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. 2022 Jun 7;13(6):904.
doi: 10.3390/mi13060904.

Sensitivity Enhancement and Probiotic Detection of Microfluidic Chips Based on Terahertz Radiation Combined with Metamaterial Technology

Yen-Shuo Lin  1 , Shih-Ting Huang  2 , Shen-Fu Steve Hsu  3 , Kai-Yuan Tang  3 , Ta-Jen Yen  4 , Da-Jeng Yao  1
Affiliations

Sensitivity Enhancement and Probiotic Detection of Microfluidic Chips Based on Terahertz Radiation Combined with Metamaterial Technology

Yen-Shuo Lin et al. Micromachines (Basel). .

Abstract

Terahertz (THz) radiation has attracted wide attention in recent years due to its non-destructive properties and ability to sense molecular structures. In applications combining terahertz radiation with metamaterial technology, the interaction between the terahertz radiation and the metamaterials causes resonance reactions; different analytes have different resonance performances in the frequency domain. In addition, a microfluidic system is able to provide low volume reagents for detection, reduce noise from the environment, and concentrate the sample on the detection area. Through simulation, a cruciform metamaterial pattern was designed; the proportion, periodicity, and width of the metamaterial were adjusted to improve the sensing capability of the chip. In the experiments, the sensing capabilities of Type A, B, and C chips were compared. The Type C chip had the most significant resonant effect; its maximum shift could be increased to 89 GHz. In the probiotic experiment, the cruciform chip could have a 0.72 GHz shift at a concentration of 0.025 mg/50 μL, confirming that terahertz radiation combined with a metamaterial microfluidic chip can perform low-concentration detection.

Keywords: metamaterials; microfluidics; probiotic; sensitivity enhancement; terahertz.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) The design of the microfluidic system. (b) Perspective view of the microfluidic system. (c) The design of the XPS metamaterial. (d) Simulation result shows a resonant dip at frequency of 0.295 THz.
Figure 2
Figure 2
Fabrication process flow and (a) metamaterial; (b) SU8 mold; (c) PDMS microfluidic layer; (d) finished product (detection chip). (e) Schematic diagram of experimental setup; (f) TeraPulse System structure diagram; (g) VDI System structure diagram.
Figure 2
Figure 2
Fabrication process flow and (a) metamaterial; (b) SU8 mold; (c) PDMS microfluidic layer; (d) finished product (detection chip). (e) Schematic diagram of experimental setup; (f) TeraPulse System structure diagram; (g) VDI System structure diagram.
Figure 3
Figure 3
(a) Schematic diagram. (b) Simulated resonance position of three XPS pattern designs.
Figure 4
Figure 4
(a) Sensitivity of XPS (30, 60, 90 degrees). (b) Sensitivity of 90 degrees (XPS, Cruciform, CSA).
Figure 5
Figure 5
Adjustments to the resonance position by (a) increasing proportion, (b) increasing periodicity, and (c) decreasing width. (d) Comparison of redshift/geometric ratio change.
Figure 6
Figure 6
Schematic diagram of original design (XPS) and new design (Cruciform).
Figure 7
Figure 7
(a) Resonance curves of analytes with dielectric constants of 1, 1.5, 2.5, 3.5, and 4.5. (b) The relationship between the refractive index and shifts. (c) Resonance curves of analytes with absorption coefficients of 50, 100, 150, and 200. (d) The relationship between absorption coefficients and the electric field. (e) The influence of the dielectric constant and absorption coefficient on the position of the X- and Y-axes.
Figure 8
Figure 8
(a) Experimental results of different concentrations of IPA in Type A, B, and C chips. (b) Shift comparison chart for Type A, B, and C chips.
Figure 9
Figure 9
Probiotic measurement results of (a) Type C chip and (b) Cruciform chip. (c) Shift comparison chart of Type C and Cruciform chips.
Figure 10
Figure 10
Experimental results of mixed solution of (a) IPA+ ethanol and (b) methanol + acetone. (c) Absorption coefficients of IPA, ethanol, methanol, and acetone.
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