Development of a microfiber optical sensor for humidity monitoring /
Humidity monitoring has a substantial importance in a variety of application, such as; building and ventilation control, automotive, semiconductor, biomedical and chemicals industries. Microfiber-based devices have great potential in many applications due to their extraordinary optical and mechanica...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
Kuala Lumpur :
Kuliyyah of Islamic Revealed Knowledge and Human Sciences, International Islamic University Malaysia,
2016
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| Subjects: | |
| Online Access: | Click here to view 1st 24 pages of the thesis. Members can view fulltext at the specified PCs in the library. |
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| Summary: | Humidity monitoring has a substantial importance in a variety of application, such as; building and ventilation control, automotive, semiconductor, biomedical and chemicals industries. Microfiber-based devices have great potential in many applications due to their extraordinary optical and mechanical properties. Humidity fiber-based sensors rely on humidity-induced refractive index change in the sensing material to modulate the transmitted optical spectrum as a function of the relative humidity (RH). Silica-based microfibers have to be coated by hydrophilic materials through sophisticated methods in order to optimize their sensitivity. On the other hand, polymer-based microwires can absorb water vapor molecules and detect humidity changes without the need of further coating. Yet, polymer device sensitivity can be further enhanced by doping the polymers by high porosity hydrophilic materials following a low cost fabrication method. A new relative humidity sensor based on agarose-doped PMMA microwire is therefore proposed and experimentally demonstrated to enhance the sensitivity of existing polymer-based sensors. To launch light into such sensor, an adiabatic silica-based taper is required. Adiabaticity criterion has to be estimated and satisfied to avoid high optical loss emerging when taper's profile is not controlled properly. A method to model the taper profile and simulate it using Finite Element Analysis software, is proposed and adiabaticity is then evaluated efficiently. The model facilitates design phase and optimize fabrication process for any fiber-based device. The designed taper is fabricated and used to launch light into un-doped and agarose-doped PMMA microwires in a relative humidity sensor. The performance of both sensors is investigated and characterized. The results show that the agarose-dope PMMA microfiber has a higher sensitivity of 0.1µW/%RH in comparison with 0.068 µW/%RH in un-doped PMMA microwire. The proposed sensor shows a great linearity of 98% and wavelength shifts of 28 pm/%RH which is about three times higher than the reported bare PMMA RH sensors. The doped-agarose PMMA material can be further used to construct other fiber structures and to be applied in humidity monitoring applications. |
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| Physical Description: | xvii, 87 leaves : illustrations ; 30cm. |
| Bibliography: | Includes bibliographical references (leaves 81-85). |