Microfluidic technology can control the fluidic thickness accurately in less than 100 micrometers. So the combination of terahertz (THz) and microfluidic technology becomes one of the most interesting directions towards biological detection. We designed microfluidic chips for terahertz spectroscopy of biological samples in aqueous solutions. Using the terahertz time-domain spectroscopy (THz-TDS) system, we experimentally measured the transmittance of the chips and the THz absorption spectra of L-threonine and L-arginine, respectively. The results indicated the feasibility of performing high sensitivity THz spectroscopy of amino acids solutions. Therefore, the microfluidic chips can realize real-time and label-free measurement for biochemistry samples in THz-TDS system.
Many Biomolecules vibration frequencies are in terahertz (0.1THz-10THz) frequency range, so terahertz (THz) technology is an essential tool for detecting biological molecules. However, due to terahertz strongly absorbed by water, it is difficult to detect these molecules for biological and chemical liquid samples. Therefore, we present a novel detection method by combining terahertz technology with microfluidic technology. The strong absorption of water is effectively overcome by controlling the length that terahertz passes through liquid samples. What’s more, a higher signal to noise ratio is obtained through using less samples. In this paper, we designed a THz microfluidic chip that is easy to be fabricated by using the materials of Zeonor and polydimethylsiloxane (PDMS). Using terahertz time-domainspectroscopy (THz-TDS) system, we find that the chip has a high transmittance above 80% in the range from 0.2 THz to 2.6 THz. Then the THz spectra of deionized water and different kinds of solutions with different concentrations in the microfluidic chip were measured, respectively. In our research, it is found that different kinds of solutions have different transmission coefficients for THz. In addition, the THz transmission and absorption spectrum changes with the concentration of the same kind of solution.
Waveguides, which can transmit high frequency electromagnetic waves, have a lot of types, such as microstrip line (MSL), coplanar waveguides (CPW), coplanar-strip-line (CPS) and so forth. In the waveguides mentioned above, CPW has the advantages of easy fabrication and superior performance. Meanwhile MSL also has many advantages such as small size, light weight and high spectral resolution, but it also shows a higher attenuation and dispersion compared with the free-space waveguides. So in on-chip terahertz system, CPW and MSL was used as waveguides to transmit terahertz waves and the HFSS software was used to simulate and analyze the transmission characteristics of the MSL and CPW based on the on-chip system researched by University of Leeds (America) and Hiroshima University (Japan). The simulation results show that the scattering parameters of the two waveguides are similar to the known literatures. Meanwhile we also have designed a new structure of MSL which is applicable for our on-chip system.
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