Fabricating 90 nm Resolution Structures in Sol-Gel Silica Optical Waveguides for Biosensor Applications

Bragg grating structure in a sol-gel silica waveguide is fabricated on the basis of nanoimprint lithography for biophotonic applications. The process realizes nonstandardized lithography in sol-gel silica at a high resolution for a relatively large area in the range of several micrometers with a resolution in the order of several nanometers. Here we demonstrate structures of 250 and 90 nm resolutions in a sol-gel silica optical waveguide for a large area that is not optimized to date. Bragg grating of a 250 nm periodic structure is realized for a 1 mm long area

Estudio y diseño de dispositivos ópticos biosensores depositados con películas delgadas basados en detección de longitud de onda de resonancias

A lo largo de esta tesis se presenta el estudio y diseño de varias plataformas de guía-ondas ópticas, con el fin de ver su viabilidad a la hora de usarlas como biosensores sobre fibra óptica u otros sustratos fotónicos. En este trabajo se depositan estructuras ópticas como una fibra monomodo desnuda, un estrechamiento en fibra óptica o una fusión de fibras mono – multi – monomodo (SMS) con películas delgadas de materiales usando técnicas nanotecnológicas como el ensamblado capa a capa (LbL-assembly) o el sputtering. Además, se dedica un capítulo al estudio de microresonadores toroidales depositados por rotación (spin-coating). El objetivo es generar o mejorar las prestaciones en resolución y sensibilidad de los fenómenos resonantes que se pueden obtener en estas estructuras ópticas, para luego detectar reacciones biológicas que den lugar a un futuro diagnóstico precoz de enfermedades.Along this thesis, the study and design of several optical waveguide platforms is presented, in order to check their viability when used as biosensors based on either optical fiber or other photonic substrates. In this work, some fiber-optic-based structures such as cladding removed multimode structures, tapered single-mode fibers and single-mode – multimode – single-mode fibers are deposited with thin-films of materials, using nanotechnology-based methods such as layer-by-layer assembly (LbL-assembly) or sputtering. Moreover, a brief chapter is focused on the study of toroidal microring resonators deposited by spin-coating. The final objective is to generate or enhance the parameters of the resonant phenomena obtained in these structures, in terms of resolution and sensitivity. Then, a biological detection is addressed and characterized, to see if they are able to perform a future early diagnosis for illnesses.La realización de este trabajo ha sido posible gracias a las aportaciones económicas recibidas por parte de la Universidad Pública de Navarra (UPNA), así como del patrocinio de la UPNA y del Ministerio de Economía y Competitividad, a través de los proyectos CICYT fondos FEDER TEC2010-17805, TEC2013-43679-R e IPT-2011-1212-920000 (PMEL).Programa Oficial de Doctorado en Ingeniería y Arquitectura (RD 1393/2007)Ingeniaritzako eta Arkitekturako Doktoretza Programa Ofiziala (ED 1393/2007

Development and Characterisation of High Surface Energy Microstructured Sol-gel Coatings for Sensing Applications

This study investigates the development of high surface energy photoreactive organic inorganic hybrid sol-gel coatings for the microstructuration of high-resolution microfluidic platforms and optofluidic biosensor platforms by standard photolithography processes. To achieve this, the first step of our work consisted of identifying the fundamental physico chemical processes governing the structuration and surface properties of hybrid organic inorganic sol-gel coatings. For this purpose, a reference material based on the combination of an organosilane (3-Methacryloxypropytrimethoxysilane, MAPTMS) and a transition metal (zirconium propoxide, ZPO), was firstly developed and characterised. It was highlighted that chemical, physical and combined physical and chemical processes can be performed to impact the structure, morphology and surface properties of hybrid sol-gel coatings. Therefore, our work progressed towards the investigations of chemical strategies that may impact the general properties of hybrid coatings, with a specific objective on the alteration of their surface properties. For this purpose, 3 strategies have identified including (1) to alter the content of transition metal, (2) to vary the hydrolysis degree and (3) to form core-shell nanoparticle by the surface functionalisation of the reference material during its preparation along with the curing process of the coatings. The materials were characterised employing a set of structural, thermal and surface characterisations techniques namely Contact Angle measurements (CA), DLS, DSC, FTIR, 29Si-NMR. Fundamentally, a triangular relationship between the wettability, the condensation and curing process of the coatings was taking place. More specifically, the wettability was governed by the occurrence of parallel and competitive hydroxylation and condensation processes of the coatings. Having performed the identified chemical strategies, our work has progressed towards the investigations of physical and physico-chemical treatments of the final coatings. Here, the effects of air-plasma, nitrogen-plasma and plasma treatments combined with post-silane ii surface functionalisation were performed and the durability of the treatments investigated. Although hydrophobic recovery was observed for all materials, it was found that air-plasma enabled to achieve the most stable surface properties due to the formation of hydrophilic hydroxyl groups at the surface of the coatings. The next step of the work focussed on the microstructuration fabrication of a microfluidic platform. The photolithography fabrication conditions were established to enable the successful preparation of well-defined microchannels with resolutions ranging from 50 to 500 microns. Having developed our microfluidic platform, our work concentrated on developing strategies to integrate an optical transducer onto the platform to enable the fabrication of an optofluidic device that may be applied as biosensor, thus demonstrating the potential of our technology for biosensing applications. The biosensor design we proposed consisted of integrated optical waveguides onto microfluidics that would also be fabricated employing a photolithography process. The fabrications conditions of the optofluidic platform were established by considering the required optical conditions that enable efficient light propagation in the waveguides, which can be used as an optical excitation to fluorophores located within sensor spots in the microchannels. The successful demonstration of concept of the optofluidic-based biosensor concept was successfully performed by recording optical emissions of biomolecules fluorophores under optical excitations with the optical waveguides integrated on the microfluidic platform. The work reported in this thesis has been multidisciplinary requiring chemistry, physics, biotechnology and engineering competencies which have been synergised for the development of the first “whole hybrid sol-gel optofluidic biosensor platform”. It is also showing the potential of the proposed technology for applications where functional microstructured coatings are required

Development of optical sensor platforms based on evanescent wave interactions

A study of the principles, fabrication and behaviour of a range of optical sensor platforms based on evanescent wave interactions is presented. The platforms utilise a range of sensing techniques including absorption, fluorescence quenching and surface plasmon resonance. The absorbance-based platforms employ sol-gel-derived planar waveguides and grating couplers to launch light into guided modes, the evanescent fields of which can interrogate a sensing layer. A detailed characterisation of these integrated optic devices is presented. Two platforms employing few-mode and multimode waveguides, respectively, are described and applied to the detection of gaseous ammonia and carbon dioxide. A fluorescence-based sensor platform which utilises the anisotropy of fluorescence emitted near an interface is also presented. The platform consists of a planar waveguide coated with a sol-gel-derived fluorescent layer. A substantial amount of the analytesensitive fluorescence is captured by guided modes in the planar waveguide. This configuration is described in detail and is applied to the detection of gaseous oxygen as a proof of principle. Finally, work leading to the development of a fibre optic probe biosensor based on surface plasmon resonance is presented together with its application to the detection of red blood cells. In summary, this work highlights the feasibility of combining evanescent wave interactions and sol-gel technology to fabricate miniature sensor platforms which may be applied to the detection of a wide range of target analytes in a reliable and cost effective manner

Planar waveguides obtained on commercial glass substrates by sol-gel and laser irradiation methods

The aim of the thesis is the fundamental study, design, fabrication and characterisation of photonic structures for spatial optic and, particulary, the interconnexion of optical devices. The research explored technologies and substrates for the fabrication of photonic structures based on the guided propogation of light and its application to research and development of integrated optical devices and improving the functionality of communication systems, which realises intelligent optical operations based on Fourier spatial transformed and image formation properties.At the same time, aims to explore new technologies for fabrication ofphotonic structures; which are repeatibility and not contaminants; and the product of well-defined charactericstics and low price

New organic-inorganic sol-gel resists for micro and nanoimprinting

In this study new hybrid organic-inorganic TiO2 sol-gel materials with high TiO2 content (more than 50% respect silicon dioxide (SiO2) content) are synthesized, characterized and micro-/nano-patterned using thermal nanoimprint lithography

Design and characterisation of a photonic sensor platform for the detection of biofilm formation

This thesis focuses on the development and characterisation of a waveguide-based photonic sensing platform for the detection of biofilm. This integrated photonic platform is based upon the high sensitivity of an optical field distribution formed in optical waveguides and the resulting changes in the refractive index and absorption of this environment. The sensor platform and materials formulations were established from simulation studies conducted with the Olympios software. These simulations demonstrated the importance of correctly specifying the material refractive index to achieve single-mode waveguides. They also highlighted the necessity to deposit a high refractive index layer (HRIL) on top of the optical waveguides in order to increase the intensity of the evanescent field responsible for the sensing performance of the platform. Platform fabrication exploited a low-cost process using photocurable organic-inorganic hybrid sol–gel materials, which were microstructured by UV-photolithography to form channel optical waveguides. A tantalum-based material was synthesized using the sol–gel process with refractive index as high as 1.87. This material was developed, optically characterised and applied as an evanescent field enhancement layer, deposited at the surface of the waveguide to increase the sensitivity of the sensing platform. The sensor characterisation was performed by monitoring the output intensity of the optical waveguide while contaminated water was monitored in both quasi-static and dynamic flow-rates on the platform. It is shown that the sensing performance of this biosensor platform relies on the applied flow-rate. In quasi-static flow rate, the biofilm formation was detected after 10 min of reactions, demonstrating the early stage biofilm formation in quasi-static flow-rate. The progressive increase of the flow-rate showed an increase of the detection time. Furthermore, the sensing performances of this photonic platform were found to be strongly dependent on the thickness of the HRIL, confirming the simulations studies. This work proved the concept of employing a waveguide-based photonic platform for the early detection of biofilm formation, including the induction phase, and as such, I believe this system has immense potential for future applications as a label-free and real-time biosensor platform for bioenvironmental applications

Nonlinear nanophotonic devices in the Ultraviolet to Visible wavelength range

Although the first lasers invented operated in the visible, the first on-chip devices were optimized for near-infrared (IR) performance driven by demand in telecommunications. However, as the applications of integrated photonics has broadened, the wavelength demand has as well, and we are now returning to the visible (Vis) and pushing into the ultraviolet (UV). This shift has required innovations in device design and in materials as well as leveraging nonlinear behavior to reach these wavelengths. This review discusses the key nonlinear phenomena that can be used as well as presents several emerging material systems and devices that have reached the UV-Vis wavelength range.Comment: 58 pages, 10 figure

Biochemical sensing using Siloxane polymer waveguides

The objective of this work presented here is to extend the capabilities of siloxane waveguide technology in the field of biochemical sensing. Recent advances in the integration of polymeric optical waveguides with electronics onto standard printed circuit boards (PCBs) allow the formation of cost-effective lab-on-achip modules suitable for mass production. This technology has been primarily designed for on-board data communication. The focus of this research is to investigate the possibility of realising a Siloxane polymer based lab-on-chip sensor. Different siloxane-polymer-based optical waveguide sensor structures have been designed and analysed from the aspect of biochemical sensing. An evanescent-wave absorption sensor based on mode-selective asymmetric waveguide junctions is proposed for the first time. The device mitigates the common optical effect of spurious response in absorption sensors due to the analyte transport fluid. Head injury is the leading cause of death in the population of people under 40 years. Currently, 3 out of 5 deaths in emergency rooms are due to severe brain injuries in the developed world. Researchers at the Neurosciences Critical Care Unit (NCCU) at Addenbrooke’s Hospital have managed to correlate biochemical changes with the severeness of the injury and the likelihood of patient recovery. Considerable progress has been made to develop a lab-on-chip sensor capable of continuously monitoring glucose, lactate and pyruvate concentrations in the brain fluid, hence the contribution to the current trend in the advancement of portable lab-on-chip technologies for the deployment of point-of-care diagnostic tools. A novel recognition layer has been developed based on porphyrin in combination with glucose, lactate and pyruvate oxidase for measuring all the analytes, enabling fast and reversible chemical reactions to be monitored by optical interrogation. The operational wavelength of the developed recognition layer is 425 nm, which required the formation of polymer features that were beyond the fabrication capabilities at the time. Through considerable process development and the adoption of nanoimprinting lithography, siloxane polymer based optical waveguides were fabricated allowing the realisation of highly sensitive optical sensors. Based on the results that are presented here, it can be concluded the functionalization of siloxane polymer waveguide have a potential for realising biochemical sensors in the future. The new fabrication technique will allow the formation of more robust and complex lab-on-chip sensors based on this material.ESPR