| Summary: | 博士 === 國立清華大學 === 工程與系統科學系 === 93 === The development of the fiber optic sensors in this research is based on the principle of Fabry-Perot interferometry and the Polymer MEMS fabrication technology. One of the designs is for the application of the shear stress and nano-displacement measurement, and the other is for the in-situ and in-vivo detection of protein molecules such as the immunoreaction of antigen and antibody.
The fiber optic floating-element type sensor is designed to measure the shear stress directly. The surface roughness of the floating element fabricated by UV lithography on SU-8 photoresist is better than 7nm (Ra value) on 35*35 μm2 area and can be served as the reflection mirror. Silicon oil with the refractive index 1.406 is filled into the sensor cavity as an index matching medium for signal and sensitivity enhancement as well as a buffer material for pressure resistance and vibration reduction. With silicon oil filling, the sensitivity of displacement and shear stress sensing are 0.1249 nm/nm (wavelength shift/floating element displacement) and 6.825 nm/Pa (wavelength shift/shear stress), respectively. The sensor sensitivity and signal intensity can be improved by 1.85 times and 3.6dB compared to no silicon oil filling. The minimum detectable displacement and shear stress have been demonstrated to be 10nm and 0.33Pa. Besides, the signal spectrum shifts have been tested within 1nm under static pressure from 1atm to 6atm or acoustic vibration from 1Hz to 5kHz, because of the incompressibility and damping effect of the silicon oil. However, the temperature dependency and hysteresis effect of the sensor need to be improved or compensated for practical applications in the future.
The fiber optic biosensor for the protein molecules detection is prepared by the dip coating of SU8, depositing of gold film and followed by the surface modification with thiol groups, respectively. As the fiber probe inserting into the sample solution, the immobilization of the Rabbit IgG and Anti Rabbit IgG-Cy3 molecules on the fiber tip will result in the variation of the refractive index of interface as well as the reflectivity, and contribute to the wavelength shift of interference spectrum. The surface roughness and reflectance of the deposited gold film modified by the annealing process has been demonstrated. The non-specific adhesion of the suspended substances in the buffer solution onto the sensor tips needs to be avoided. Finally, the regeneration process of the sensor has been verified on the glass substrate by the surface plasmon resonance detection system.
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