3D Surface Profilometry Research Articles

A stent for co-delivering paclitaxel and nitric oxide from abluminal and luminal surfaces: Preparation, surface characterization, and in vitro drug release studies

Most drug-eluting stents currently available are coated with anti-proliferative drugs on both abluminal (toward blood vessel wall) and luminal (toward lumen) surfaces to prevent neointimal hyperplasia. While the abluminal delivery of anti-proliferative drugs is useful for controlling neointimal hyperplasia, the luminal delivery of such drugs impairs or prevents endothelialization which causes late stent thrombosis. This research is focused on developing a bidirectional dual drug-eluting stent to co-deliver an anti-proliferative agent (paclitaxel – PAT) and an endothelial cell promoting agent (nitric oxide – NO) from abluminal and luminal surfaces of the stent, respectively. Phosphonoacetic acid, a polymer-free drug delivery platform, was initially coated on the stents. Then, the PAT and NO donor drugs were co-coated on the abluminal and luminal stent surfaces, respectively. The co-coating of drugs was collectively confirmed by the surface characterization techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), 3D optical surface profilometry, and contact angle goniometry. SEM showed that the integrity of the co-coating of drugs was maintained without delamination or cracks formation occurring during the stent expansion experiments. In vitro drug release studies showed that the PAT was released from the abluminal stent surfaces in a biphasic manner, which is an initial burst followed by a slow and sustained release. The NO was burst released from the luminal stent surfaces. Thus, this study demonstrated the co-delivery of PAT and NO from abluminal and luminal stent surfaces, respectively. The stent developed in this study has potential applications in inhibiting neointimal hyperplasia as well as encouraging luminal endothelialization to prevent late stent thrombosis.

Abrasive wear under multiscratching of polystyrene + single-walled carbon nanotube nanocomposites. Effect of sliding direction and modification by ionic liquid

Single-walled carbon nanotubes (NTs) and single-walled carbon nanotubes modified (NTms) by the room-temperature ionic liquid (IL) 1-octyl, 3-methylimidazolium tetrafluoroborate ([OMIM]BF 4) were added in a 1 wt.% to polystyrene (PS) and processed by compression or injection moulding to obtain PS + NT and PS + NTm, respectively. Friction coefficients and abrasive wear from penetration depth, residual depth and viscoelastic recovery were determined under multiple scratching. The effect of the moulding process, the additives and the sliding direction was studied. Compression moulded PS shows a transition to more severe damage after a critical number of successive passes. Addition of NTs or NTms to compression moulded PS induces a strain hardening effect and reduces friction, residual depth and viscoelastic recovery. Strain hardening is also observed in injection moulded PS with sliding in the longitudinal and random directions, but not in the transverse direction. The scratch resistance of PS + NTm depends on sliding direction. The lowest friction coefficient and residual depth values, and the highest viscoelastic recovery were found for injection moulded PS + NTm, in the sliding direction parallel to injection flow. Mechanisms of surface damage are discussed upon scanning electron microscopy (SEM), focused ion beam-field emission scanning electron microscopy (FIB-FESEM), 3D surface topography, surface roughness and profilometry observations.

Near‐infrared fluorescence imaging of lymphatics in head and neck lymphedema

Lymphedema is a complication that may occur after surgical resection and radiation treatment in a number of cancer types and is especially debilitating in regions where treatment options are limited. Although upper and lower extremity lymphedema may be effectively treated with manual lymphatic drainage (MLD) therapies and devices that use compression to direct proximal flow of lymph fluids, head and neck lymphedema is more challenging. Herein, we describe the compassionate use of an investigatory technique of near-infrared (NIR) fluorescence imaging to understand the lymphatic anatomy and function, help direct MLD, and use 3-dimensional (3D) surface profilometry to monitor response to therapy in a patient with head and neck lymphedema after surgery and radiation treatment. NIR fluorescence imaging provides a mapping of functional lymph vessels for direction of efficient MLD therapy in the head and neck. Additional studies are needed to assess the efficacy of MLD therapy when directed by NIR fluorescence imaging.

Surface transformation of AISI 304 stainless steel by high power diode laser

A high power diode laser was used in continuous mode to irradiate milled AISI 304 substrates in order to modify their surface morphology. Milling of the steel substrates was operated at different feeds, thus allowing the achievement of a broad range of starting surface texture, characterized by average roughness of ∼0.65–1.5 μm. Laser finishing was then operated on them by varying laser power and scan speed. The effectiveness of the laser finishing was evaluated by 3D surface profilometry and SEM imaging. Laser was found to modify the surface morphology of the irradiated zones and achieve high quality surface textures. Further, consistent trends of the amplitude, spacing and hybrid roughness parameters according to laser operational settings can often be found. Finally, mapping of the experimental data can lead to the definition of a first approximation tool, which can be profitably used for simulation and process control.

High-speed 3D surface profilometry employing trapezoidal phase-shifting method with multi-band calibration for colour surface reconstruction

This paper presents a new optical measurement method employing a HSI (hue, saturation and intensity) colour model to form trapezoidal structured patterns for morphology reconstruction of a measured object at high speed. Profilometry on objects having non-monochromatic surfaces is considered as one of the remaining challenges most faced by the currently existing structured-light projection methods since the surface reflectivity to red, green and blue light may vary significantly. To address this, an innovative colour calibration method for a hue component is developed to determine the accurate reflectivity response of the measured surface. The trapezoidal colour pattern is calibrated to compensate the hue-shifted quantity induced by the reflective characteristics of the object's surface. The developed method can reconstruct precise 3D surface models from objects by acquiring a single-shot image, which can achieve high-speed profilometry and avoid in situ potential measurement disturbances such as environmental vibration. To verify the feasibility of the developed methodology, some experiments were conducted to confirm that the measurement accuracy can be controlled within 2.5% of the overall measurement range and the repeatability of 3.0% within ±3σ can be achieved.

Effect of the initial microstructure on the plasma nitriding behavior of AISI M2 high speed steel

The nitriding behavior of AISI M2 steel was studied on samples previously submitted to two different heat treatments in order to investigate the effects of the initial microstructure on the thickness and hardness of nitrided layer. Prior to nitriding, one group of samples was fully annealed while the other group was quenched and tempered, thus acquiring the lowest and highest hardness respectively. Plasma nitriding was performed at 450 °C for 8 h with a mixture of N2 and H2 in a plasma reactor working under floating potential. Structural and mechanical properties of nitrided layers were characterized using X-ray diffraction (XRD), optical microscopy and microhardness testing. Variations in surface roughness were obtained by 3D surface profilometry analysis. The thicker nitrided layer was obtained for the fully annealed samples, in which the nitrided layer is composed of γ′-Fe4N and ε-Fe2–3N phases plus a diffusion zone. For the hardened–tempered samples, the nitrided region mainly consisted of a diffusion zone. Plasma nitriding increased the surface hardness of the fully annealed samples by 330% and that of the quenched–tempered samples by 50%. The nitrided depth was also estimated using cross-sectional microhardness profiles; giving about 140 µm and ∼ 70 µm for the fully annealed and quenched–tempered samples, respectively. Due to the grain to grain nitrogen diffusion, plasma nitriding also increased the surface roughness. The largest roughness was obtained for the fully annealed samples, in accordance with the largest nitrided depth. The difference in the nitriding behavior was explained on the basis of the microstructural aspects of the substrates such as the concentration of the freely dispersed alloying elements and the level of compressive residual stresses.

Dynamic 3D surface profilometry using a novel colour pattern encoded with a multiple triangular model

In this paper, a novel active structured fringe method for dynamic 3D surface profilometry is presented using a colour fringe pattern encoded with multiple phase-shifted triangular modulations. Rapid 3D surface profilometry is extremely important to automatic optical inspection (AOI), especially for in situ optical surface profilometry. In the proposed approach, three-step phase shifting can be simultaneously performed by encoding and analyzing components of red, green and blue colours in the projected colour fringe patterns. A significant advantage can be obtained in eliminating arctangent calculation and one-shot imaging for obtaining dynamic full-field 3D surface profile reconstruction. Experimental tests were conducted to verify the capability of the developed method in achieving high-speed 3D measurement with an average measurement error of less than 2.8% of the overall detection range.

LASER ULTRASONIC INSPECTION SYSTEM WITH A 3D SURFACE PROFILOMETRY TO DETECT SURFACE CRACKS

We have developed a nondestructive surface-crack detection system by using laser ultrasound and optical 3D surface profilometry. The system can robustly acquire crack information by using the laser ultrasonic analysis data with visual surface profiling data where both data are produced by the same line-shaped pulse laser beam. By the help of the visual 3D shape data for a surface crack, this ultrasonic inspection system can provide reliable surface crack information. In this paper, the hardware configuration of the combined nondestructive laser inspection system to detect surface cracks will be described. Also, the experimental results to detect multi surface cracks by using the developed system will be presented.