Non-contact Laser Interferometer Method to Characterize Tablet Punches: New Methodology to Assess Surface Roughness

Sticking to tablet punches is a major issue during drug product manufacturing. Research has shown that sticking involves the interrelationship of powder properties, compression force, length of manufacturing runs and punch quality. Here, we present a novel non-destructive methodology to study the surface metrology of punches to monitor them over their lifetime. This investigation used a non-contact laser interferometer to characterise roughness of commercial standard S7 steel punches coated with chrome that were originally used for commercial scale production that developed a sticking issue. During the development, this phenomenon had not been observed and was not considered a scale-up risk. The profilometer was used to examine the complete surface of these punches to investigate whether they met the acceptability criteria based on BS_ISO_18804 tooling standard. To improve data analysis during changeover, a 3D-printed holder was designed to enable analysis with minimal set-up requirements. Upon investigation, the punches were found to be of an unacceptable roughness and, particularly rough areas of the punch surface profiled, correlated well with areas of visually pronounced sticking. This non-destructive method can be used to produce a more detailed characterisation of punch roughness to ensure surfaces are of an acceptable quality after treatment with coatings.

Surface Metrology Based on Scanning Conoscopic Holography for In Situ and In-Process Monitoring of Microtexture in Paintings

In the field of engineering, surface metrology is a valuable tool codified by international standards that enables the quantitative study of small-scale surface features. However, it is not recognized as a resource in the field of cultural heritage. Motivated by this fact, in this work, we demonstrate the use and the usefulness of surface metrology based on scanning conoscopic holography for monitoring treatments on the Venetian masterpiece by Tintoretto St. Martial in Glory with the Saints Peter and Paul. We carried out in situ and in-process monitoring of the painting microtexture during an experimental, innovative laser-chemical treatment, and we performed a statistical analysis based on ISO areal field parameters. A wide and in-band roughness analysis through the complementary use of amplitude, spatial, and hybrid parameters confirmed the noninvasive nature of the whole treatment on the painting surface topography, giving us the chance to review and critically discuss the use of these parameters in a real case in heritage science.

Experimental approaches to assess the effect of composition of abrasives in the cause of dental microwear

Dental microwear is used to investigate feeding ecology. Animals ingest geological material in addition to food. The full effect of geological abrasives on tooth wear is unknown. To evaluate mineralogical abrasives as tooth wear agents, rats were fed food manufactured with quartz silt, diatomaceous earth, and calcium carbonate. Rats were assigned to treatments and fed for 15 days. Molars were scanned with a Sensofar Plu Neox confocal microscope and evaluated using ISO-25178-2 parameters and traditional microwear variables using light microscopy. Using a pellet-diet as the control, all treatments had influence on microwear and discriminant function analyses indicated that unique surface textures had been produced. ISO variables with high discriminatory values were correlated to scratch and pit frequencies, but more ISO parameters identified changes associated with numbers of scratches than changes associated with pits. The microwear changes associated with the abrasive inclusions were co-dependent on the type of diet that the abrasives had been added to. The abrasives had less effect with pellets but produced more modified and more differentiated microwear when added to the transgenic dough. Although abrasives produce distinctive surface textures, some knowledge of the properties of food with the abrasives is needed to identify the abrasive agent.

Effect of Surface Texture on the Structural Adhesive Joining Properties of Aluminum 7075 and TEPEX®

In the process of continuous improvement of manufacturing processes, this study was developed within the framework of the Ecovoss project, based on the inclusion of lightweight and new materials parts in the automotive sector. The objective was based on the replacement of aluminum welding operations with the option of adhesive operations with other types of materials such as polyamides or, in this case, a TEPEX^® composite material (Dynalite 202-c200/50% TYP 13). The aim of this work is to test the best texturing of substrate made in 7075 aluminum specimens manufactured by robotic polishing with an ABB 6640 robot. Another substrate is TEPEX composite. A structural adhesive film AF-163-2 from the 3M company (St Paul, MN, USA) is used, which must be applied according to the manufacturing procedure. The tests carried out are based on the topographic measurement of the surfaces to be joined with an Alicona focus variation microscope, and the uniaxial shear tests of adhesive samples have been analyzed. The texture of the surface failure has been analyzed, and the results confirm a significant correlation between the texture parameters of initial surfaces and maximum shear stress. The expected results should provide a better understanding of the surfaces aimed to optimize the adhesion of the studied materials.

Fracture Surface Behavior of 34CrNiMo6 High-Strength Steel Bars with Blind Holes under Bending-Torsion Fatigue

The present study evaluates the fracture surface response of fatigued 34CrNiMo6 steel bars with transverse blind holes subjected to bending with torsion loading. The analysis of the geometric product specification was performed by means of height parameters Sx, functional volume parameters Vx, and fractal dimension Df. Surface topography measurements were carried out using an optical profilometer with focus variation technology. The experimental results show that the doubling the bending to torsion moment ratio B/T from B/T = 1 to B/T = 2, maintaining the same normal stress amplitude, greatly reduces both Sa, Vv as well as the fractal dimension Df of the analyzed specimen fractures by 32.1%, 29.8%, and 16.0%, respectively. However, as expected, a two-fold increase in the B/T ratio, maintaining the same normal stress amplitude, resulted in a larger number of cycles to fatigue crack initiation, Ni, which can be explained by the lower shear stress level. These experiments prove that parameters Sx, Vx, Df are smaller for larger Ni values, which is an important finding. In addition, it was found a high consistency of surface topography measurements for the two sides of the broken specimens. The proposed methodology is both reliable and applicable for other engineering applications involving different geometries and loading conditions.

Suppression of the High-Frequency Errors in Surface Topography Measurements Based on Comparison of Various Spline Filtering Methods

The metrology of so-called “engineering surfaces” is burdened with a substantial risk of both measurement and data analysis errors. One of the most encouraging issues is the definition of frequency-defined measurement errors. This paper proposes a new method for the suppression and reduction of high-frequency measurement errors from the surface topography data. This technique is based on comparisons of alternative types of noise detection procedures with the examination of profile (2D) or surface (3D) details for both measured and modelled surface topography data. In this paper, the results of applying various spline filters used for suppressions of measurement noise were compared with regard to several kinds of surface textures. For the purpose of the article, the influence of proposed approaches on the values of surface topography parameters (from ISO 25178 for areal and ISO 4287 for profile standards) was also performed. The effect of the distribution of some features of surface texture on the results of suppressions of high-frequency measurement noise was also closely studied. Therefore, the surface topography analysis with Power Spectral Density, Autocorrelation Function, and novel approaches based on the spline modifications or studies of the shape of an Autocorrelation Function was presented.

Thickness Effect on Some Physical Properties of RF Sputtered ZnTe Thin Films for Potential Photovoltaic Applications

Zinc telluride thin films with different thicknesses were grown onto glass substrates by the rf magnetron sputtering technique, using time as a variable growth parameter. All other deposition process parameters were kept constant. The deposited thin films with thickness from 75 to 460 nm were characterized using X-ray diffraction, electron microscopy, atomic force microscopy, ellipsometry, and UV-Vis spectroscopy, to evaluate their structures, surface morphology, topology, and optical properties. It was found out that the deposition time increase leads to a larger growth rate. This determines significant changes on the ZnTe thin film structures and their surface morphology. Characteristic surface metrology parameter values varied, and the surface texture evolved with the thickness increase. Optical bandgap energy values slightly decreased as the thickness increased, while the mean grains radius remained almost constant at ~9 nm, and the surface to volume ratio of the films decreased by two orders of magnitude. This study is the first (to our knowledge) that thoroughly considered the correlation of film thickness with ZnTe structuring and surface morphology characteristic parameters. It adds value to the existing knowledge regarding ZnTe thin film fabrication, for various applications in electronic and optoelectronic devices, including photovoltaics.

Personalised 3D Printed Fast-Dissolving Tablets for Managing Hypertensive Crisis: In-Vitro/In-Vivo Studies

Hypertensive crisis (HC) is an emergency health condition which requires an effective management strategy. Over the years, various researchers have developed captopril based fast-dissolving formulations to manage HC; however, primarily, the question of personalisation remains unaddressed. Moreover, commercially these formulations are available as in fixed-dose combinations or strengths, so the titration of dose according to patient's prerequisite is challenging to achieve. The recent emergence of 3D printing technologies has given pharmaceutical scientists a way forward to develop personalised medicines keeping in view patients individual needs. The current project, therefore, is aimed at addressing the limitations as mentioned above by developing fast-dissolving captopril tablets using 3D printing approach. Captopril unloaded (F1) and loaded (F2-F4) filaments were successfully produced with an acceptable drug loading and mechanical properties. Various captopril formulations (F2-F4) were successfully printed using fused deposition modelling technique. The results revealed that the formulations (F2 and F3) containing superdisintegrant had a faster extent of dissolution and in-vivo findings were endorsing these results. The present study has successfully exhibited the utilisation of additive manufacturing approach to mend the gap of personalisation and manufacturing fast-dissolving captopril 3D printed tablets. The procedure adopted in the present study may be used for the development of fused deposition modelling (FDM) based fast-dissolving 3D printed tablets.

Characterization of Soft Tooling Photopolymers and Processes for Micromixing Devices with Variable Cross-Section

In this paper, we characterized an assortment of photopolymers and stereolithography processes to produce 3D-printed molds and polydimethylsiloxane (PDMS) castings of micromixing devices. Once materials and processes were screened, the validation of the soft tooling approach in microfluidic devices was carried out through a case study. An asymmetric split-and-recombine device with different cross-sections was manufactured and tested under different regime conditions (10 < Re < 70). Mixing performances between 3% and 96% were obtained depending on the flow regime and the pitch-to-depth ratio. The study shows that 3D-printed soft tooling can provide other benefits such as multiple cross-sections and other potential layouts on a single mold.

Results of the 3D Virtual Comparison Microscopy Error Rate (VCMER) Study for firearm forensics

The digital examination of scanned or measured 3D surface topography is referred to as Virtual Comparison Microscopy (VCM). Within the discipline of firearm and toolmark examination, VCM enables review and comparison of microscopic toolmarks on fired ammunition components. In the coming years, this technique may supplement and potentially replace the light comparison microscope as the primary instrument used for firearm and toolmark examination. This paper describes a VCM error rate and validation study involving 107 participants. The study included 40 test sets of fired cartridge cases from firearms with a variety of makes, models, and calibers. Participants used commercially available VCM software which allowed digital data distribution, specimen visualization, and submission of conclusions. The software also allowed participants to annotate areas of similarity and dissimilarity to support their conclusions. The primary cohort of 76 qualified United States and Canadian examiners that completed the study had an overall false-positive error rate of 3 errors from 693 comparisons (0.43%) and a false-negative error rate of 0 errors from 491 comparisons (0.0%). This accuracy is supplemented by the participant's provided surface annotations which provide insight into the cause of errors and the overall consistency across the independent examinations conducted in the study. The ability to obtain highly accurate conclusions on test fires from a wide range of firearms supports the hypothesis that VCM is a useful tool within the crime laboratory.

Atomic defect classification of the H-Si(100) surface through multi-mode scanning probe microscopy

The combination of scanning tunnelling microscopy (STM) and non-contact atomic force microscopy (nc-AFM) allows enhanced extraction and correlation of properties not readily available via a single imaging mode. We demonstrate this through the characterization and classification of several commonly found defects of the hydrogen-terminated silicon (100)-2 × 1 surface (H-Si(100)-2 × 1) by using six unique imaging modes. The H-Si surface was chosen as it provides a promising platform for the development of atom scale devices, with recent work showing their creation through precise desorption or placement of surface hydrogen atoms. While samples with relatively large areas of the H-Si surface are routinely created using an in situ methodology, surface defects are inevitably formed reducing the area available for patterning. By probing the surface using the different interactivity afforded by either hydrogen- or silicon-terminated tips, we are able to extract new insights regarding the atomic and electronic structure of these defects. This allows for the confirmation of literature assignments of several commonly found defects, as well as proposed classifications of previously unreported and unassigned defects. By combining insights from multiple imaging modes, better understanding of their successes and shortcomings in identifying defect structures and origins is achieved. With this, we take the first steps toward enabling the creation of superior H-Si surfaces through an improved understanding of surface defects, ultimately leading to more consistent and reliable fabrication of atom scale devices.

Profile and Areal Surface Parameters for Fatigue Fracture Characterisation

Post-mortem characterisation is a pivotal tool to trace back to the origin of structural failures in modern engineering analyses. This work compared both the crack propagation and rupture roughness profiles based on areal parameters for total fracture area. Notched and smooth samples made of weather-resistant structural steel (10HNAP), popular S355J2 structural steel and aluminium alloy AW-2017A under bending, torsion and combined bending–torsion were investigated. After the fatigue tests, fatigue fractures were measured with an optical profilometer, and the relevant surface parameters were critically compared. The results showed a great impact of the loading scenario on both the local profiles and total fracture areas. Both approaches (local and total fracture zones) for specimens with different geometries were investigated. For all specimens, measured texture parameters decreased in the following order: total area, rupture area and propagation area.

A Simple and Fast Spline Filtering Algorithm for Surface Metrology

Spline filters and their corresponding robust filters are commonly used filters recommended in ISO (the International Organization for Standardization) standards for surface evaluation. Generally, these linear and non-linear spline filters, composed of symmetric, positive-definite matrices, are solved in an iterative fashion based on a Cholesky decomposition. They have been demonstrated to be relatively efficient, but complicated and inconvenient to implement. A new spline-filter algorithm is proposed by means of the discrete cosine transform or the discrete Fourier transform. The algorithm is conceptually simple and very convenient to implement.

Surface metrology and 3-dimensional confocal profiling of femtosecond laser and mechanically dissected ultrathin endothelial lamellae

PURPOSE

To determine the feasibility of confocal profiling in measuring surface roughness and obtaining 3-dimensional reconstructions of mechanically dissected and femtosecond (fs)-laser photodisrupted endothelial lamellae. To determine the predictability of single-pass dissection of ultrathin endothelial lamellae using a novel motor-driven linear microkeratome.

METHODS

Thirty (n = 30) human corneas were harvested using a motor-driven linear microkeratome (n = 20); a hand-driven rotatory microkeratome (n = 6); and a 60-kHz fs laser (n = 4). Surface roughness was measured using an optical profiler operated in confocal microscopy mode followed by environmental scanning-electron-microscopy.

RESULTS

Mean surface roughness for the fs laser, motor-driven linear microkeratome, and hand-driven rotatory microkeratome measured 1.90 ± 0.48 μm, 1.06 ± 0.42 μm, and 0.93 ± 0.25 μm, respectively. Femtosecond photodisrupted lamellae were significantly rougher than mechanically dissected lamellae (P < 0.001). Mean (±SD) cutting depth with the motor-driven linear microkeratome measured: 552 ± 11 μm (550-μm head); 505 ± 19 μm (550-μm head); 459 ± 19 μm (450-μm head); and 392 ± 20 μm (400-μm head).

CONCLUSIONS

Confocal microscopy allows quantitative surface roughness analysis and 3-dimensional reconstruction of human corneal lamellae. Femtosecond-laser photodisruption at 60 kHz results in rougher surfaces compared with mechanical dissection. The motor-driven linear microkeratome allows single-pass dissection of ultrathin endothelial lamellae with a standard deviation ≤20 μm.

Femtosecond laser ablation of polypropylene: A statistical approach of morphological data

We have investigated femtosecond (fs) laser (130 fs, 800 nm, 5 kHz) ablation of polypropylene (PP). The following laser process conditions were varied: power density and number of pulses. The morphological parameters' response (depth, ablation diameter, ablation volume) to the laser process conditions, measured by an optical profiler, was investigated by the statistical analysis technique to determine the relationship between them. For this, the simple linear regression and the multiple linear regressions are compared. The simple linear regression shows that the ablation volume follows a linear relationship with the product of the power and the number of pulse.

In situ roughness measurements for the solar cell industry using an atomic force microscope

Areal roughness parameters always need to be under control in the thin film solar cell industry because of their close relationship with the electrical efficiency of the cells. In this work, these parameters are evaluated for measurements carried out in a typical fabrication area for this industry. Measurements are made using a portable atomic force microscope on the CNC diamond cutting machine where an initial sample of transparent conductive oxide is cut into four pieces. The method is validated by making a comparison between the parameters obtained in this process and in the laboratory under optimal conditions. Areal roughness parameters and Fourier Spectral Analysis of the data show good compatibility and open the possibility to use this type of measurement instrument to perform in situ quality control. This procedure gives a sample for evaluation without destroying any of the transparent conductive oxide; in this way 100% of the production can be tested, so improving the measurement time and rate of production.

Form-Profiling of Optics Using the Geometry Measuring Machine and the M-48 CMM at NIST

We are developing an instrument, the Geometry Measuring Machine (GEMM), to measure the profile errors of aspheric and free form optical surfaces, with measurement uncertainties near 1 nm. Using GEMM, an optical profile is reconstructed from local curvatures of a surface, which are measured at points on the optic's surface. We will describe a prototype version of GEMM, its repeatability with time, a measurements registry practice, and the calibration practice needed to make nanometer resolution comparisons with other instruments. Over three months, the repeatability of GEMM is 3 nm rms, and is based on the constancy of the measured profile of an elliptical mirror with a radius of curvature of about 83 m. As a demonstration of GEMM's capabilities for curvature measurement, profiles of that same mirror were measured with GEMM and the NIST Moore M-48 coordinate measuring machine. Although the methods are far different, two reconstructed profiles differ by 22 nm peak-to-valley, or 6 nm rms. This comparability clearly demonstrates that with appropriate calibration, our prototype of the GEMM can measure complex-shaped optics.