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Integration of terahertz and microfluidics technologies for effective spectroscopic analysis on a chip

University of British Columbia

Terahertz (THz) spectroscopy is of growing interest in scientific applications. However, the realization of this technology to characterize the different types of fluids remains a challenge. This challenge comes about from the high-water absorption within the THz spectrum, which leads to rapid attenuation of the THz radiation and limited spectroscopic measurements of the fluids. As such, an effective method to overcome this issue would be to use a microfluidics platform that injects the fluid to be interrogated within microchannels. This thesis studies the prospects for the integration of THz spectroscopy with microfluidics and introduces the key benefits and limitations. The foremost technology to generate THz radiation is the photoconductive (PC) THz emitter. The performance of PC THz emitters is investigated under bias fields up to 5.0 kV/cm and optical fluences up to 340 μJ/cm² for two PC materials being semi-insulating (SI) GaAs and SI-InP. With respect to the bias field, the two PC materials behave contrarily due to the space-charge-limited current in SI-GaAs and sustained current in SI-InP. With respect to the optical fluence, a saturation effect due to space-charge and near-field screening was observed in the two PC materials. Moreover, an array of PC antenna structures was investigated as PC THz emitters. The performance of the PC THz emitters was influenced by different polarization properties resulting from different PC antenna structures; however, SI-GaAs emitters presented better performance compared to SI-InP emitters over the spectral bandwidth. As the foremost microfluidics platforms are polymer-based, a variety of polar and nonpolar polymers have been investigated as potential materials for THz-microfluidics platforms. Notably, the nonpolar polymers such as cyclic olefin copolymer (COC) and ultra-high-molecular-weight polyethylene (UHMWPE) exhibit low iv absorption in the THz spectrum. With this in mind, the fabricated THz-microfluidics platforms based upon COC and UHMWPE show a wider bandwidth and higher sensitivity for spectroscopic measurements of fluids compared to THz-microfluidics platform based upon polar polymers such as polyethylene terephthalate (PET), leading to better performance for THz spectroscopic characterization of fluids. Overall, the introduced THz-microfluidic platforms can lay the foundation for future realization and studies of THz spectroscopy on a chip.

Text

2021-01-06

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/76962

Electrical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/