Publicação
Graded-index fibre-based absorption spectroscopy using microfluidic devices
| Resumo: | In recent years, increasing efforts of developing novel micro and nano technologies have been dedicated to improve human health. These advances in the field of nanotechnology have facilitated the development of miniaturized microfluidic lab-on-a-chip (LOC) devices, which are frequently described as miniature versions of their macro-scale counterparts. Microfluidic LOC devices present great benefits in terms of small sample volumes and fast analysis times. From an optical point of view, these devices still suffer a drastic reduction in the optical pathlength compared to macroscale experiments. Obviously the reduced optical pathlength complicates or reduces the effectiveness of the application of various optical techniques in lab-on-a-chip systems. Meanwhile these devices are gaining a broader acceptance in clinical medicine for disease diagnosis. This thesis describes the recent work performed in the field of optofluidics with the application of optical sensing systems for microfluidic devices. Optofluidics is a combination of optics/photonics and microfluidics field. In optofluidic devices the micro-photonic components are integrated on microfluidic devices, which are able to hold the fluids at the microlitre scale. Optofluidic devices are used to perform interactions between light and fluids at micro scale level for applications in physics, chemistry and biology. These chip-scale devices could be easily integrated into a LOC system that is a compact platform and does not require free-space optics to perform laser-based spectroscopy, such as absorption spectroscopy. Absorption spectroscopy (AS) is a powerful technique for studies of species (atoms and molecules) and detection of unknown concentrations. The spectroscopic analysis is not only applied in physics and chemistry but also in biology and medicine [1]. Although a large number of molecular species can successfully be detected with established AS techniques, there are some applications that require higher sensitivity, selectivity and accuracy, yet robust and compact instrumentation. In this work, a LOC device was developed based on the optofluidics concept. The relevance of integration of micro-optical components in an “on-chip” approach is compared with the “off-chip” approach which was coupled with macro-scale optical infrastructure. The design and characterization of miniaturized optofluidic devices for sensing based on integrating collimating optical fibers with custom microfluidic chips is presented. The usage of graded-index (GRIN) fiber tips or GIF tips is to develop a compact device which does not require free space optics and the collection efficiency of GRIN fiber tips is significantly higher compared to standard single-mode fiber. The absorption spectroscopy on-chip is performed with both GIF tips and SMF configurations. To compare the performance of both fibres, the beam divergence and the insertion losses were measured. The reduction in both beam divergence and insertion losses for the GIF configuration compared with SMF were found to be 4-fold, for a 10 mm channel. Absorption spectroscopy was demonstrated on chip for the measurement of red colour dye (Ponceau 4R) and the detection of thiocyanate (SCN) which is an indicator of oral health and a detoxification product of cancer treatments. The thiocyanate concentrations were detected in water and also in a complex biofluid i.e. artificial human saliva. The proposed optofluidic setup allows for absorption spectroscopy measurements to be performed with only 200 µL of solution which is an order of magnitude smaller than for standard cuvettes but provides comparable sensitivity. To assess the performance of the miniaturized device, the absorption measurements are also compared with a standard cuvette of the same pathlength (~10 mm). A quantitative comparison of both devices demonstrates the consistency of linearity of absorbance against the concentration of analyte, accordingly to the Beer-Lambert law. The demonstrated approach has the potential to be used for chemical and biochemical analysis of DNA, proteins or saliva where the use of small volumes is critical. In order to perform spectroscopic analysis of human body proteins, a new sensing device was developed using a compacted chip with micropillar arrays called “Pillar Cuvette (PC)”. The PCs are fabricated at ANFF-SA (Australian National Fabrication Facility - South Australia Node). The design and fabrication process of PCs is briefly presented in this thesis. The CLIC3-HIS tag protein (human body protein) and BSA protein (Bovine protein) spectroscopic analysis were performed in UV range of spectrum. We developed a new approach to optical manipulation of excitation fibre and collection fiber setup. The proposed design and setup are presented in which optical fibers and the PC are integrated directly on a compact platform that doesn’t require alignment. It is an integrated pre-aligned device which is wholly portable. |
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| Autores principais: | Gill, Kamalpreet Kaur |
| Assunto: | Lab-on-a-chip (laboratório num chip) Deteção ótica Ótica integrada Opto-fluídos Espectroscopia Teses de mestrado - 2021 |
| Ano: | 2021 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | In recent years, increasing efforts of developing novel micro and nano technologies have been dedicated to improve human health. These advances in the field of nanotechnology have facilitated the development of miniaturized microfluidic lab-on-a-chip (LOC) devices, which are frequently described as miniature versions of their macro-scale counterparts. Microfluidic LOC devices present great benefits in terms of small sample volumes and fast analysis times. From an optical point of view, these devices still suffer a drastic reduction in the optical pathlength compared to macroscale experiments. Obviously the reduced optical pathlength complicates or reduces the effectiveness of the application of various optical techniques in lab-on-a-chip systems. Meanwhile these devices are gaining a broader acceptance in clinical medicine for disease diagnosis. This thesis describes the recent work performed in the field of optofluidics with the application of optical sensing systems for microfluidic devices. Optofluidics is a combination of optics/photonics and microfluidics field. In optofluidic devices the micro-photonic components are integrated on microfluidic devices, which are able to hold the fluids at the microlitre scale. Optofluidic devices are used to perform interactions between light and fluids at micro scale level for applications in physics, chemistry and biology. These chip-scale devices could be easily integrated into a LOC system that is a compact platform and does not require free-space optics to perform laser-based spectroscopy, such as absorption spectroscopy. Absorption spectroscopy (AS) is a powerful technique for studies of species (atoms and molecules) and detection of unknown concentrations. The spectroscopic analysis is not only applied in physics and chemistry but also in biology and medicine [1]. Although a large number of molecular species can successfully be detected with established AS techniques, there are some applications that require higher sensitivity, selectivity and accuracy, yet robust and compact instrumentation. In this work, a LOC device was developed based on the optofluidics concept. The relevance of integration of micro-optical components in an “on-chip” approach is compared with the “off-chip” approach which was coupled with macro-scale optical infrastructure. The design and characterization of miniaturized optofluidic devices for sensing based on integrating collimating optical fibers with custom microfluidic chips is presented. The usage of graded-index (GRIN) fiber tips or GIF tips is to develop a compact device which does not require free space optics and the collection efficiency of GRIN fiber tips is significantly higher compared to standard single-mode fiber. The absorption spectroscopy on-chip is performed with both GIF tips and SMF configurations. To compare the performance of both fibres, the beam divergence and the insertion losses were measured. The reduction in both beam divergence and insertion losses for the GIF configuration compared with SMF were found to be 4-fold, for a 10 mm channel. Absorption spectroscopy was demonstrated on chip for the measurement of red colour dye (Ponceau 4R) and the detection of thiocyanate (SCN) which is an indicator of oral health and a detoxification product of cancer treatments. The thiocyanate concentrations were detected in water and also in a complex biofluid i.e. artificial human saliva. The proposed optofluidic setup allows for absorption spectroscopy measurements to be performed with only 200 µL of solution which is an order of magnitude smaller than for standard cuvettes but provides comparable sensitivity. To assess the performance of the miniaturized device, the absorption measurements are also compared with a standard cuvette of the same pathlength (~10 mm). A quantitative comparison of both devices demonstrates the consistency of linearity of absorbance against the concentration of analyte, accordingly to the Beer-Lambert law. The demonstrated approach has the potential to be used for chemical and biochemical analysis of DNA, proteins or saliva where the use of small volumes is critical. In order to perform spectroscopic analysis of human body proteins, a new sensing device was developed using a compacted chip with micropillar arrays called “Pillar Cuvette (PC)”. The PCs are fabricated at ANFF-SA (Australian National Fabrication Facility - South Australia Node). The design and fabrication process of PCs is briefly presented in this thesis. The CLIC3-HIS tag protein (human body protein) and BSA protein (Bovine protein) spectroscopic analysis were performed in UV range of spectrum. We developed a new approach to optical manipulation of excitation fibre and collection fiber setup. The proposed design and setup are presented in which optical fibers and the PC are integrated directly on a compact platform that doesn’t require alignment. It is an integrated pre-aligned device which is wholly portable. |
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