Detection Of Surface Defects And Subsurface Defects Of Polished Optics With Multisensor Image Fusion

Surface defects (SDs) and subsurface defects (SSDs) are the key factors decreasing the laser damage threshold of optics. Due to the spatially stacked structure, accurately detecting and distinguishing them has become a major challenge. Herein a detection method for SDs and SSDs with multisensor image fusion is proposed. The optics is illuminated by a laser under dark field condition, and the defects are excited to generate scattering and fluorescence lights, which are received by two image sensors in a wide-field microscope. With the modified algorithms of image registration and feature-level fusion, different types of defects are identified and extracted from the scattering and fluorescence images. Experiments show that two imaging modes can be realized simultaneously by multisensor image fusion, and HF etching verifies that SDs and SSDs of polished optics can be accurately distinguished. This method provides a more targeted reference for the evaluation and control of the defects of optics, and exhibits potential in the application of material surface research.

FEM ANALYSIS OF ENERGY LOSS DUE TO WAVE PROPAGATION FOR MICRO-PARTICLE IMPACTING SUBSTRATE WITH HIGH VELOCITIES

The impact between particles and material surface is a micro-scaled physical phenomenon found in various technological processes and in the study of the mechanical properties of materials. Design of materials with desired properties is a challenging issue for most industries. And especially in aviation one of the most important factors is mass. Recently with the innovations in 3D printing technologies, the importance of this phenomenon has increased. Numerical simulation of multi-particle systems is based on considering binary interactions; therefore, a simplified but as much accurate as possible particle interaction model is required for simulations. Particular cases of axisymmetric particle to substrate contact is modelled at select impact velocities and using different layer thicknesses. When modelling the particle impact at high contact velocity, a substrate thickness dependent change in the restitution coefficient was observed. This change happens is due to elastic waves and is important both to coating and 3D printing technologies when building layers of different properties materials.

A viewpoint on material and design considerations for oesophageal stents with extended lifetime

Oesophageal stents are meshed tubular implants designed to maintain patency of the oesophageal lumen and attenuate the symptoms of oesophageal cancer. Oesophageal cancers account for one in twenty cancer diagnoses and can lead to dysphasia, malnutrition and the diminishment of patient quality of life (QOL). Self-expanding oesophageal stents are the most common approach to attenuate these symptoms. Recent advances in oncological therapy have enabled patient survival beyond the lifetime of current devices. This introduces new complications for palliation, driving the need for innovation in stent design. This review identifies the factors responsible for stent failure. It explores the challenges of enhancing the longevity of stent therapies and outlines solutions to improving clinical outcomes. Discussions focus on the role of stent materials, construction methods, and coatings upon device performance. We found three key stent enhancement strategies currently used; material surface treatments, anti-migratory modifications, and biodegradable skeletons. Furthermore, radioactive and drug eluting stent designs were identified as emerging novel treatments. In conclusion, the review offers an overview of remaining key challenges in oesophageal stent design and potential solutions. It is clear that further research is needed to improve the clinical outcome of stents and patient QOL.

Corrosion resistance evaluation of carbon and vanadium-based sputtered coatings on steel substrates

Steels are in constant contact with fluids that could generate corrosion regardless the application in which this steel is located. AISI-SAE 1045 like steels is widely used in different applications in engineering, even several of these parts made of this steel suffers wear processes. The synergy between corrosion and wear phenomena exacerbates the detriment of some physical properties of the material conducing it to a failure. A potential alternative to avoid this issue is to coat the material surface with an anticorrosive material, and among different techniques to produce coatings, physical vapor deposition ones are environmentally friendly, secure and with excellent properties on the final product. We report the production of coatings based on vanadium and carbon on AISI-SAE 1045 steels substrates varying some of the deposition parameters in a sputtering coatings machine. A 23-factorial design of experiments was done with power applied to the vanadium target, power applied to the carbon target and temperature as active factors with two levels each one. A relevant effect of the power applied to V target and temperature on the anticorrosive properties of the coatings was found, thus increasing these factors levels always gives higher surface roughness and higher corrosion rates, this result together provides an important insight into the values that must be considered to achieve good anticorrosive properties on the material. Overall, these results indicate that with low V target power and room temperature, and high C target power the lowest corrosion rates and roughness of the group are achieved, both results agree.

Preparation and Research of a High-Performance ZnO/SnO2 Humidity Sensor

A high-performance zinc oxide/tin dioxide (ZnO/SnO2) humidity sensor was developed using a simple solvothermal method. The sensing mechanism of the ZnO/SnO2 humidity sensor was evaluated by analyzing its complex impedance spectra. The experimental results prove that the ZnO/SnO2 composite material has a larger specific surface area than pure SnO2, which allows the composite material surface to adsorb more water to enhance the response of the ZnO/SnO2 humidity sensor. ZnO can also contribute to the generation of oxygen-rich vacancies on the ZnO/SnO2 composite material surface, allowing it to adsorb a large amount of water and rapidly decompose water molecules into conductive ions to increase the response and recovery speed of the ZnO/SnO2 humidity sensor. These characteristics allowed the Z/S-2 humidity sensor to achieve a higher response (1,225,361%), better linearity, smaller hysteresis (6.6%), faster response and recovery speeds (35 and 8 s, respectively), and long-term stability at 11–95% relative humidity. The successful preparation of the ZnO/SnO2 composite material also provides a new direction for the design of SnO2-based resistance sensors with high humidity-sensing performance.

Photolon Nanoporous Photoactive Material with Antibacterial Activity and Label-Free Noncontact Method for Free Radical Detection

The worldwide increase in bacterial resistance and healthcare-associated bacterial infections pose a serious threat to human health. The antimicrobial photodynamic method reveals the opportunity for a new therapeutic approach that is based on the limited delivery of photosensitizer from the material surface. Nanoporous inorganic–organic composites were obtained by entrapment of photosensitizer Photolon in polysiloxanes that was prepared by the sol–gel method. The material was characterized by its porosity, optical properties (fluorescence and absorbance), and laser-induced antimicrobial activity against Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The permanent encapsulation of Photolon in the silica coating and the antimicrobial efficiency was confirmed by confocal microscope and digital holotomography. The generation of free radicals from nanoporous surfaces was proved by scanning Kelvin probe microscopy. For the first time, it was confirmed that Kelvin probe microscopy can be a label-free, noncontact alternative to other conventional methods based on fluorescence or chemiluminescence probes, etc. It was confirmed that the proposed photoactive coating enables the antibacterial photodynamic effect based on free radicals released from the surface of the coating. The highest bactericidal efficiency of the proposed coating was 87.16%. This coating can selectively limit the multiplication of bacterial cells, while protecting the environment and reducing the risk of surface contamination.

Nanostructured Modifications of Titanium Surfaces Improve Vascular Regenerative Properties of Exosomes Derived from Mesenchymal Stem Cells: Preliminary In Vitro Results

(1) Background: Implantation of metal-based scaffolds is a common procedure for treating several diseases. However, the success of the long-term application is limited by an insufficient endothelialization of the material surface. Nanostructured modifications of metal scaffolds represent a promising approach to faster biomaterial osteointegration through increasing of endothelial commitment of the mesenchymal stem cells (MSC). (2) Methods: Three different nanotubular Ti surfaces (TNs manufactured by electrochemical anodization with diameters of 25, 80, or 140 nm) were seeded with human MSCs (hMSCs) and their exosomes were isolated and tested with human umbilical vein endothelial cells (HUVECs) to assess whether TNs can influence the secretory functions of hMSCs and whether these in turn affect endothelial and osteogenic cell activities in vitro. (3) Results: The hMSCs adhered on all TNs and significantly expressed angiogenic-related factors after 7 days of culture when compared to untreated Ti substrates. Nanomodifications of Ti surfaces significantly improved the release of hMSCs exosomes, having dimensions below 100 nm and expressing CD63 and CD81 surface markers. These hMSC-derived exosomes were efficiently internalized by HUVECs, promoting their migration and differentiation. In addition, they selectively released a panel of miRNAs directly or indirectly related to angiogenesis. (4) Conclusions: Preconditioning of hMSCs on TNs induced elevated exosomes secretion that stimulated in vitro endothelial and cell activity, which might improve in vivo angiogenesis, supporting faster scaffold integration.