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. 2018 Sep 11;9(9):453.
doi: 10.3390/mi9090453.

Characterization and Integration of Terahertz Technology within Microfluidic Platforms

Salman Alfihed  1   2 , Mark H Bergen  3 , Antonia Ciocoiu  4 , Jonathan F Holzman  5 , Ian G Foulds  6
Affiliations

Characterization and Integration of Terahertz Technology within Microfluidic Platforms

Salman Alfihed et al. Micromachines (Basel). .

Abstract

In this work, the prospects of integrating terahertz (THz) time-domain spectroscopy (TDS) within polymer-based microfluidic platforms are investigated. The work considers platforms based upon the polar polymers polyethylene terephthalate (PET), polycarbonate (PC), polymethyl-methacrylate (PMMA), polydimethylsiloxane (PDMS), and the nonpolar polymers fluorinated ethylene propylene (FEP), polystyrene (PS), high-density polyethylene (HDPE), and ultra-high-molecular-weight polyethylene (UHMWPE). The THz absorption coefficients for these polymers are measured. Two microfluidic platforms are then designed, fabricated, and tested, with one being based upon PET, as a representative high-loss polar polymer, and one being based upon UHMWPE, as a representative low-loss nonpolar polymer. It is shown that the UHMWPE microfluidic platform yields reliable measurements of THz absorption coefficients up to a frequency of 1.75 THz, in contrast to the PET microfluidic platform, which functions only up to 1.38 THz. The distinction seen here is attributed to the differing levels of THz absorption and the manifestation of differing f for the systems. Such findings can play an important role in the future integration of THz technology and polymer-based microfluidic systems.

Keywords: THz time-domain spectroscopy; lab-on-a-chip; microfluidics; polymer absorption.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Isometric schematic of THz time-domain spectroscopy (THz-TDS) system, with the microfluidic platform at the top right. Ultrafast laser pulses are split into two beams: a pump beam (PUB), focused on the photoconductive SI-GaAs THz emitter (PE), and a probe beam (PRB). The THz beam (yellow) is generated at the emitter and then collected, collimated, and focused by parabolic mirrors (PMs). The probe beam is overlaid with the THz beam by a pellicle beamsplitter (PBS). An electro-optic ZnTe crystal (EOC) and quarter waveplate (QWP), allow the THz beam to modulate the probe beam’s polarization. A polarizing beamsplitter (POS) splits the probe beam into beams with orthogonal polarizations, and the power difference between the beams is measured by a differential photodetector (DPD). The microfluidic platform windows (WD) and PMMA spacer (SC) are shown in the inset.
Figure 2
Figure 2
Terahertz absorption coefficient, α, versus frequency, f, from 0.5 to 2.0 THz for the polar polymers: PET (green curve), PC (purple curve), PMMA (red curve), and PDMS (blue curve).
Figure 3
Figure 3
Terahertz absorption coefficient, α, versus frequency, f, from 0.5 to 2.0 THz for the nonpolar polymers: FEP (green curve), PS (purple curve), HDPE (red curve), and UHMWPE (blue curve).
Figure 4
Figure 4
Terahertz absorption coefficient, α, versus frequency, f, from 0.5 to 2.0 THz for PDMS-CA as the test fluid in PET (red curve) and UHMWPE (blue curve) microfluidic platforms.
Figure 5
Figure 5
Terahertz absorption coefficient, α, and maximum measurable THz absorption coefficient, αmax, versus frequency, f, from 0.5 to 2.0 THz for PDMS-CA as the test fluid. The results are shown for the (a) PET microfluidic platform and (b) UHMWPE microfluidic platform.
See this image and copyright information in PMC

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