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Enhancement of osteoblast activity on nanostructured NiTi/hydroxyapatite coatings on additive manufactured NiTi metal implants by nanosecond pulsed laser sintering
摘要： Background: The osteoinductive behaviors of nitinol (NiTi)-based metal implants for bone regeneration are largely dependent on their surface composition and topology. Continuous-mode laser sintering often results in complete melting of the materials and aggregation of particles, which lack control of heat transfer, as well as microstructural changes during sintering of the nanocomposite materials. Methods: In the current study, in situ direct laser deposition was used to additively manufacture three-dimensional NiTi structures from Ni and Ti powders. The mechanical property of NiTi has been shown to be similar to bone. Nanosecond pulsed laser sintering process was then utilized to generate a nanoporous composite surface with NiTi alloy and hydroxyapatite (HA) by ultrafast laser heating and cooling of Ni, Ti, and HA nanoparticles mixtures precoated on the 3D NiTi substrates; HA was added in order to improve the biocompatibility of the alloy. We then studied the underlying mechanism in the formation of NiTi/HA nanocomposite, and the synergistic effect of the sintered HA component and the nanoporous topology of the composite coating. In addition, we examined the activity of bone-forming osteoblasts on the NiTi/HA surfaces. For this, osteoblast cell morphology and various biomarkers were examined to evaluate cellular activity and function. Results: We found that the nanoscale porosity delivered by nanosecond pulsed laser sintering and the HA component positively contributed to osteoblast differentiation, as indicated by an increase in the expression of collagen and alkaline phosphatase, both of which are necessary for osteoblast mineralization. In addition, we observed topological complexities which appeared to boost the activity of osteoblasts, including an increase in actin cytoskeletal structures and adhesion structures. Conclusion: These findings demonstrate that the pulsed laser sintering method is an effective tool to generate biocompatible coatings in complex alloy-composite material systems with desired composition and topology. Our findings also provide a better understanding of the osteoinductive behavior of the sintered nanocomposite coatings for use in orthopedic and bone regeneration applications.
关键词： metal implants,pulsed laser coating,biocompatibility,differentiation,bone regeneration,alkaline phosphatase,osteoinductive behavior
更新于2025-09-23 15:22:29
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Synthesis and characterization of spin-coated clay/PVDF thin films
摘要： This paper reports the fabrication of Cloisite-15A (C-15A)-dispersed polyvinylidene fluoride (PVDF) nanocomposite thin films by spin coating and their characterization for sensor applications. The effects of nanoclay, duration of ultrasonication and spinning speed on the morphology and properties of thin films were studied. The influence of these parameters on the amount of β-phase was analysed using Fourier transform infrared (FTIR) and X-ray diffraction (XRD) techniques. The influence of C-15A on the morphology and surface quality of thin films was analysed by scanning electron microscopy (SEM). Piezoelectric coefficient was measured at 110 Hz and 0.25 N. Contact angle was measured to assess the hydrophobicity of thin films. The β-phase of 82.97% was obtained in the specimens with 5 wt% C-15A, processed at 500 rpm and spun for 35 min. The piezoelectricity of the specimens increased from ?18 to ?25 pC N?1. Experiments were conducted as per L16 orthogonal array.
关键词： spin coating,Cloisite-15A,β-crystals,PVDF/clay thin films,piezoelectricity
更新于2025-09-23 15:22:29
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Development of a photon induced drug-delivery implant coating
摘要： A thin surface coating intended for medical devices such as implants where local drug release is enabled using near infrared light (NIR) as an external stimulus has been developed. The delivery system consists of a thin Poly (N-isopropylacrylamide)-co-acrylamide (PNIPAAm-AAm) polymer layer with incorporated gold nanorods (GNRs). The aspect ratio of the GNRs were chosen to absorb NIR light, thus ?tting the biological window of low tissue absorption, to locally heat the polymeric layer to initiate a drug release. Hence, controlled drug delivery from a surface within tissue orchestrated from outside the body is achievable. Composition of the PNIPAAm-AAm co-polymer was systematically varied to ?nd a suitable phase transition temperature for in vivo applications. Di?erential scanning calorimetry (DSC) analysis showed that PNIPAAm-AAm containing 10% acrylamide had an appropriate phase transition temperature of 42 °C. As visualized by scanning electron microscopy (SEM), the surface coating consisted of 200 nm uniform polymer layer. Quartz crystal microbalance with dissipation monitoring (QCM-D) analysis coupled with in situ NIR irradiation demonstrated a dramatic shift in frequency that was attributed to mass being released from the surface upon irradiation. This mass release correlated well with the drug release pro?le as determined using UV/VIS spectroscopy with phenol as a model drug. In addition, proof-of-concept of the drug-delivery system was demonstrated by releasing the antibiotic vancomycin to eradicate Staphylococcus epidermidis bacteria in culture.
关键词： Thermo-sensitive,Drug delivery,Controlled release,Poly(N-isopropylacrylamide),Implant coating
更新于2025-09-23 15:22:29
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[IEEE 2018 13th International Congress Molded Interconnect Devices (MID) - Wu?rzburg (2018.9.25-2018.9.26)] 2018 13th International Congress Molded Interconnect Devices (MID) - Applications of Three Dimensional Laser Induced Metallization Technology with Polymer Coating
摘要： A fully developed three dimensional laser induced metallization (LIM) on molded interconnect devices (MIDs) is widely used on various products. The target substrate is sprayed with a special thin layer (50 μm) polymer coating first, and heated at 80°C to cure. Then using laser to define the pattern of conductors and induce the catalyst in the special polymer layer. After the electroless copper plating, the pattern is metallized. The whole process can be fully copy again on layer-by-layer to achieve the idea of multi-layer. For the high feasibility on any complex surface and material, such as glass, plastic, ceramic, etc., the LIM technology can be used for vary kind of products. In this paper, the LIM technology has applied on QR code stickers, 2G/3G/4G all-in-one compact antenna, mm-wave antenna, built-in antenna on mobile phone case, multi-layer NFC antenna, and humanoid robot finger. The QR code can be patterning on a thin film of 100 um and with a great flexibility. In addition, the return loss of 2G/3G/4G all-in-one compact antenna reaches the 3:1 VSWR standard, and the radiation efficiency is larger than 60% within the operation frequency. The built-in antenna on mobile phone case can reduce the waste of space and strongly secure the antenna from detachment. The LIM technology applied on the ceramic substrate can successfully fabricate a high directionality 38GHz mm-wave antenna and with above 10dBi of array gain, average efficiency up to 50%, and bandwidth up to 2 GHz. Furthermore, the multi-layer NFC antenna can successfully reduce the size and reach the maximum read distance of 3 cm. Using the same idea of multi-layer, the capacitive tactile sensor that can sense both normal and shear force is placed on humanoid robot finger to provide the tactile ability. The products described above will be briefly introduced in this paper and related testing results will be mentioned.
关键词： Antenna,Multilayer,3D-MID,Polymer Coating,Laser Induced Metallization
更新于2025-09-23 15:22:29
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Understanding Film-to-Stripe Transition of Conjugated Polymers Driven by Meniscus Instability
摘要： Meniscus instability during meniscus-guided solution coating and printing of conjugated polymers has significant impact on the deposit morphology and the charge transport characteristics. The lack of quantitative investigation on meniscus-instability-induced morphology transition for conjugated polymers hindered the ability to precisely control conjugated polymer deposition for desired applications. Herein, we report a film-to-stripe morphology transition caused by stick-and-slip meniscus instability during solution coating seen in multiple donor-acceptor polymer systems. We observe the coexistence of film and stripe morphologies at the critical coating speed. Surprisingly, higher charge carrier mobility is measured in transistors fabricated from stripes despite their same deposition condition as the films at the critical speed. To understand the origin of the morphology transition, we further construct a generalizable surface free energy model to validate the hypothesis that the morphology transition occurs to minimize the system surface free energy. As the system surface free energy varies during a stick-and-slip cycle, we focus on evaluating the maximum surface free energy at a given condition, which corresponds to the sticking state right before slipping. Indeed, we observe increase of the maximum system surface free energy with increase in coating speed prior to film-to-stripe morphology transition and abrupt drop in the maximum system surface free energy post-transition when the coating speed is further increased, which is associated with reduced meniscus length during stripe deposition. Such energetic change originates from the competition between pinning and depinning forces on a partial wetting substrate which underpins the film-to-stripe transition. This work establishes a quantitative approach for understanding meniscus-instability-induced morphology transition during solution coating. The mechanistic understanding may further facilitate the use of meniscus instability for lithography-free patterning or to suppress instability for highly homogeneous thin film deposition.
关键词： conjugated polymer,meniscus instability,printed electronics,morphology transition,solution coating
更新于2025-09-23 15:21:21
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Setup to Study the in Situ Evolution of Both Photoluminescence and Absorption during the Processing of Organic or Hybrid Semiconductors
摘要： In situ measurement techniques, applied during the solution processing of novel semiconductors such as organic semiconductors or hybrid perovskites, have become more and more important to understand their film formation. In that context, it is crucial to determine how the optical properties, namely photoluminescence (PL) and absorption, evolve during processing. However, until now PL and absorption have mostly been investigated independently, significantly reducing the potential insights into film formation dynamics. To tackle this issue we present the development of a detection system that allows simultaneous measurement of full absorption and PL spectra during solution processing of the investigated film. We also present a spin-coater system attachable to the detection system, where the temperature of the substrate on which the film is processed can be changed. We performed test measurements by spin coating the well-known conjugated polymer P3HT demonstrating the potential of this technique. By considering absorption and corresponding PL, we extract the PL quantum yield (PLQY) during processing, which decreases with substrate temperature. Furthermore, we identify a significant red shift of the PL just prior to the onset of the aggregation process, indicating the importance of chain planarization prior to solid film formation.
关键词： photoluminescence,in situ measurement,organic semiconductors,hybrid perovskites,spin-coating,film formation,absorption,P3HT
更新于2025-09-23 15:21:21
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Thermal stability investigation of the SS/MO/Al <sub/>2</sub> O <sub/>3</sub> spectrally selective solar absorber coatings
摘要： A novel Mo/Al2O3 spectrally selective solar absorber coating is deposited onto stainless steel (SS) substrates using magnetron sputtering method, which exhibits a high absorptance (α) of 0.90 and a low emittance (ε) of 0.08. In order to investigate the thermal stability, the SS/Mo/Al2O3 coatings are annealed in air and vacuum at di?erent temperatures. The surface morphology, microstructure, composition distribution, di?usion and optical properties before and after high-temperature annealing are characterised by scanning electronic microscopy (SEM), atom force microscopy (AFM), X-ray di?raction (XRD), micro-Raman spectroscopy, UV–vis spectrophotometer and emissometer. Experimental results indicate that the coatings are stable in air at 350°C. The values of solar absorptance and emittance below 350°C are 0.87–0.90 and 0.06–0.08, respectively. The coatings remain stable after annealed at 600°C in vacuum for 2 h with a good spectral selectivity (α/ε) of 0.89/0.06.
关键词： microstructure,Spectrally selective coating,annealing,thermal stability
更新于2025-09-23 15:21:21
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Sol-gel coating of colloidal particles deposited glass surface pertinent to self-cleaning applications
摘要： A sol-gel coating using colloidal silica on a glass surface is carried out towards improving the self-cleaning properties. The optical transmittance and hydrophobic characteristics of the resulting coating are analyzed using analytical tools. Since the sol-gel coating reduces the optical transmittance of the glass samples, due to scattering and diffusion of the incident optical radiation at the coating surface, silicon oil (Sigma-Aldrich, 10 cSt) impregnation method is introduced to improve the optical transmittance. Silicon oil has good heat transfer characteristics, stable properties over range of temperatures, and optically transparent characteristics with refractive index of 1.4034. The resulting coated surface is tested in outdoor environments to examine the dust effect on the optical transmittance of the sol-gel coated and oil impregnated glass samples. It is found that deposition of 75 nm size silica particles on the glass surface modifies the texture height of the sol-gel coating, which in turn, improves the surface hydrophobicity. Sol-gel coating results in a web-type fully connected porous structures; in which case, agglomeration of the synthesized particles is responsible for the fully connected porous texture at the coating surface. The optical transmittance remains low for the sol-gel coated glass samples because of scattering and diffusion of the incident optical radiation at the coating surface. Silicon oil impregnation improves the optical transmittance of the sol-gel coated samples. The dust particles immerse into the oil film and reduce the optical transmittance of the oil impregnated samples in outdoor environments.
关键词： Sol-gel coating,Hydrophobicity,Silicon oil impregnation,Silica,Outdoor testing
更新于2025-09-23 15:21:21
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Photoluminescence of silicon vacancy centres as conceptual indicator for the condition of diamond protection coatings
摘要： Due to the outstanding properties polycrystalline diamond coatings are used for wear protection on tools and work pieces. Thereby adhesive and abrasive wear as well as spalling of the coating can lead to damage and downtimes of the working machines. By depositing silicon doped multilayer diamond coatings, an indication of the condition of the coatings could be achieved. In this study the behaviour and transmission of the zero-phonon line of silicon vacancy centres is investigated in doped multilayer diamond coatings. The in-situ silicon doped diamond coatings were synthesized in use of an atmospheric laser-based plasma chemical vapour deposition. Photoluminescence measurements were performed with an excitation area of 18 mm2 and a wavelength of 248 nm. While the photoluminescence of the doped layers conceptually proves suitability as an indicator for the condition of the coating, the undoped diamond layers in the coatings show a high transmissivity to the zero-phonon line for the used parameters.
关键词： Wear,Luminescent materials,Protective coating,Diamond films,Chemical vapour deposition
更新于2025-09-23 15:21:21
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Water Impact Resistant and Antireflective Superhydrophobic Surfaces Fabricated by Spray Coating of Nanoparticles: Interface Engineering via End-Grafted Polymers
摘要： Fully transparent and water impact resistant superhydrophobic coatings are of great importance for a range of applications including photovoltaics, photonics, automotive windshields, and building windows. A widely utilized approach to fabricate such coatings involves solution-based deposition of hydrophobic nanoparticles. A central challenge is that these coatings do not simultaneously offer high levels of water repellency, perfect transparence, and water impact resistance. Here we demonstrate that end-grafted polymers present excellent interfaces for spray-coated hydrophobic nanoparticles and enable fabrication of water impact resistant and antireflective superhydrophobic coatings (SHPARCs). Depending on the backbone chemistry and thickness, end-grafted polymers uniquely interacted with the fluorinated nanoparticles, resulting in nanostructured films that provided reduction of reflective losses and protection from the impact of water droplets. Counterintuitively, substrates modified with end-grafted hydrophilic polymers exhibited high water impact resistance: the sliding angle of SHPARC on 12 nm thick end-grafted poly(ethylene glycol) layer was <2° after exposure to 100000 water droplets. SHPARC increased the transparency of the glass substrate by ～5% through omnidirectional antireflectivity. We finally demonstrate application of SHPARC on a large area (156 × 156 mm2) silicon solar cell without significant (<0.23%) reduction of the power conversion efficiency, illustrating the promise of the presented approach in fabrication of self-cleaning photovoltaic modules.
关键词： water impact resistance,antireflective,spray coating,nanoparticles,end-grafted polymers,superhydrophobic coatings
更新于2025-09-23 15:21:21