Femtosecond laser microfabrication of spiral optofluidic sensor and its sensing applications

Man, Xiaoxi (2017) Femtosecond laser microfabrication of spiral optofluidic sensor and its sensing applications. Masters thesis, Memorial University of Newfoundland.

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Optofluidics combines the advantages of optics and microfluidics to achieve new functionalities. On account of cost-effectiveness, size-miniaturization, and structure-flexibility of optofluidic devices, there has been an increasing interest in optofluidics- related research since the emergence of the concept of optofluidics, such as lab-on-a-chip devices, optofluidic-based lenses and sensors, fluid-based particle sorters, optofluidic lasers, and imaging tools. In this thesis, femtosecond laser is explored to study the nonlinear interactions between ultrashort laser pulses and photoresist materials, and the possible applications in optofluidics. Based on the effect of two-photon absorption occurred in transparent photoresist materials, spiral-shaped waveguides of different specifications are fabricated with femtosecond laser in photoresist SU-8-2. Each of the waveguides, which contains one bus waveguide and one spiral-shaped waveguide with a distinct circumference, can be integrated into one microchannel on a glass substrate to form a spiral optofluidic device as an optofluidic sensor. The sensor with the highest sensitivity is utilized to measure physical properties of various fluidic samples (calcium chloride, cow milk and its related products, non-diary milk, and sucrose). These properties include temperature, refractive index, positive pressure and concentration. Experimental results indicate that the highest sensitivities for fluidic measurement are -0.47±0.02 nm/ᴼC for temperature sensing, 188.78±3.76 nm/RIU for refractive index sensing, 0.089±0.03 nm/ (N/m²) for positive pressure sensing, and 1.66±0.06 nm/wt% for concentration sensing. All devices have been fabricated with the use of small-sized low-cost materials and easy-to-replicate fabrication techniques. The effectiveness and applicability of the spiral optofluidic devices demonstrated in this thesis revealed the significance of nonlinear optical interactions between ultrashort light pulses and photosensitive materials, and their importance in many applications.

Item Type: Thesis (Masters)
URI: http://research.library.mun.ca/id/eprint/13180
Item ID: 13180
Additional Information: Includes bibliographical references (pages 51-172).
Keywords: Femtosecond laser, Optofluidics, Refractive index, Bio-sensing, Polymerization
Department(s): Science, Faculty of > Physics and Physical Oceanography
Date: December 2017
Date Type: Submission
Library of Congress Subject Heading: Femtosecond lasers; Lasers in engineering; Optofluidics -- Equipment and supplies

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