Coatings Functionalization via Laser versus Other Deposition Techniques for Medical Applications: A Comparative Review

The development of new biological devices in response to market demands requires continuous efforts for the improvement of products’ functionalization based upon expansion of the materials used and their fabrication techniques. One viable solution consists of a functionalization substrate covered by layers via an appropriate deposition technique. Laser techniques ensure an enhanced coating’s adherence to the substrate and improved biological characteristics, not compromising the mechanical properties of the functionalized medical device. This is a review of the main laser techniques involved. We mainly refer to pulse laser deposition, matrix-assisted, and laser simple and double writing versus some other well-known deposition methods as magnetron sputtering, 3D bioprinting, inkjet printing, extrusion, solenoid, fuse-deposition modeling, plasma spray (PS), and dip coating. All these techniques can be extended to functionalize surface fabrication to change local morphology, chemistry, and crystal structure, which affect the biomaterial behavior following the chosen application. Surface functionalization laser techniques are strictly controlled within a confined area to deliver a large amount of energy concisely. The laser deposit performances are presented compared to reported data obtained by other techniques.

Review of the coatings used for brake discs regarding their wear resistance and environmental effect

Wear of a friction pair of brake (brake disc and pads), in addition to reducing the active safety of vehicles, leads to the formation of particles that can affect the environment and human health. In addition to the technologies that are being developed for the collection of particles created by the wear of brakes during braking process, today new materials are being introduced, as well as various technologies for processing friction pairs with the aim of reducing brake wear and thus the formation of particles. Furthermore, today, technologies for coating (cladding) the friction surfaces of disc brakes with some materials are increasingly applied and researched, in order to reduce the wear intensity (wear rate) of disc brakes, i.e. the emission of particles created by wear of friction pairs. The aim of this paper is to analyse and review different deposition techniques and materials used for brake discs coatings, as well as the effect it has on the wear rate of friction pair. There are many coating deposition techniques, and special attention is paid to the technology of laser hardfacing of brake rotors.

Comparative studies on the morphological, structural and optical properties of NiO thin films grown by vacuum and non-vacuum deposition techniques

The structural and optical characteristics of Nickel oxide thin films (NiOTF) formed on the soda-lime glass substrate (SLG) under vacuum and non-vacuum conditions are investigated in this work. The difference between RFMS (Radio Frequency Magnetron Sputtering; vacuum) and SP (spray pyrolysis; non-vacuum) was helpful in the development of NiOTF. Deposited films data for this study were characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), scanning probe microscopy (SPM), and optical spectrophotometer. Structural studies disclosed that NiOTF developed via RFMS technique was more uniform with large crystals and lower surface roughness in contrast to that of developed via SP technique. Transmittance spectrum divulged that the transmittance of spray pyrolyzed NiO films are ~10% less than that of ones produced by RFMS. Urbach energy analysis of NiOTF developed by RFMS and SP affirmed the findings of structural studies.

Characterizing the stress and electrical properties of superconducting molybdenum films

In the process of minimizing stress in sputtered Molybdenum (Mo) films for fabricating transition-edge sensor (TES) devices, we have investigated correlations between the stress and film deposition parameters. At a fixed sputtering power, the tensile stress of our film samples decreases toward both low and high ends of Ar pressure, suggestive of two physical mechanisms at work: an “atomic peening” effect at low Ar pressure and the development of voids at high Ar pressure. We have also carried out correlative studies of the stress and electrical properties (including superconducting critical temperature and residual resistivity) of the film samples, and found that the results are complex. We have made extensive comparisons with the published results, and attempted to explain the discrepancies in terms of film deposition techniques, sample preparation and treatment, and dynamical ranges of measurements. It is fairly clear that the microscopic properties, including porosity and disorder, of Mo films may have significant impact on the correlations.

Laser Actuated Microgripper Using Optimized Chevron-Shaped Actuator

In this paper, we propose a laser actuated microgripper that can be activated remotely for micromanipulation applications. The gripper is based on an optothermally actuated polymeric chevron-shaped structure coated with optimized metallic layers to enhance its optical absorbance. Gold is used as a metallic layer due to its good absorption of visible light. The thermal deformation of the chevron-shaped actuator with metallic layers is first modeled to identify the parameters affecting its behavior. Then, an optimal thickness of the metallic layers that allows the largest possible deformation is obtained and compared with simulation results. Next, microgrippers are fabricated using conventional photolithography and metal deposition techniques for further characterization. The experiments show that the microgripper can realize an opening of 40 µm, a response time of 60 ms, and a generated force in the order of hundreds of µN. Finally, a pick-and-place experiment of 120 µm microbeads is conducted to confirm the performance of the microgripper. The remote actuation and the simple fabrication and actuation of the proposed microgripper makes it a highly promising candidate to be utilized as a mobile microrobot for lab-on-chip applications.

Review—(Mn,Co)3O4-Based Spinels for SOFC Interconnect Coating Application

With the reduction of solid oxide fuel cell (SOFC) operating temperature to the range of 600 − 800℃, Cr-containing ferritic alloys have become the preferred interconnect material, which unfortunately are susceptible to continuous scale growth and Cr volatility at the SOFC operating temperatures. The (Mn,Co)3O4 spinel system is widely regarded as the most effective coating for SOFC interconnect protection, due to its high thermal and electrical conductivity, adequate coefficient of thermal expansion, and excellent Cr blocking capability. This article reviews the physical and chemical properties of the (Mn,Co)3O4-based spinels; different types of coating precursors and deposition techniques; and the effects of spinel composition, quality and thickness on the coating performance. It is concluded that the spinel coating composition, quality, and thickness are more critical than the coating process in affecting the overall coating performance.

Polymer Blends and Polymer Nanocomposites for Photovoltaic (PV) Cells and an Investigation of the Material Deposition Techniques in PV Cell Fabrication

Polymer photovoltaics (PV) offer the advantage of low-cost, mass-produced, flexible PV films, but they generally suffer from a low-power conversion efficiency (PCE) compared to silicon. This paper studies ITO/PEDOT:PSS/bulk heterojunction/Al PV cells, where two different bulk heterojunction blends are researched: P3HT/PC61BM and PCDTBT/PC70BM. The addition of multiwall carbon nanotubes (CNT) is explored as a conductive network to accelerate the electron transport and extraction to the outer aluminium current collector while reducing the chance of charge recombinations. Several layer deposition techniques are investigated: spin coating and casting, as well as techniques that would induce transverse orientation of polymer grains, including inkjet printing, electrophoresis and the application of a transverse AC field during annealing. Transverse orientation techniques produced architectures that would facilitate charge transport without recombinations, but it is recommended to avoid such techniques for the deposition of conductive PEDOT:PSS and CNT layers as they create a high surface roughness that leads to short circuiting. The best performing PV cell is the ITO/PEDOT:PSS/PCDTBT/PC70BM/CNT/Al structure with a PCE of 11%.