Measurement Of Surface Properties Research Articles

Cleaning and Particle Challenges in the Temporary Bonding and Debonding Process

The demands of 5G, Internet of Things and other global technology trends, combined with the increasing cost of scaling down process nodes, have created a shift towards more integrated packaging requirements. The emergence of advanced packaging technologies, such as Fan-Out Wafer Level Packaging (FOWLP), 2.5D/3D IC packaging, and heterogenous integration, brings potential for smaller form factors with increased functionality and bandwidth [1]. Backside processing or thinning of the device wafer is often needed for enabling these technologies. This requires the device wafer be adhered to a rigid carrier wafer using a temporary bonding material (TBM) for mechanical support during handling and processing. Following carrier release, the TBM must be thoroughly removed and cleaned from the device wafer. Many of these adhesives are exposed to high-power lasers or elevated temperatures, making removal more challenging. Sub-micron particle level clean demands for temporary bonding material (TBM) removal are also reaching standards typically reserved for front-end-of-line (FEOL) processing. This is especially crucial in 3D processes such as hybrid bonding where feature and pitch sizes are nearing <1 µm and insufficient cleaning can lead to failures in subsequent bonding processes [2]. Thus, careful consideration of all processing steps is necessary to meet stringent particle demands. This work investigates the removal of coated and baked TBM on silicon wafers, with an emphasis on processing conditions that obtain best particle results. Several chemistries were assessed at the beaker level by performing coupon-level studies and measuring surface properties. Based on these findings, studies with 300-mm wafers were performed using a customizable single-wafer processing tool.

Active Whisker‐Inspired Food Material Surface Property Measurement Using Deep‐Learned Mechanosensor

Rat whiskers are an exceptional sensing system, extracting information from their surrounding environment. Inspired by this concept, active whisker sensors measure various physical and geometric properties through contact with objects. However, previous research has focused on measuring the object geometry, often overlooking the potential for broader applications of the sensors. Herein, an active whisker sensor that enables simple measurement of the surface properties such as surface hardness and adhesiveness is reported. Composed of motor‐, wire‐, and crack‐based mechanosensor, the active whisker sensor implements a tapping process inspired by the movement of a rat's whiskers to quickly evaluate the object surface. One area of potential application is the food industry. The active whisker sensors offer a new approach to measuring surface properties of viscoelastic and inelastic food that are difficult to measure with traditional bulky systems. Herein, it is validated that the tapping process can be used to measure the surface properties of a various foods. With the aid of machine learning algorithms, sensor can also recognize differences in the surface properties of bananas at different ripeness stages and classify them with 99% accuracy. In this report, the possibilities for applications of active whisker sensors, including food industry, robotics, and medical devices, are opened up.

Assessment of enamel surface roughness and hardness with metal and ceramic orthodontic brackets using different etching and adhesive systems: An in vitro study

BackgroundThis study aimed to evaluate enamel surface roughness and microhardness following the use of different bracket materials (metal or ceramic), etchants (total- and self-etchants), and adhesive systems (precoated or flash-free). MethodA total of 99 extracted human premolars were selected for the analysis. The surface roughness was first assessed (roughness control). One specimen from each subgroup was examined using a scanning electron microscope to illustrate the surface topography. Eighty-eight teeth were prepared using total- or self-etchants and bonded to precoated or flash-free adhesive metal or ceramic brackets. The remaining 11 specimens were not bonded to brackets (microhardness controls). The brackets were debonded after immersion in distilled water for 24 h. The specimens were again scanned for surface roughness and topography imaging. Finally, the microhardness was assessed using a micro-Vickers hardness test at a force of 200 g for 10 s. ResultAn overall statistically significant increase in surface roughness and reduced surface microhardness were observed in all experimental groups when compared with those in the control groups. The etchant type was the only variable found to contribute to the measured surface properties, with increased roughness and reduced microhardness introduced by total-etching compared to those by self-etching. ConclusionOrthodontic brackets introduced a significant increase in enamel surface roughness and reduce microhardness compared with untreated enamel, regardless of the bracket material, etchant type, and adhesive system. The etchant type was the only variable contributing to these changes, with total etching having a more pronounced effect.

SILVER-INTEGRATED EDM PROCESSING OF TIAL6V4 IMPLANT MATERIAL HAS ANTIBACTERIAL CAPACITY WHILE OPTIMIZING OSSEOINTEGRATION

Periprosthetic joint infections (PJI) are one of the most common reasons for orthopedic revision surgeries. In previous studies, it has been shown that silver modification of titanium (Ti-6Al-4V) surfaces by PMEDM (powder mixed electrical discharge machining) has an antibacterial effect on Staphylococcus aureus adhesion. Whether this method also influences the proliferation of bacteria has not been investigated so far. Furthermore, the effect is only limitedly investigated on the ossification processes. Therefore, the aim of this work is to investigate the antibacterial effect as well as the in vitro ossification process of PMEDM machined surfaces modified by integration of silver.In this study, we analyzed adhesion and proliferation of S. aureus in comparison to of surface roughness, silver content and layer thickness of the silver-integrated-PMEDM surfaces (N = 5). To test the in vitro ossification, human osteoblasts (SaOs-2) and osteoclasts (differentiated from murine-bone-marrow-macrophages) were cultured on the silver surfaces (N = 3).We showed that the attachment of S. aureus on the surfaces was significantly lower than on the comparative control surfaces of pure Ti-6Al-4V without incorporated silver, independently of the measured surface properties. Bacterial proliferation, however, was not affected by the silver content. No influence on the in vitro ossification was observed, whereas osteoclast formation was drastically reduced on the silver-modified surfaces.We showed that 1 to 3% of silver in the surface layer significantly reduced the adhesion of S. aureus, but not the proliferation of already attached bacteria. At the same time, no influence on the in vitro ossification was observed, while no osteoclasts were formed on the surface. Therefore, we state that PMEDM with simultaneous silver modification of the machined surfaces represents a promising technology for endoprostheses manufacturing to reduce infections while at the same time optimizing bone ingrowth.

Boundary conditions determined by experimentally measured surface properties for wave-based time-domain simulations

Boundary conditions are essential and necessary when simulating sound wave propagation inside an enclosed space. In this work, complex-valued surface acoustical properties for the actual materials are obtained from impedance tube measurements. This work applies model-based Bayesian inference to estimate the exact parameters for arbitrary boundary conditions. The Bayesian approach presented in this work demonstrates the capability to predict the complex-valued surface boundary function of frequency in broadband ranges. This approach is equivalently applicable in different boundary models in time domain depending on wave-based numerical methods used for acoustic modelings, such as the spectral element method or finite-difference time-domain method. With the accurately estimated boundary models, the efficacy of the boundary conditions is explored within the time-domain approaches.

Removal Analysis of Residual Photoresist Particles Based on Surface Topography Affected by Exposure Times of Ultraviolet and Developer Solution

Particle removal from the surface of a substrate has been an issue in numerous fields for a long time. In semiconductor processes, for instance, the formation of clean surfaces by removing photoresist (PR) must be followed in order to create neat patterns. Although PR removal has been intensively investigated recently, little is known about how ultraviolet (UV) and developer solutions alter the PR resin (and in what manner) near the surface. While varying the exposure times of UV and developer solution, we investigated the topographic changes on the surfaces of PR resin films and particles. The measured surface properties were then correlated with the detachment force determined using films, and eventually with the residual PR particle removal percentages obtained in a microchannel. Using a positive PR and a base developer solution, we demonstrated that UV causes the surface of PR resin to become hydrophilic and wavy, whereas the developer solution produces a surface with a larger degree of roughness by swelling and partially dissolving the resin. Ultimately, the increased roughness decreased the effective contact area between PR resins, hence decreasing the detachment force and increasing the particle removal percentages. We anticipate that our findings will help understand residual particle issues, particularly on the removal mechanism of PR resins based on surface topography.

Wettability-based ultrasensitive detection of amphiphiles through directed concentration at disordered regions in self-assembled monolayers

Various forms of ecological monitoring and disease diagnosis rely upon the detection of amphiphiles, including lipids, lipopolysaccharides, and lipoproteins, at ultralow concentrations in small droplets. Although assays based on droplets' wettability provide promising options in some cases, their reliance on the measurements of surface and bulk properties of whole droplets (e.g., contact angles, surface tensions) makes it difficult to monitor trace amounts of these amphiphiles within small-volume samples. Here, we report a design principle in which self-assembled monolayer-functionalized microstructured surfaces coated with silicone oil create locally disordered regions within a droplet's contact lines to effectively concentrate amphiphiles within the areas that dominate the droplet static friction. Remarkably, such surfaces enable the ultrasensitive, naked-eye detection of amphiphiles through changes in the droplets' sliding angles, even when the concentration is four to five orders of magnitude below their critical micelle concentration. We develop a thermodynamic model to explain the partitioning of amphiphiles at the contact line by their cooperative association within the disordered, loosely packed regions of the self-assembled monolayer. Based on this local analyte concentrating effect, we showcase laboratory-on-a-chip surfaces with positionally dependent pinning forces capable of both detecting industrially and biologically relevant amphiphiles (e.g., bacterial endotoxins), as well as sorting aqueous droplets into discrete groups based on their amphiphile concentrations. Furthermore, we demonstrate that the sliding behavior of amphiphile-laden aqueous droplets provides insight into the amphiphile's effective length, thereby allowing these surfaces to discriminate between analytes with highly disparate molecular sizes.

Recent Advances in the Interfacial Shear and Dilational Rheology of Polymer Systems: From Fundamentals to Applications.

The study of the viscoelastic properties of polymer systems containing huge internal two-dimensional interfacial areas, such as blends, foams and multilayer films, is of growing interest and plays a significant role in a variety of industrial fields. Hence, interfacial rheology can represent a powerful tool to directly investigate these complex polymer–polymer interfaces. First, the current review summarizes the theoretical basics and fundamentals of interfacial shear rheology. Particular attention has been devoted to the double-wall ring (DWR), bicone, Du Noüy ring and oscillating needle (ISR) systems. The measurement of surface and interfacial rheological properties requires a consideration of the relative contributions of the surface stress arising from the bulk sub-phases. Here, the experimental procedures and methodologies used to correct the numerical data are described considering the viscoelastic nature of the interface. Second, the interfacial dilational rheology is discussed, starting with the theory and underlying principles. In particular, the Langmuir trough method, the oscillating spinning drop technique and the oscillating pendant drop technique are investigated. The major pioneering studies and latest innovations dedicated to interfacial rheology in both shear and dilatation–compression are highlighted. Finally, the major challenges and limits related to the development of high-temperature interfacial rheology at the molten state are presented. The latter shows great potential for assessing the interfaces of polymer systems encountered in many high-value applications.

Impact of Stagnation Temperature and Nozzle Configuration on Rarefied Jet Plume Interactions

The canting axis of thrusters on space platforms, which likely operate in a vacuum environment with a high degree of flow rarefaction, is significant in order to create the desired torque for maneuvering, maintaining orbit, eliminating perturbation forces, docking, etc. Therefore, the interactions of expanding plumes with one another and with solid surfaces in multinozzle arrays are inevitable. To gain a better understanding of the effect of nozzle configurations and conditions on the plume–plume and plume–surface interactions, a simulation matrix is carried out for a sonic nozzle using the direct simulation Monte Carlo method with the dsmcFoam+ code. As nozzle arrays are packed more tightly together, the plume–plume interactions become stronger, which has an influence on the stagnation line density and temperature profiles. For a given stagnation temperature, the spacing between nozzles in the array does not have a strong influence on the normalized surface pressure, but there is an increase in the maximum normalized shear stress as the distance between the nozzles increases. There is a significant difference in the results for double and quadruple nozzle arrays, with greater normalized stagnation pressures and shear stresses found as the number of nozzles in the array is increased. For a single nozzle, increasing the stagnation temperature does not have a significant effect on the normalized surface pressures, but does increase the maximum normalized shear stress and increases the measured heat flux on the surface. For arrays of double and quadruple nozzles, the number of nozzles has a much greater influence on the measured surface properties than the stagnation temperature.

Impact of Molecular Surface Diffusion on the Physical Stability of Co-Amorphous Systems.

In this study, surface diffusion of l-aspartic acid-carvedilol (ASP-CAR) co-amorphous systems at different ASP concentrations is measured and correlated with their physical stability. ASP-CAR films at ASP concentrations of 1-5% (w/w) were prepared by a newly developed method based on a vacuum compression molding process. Surface diffusion measurements were conducted on these systems based on the surface grating decay method using atomic force microscopy (AFM). The results demonstrate that a small amount of ASP (i.e., ≤ 5% w/w) in the co-amorphous systems could significantly slow down the grating decay process compared with that of pure amorphous CAR, indicating a reduced surface diffusion of CAR molecules. The decay time gradually increased in co-amorphous systems with increasing ASP concentration from 1 to 5% (w/w), with the longest observed decay time of around 800 h for the 5%ASP-CAR system, which was more than 200 times longer compared to the decay time of pure amorphous CAR (approximately 3 h). A good correlation between the decay constants of the pure amorphous CAR and co-amorphous films at ASP concentrations of 1-5% (w/w) and the physical stability of corresponding amorphous powder samples was found. Overall, this study provides a new method to prepare co-amorphous films for surface property measurements and reveals the impact of surface diffusion on the physical stability of co-amorphous systems.

Spectral measurement of daylights and surface properties of natural objects in Japan.

We present a spectral dataset of daylights and surface reflectances and transmittances of natural objects measured in Japan. Daylights were measured under the sun and under shadow from dawn to dusk on four different days to capture their temporal spectral transition. We separately measured daylight spectra at five different locations (including an open space and a forest) with minimum time difference to reveal whether a local environment alters daylight spectra reaching the ground. We found that colors of natural objects were spread in a limited area of color space, and data points were absent around saturated green regions. Daylight spectra were found to have a larger variation across time, weather, and local environments than previously thought. Datasets are made freely available, expanding past public datasets mainly collected in Northern America and Europe.

Charge Effects Provide Ångström-Level Control of Lipid Bilayer Morphology on Titanium Dioxide Surfaces.

Interfaces between molecular organic architectures and oxidic substrates are a central feature of biosensors and applications of biomimetics in science and technology. For phospholipid bilayers, the large range of pH- and ionic strength-dependent surface charge densities adopted by titanium dioxide and other oxidic surfaces leads to a rich landscape of phenomena that provides exquisite control of membrane interactions with such substrates. Using neutron reflectometry measurements, we report sharp, reversible transitions that occur between closely surface-associated and weakly coupled states. We show that these states arise from a complex interplay of the tunable length scale of electrostatic interactions with the length scale arising from other forces that are independent of solution conditions. A generalized free energy potential, with its inputs only derived from established measurements of surface and bilayer properties, quantitatively describes these and previously reported observations concerning the unbinding of bilayers from supporting substrates.

The Shortwave Spectral Radiometer for Atmospheric Science: Capabilities and Applications from the ARM User Facility

AbstractIndustry advances have greatly reduced the cost and size of ground-based shortwave (SW) sensors for the ultraviolet, visible, and near-infrared spectral ranges that make up the solar spectrum, while simultaneously increasing their ruggedness, reliability, and calibration accuracy needed for outdoor operation. These sensors and collocated meteorological equipment are an important part of the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) User Facility, which has supported parallel integrated measurements of atmospheric and surface properties for more than two decades at fixed and mobile sites around the world. The versatile capability of these ground-based measurements includes 1) rich spectral information required for retrieving cloud and aerosol microphysical properties, such as cloud phase, cloud particle size, and aerosol size distributions, and 2) high temporal resolution needed for capturing fast evolution of cloud microphysical properties in response to rapid changes in meteorological conditions. Here we describe examples of how ARM’s spectral radiation measurements are being used to improve understanding of the complex processes governing microphysical, optical, and radiative properties of clouds and aerosol.

Direct Measurements of the Forces between Silver and Mica in Humic Substance-Rich Solutions.

Deposition of engineered nanoparticles onto porous media from flowing suspensions is important for soil and groundwater quality. The deposition mechanism is controlled by interaction forces between particles and collectors. We investigated the origin and magnitude of opposing forces between silver and mica surfaces (representing nanosilver and sand grains) in solutions relevant to agricultural soils with direct measurements using a surface force apparatus. Solutions of variable NaNO3, Ca(NO3)2, and humic acid (HA) concentrations were used to differentiate individual contributing forces and quantify surface properties. The measured Hamaker constant for silver-water-mica was consistent with Lifshitz theory. Our results indicate that HA forms an adsorbed surface layer, but its charge, thicknesses, compressibility, and mass are significantly larger on mica than silver. Ca2+ primarily reduced the differences between the initially adsorbed HA layer properties on each surface, making them more similar. Force-distance profiles indicate that, when silver-mica systems were exposed to HA, osmotic-steric, electrostatic, and van der Waals forces dominate. Soft particle theory was deemed inappropriate for this system. Derjaguin's approximation was utilized to translate force measurements into interaction energy between nanosilver particles and mica collectors. We propose attachment efficiency estimates from measured surface properties, which suggest high particle mobility when nanosilver is applied to HA-rich agricultural soils with modest ionic strength.

Comprehensive in-orbit performance evaluation of the BepiColombo Laser Altimeter (BELA)

The BepiColombo Laser Altimeter (BELA) is on its way to Mercury on board the Mercury Planetary Orbiter (MPO), one of the two spacecraft of the BepiColombo mission. It will arrive at Mercury in December 2025 and start measurements of Mercury’s surface and environment. The goal of this study is to analyze the performance of BELA by using a comprehensive in-orbit performance model of the instrument.To determine the in-flight performance, we model the laser altimeter instrument noise based on laboratory tests performed on BELA. In order to obtain the most realistic in-flight performance, we add a realistic instrument degradation model on top of it. We thus obtain the probability of false detection for each simulated observation and based on that, we produce a coverage map over different surface terrains.We show that the pointing uncertainty dominates the range measurement error. Moreover, we compare the predicted working limit using different gain settings and we show that instrument degradation can lower the working limit of the instrument by around 200 ​km in the worst case scenario.Finally, we produce BELA measurement performance maps over the surface of Mercury, study the attainable quality of topography recovery and determine the expected accuracy of the measurements of surface properties, e.g., local slopes, surface roughness and albedo in different conditions and over different terrains.We also suggest potential improvements to instrument operations by choosing an optimum gain setting and by combining different measurements together when constructing a digital terrain model of Mercury.

Airborne LiDAR Measurements of Sea Surface Properties in the German Bight

Sea surface measurements are mainly gathered using satellite altimeter, buoy, and platform measurements. Satellite measurements typically have a coarse spatial resolution and need recalibration in coastal regions, whereas point measurements of buoys only represent limited areas around the measurement point because of the complex coastal bathymetry. Wave models (WAM) are used to expand the sparse observations in space and time. As a part of the project WIndPArk far-field (WIPAFF), which focused on wakes behind offshore wind farms, extensive airborne light detection and ranging (LiDAR) measurements of ocean waves in the German Bight were performed for more than 90 h. The LiDAR data processed for significant wave height can be used to validate and improve WAM models for complex areas and fill the observation gap between satellite altimeter and point measurements. This creates a detailed picture of the sea surface for coastal engineering and environmental applications. After introducing the measurement techniques and the data situation, intercomparisons between the available airborne measurements, buoy data, and WAM model output are presented to provide an insight into the potential of airborne LiDAR measurements for wave characterization and wave model validation.

Preparation of Twisted Bilayer Graphene via the Wetting Transfer Method.

Assembling monolayers into a bilayer system unlocks the rotational free degree of van der Waals (vdW) homo/heterostructure, enabling the building of twisted bilayer graphene (tBLG) which possesses novel electronic, optical, and mechanical properties. Previous methods for preparation of homo/heterstructures inevitably leave the polymer residue or hexagonal boron nitride (h-BN) mask, which usually obstructs the measurement of intrinsic mechanical and surface properties of tBLG. Undoubtedly, to fabricate the designable tBLG with clean interface and surface is necessary but challenging. Here, we propose a simple and handy method to prepare atomically clean twisted bilayer graphene with controllable twist angles based on wetting-induced delamination. This method can transfer tBLG onto a patterned substrate, which offers an excellent platform for the observation of physical phenomena such as relaxation of moiré pattern in marginally tBLG. These findings and insight should ultimately guide the designable packaging and atomic characterization of the two-dimensional (2D) materials.

Probabilistic bulk property estimation using multimodality surface non-destructive measurements for vintage pipes

Serving as energy lifelines, pipelines remain one of the most efficient and economical ways to move natural resources. The mechanical properties of pipelines installed decades ago decline with time. To maintain the safety of vintage pipelines requires accurate estimation of the strength. This paper focus on the reliability-based strength prediction using nondestructive multimodality information by the method of Bayesian model averaging (BMA). A class of models are formed from all cases of linear combinations of the surface property measurements. The models are averaged based on the posterior model probabilities. Occam’s window is introduced to reduce the number of models under consideration while keeping the predictive accuracy. By not conditioning on any single model, BMA provide more reliable strength prediction by accounting for model uncertainties. In addition, the usefulness of the variables used to predict the strength are evaluated according to the frequency of appearance in the models with high posterior probabilities. The variables with paramount predictive importance can be selected by this way. Thus, BMA method shows advantages in both vintage pipe strength prediction and model selection.

Time-frequency analysis of laser-excited surface acoustic waves based on synchrosqueezing transform

Laser-excited surface acoustic wave (LSAW) techniques can realize the measurement of surface properties through dispersion curve inversion. In addition to the conventional phase spectrum method, time-frequency analysis can also be used as a calculation tool for the dispersion curve. An accurate time-frequency analysis method is important in precisely inverting the surface properties. In this paper, synchrosqueezing transform (SST) is applied to the analysis of LSAW. By comparing the processing results of the constructed LSAW signal, SST shows higher time-frequency resolution and robustness than other common time-frequency analysis algorithms. Finite element model is used to simulate the propagation of LSAW in the film/substrate structure. And SST is used to calculate the dispersion curve of SAW information extracted during the simulation. A fast algorithm is introduced, where the film thickness is initially estimated by calculating the midrange. Through inversion, the resulting film thickness error is only 1.20% from the theoretical value. Therefore, SST is an effective tool for analyzing LSAW and calculating its dispersion curve.

Fundamental investigation on the correlation between surface properties and acceleration data from a sensor integrated milling tool

The detection, analysis, compensation, or even the targeted modification of workpiece surfaces of complex components plays an essential role in the machining of metals. Surface properties of e.g. an aircraft engine component or sheet metal draw die have a significant influence on the usage and durability of the component. In order to be able to process the free-form surfaces of these components, the used end-milling tools need to be long-cantilevered and slender. Due to their less rigid construction, these end-milling tools are prone to process-induced vibration. That, in turn, affects the workpiece surface negatively and requires reworking or even new production of the part. Today, the characterisation of the component surfaces is carried out downstream and partly by extensive quality investigations. A 100 % inspection of the entire surface is usually not carried out. To be able to influence the surface properties during machining and thus to make the process more efficient, a sensor integrated end-milling tool has been developed. This tool continuously records the data from an acceleration sensor to refer to the milled component surface and documents the results in a database. The significant advantage of this tool is the high sensitivity due to the accelerometer installed close to the Tool Center Point. The work presented here focuses on the fundamental investigations of the correlation between the acceleration data acquired from the sensor and the resulting surface properties. The paper shows that the acceleration data is a decent reflection of the measured surface properties. Additionally, the investigations show that the acceleration data of the sensor integrated tool are suitable for realising a specified surface conditioning. Lastly, an outlook is given which shows how a process control can accomplish an adjustment of the surface properties by adjusting the spindle speed and the feed rate.