FAN Ning, SU Bo*, WU Ya-xiong, ZHANG Hong-fei, ZHANG Cong, ZHANG Sheng-bo, ZHANG Cun-lin
Key Laboratory of Terahertz Optoelectronics, Ministry of Education; Beijing Key Laboratory for Terahertz Spectroscopy and Imaging; Beijing Advanced Innovation Center for Imaging Technology, Department of Physics, Capital Normal University, Beijing 100048, China
Abstract：The vibrational and rotational model of many biological macromolecules fall in the THz range, so THz can be used for the qualitative identification of samples. It is well known that the activity of most biomolecules can be expressed in aqueous solution. However, water, as a polar substance, has a strong absorption to THz. Therefore, many measures are adopted to reduce the impact of water for getting more information of biological samples in liquid environment. In this paper, we designed two kinds of PDMS-based sandwich microfluidic chips, which couldreduce the absorption of THz by means of micro channel. Thereforea higher THz transmission of sampleswas achieved through the terahertz time-domain spectroscopy (THz-TDS) system. The material of Zeonor 1420r wasused as substrate and cover plate, and the PDMS as channel interlayer. The transmission of the empty microfluidic chip is more than 80% in the range of 0.2～2.6 THz by THz-TDS system. Then the THz spectra of deionized water and 1,2-propanediol with different concentrations in the microfluidic chip weremeasured, respectively. The results indicatethat the THz transmission of mixtures with different volume ratios has obvious difference. The feasibility of the chip to measure liquid samples has beenproved. In addition, the solutions of potassium chloride and potassium iodide with different concentrations were detected by using the microfluidic chip, and the results show that the transmittance of THz decreases with the increase of the concentration of potassium chloride solution, while the potassium iodide solution has the reverse result. It is found that the electrolyte changes the hydrogen bond density in the aqueous solution, which leads to the change of THz absorption in solution.
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