Opto-Mechanical Applications of Microstructured Materials: 1)Fiber Bragg grating sensors 2)Laser-driven polymer micro-sensors
Date Issued
2004
Date
2004
Author(s)
Lin, Chih-Lang
DOI
en-US
Abstract
This work involves two topics which are fiber Bragg grating (FBG) sensors and laser driven microsensors. In the first part, a framework for the interpretation of reflected FBG spectra under a non-uniform strain field is proposed and experimental results for a crack tip strain field are presented. The effect of FBG gauge lengths on the measurements is examined and interpreted. The results are analyzed to see what information can be derived and how accurate the interpreted strain results are. In the second part, the fabrication of laser driven polymer microsensors for viscosimetry, velocimetry and micropump applications is considered. These sensors are readily made with a low-cost polymerization technique based on two-photon absorption. A linearly polarized optical tweezers is used to trap one sensor, freely floating in the liquid to be characterized, at the laser focal point and to generate the optical torque needed for local hydrodynamic measurements. Viscosity and velocity microsensors have slab shapes that align in the polarization direction. The local viscosity is deduced from the maximum rotation frequency generated by the rotating linear polarization, while the fluid velocity is obtained by measuring the maximum angle that equilibrates the optical and drag torques. The experimental results are in good agreement with the theoretical calculations. Micropumps are micron-size Archimedes screws that rotate around their long axis when trapped at the focal point. The rotation is due to the optical torque that is transferred by the laser scattering on the screw.
Subjects
阿基米德螺旋
非均佈應變場
微幫浦
光鉗
雙光子吸收
FBG感測器
光譜
微黏度計
微感測器
光纖布拉格光柵
micropump
non-uniform strain field
polymer
microsensor
spectrum
FBG sensor
micro-velocimetry
two-photon absorption
polymerization
micro-viscosimetry
Archimedes screw
fiber Bragg gratings
optical tweezers
Type
thesis