J. del Val

Three-dimensional bioactive glass implants fabricated by rapid prototyping based on CO2 laser cladding

Three-dimensional bioactive glass implants were produced by rapid prototyping based on laser cladding without using moulds. CO(2) laser radiation was employed to melt 45S5 and S520 bioactive glass particles and to deposit the material layer by layer following a desired geometry. Controlled thermal input and cooling rate by fine tuning of the processing parameters allowed the production of crack-free fully dense implants. Microstructural characterization revealed chemical composition stability, but crystallization during processing was extensive when 45S5 bioactive glass was used. Improved results were obtained using the S520 bioactive glass, which showed limited surface crystallization due to an expanded sintering window (the difference between the glass transition temperature and crystallization onset temperature). Ion release from the S520 implants in Tris buffer was similar to that of amorphous 45S5 bioactive glass prepared by casting in graphite moulds. Laser processed S520 scaffolds were not cytotoxic in vitro when osteoblast-like MC3T3-E1 cells were cultured with the dissolution products of the glasses; and the MC3T3-E1 cells attached and spread well when cultured on the surface of the materials.

Laser-assisted production of spherical TiO2 nanoparticles in water

TiO(2) nanoparticles with controllable average diameter have been obtained by laser ablation in water. A monomode ytterbium doped fiber laser (YDFL) was used to ablate a metallic titanium target placed in deionized water. The resulting colloidal solutions were subjected to laser radiation to study the resizing effect. The crystalline phases, morphology and optical properties of the obtained nanoparticles were characterized by means of transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), x-ray energy dispersive spectroscopy (EDS) and UV-vis absorption spectroscopy. The colloidal suspensions produced consisting of titanium dioxide crystalline nanoparticles show almost perfect spherical shape with diameters ranging from 3 to 40 nm. The nanoparticles are polycrystalline and exhibit anatase as well as rutile phases.

Laser surface texturing of bioactive materials

Surface topography and chemical composition are two factors affecting the osseointegration of an implant, extremely relevant to satisfy all the requirements needed for bio-implant applications. Nevertheless, some of the materials used for implants do not satisfy properties such as biocompatibility and osteointegration. In this sense, lasers are adequate tools to produce macro-and micro-structures on metallic alloys or polymer surfaces in order to improve their biological response. In view of this, the process of laser surface texturing of two common materials used in implants, such as titanium and PEEK (polyetheretherketone) is investigated in the present work, both from a theoretical and experimental point of view. In order to perform this process, influence of different laser wavelengths has also been studied (λ = 10600, 1064, 532, and 355 nm).Surface topography and chemical composition are two factors affecting the osseointegration of an implant, extremely relevant to satisfy all the requirements needed for bio-implant applications. Nevertheless, some of the materials used for implants do not satisfy properties such as biocompatibility and osteointegration. In this sense, lasers are adequate tools to produce macro-and micro-structures on metallic alloys or polymer surfaces in order to improve their biological response. In view of this, the process of laser surface texturing of two common materials used in implants, such as titanium and PEEK (polyetheretherketone) is investigated in the present work, both from a theoretical and experimental point of view. In order to perform this process, influence of different laser wavelengths has also been studied (λ = 10600, 1064, 532, and 355 nm).

Processing of pure Ti by rapid prototyping based on laser cladding

Rapid prototyping based on laser cladding is an additive manufacturing (AM) process based on the overlapping of cladding tracks to produce functional components. Powder or wire are fed into a melting pool created using laser radiation as a heat source and the relative movement between the beam and the work piece makes possible to generate pieces layer-by-layer. This technique can be applied for any material which can be melted and the components can be manufactured directly according to a computer aided design (CAD) model. Additive manufacturing is particularly interesting to produce titanium components because, in this case, the loss of material produced by subtractive manufacturing methods is highly costly. Moreover, titanium and its alloys are widely used in biomedical, aircraft, chemical and marine industries due to their biocompatibility, excellent corrosion resistance and superior strength-to-weight ratio. In this research work, a near-infrared laser delivering a maximum power of 500W is used to produce pure titanium thin parts. Dimensions and surface morphology are characterized using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), the hardness by nanoindentation and the composition by X-Ray Diffraction (XRD) and Energy Dispersive X-Ray Spectroscopy (EDS). The aim of this work is to establish the conditions under which satisfactory properties are obtained and to understand the relationship between microstructure/properties and deposition parameters.

Laser bioengineering of glass-titanium implants surface

Osseointegration is the mean challenge when surgical treatments fight against load-bearing bone diseases. Absolute bone replacement by a synthetic implant has to be completed not only from the mechanics point of view, but also from a biological approach. Suitable strength, resilience and stress distribution of titanium alloy implants are spoiled by the lack of optimal biological characteristics. The inert quality of extra low interstitial titanium alloy, which make it the most attractive metallic alloy for biomedical applications, oppose to an ideal surface with bone cell affinity, and capable to stimulate bone attachment bone growth. Diverse laser treatments have been proven as effective tools to modify surface properties, such as wettability in contact to physiological fluids, or osteoblast guided and slightly enhanced attachment. The laser surface cladding can go beyond by providing titanium alloy surfaces with osteoconduction and osteoinduction properties. In this research work, the laser radiation is used to produce bioactive glass coatings on Ti6Al4V alloy substrates. Specific silicate bioactive glass compositions has been investigated to achieve suitable surface tension and viscosity temperature behavior during processing, and to provide with the required release of bone growth gene up regulation agents in the course of resorption mediated by physiological fluids. The produced coatings and interfaces, the surface osteoconduction properties, and the chemical species release in simulated physiological fluid were characterized by scanning electron microscopy (SEM), hot stage microscopy (HSM), X-ray diffraction (XRD), X ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR).

The influence of the assist gas flow regime on the laser cutting of aeronautic aluminium alloys

The aerodynamic interactions of the assist gas during fusion laser cutting determine the cutting performance. Therefore, this subject has been object of multiple studies in order to surpass the drawbacks exhibited by conventional cutting heads. Utilization of off-axis De Laval nozzles to inject a supersonic gas jet has been demonstrated to be an effective option to increase performance and cut quality during fusion laser cutting. However, all attempts performed in this direction have been carried out using axisymmetric supersonic nozzles.In this work, cutting results performed by means of a novel cutting head incorporating an off-axis nozzle with rectangular cross section are presented. The results demonstrate the capability of this novel approach to laser cut difficult materials such as Al-Cu alloys for aeronautic applications.The aerodynamic interactions of the assist gas during fusion laser cutting determine the cutting performance. Therefore, this subject has been object of multiple studies in order to surpass the drawbacks exhibited by conventional cutting heads. Utilization of off-axis De Laval nozzles to inject a supersonic gas jet has been demonstrated to be an effective option to increase performance and cut quality during fusion laser cutting. However, all attempts performed in this direction have been carried out using axisymmetric supersonic nozzles.In this work, cutting results performed by means of a novel cutting head incorporating an off-axis nozzle with rectangular cross section are presented. The results demonstrate the capability of this novel approach to laser cut difficult materials such as Al-Cu alloys for aeronautic applications.

Laser micro-cladding: A novel laser additive technique to produce hard micro-coatings

The high demand of the micro-products manufacturing, driven by the micro-electromechanical systems (MEMS), has generated a series of new production techniques. Micro-cladding laser technique can be considered as an evolution of the conventional laser cladding. We propose this additive technique as an alternative to thin film techniques, based on its capability to process different kind of materials having higher deposition rates. Lateral powder injection laser micro-cladding has been applied to produce metallic clad strips with geometrical characteristics in the micrometer range (i.e.: features in the range of the tenths of microns). Main feature of laser micro-cladding processing is the ability to reduce the thermal load applied to the substrate, a critical parameter in some applications where the laser interaction zone is close to sensitive elements, but keeping the good mechanical properties of the coating material. Reparation of defective micro-parts and rapid prototyping are areas of application of this rapid one step micro-coating laser technique to explore.A new experimental set-up based on the use of a single mode fibre laser and a novel powder stream conveying system adequate to supply submicron particles was used to produce the micro-coatings. A systematic study of the influence of several processing parameters on the geometric features of the clad strips was carried out.The high demand of the micro-products manufacturing, driven by the micro-electromechanical systems (MEMS), has generated a series of new production techniques. Micro-cladding laser technique can be considered as an evolution of the conventional laser cladding. We propose this additive technique as an alternative to thin film techniques, based on its capability to process different kind of materials having higher deposition rates. Lateral powder injection laser micro-cladding has been applied to produce metallic clad strips with geometrical characteristics in the micrometer range (i.e.: features in the range of the tenths of microns). Main feature of laser micro-cladding processing is the ability to reduce the thermal load applied to the substrate, a critical parameter in some applications where the laser interaction zone is close to sensitive elements, but keeping the good mechanical properties of the coating material. Reparation of defective micro-parts and rapid prototyping are areas of application of t...

Effects of internal design geometry in de laval nozzles for off-axis assist gas injection on inert-gas laser cutting performance

The aerodynamic interactions of the assist gas during fusion laser cutting are an essential parameter determining cutting performance. This subject has been object of multiple studies to determine the influence of the assist gas jet interactions with the workpiece in order to design assist gas injection systems which surpass the drawbacks exhibited by conventional cutting heads. Cutting heads incorporating off-axis de Laval nozzles to inject a supersonic gas jet has been demonstrated, by different authors, to be an effective option to increase performance and cut quality during fusion laser cutting of difficult materials. However, all efforts performed in this direction, have been accomplished using nozzles with axial symmetry.In this work, the fundamentals of a novel cutting head incorporating an off-axis nozzle, with non-axial internal symmetry are described. Gas flow inside the cut kerf is analyzed by means of flow visualization techniques. Moreover, cutting results are compared to those obtained through cutting heads assisted by axial-symmetric de Laval nozzles and sonic nozzles in a configuration off-axis and coaxial respectively with the laser beam.The aerodynamic interactions of the assist gas during fusion laser cutting are an essential parameter determining cutting performance. This subject has been object of multiple studies to determine the influence of the assist gas jet interactions with the workpiece in order to design assist gas injection systems which surpass the drawbacks exhibited by conventional cutting heads. Cutting heads incorporating off-axis de Laval nozzles to inject a supersonic gas jet has been demonstrated, by different authors, to be an effective option to increase performance and cut quality during fusion laser cutting of difficult materials. However, all efforts performed in this direction, have been accomplished using nozzles with axial symmetry.In this work, the fundamentals of a novel cutting head incorporating an off-axis nozzle, with non-axial internal symmetry are described. Gas flow inside the cut kerf is analyzed by means of flow visualization techniques. Moreover, cutting results are compared to those obtained throu...

Laser assisted production of calcium phosphate nanoparticles from marine origin

The first calcium phosphate based biomaterials were introduced in the market almost forty years ago and, due to the compositional resemblance with the mineral constituents of bones and teeth, they became extensively employed in biomedical applications involving bone defects repair. Nowadays, research on calcium phosphate biomaterials is focused on developing the potential of additional dimensional and morphological similarities to those biological structures. Thus, specific physiochemical properties of hydroxylapatite (HA), Ca10(PO4)6(OH)2, are considered to be influenced by its presence as nanometric particles with a platelet shape in bones and teeth. Moreover, the use of β-tricalcium phosphate (β-TCP), Ca3(PO4)2 in nanosize scale and low crystallinity has been reported to improve the bioactivity.Among the different methods of nanoparticle production, laser ablation is a powerful technique to improve the dimensional and morphological characteristics of calcium phosphate biomaterials. Direct formation of nanoparticles in solutions, the absence of contamination, maximum particle collection efficiency, easiness of preparation, or low processing costs constitute some of the advantages of this technique. In this work, we report the results of nanoparticles obtained by laser ablation of calcium phosphate targets in liquid media. Different infrared laser sources, operating at wavelengths 1064, 1075 and 10600 nm and coupled to identical focal length focusing heads were employed to study the influence of processing conditions, such as pulse energy, operating frequency, or irradiance, on the properties of the produced nanoparticles. The morphology and the composition of these calcium phosphate nanoparticles were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and conventional and high resolution transmission electron microscopy (TEM, HRTEM).The first calcium phosphate based biomaterials were introduced in the market almost forty years ago and, due to the compositional resemblance with the mineral constituents of bones and teeth, they became extensively employed in biomedical applications involving bone defects repair. Nowadays, research on calcium phosphate biomaterials is focused on developing the potential of additional dimensional and morphological similarities to those biological structures. Thus, specific physiochemical properties of hydroxylapatite (HA), Ca10(PO4)6(OH)2, are considered to be influenced by its presence as nanometric particles with a platelet shape in bones and teeth. Moreover, the use of β-tricalcium phosphate (β-TCP), Ca3(PO4)2 in nanosize scale and low crystallinity has been reported to improve the bioactivity.Among the different methods of nanoparticle production, laser ablation is a powerful technique to improve the dimensional and morphological characteristics of calcium phosphate biomaterials. Direct formation of ...

A highly versatile novel technique based on laser cladding to produce coatings in the micrometer range

The fabrication of microproducts is being one of the most important industries in the last years, with a huge increase in the demand of new solutions and products in different fields of application like medicine, microelectronics, automotive and telecommunication industry.There is an appreciable amount of well-established techniques to produce microproducts; subtractive techniques as microdrilling, microcutting and microtexturing, as well as additive techniques like thin film or sputtering. However to face new challenges in the world of micromanufacturing the industry has to develop new techniques. In that sense, the laser microcladding is shown in this work as a promising new technique to obtain microproducts, which can be seen as a downscaling of the firmly established conventional laser cladding technique, that combine the easy implementation and automation of laser cladding in the industry, as well as a high versatility, with the production of coatings and pieces in the micrometer range, allowing to work close to sensitive elements due to the reduced thermal load applied and keeping the good mechanical properties of the coating material.With the objective of giving an adequate response to the new requirements of microproducts, a new experimental set-up has been built based on a high brightness and high quality laser beam. Moreover, a novel powder stream conveying system has been developed to obtain a stable stream of micron and submicron particles of different materials. The feasibility of the laser microcladding has been tested with a systematic study of the influence of several processing parameters, with a wide range of materials of different nature, to create tracks whose geometrical and mechanical properties have been studied.The fabrication of microproducts is being one of the most important industries in the last years, with a huge increase in the demand of new solutions and products in different fields of application like medicine, microelectronics, automotive and telecommunication industry.There is an appreciable amount of well-established techniques to produce microproducts; subtractive techniques as microdrilling, microcutting and microtexturing, as well as additive techniques like thin film or sputtering. However to face new challenges in the world of micromanufacturing the industry has to develop new techniques. In that sense, the laser microcladding is shown in this work as a promising new technique to obtain microproducts, which can be seen as a downscaling of the firmly established conventional laser cladding technique, that combine the easy implementation and automation of laser cladding in the industry, as well as a high versatility, with the production of coatings and pieces in the micrometer range, allowing to w...