Joris Lousteau

Novel biocompatible and resorbable UV-transparent phosphate glass based optical fiber

In this paper the first glass based resorbable optical fiber is manufactured and characterized, showing values of attenuation loss from one to two orders of magnitude lower than the polymeric based bioresorbable devices reported in literature. The fiber behaves as a single-mode waveguide at the lower limit of the first biological window (1300 nm) and as a multi-mode waveguide in the visible region (630 nm). Highly transparent calcium-phosphate glasses (PGs) are proposed as a new class of materials for biomedical optics, managing to combine for the first time in a vitreous material solubility in aqueous media, transparency in the near UV region, low intrinsic attenuation loss and thermal stability during fiber drawing. In-vitro tests in physiological conditions show dissolution kinetics of glass fibers in about a month.

Phosphate glass fibre scaffolds: tailoring of the properties and enhancement of the bioactivity through mesoporous glass particles

Novel bone glass fibre scaffolds were developed by thermally bonding phosphate glass fibres belonging to the P2O5-CaO-Na2O-SiO2-MgO-K2O-TiO2 system (TiPS2.5 glass). Scaffolds with fibres of 85 or 110μm diameter were fabricated, showing compressive strength in the range of 2-3.5MPa, comparable to that of the trabecular bone. The effect of different thermal treatments and fibre diameters and length on the final scaffold structure was investigated by means of micro-CT analysis. The change of the sintering time from 30 to 60min led to a decrease in the scaffold overall porosity from 58 to 21vol.% for the 85μm fibre scaffold and from 50 to 40vol.% when increasing the sintering temperature from 490 to 500°C for the 110μm fibre scaffold. The 85μm fibres resulted in an increase of the scaffold overall porosity, increased pore size and lower trabecular thickness; the use of different fibre diameters allowed the fabrication of a scaffold showing a porosity gradient. In order to impart bioactive properties to the scaffold, for the first time in the literature the introduction in these fibre scaffolds of a bioactive phase, a melt-derived bioactive glass (CEL2) powder or spray-dried mesoporous bioactive glass particles (SD-MBG) was investigated. The scaffold bioactivity was assessed through soaking in simulated body fluid. CEL2/glass fibre scaffold did not show promising results due to particle detachment from the fibres during soaking in simulated body fluid. Instead the use of mesoporous bioactive powders showed to be an effective way to impart bioactivity to the scaffold and could be further exploited in the future through the ability of mesoporous particles to act as systems for the controlled release of drugs.

Hollow Core Antiresonant Fibers in Borosilicate Glass

We report the design and fabrication of the first hollow core optical fibers made of low quality borosilicate glass. Their negligible material absorption loss stemming from an ultralow overlap with the glass opens up the prospect of using very cheap glasses in the optoelectronics industry.

Development of Mid-IR Fiber Bundle for Thermal Imaging

We present and discuss the fabrication and characterization of a Mid-Infrared (Mid-IR) transparent flexible bundle based on 1200 fibers whose cores consist of a Ge30As13Se32Te25 chalcogenide glass and the cladding of a Fluorinated Ethylene Propylene (FEP). The Mid-IR fiber bundle was manufactured using the stack and draw method. The high index contrast between the glass and the cladding allows for strong field confinement of the well guided modes within the chalcogenide glass core transparent across the Mid-IR. Higher order modes, which could be prone to cross talk, suffered high losses thanks to the high attenuation offered by the polymer cladding. Additionally, the FEP cladding confers the bundle mechanical flexibility. Following a qualitative thermal imaging assessment, we also present and discuss the experimental loss measurements of the fiber bundle and we compare them to values obtained through modelling to conclude on the potential prospect of the manufactured bundle and its possible improvements.

Phosphate glass fibers for optical amplifiers and biomedical applications

Phosphate glass optical fibers were designed and fabricated for applications in the fields of remote sensing and biomedicine. Main results are reported together with the recent developments.

Design, processing and characterization of custom phosphate glasses for photonic and biomedical applications

Phosphate glasses (PGs) are promising host materials for the development of compact fiber amplifiers and lasers thanks to their good chemical durability, easy processing, outstanding optical properties, no clustering effect and very high solubility of rare-earth (RE) ions. Furthermore, some particular calcium-phosphate glasses exhibit unique dissolution properties in aqueous media with degradation rates that can be tailored by properly designing the glass composition. This feature makes them attractive biomaterials and allows the engineering of novel biomedical devices for deep-tissue diagnosis and therapy. In this work we will report the ongoing activities and the recent results obtained by our research group on the design, processing and characterization of novel custom phosphate glasses for both photonic and biomedical applications.

Multimaterial mid-infrared transmitting fibre bundle for thermal imaging

Thanks to the continuous progress of Mid-Infrared (MIR) detectors, related electronics and lenses, thermal imaging has now become a standard inspection technique in numerous industrial sectors, as well as in biomedical science and defence. Fibre endoscopy is a well-developed technology and often a critical component for imaging inaccessible areas. So far, the development of a MIR version that can be applied to thermal rather than optical imaging has proved challenging. Despite its large potential scientific and industrial impact, no commercial product is yet available on the market. Several fabrication approaches have been proposed over the years, using a broad range of material combinations [1, 3]. However, the overall performance of these bundles has been so far limited in terms of either optical properties (loss, size, cross-talk, _), compactness or mechanical flexibility. Indeed, the challenge consists in combining adequate materials, adopting suitable optical design engineering and developing a manufacturing process.

Bioactive glasses for nerve repair

For short nerve defects, polymeric nerve guidance channels are available for entubulation of the nerve stumps favouring the spontaneous regeneration of peripheral nerves. However, an ideal device has still to be found while the use of autograft or allograft represents the gold standard for long nerve gaps. For this reason, the investigation of new materials and functionalities in the design of nerve guidance channels is still needed. Different bioactive glasses have been proposed in the form of bulk, powders or fibres for the development of nerve regeneration devices. Micro- or nano-sized glass powders are studied in combination with polymers to obtain nerve guides with tailored physical, biological and mechanical properties. Aligned glass fibres, potentially carrying soluble factors, can sustain and direct the axonal re-growth trying to overcome the intrinsic limit of peripheral nerve regeneration over long distances, also showing promising results in the treatment of spinal cord injuries. In addition, the release of suitable ions from the bioactive glasses at appropriate concentrations has been shown to promote angiogenesis and the wound healing process, which are key factors to promote tissue healing. Moreover, the influence of some specific ions on the nerve regeneration process is currently being investigated.

Self-Cleaning Coatings: Structure, Fabrication and Application

For short nerve defects, polymeric nerve guidance channels are available for entubulation of the nerve stumps favouring the spontaneous regeneration of peripheral nerves. However, an ideal device has still to be found while the use of autograft or allograft represents the gold standard for long nerve gaps. For this reason, the investigation of new materials and functionalities in the design of nerve guidance channels is still needed. Different bioactive glasses have been proposed in the form of bulk, powders or fibres for the development of nerve regeneration devices. Micro- or nano-sized glass powders are studied in combination with polymers to obtain nerve guides with tailored physical, biological and mechanical properties. Aligned glass fibres, potentially carrying soluble factors, can sustain and direct the axonal re-growth trying to overcome the intrinsic limit of peripheral nerve regeneration over long distances, also showing promising results in the treatment of spinal cord injuries. In addition, the release of suitable ions from the bioactive glasses at appropriate concentrations has been shown to promote angiogenesis and the wound healing process, which are key factors to promote tissue healing. Moreover, the influence of some specific ions on the nerve regeneration process is currently being investigated.

Bioresorbable calcium-phosphate glasses for biophotonic applications

Calcium-phosphate glasses (CPGs) are unique materials for hard and soft tissue engineering, as they can be fully resorbed in physiological conditions and can interact in various ways with the human body. Moreover, they have interesting properties for applications in optics and photonics. We will report the recent progress in the development of a new calcium-phosphate glass composition able to combine intriguing optical, biological and thermal features, in particular transparency in the near UV region, solubility in aqueous media, low intrinsic attenuation loss and good thermal stability. We will also present the fabrication of hollow fibres in the prospect of drug delivery combined with light guiding for photodynamic therapy (PDT).