameters ranging from 1 to 100 nm. The MNPs have been used for various applications in biomedical, cancer theranostic, imaging, drug delivery, biosensing, environment, and agriculture. MNPs have been extensively researched for molecular diagnosis, treatment, and therapeutic outcome monitoring in a range of illnesses. They are perfect for biological applications, including cancer therapy, thrombolysis, and molecular imaging, because of their nanoscale size, surface area, and absence of side effects. In particular, MNPs can be used to conjugate chemotherapeutic medicines (or) target ligands/proteins, making them beneficial for drug delivery. However, up until that time, some ongoing issues and developments in MNPs include toxicity and biocompatibility, targeting accuracy, regulation and safety, clinical translation, hyperthermia therapy, immunomodulatory effects, multifunctionality, and nanoparticle aggregation.

Nanoscale surface modifications of diamond-like carbon films by in situ laser irradiation in atomic force microscope

Nanoscale surface modifications of diamond-like carbon films by in situ laser irradiation in atomic force microscope

Investigating the interplay between environmental conditioning and nanotopographical cueing on the response of human MG63 osteoblastic cells to titanium nanotubes.

Titanium nanotubular surfaces have been extensively studied for their potential use in biomedical implants due to their ability to promote relevant phenomena associated with osseointegration, among other functions. However, despite the large body of literature on the subject, potential synergistic/antagonistic effects resulting from the combined influence of environmental variables and nanotopographical cues remain poorly investigated. Specifically, it is still unclear whether the nanotube-induced variations in cellular activity are preserved across different biochemical contexts. To bridge this gap, this study systematically evaluates the combined influence of nanotopographical cues and environmental factors on human MG63 osteoblastic cells. To this end, we capitalized on a triphasic anodization protocol to create nanostructured surfaces characterized by an average nanotube inner diameter of 25 nm (NT1) and 82 nm (NT2), as well as a two-tiered honeycomb (HC) architecture. A variable glucose content was chosen as the environmental modifier due to its well-known ability to affect specific functions of MG63 cells. Alkaline phosphatase (ALP), viability/metabolic activity and proliferation were quantified to identify the suitable preconditioning window required for dictating a change in behaviour without significantly damaging cells. Successively, a combination of immunofluorescence, colorimetric assays, live cell imaging and western blots quantified viability/metabolic activity and cell proliferation, migration and differentiation as a function of the combined effects exerted by the nanostructured substrates and the glucose content. To achieve a thorough understanding of MG63 cell adaptation and response, a comparative analysis table that includes and systematically cross-analyzes all variables from this study was used for interpretation and discussion of the results. Taken together, we have demonstrated that all surfaces mitigate the negative effects of high glucose. However, nanotubular topographies, particularly NT2, elicit a more beneficial outcome in high glucose in respect to untreated titanium. In addition, while NT1 surfaces are associated with the most stable cellular response across varying glucose levels, the NT2 and HC substrates exhibit the strongest enhancement of cell migration, viability/metabolism and differentiation. Moreover, shorter-term processes such as adhesion and proliferation are favored on untreated titanium, while anodized samples support later-term events. Lastly, the role of anodized surfaces is dominant over the effects of environmental glucose, underscoring the importance of carefully considering nanoscale surface features in the design and development of cell-instructive titanium surfaces.

Investigating the Role of Hydrofluoric Acid Concentration in Tailoring the Morphology and Enhancing the Photonic Properties of Nanoporous Silicon Wafers

At This research used an electrochemical method to convert bulk silicon wafers into porous silicon (PS). The wafers, chosen with a (100) orientation and (8-3) Ω.cm resistivity, the time of etching was 25 min and the current density of etching 25 mA/cm². It was carried out nanoscale surface morphology on the PS substrates by modify the hydrofluoric acid (HF) to ethanol ratio (1:3, 1:6, and 1:9). In the compositional aspect it was used (AFM) to show that higher hydrofluoric: ethanol concentricity augment the porosity and particles density of wafer surface. subsequently, the etching depth given changeful directions with changing HF concentration, and the nanodimensions were clearly showed within the porous silicon layers were they produced. The anatomy of Photo luminescence (PL) specified that the energy gap E.G. was widened with increasing the porosity of wafers and the density of particles, as seem by a shifting to the blue in the PL spectrum

Surfactants and polymers on nanoscale surfaces: the interface landscape of plasmonic nanostars

Surfactants and polymers are widely used as shape-directing agents in the synthesis of colloidal plasmonic nanostars, consequently acting as non-negligible players in all those high-performance applications in which processes occur at their interfaces, such as surface enhanced Raman spectroscopy (SERS) and plasmon-induced catalysis. Therefore, elucidating surfactant- and polymer-metal interactions is critical to rationally improving the performance of nanostars in the same range of applications. In this mini-review, we present traditional and state-of-the-art characterization methods that can be used to investigate the ligand-surface interactions that occur on mature nanostars. Due to historically based limitations in the availability of nanostar-specific literature, we utilize nanorod literature as a starting point to critically infer which analytical approaches can be seamlessly translated to nanostar systems, and which instead need to be adapted to intercept the peculiar needs imposed by the branched nanoparticle morphology.

Impact of Sub-Nanoscale Surface Topography on Contact Line Profile: Insights from Coherence Scanning Interferometry.

Despite the importance of the effect of subnanoscale roughness on contact line behavior, it is difficult to directly observe the local behavior of contact lines at the micro- and nanoscale, leaving significant gaps in our current understanding. In this research, we investigate contact line motions and their relationship with nanoscale surface topography using coherence scanning interferometry. Our experiments were conducted on the substrates with different wettability without changing nanoscale surface topography. Titanium dioxide was used as a substrate, the wettability of which was varied under UV-light irradiation. A ridge-like structure with a height of approximately 1 nm was observed to cause contact line deformation toward the droplet side, regardless of the direction of the contact line motion. This was explained in terms of an imbalance in the local capillary pressure at the nanoscale contact line. We also found that the deformation becomes larger on the more hydrophilic surface, which was rationalized by theoretical prediction based on analysis of the work done by the force acting on the contact line and the change in surface free energy associated with the deformation of the liquid/gas interface. Furthermore, it was revealed by contact angle measurements that the maximum pinning forces on a hydrophilic surface were less than half of those on a hydrophobic surface. We attributed the weak pinning force on the hydrophilic surface to cascading depinning, where the initial depinning event triggers a chain reaction of subsequent depinning events, driven by the conversion of excess surface energy to kinetic energy. Our experimental works provide new insights of the relationship between the subnanoscale surface roughness and macroscopic contact line motion.

Mg-Doped Carbonated Hydroxyapatite and Tricalcium Phosphate Anodized Coatings on Titanium Implant Alloys

The rising demand for dental and orthopedic implants and their frequent aseptic loosening failure mode necessitate the drive to continue modifying implant surfaces to improve osseointegration outcomes. Plasma-sprayed hydroxyapatite coatings are widely used but are prone to delamination. This study involves a single-step anodization process utilizing a novel electrolyte to produce Mg-doped carbonated hydroxyapatite and tricalcium phosphate-containing coatings on four titanium alloy surfaces. XRD confirmed hydroxyapatite and tricalcium phosphate formation, with FTIR examination revealing carbonate substitutions indicative of bone-like apatite formation in each oxide. SEM analyses revealed micro- and nano-scaled surface features on each oxide. SEM and EDS analyses of the oxide coating cross-sections showed each group to be bi-layered with an inner titanium dioxide-rich layer and an outer hydroxyapatite/tricalcium phosphate-rich layer. The oxide layer adhesion quality was shown to be good on CPTi, TAV, and TiMo α + β implant alloy surfaces. Unfortunately, the anodization process also resulted in an undesirable and embrittling omega phase at the substrate–oxide interface due to the migration of molybdenum into the inner oxide. Nonetheless, the anodized coatings on the CPTi and TAV alloy substrates, which are the most widely used titanium alloys for implant applications, show much potential for improving future patient outcomes.

Double-Oxidant-Induced Slurry Reaction Mechanism and Performance on Chemical Mechanical Polishing of 4H-SiC (0001) Wafer.

Single-oxidant slurries are prevalently utilized in chemical and mechanical polishing (CMP) of 4H-SiC crystal. Nevertheless, it is a challenge to achieve a high material removal rate (MRR) and surface quality using single oxidant slurries to meet the needs of global planarization and damage-free nanoscale surface processing of SiC wafers. To solve this challenge, a novel method is proposed for SiC CMP processing using the double oxidant slurry. This slurry mainly consists of alumina (Al2O3) abrasive particles, potassium permanganate (KMnO4), potassium persulfate (K2S2O8), and deionized water. Post CMP, MRR is 1045 nm/h calculated by scratch method, and surface roughness Sa is 0.33 nm measured by 3D optical surface morphometer, with the measurement area of 868 μm × 868 μm. Both the MRR and Sa are far better than those under the single oxidant slurry condition. CMP mechanism with double-oxidant slurry conditions is elucidated by energy dispersive spectrometer and X-ray photoelectron spectrometer. Initially, the Si-C bond on the SiC wafer surface was oxidized by KMnO4, then MnO2 as the reduction product of KMnO4 can also catalyze the S2O82- to further oxidize SiC wafer surface, and eventually the oxidation layers were removed by mechanical action of nano-Al2O3 abrasive particles during CMP processing. These findings offer a pioneering approach and novel perspectives to achieve a higher MRR of 4H-SiC CMP, with potential implications for the application in high-performance SiC devices.

Wavelength optimization of fine optical surface defect detection based on FDTD

Due to the similar order of magnitude of the defect size and the detection wavelength, when detecting micro-/nano-scale defects on the surface of a fine optical component, the intense modulation of the optical field poses challenges in correlating imaging widths of defects with actual widths. A dark-field scattering imaging (DFSI) model, based on the finite difference time domain (FDTD) method, is established to study the imaging for triangular and circular section defects and investigate the influence of wavelength on defect width detection. Simulated results indicate that a shorter wavelength of the light source in a DFSI detection system leads to a larger mapping range between the imaging width and the actual defect width, which makes calibration less difficult. A DFSI detection system for micro-/nano-scale surface defects on optical components is built to test defects with rectangular cross-sections on a calibration board. The defect widths estimated from the experimental and simulated results are in good agreement, with a root-mean-square error (RMSE) of 0.11 µm.

Optimal submicron roughness for balancing degradation behavior, immune modulation, and microbial adhesion on zinc-based barrier membranes.

Metallic zinc (Zn) has been demonstrated to be a promising alternative to barrier membrane materials for guided bone regeneration. Surface roughness significantly affects the properties of degradable Zn-based metals, especially within the Janus micro-environments of tissue regeneration. However, the effects of optimal surface roughness on Zn remain unknown. In this study, pure Zn surfaces were fabricated with three roughness scales: nano (Sa<0.1μm), submicron (Sa: 0.5-1.0μm), and micron (Sa>1.0μm). Submicron-scale pure Zn exhibited a moderate degradation rate in simulated body fluids, and no deep corrosion pits appeared on the surface. By contrast, the degradation rate of nano-surface pure Zn decreased significantly, while localized corrosion tended to appear on micron surfaces. In addition, the degradation rate of Zn with different roughness was overall accelerated in artificial saliva, accompanied by varying degradation morphologies. Co-culturing with submicron samples inhibited macrophage polarization to the M1 phenotype. Nano-scale surfaces promoted macrophage polarization towards the M1 phenotype and exhibited significantly reduced antibacterial rates compared to rougher surfaces. These findings demonstrate that submicron-scale pure Zn could be an optimal choice for barrier membrane surfaces.

Relationships between the Surface Hydrophilicity of a Bismuth Electrode and the Product Selectivity of Electrocatalytic CO2 Reduction.

Two types of bismuth films (micro-Bi and nano-Bi) were prepared, and their electrocatalytic behavior was studied in terms of reduction current and product selectivity in a potential range of -0.776 to -1.376 V vs RHE. CO2 and H2O molecules competed with each other for reduction on the surfaces of both types of films, and formate and H2 were the respective major products of reductive reactions. Under the same conditions, nano-Bi exhibited lower selectivity for formate and higher selectivity for H2 compared to the respective micro-Bi cases with bismuth films of similar thickness. This can be attributed to the higher hydrophilicity of bismuth film surfaces of nano-Bi due to surface nanoscale roughness and lower surface-carbon content compared with those of micro-Bi. Our results suggest a new strategy for controlling the selectivity of electrocatalytic CO2 reduction under aqueous electrolytes through the use of surface engineering.

(Digital Presentation) Investigation of Electrochemical Cu Deposition on Nanoscale Sculptured Al Surfaces by FFT-Impedance Spectroscopy

Fast Fourier transform impedance spectroscopy (FFT-IS) is a well established technique to study in-situ e.g. the involved electrochemical dissolution and deposition phenomena at the electrolyte / substrate interface [1,2]. In contrast to conventional electrochemical impedance spectroscopy (EIS), FFT-IS allows for the simultaneous application of all probing frequencies at the same and thus highly time-resolved investigations of the ongoing electrochemical phenomena.FFT-IS has been employed to study the electrochemical deposition process of Cu on nano-scale-sculptured Al during the entire deposition process, since such a nanoscale-sculptured Al surface exhibits a high multitude of different-sized cubic undercut structures that must be enclosed and overgrown by Cu to generate a good mechanically interconnection between Al and Cu.The analysis of the IS data reveals that the deposition process can be modeled by an equivalent circuit consisting of a series resistance Rs and three Voigt-Kelvin elements, all connected in series to each other. The first one is a capacitor Cp1 and a resistor Rp1, followed by a Warburg element Zw and a resistor Rp2, and finally by another capacitor Cp3 and resistor Rp3 as last Voigt-Kelvin element, see Fig. 1.The time resolved analysis of the above described parameters reveals that three major processes are involved in the Cu deposition process that occur locally in series on the surface, but parallel in time. Based on the time evolution of these fit parameters the Cu deposition process can be sub-divided into three stages that were identified by investigating the nanoscale sculptured Al surface during Cu deposition at characteristic points of each stage by scanning electron microscopy. The knowledge and understanding of these processes allows tailoring and fine-tuning the Cu electrolyte and the deposition process itself.Fig. 1 Nyquist plot of recorded impedance data (boxes) and corresponding fit data (solid line) of the used equivalent circuit model[1] M. Leisner, J. Carstensen, and H. Föll, J. Electroanal. Chem. 615(2), 124 (2008). Figure 1

(Digital Presentation) Nanoscale Sculpturing of Al and Al Alloys for Heterogeneous Al-Cu Joints

Heterogeneous Al-Cu joints are nowadays generated in a huge variety of different techniques depending on the intended application, such as corrosion protection of Al components, electric connections with improved interfaces, or even lightweight current collectors for batteries. Four major techniques are commonly used that can be further subdivided into cladding (including roll cladding, thermo-compression bonding, friction welding etc.), vapor deposition (including PVD, CVD etc.), thermal spraying and chemical plating (including electroless and electrochemical plating). Each of the methods offers certain advantages and disadvantages for the formation of Al-Cu joints. Typically observed disadvantages are the formation of intermetallic Al-Cu compounds (IMC), higher electric resistivity, a rather low mechanical strength under static or cyclic mechanical load conditions.The present work follows the electrochemical route to form Al-Cu joints utilizing nanoscale sculpturing of the Al substrate [1] as a starting point to overcome these above described typically observed disadvantages of Al-Cu joints. The resulting nanoscale sculptured Al-Cu joint is intensively characterized with respect to its structural (see Fig. 1), chemical and mechanical properties. It was found that such Al-Cu joints offer a high mechanical load bearing capability because of the interlocking zone between Al and Cu offering a gradual change, so that an optimum stress transfer can occur without the risk of a stress pile-up at the interface between both metals.Furthermore, no intermetallic Al-Cu phases grow at the interface between Al and Cu during deposition which could mechanically weaken the joint due to embrittlement, especially under cyclic loading conditions. Another advantage is the absence of Al-Cu intermetallics in the joint, being of great importance if high current or high voltage applications are intended.Fig 1: Nanoscale sculptured Al surface with cubic interlocking surface structures in cross-section (left) and cross-sectional view on Al-Cu joint after electrochemical Cu deposition on nanoscale sculptured Al surface (right).[1] M. Baytekin-Gerngross, M.D. Gerngross, J. Carstensen, and R. Adelung, Nanoscale Horizon 1(6), 467 (2016). Figure 1

Optimization of hierarchical textured PDMS film with wide-angle broadband anti-reflection for light trapping in solar cells

We developed a hierarchical random pyramid (HRP)-polydimethylsiloxane (PDMS) film as an antireflective layer for metal halide perovskite solar cells (PSCs). To create the HRP structure on the PDMS surface, we first patterned the Si surface using alkaline etching and Ag-assisted chemical etching (Ag-ACE) and then transferred the pattern onto the PDMS surface. The resulting PDMS exhibited hierarchical structures of inverted micro-pyramids with nano-scale surface features. The optical performance of the textured PDMS film was observed across the entire wavelength range of visible light (λ = 300–800 nm), attributed to the enhanced light-trapping effect resulting from the increased fractal dimensions (Df) of the hierarchical nanostructures. Under optimal conditions, an average reflectance of 3.13 % was observed, along with a 14 % improvement in transmittance compared to that of the reference. Finite difference time-domain simulations were used to investigate the origins of these optical enhancements, conclusively linking them to the HRP structures. The optimized structures also showed superhydrophobicity with a contact angle (θCA) of approximately 155.2°. When applied to PSCs (MAPbI3), the optimized textured PDMS film led to a 12 % increase in short-circuit current density (Jsc) from approximately 23.1 to 25.98 mA/cm2. Furthermore, the power conversion efficiency of the MAPbI3 p-i-n structured devices was enhanced by 18.21 %, representing a 13 % improvement. Our results confirm that the HRP-PDMS film enhances superhydrophobicity and light trapping, while mitigating the transmittance loss due to changes in the incident angle. This study suggests potential strategies for overcoming the limitations of light absorption in solar cell applications.

Multimodal Imaging Unveils the Impact of Nanotopography on Cellular Metabolic Activities.

Nanoscale surface topography is an effective approach in modulating cell-material interactions, significantly impacting cellular and nuclear morphologies, as well as their functionality. However, the adaptive changes in cellular metabolism induced by the mechanical and geometrical microenvironment of the nanotopography remain poorly understood. In this study, we investigated the metabolic activities in cells cultured on engineered nanopillar substrates by using a label-free multimodal optical imaging platform. This multimodal imaging platform, integrating two photon fluorescence (TPF) and stimulated Raman scattering (SRS) microscopy, allowed us to directly visualize and quantify metabolic activities of cells in 3D at the subcellular scale. We discovered that the nanopillar structure significantly reduced the cell spreading area and circularity compared to flat surfaces. Nanopillar-induced mechanical cues significantly modulate cellular metabolic activities with variations in nanopillar geometry further influencing these metabolic processes. Cells cultured on nanopillars exhibited reduced oxidative stress, decreased protein and lipid synthesis, and lower lipid unsaturation in comparison to those on flat substrates. Hierarchical clustering also revealed that pitch differences in the nanopillar had a more significant impact on cell metabolic activity than diameter variations. These insights improve our understanding of how engineered nanotopographies can be used to control cellular metabolism, offering possibilities for designing advanced cell culture platforms which can modulate cell behaviors and mimic natural cellular environment and optimize cell-based applications. By leveraging the unique metabolic effects of nanopillar arrays, one can develop more effective strategies for directing the fate of cells, enhancing the performance of cell-based therapies, and creating regenerative medicine applications.

Chinese knot inspired isotropic linear scanning method for improved imaging performance in AFM

Atomic force microscope (AFM) is an important nano-scale surface characterization and measurement method. Raster scanning method (RSM), widely used in AFMs, faces limitations on scanning speed and imaging accuracy. In this paper, an isotropic linear scanning method (ILSM) is proposed to improve the AFM imaging performance. Inspired by Chinese knot, ILSM is constructed by integrating two iterative triangular scanning trajectories in X and Y axes, similar to triangular Lissajous. Compared with the other scanning methods, ILSM features isotropic scanning trajectory across the scanning region. It is also easy to increase either the scanning speed or scanning resolution using ILSM. Subsequently, to address the hysteresis associated with the piezoelectric actuator, a new tracking algorithm is proposed by combining adaptive Kalman filtering and direct inverse modeling approach. Finally, AFM imaging experiments are conducted to validate the effectiveness of the proposed method. It can be found that the artifacts in RSM can be efficiently eliminated using the proposed method, thus improving the imaging quality.

Hierarchically Structured Catalysts Toward Sustainable Hydrogen Economy: Electro- and Thermo-Chemical Pathways.

Hydrogen, as an important clean energy source, plays a more and more crucial role in decarbonizing the planet and meeting the global climate challenge due to its high energy density and zero-emission. The demand for sustainable hydrogen is increasing drastically worldwide as driven by the global shift towards low-carbon energy solutions. Thermochemical catalysis process dominates hydrogen production at scale given its relatively mature technology and commercialization status, as well as the established manufacturing infrastructure. While due to its environmentally friendly nature and growing abundant sources of renewable electricity, the electrochemical path for hydrogen production is rising as a major alternative to the thermochemical means. Nevertheless, hierarchically structured catalysts and devices have gradually taken the center stage toward replacing the traditional counterparts, especially with the rapid advancement of the design and manufacture of such ordered nanostructure assemblies toward high activity, efficient mass transport, and superb stability. In this review, the latest progress of the hierarchically structured catalysts for hydrogen production have been surveyed on electro- and thermo- chemical pathways comparatively. It covers the structure designs of atomic dispersion, nanoscale surfaces and interfaces for achieving highly active and durable catalysts, components, and devices. Both electrochemical and thermochemical approaches are reviewed in terms of the vast design details, engineered benefits, and understandings of various Pt-group metal (PGM) and non-PGM based transition metal catalysts for hydrogen production. As the growing trend, brief discussions are also presented toward the high-level assembly and manufacture of complexly structured components and devices at scale in the electrochemical and thermochemical energy systems.

Impact of submicron Nb3Sn stoichiometric surface defects on high-field superconducting radiofrequency cavity performance

Nb3Sn film coatings have the potential to drastically improve the accelerating performance of Nb superconducting radiofrequency (SRF) cavities in next-generation linear particle accelerators. Unfortunately, persistent Nb3Sn stoichiometric material defects formed during fabrication limit the cryogenic operating temperature and accelerating gradient by nucleating magnetic vortices that lead to premature cavity quenching. The SRF community currently lacks a predictive model that can explain the impact of chemical and morphological properties of Nb3Sn defects on vortex nucleation and maximum accelerating gradients. Both experimental and theoretical studies of the material and superconducting properties of the first 100 nm of Nb3Sn surfaces are complicated by significant variations in the volume distribution and topography of stoichiometric defects. This work contains a coordinated experimental study with supporting simulations to identify how the observed chemical composition and morphology of certain Sn-rich and Sn-deficient surface defects can impact the SRF performance. Nb3Sn films were prepared with varying degrees of stoichiometric defects, and the film surface morphologies were characterized. Both Sn-rich and Sn-deficient regions were identified in these samples. For Sn-rich defects, we focus on elemental Sn islands that are partially embedded into the Nb3Sn film. Using finite element simulations of the time-dependent Ginzburg-Landau equations, we estimate vortex nucleation field thresholds at Sn islands of varying size, geometry, and embedment. We find that these islands can lead to significant SRF performance degradation that could not have been predicted from the ensemble stoichiometry alone. For Sn-deficient Nb3Sn surfaces, we experimentally identify a periodic nanoscale surface corrugation that likely forms because of extensive Sn loss from the surface. Simulation results show that the surface corrugations contribute to the already substantial drop in the vortex nucleation field of Sn-deficient Nb3Sn surfaces. This work provides a systematic approach for future studies to further detail the relationship between experimental Nb3Sn growth conditions, stoichiometric defects, geometry, and vortex nucleation. These findings have technical implications that will help guide improvements to Nb3Sn fabrication procedures. Our outlined experiment-informed theoretical methods can assist future studies in making additional key insights about Nb3Sn stoichiometric defects that will help build the next generation of SRF cavities and support related superconducting materials development efforts. Published by the American Physical Society 2024

Nanoscale roughness to mitigate polydimethylsiloxane (PDMS) sticking in liquid crystal display (LCD) vat photopolymerization (VPP): Separation force reduction without losing resolution

Liquid crystal display (LCD) vat photopolymerization (VPP) is gaining attention among polymer-based additive manufacturing (AM) processes due to its high accuracy, superior surface finish, and cost-efficiency. However, one of the main challenges is the high layer separation force, which is heavily influenced by the flexibility of the interface. Sticking between polydimethylsiloxane (PDMS) and the LCD panel reduces flexibility, shifting the separation behavior from Johnson-Kendall-Roberts (JKR) to Derjaguin-Muller-Toporov (DMT)-like behavior. This study presents a novel approach to mitigate PDMS sticking by introducing nanoscale surface roughness. Sandblasted sheet metals with varying sand mesh sizes were used as molds to create interfaces with different roughness levels. The findings reveal that a surface roughness of 0.262µm significantly reduces PDMS sticking, making the interface more flexible. The optimized flexible interface (SP 2000) interface reduced the separation force 50-fold compared to unmodified PDMS while maintaining high print resolution. Case studies involving rigid and flexible photopolymer resins further emphasize the effectiveness of the SP 2000 interface in addressing PDMS sticking issues. This research highlights the critical role of interface flexibility and presents a promising solution for improving LCD VPP performance.