Fibre optique plastique

Résumé

vignette|Photographie d'une fibre optique plastique avec un microscope. Une fibre optique plastique (ou fibre optique polymère ; en anglais, plastic optical fiber, polymer optical fibre ou POF) est une fibre optique qui est faite de plastique. Traditionnellement, le polyméthacrylate de méthyle (acrylique ; souvent abrégé en PMMA de l'anglais poly(methyl methacrylate)) est le matériau du cœur de la fibre et les polymères fluorés sont les matériaux de gainage. Depuis la fin des années 1990, des fibres plastiques plus performantes, à base de polymères perfluorés (principalement le poly-per-fluoro-butényle-vinyl-éther) ont commencé à apparaître sur le marché. Caractéristiques Dans les fibres de grand diamètre, 96 % de la section transversale de la fibre est occupée par le cœur qui permet la transmission de la lumière. Comme la fibre de verre traditionnelle, la fibre optique plastique transmet la lumière (ou les données) à travers le cœur de la fibre. La taille du cœur de la

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https://fr.wikipedia.org/wiki/Fibre_optique_plastique

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Polymer optical fibers (POF) have received increased attention in recent years in the fields of data communication and sensing applications. The lower cost and higher flexibility are the main advantages of POF compared to silica fibers and make them interesting candidates for Fiber Bragg grating (FBG) sensor applications. FBG are convenient measurement devices for strain and temperature measurements, as they can be multiplexed within one fiber yielding a sensor array and the fiber can be embedded in structures. This work investigated the possibility of producing FBG in polymer fibers and their use as sensor units. It could be shown that using excimer laser irradiation at 308 nm, it is possible to write FBG in single-mode POF employing a standard phase mask, side writing technique. Index changes of up to 1.7 × 10-4 and reflectivies of up to 87% could be reached. The induced refractive index change due to pulsed UV irradiation was shown to be negative. The polymer material of the core (Polystyrene (PS) / Polymethyl methacrylate (PMMA)) was not sensitized prior to irradiation. During the grating formation an irradiation induced insertion loss of up to 11 dB/cm was observed. Excimer laser written FBG showed stability of over 9 months for approximately 40% of written FBG. Results of FBG writing using femto second laser irradiation showed FBG with reflectivities of up to 1.2 × 10-4, however these POFBG were not stable. The POFBG were characterized using optical low coherence reflectometry (OLCR) which enables to calculate the FBG location and length as well as the induced amplitude Δnac and mean refractive index change Δndc. Taking into account fiber and insertion losses, good agreement of these calculations and measurements were found. The results show that large variations of the induced index change result from irradiation. Local index change peaks of up to 4 times the mean value were observed, indicating inhomogeneity of the fiber material. Birefringence in the core of the POF (≈ 1.2 × 10-3) is up to a factor 3 higher than in the cladding which is due to the PS content within the core. The birefringence is due to inelastic strain and stress induced in the drawing process. Annealing, uniform irradiation and FBG writing using 308 nm excimer laser light induces a decrease of the absolute birefringence value. The changes upon irradiation are confined to the core of the fiber. Large variations in the initial and final birefringence before and after irradiation support the findings of the OLCR measurements indicating material inhomogeneities in the fiber. POFBG were found to be sensitive to relative humidity, temperature and strain. This is in contrast to glass fiber FBG which do not show humidity sensitivity. POFBG relative humidity sensitivity is non-linear with a change of up to 8 nm for a RH change of ≈ 100%. The non-linearity is introduced by a non-linear water sorption process. The POF grating response to temperature changes under dry conditions (1.5±1 % RH) is –10±0.5 pm/°C. The temperature response of the FBG submerged in water is –36±2 pm/°C due to an increased thermal expansion coefficient and a change in polarizability. Under ambient conditions the grating response to heating is typically ≈ –138 pm/°C, predominantly due to a change in POF swelling, i.e changes in relative humidity and POF water content. The diffusion coefficient of water in this POF at 23.5°C is 6.7 × 10-9cm2/s for sorption and 10 × 10-9cm2/s for desorption. Equilibrium of water content within the fiber and the surrounding air is typically reached after approximately one hour. Calculation showed that a reduction of the fiber diameter can increase this humidity sensitivity response time down to approximately 5 minutes for a fiber diameter of 25 µm.

EPFL2008

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Functionalization of polymer optical fibers for medical application

Jialuo Luo

The increasing challenges caused by the growing and aging population and the fast pace of life are calling for a change of our current medical care system towards being rapid, easy, and on-demand self-care. Empowerment with the self-caring components such as early diagnosis, treatment, and monitoring of individuals will sharply release the social burden. In this context, fibrous materials stand out for their small size, processing flexibility, designable functionalities, and the possibility to be further integrated into im-plants or wearable devices. As we know, optical fiber is widely used in the biomedical field. For example, conventional silica optical fiber has mature applications such as light guides for surgery and catheter-based endoscopy while novel types of optical fiber (hydrogel, polymer, biomedical material, and elastomer) open the door to various new application scenarios like optogenetics, active monitoring, and continuous sensing, etc. While it remains a hot topic, the use of optical fibers for drug delivery is still in lack of exploration and suggests an ideal starting point for us. Optical fiber allows light propagation and thus gives the possibility to build up a light-responsive delivery system if combined with light-responsive drug carriers. Mesoporous silica nanoparticles(MSNP) were selected to host drug substances due to their high surface area, big pore volume, and versatility of functionalization and were coated on the fiber. Optical fiber will work as a light source to trigger the release from carriers. In this thesis, we constructed the hybrid system to give an optical fiber-based release system and elucidate the interaction between light from the optical fiber and drug-hosted particles with a further expectation to integrate with sensing or monitor-ing function to have an advanced delivery device. The first part of the work involved the synthesis of mesoporous silica nanoparticles using non-surfactants as templating agents. For the first time, a systematic study has been carried out to unravel the morphogenetic mechanism of mesoporous silica nanoparticles by polyphenols. Our study has, on one side, suggested that the pKa value of the polyphenols is responsible for the particle size due to the effect on nucleation and particle growth process, and on the other side, demonstrated that the formation of the supramolecular network contributes to the porous structure by serving as the skeleton for the silica pre-cursors to polymerize around. The second part of the work is to establish a method to generate a particle-polymer optical fiber(POF) complex matrix. A robust and controlled strategy for the fabrication of particle-coated surfaces that applies to multiple genres of substrates and coating materials was proposed based on layer-by-layer(LbL) assembly. The approach enables a high drug loading as well as a low structural complexity en-dowed by a dense and homogenous monolayer coverage of particles on the substrates. The computer vision method was employed to quantitatively evaluate the particle coating, increasing dramatically the efficiency and accuracy of the coating evaluation. The final part of the work investigates the light-responsive release of photolabile coumarin-chlorambucil conjugates from optical fibers. To the best of our knowledge, it is the first study to explore the release of drugs from the side of optical fibers. Overall, this novel particle-optical fiber-based one-dimensional drug deliver

EPFL2022

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2007

Chargement

Functionalization of polymer optical fibers for medical application

Jialuo Luo

EPFL2022

EPFL2008