Study on Terahertz Absorption Characteristics of Water Based on Microfluidic Technology
WANG Guo-yang, BAI Zhi-chen, WANG Jia-hui, SU 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 Theory and Technology, Department of Physics, Capital Normal University, Beijing 100048, China
Abstract：The characteristic vibration mode and rotation mode of many biomacromolecules are located in the terahertz band, and the low electron energy characteristic of the terahertz wave makes it impossible to destroy the samples to be measured in the experimental process, so terahertz technology can be used to identify biological samples. In many studies, biological samples are in a solution state. The interaction between water and other molecules in solution involves many biological phenomena, so it is very important to study the terahertz characteristics of water.As we all know, water molecules are very common polar molecules, and hydrogen bond between molecules will have strong interaction with terahertz wave, which makes water have strong absorption of terahertz wave, so it is very difficult to use terahertz technology to study the dynamic characteristics of biological samples in aqueous solution.In order to solve this problem, microfluidic technology can be introduced. Microfluidic technology is famous for its ability to control microscale fluid precisely, and its channel depth can reach 50 μm or even less. Because microfluidic technology reduces the propagation distance of terahertz waves in the fluid, the absorption of terahertz wave by water is greatly reduced. In this study, a microfluidic sandwich chip was made of Zeonor1420R with high transmittance to the terahertz wave. The length, width and depth of microchannels on the chip are 3 cm, 4 mm and 50 μm, respectively, and the diameter of the terahertz detection area is 3 mm.In the fabrication of a microfluidic chip, a strong adhesive double-sided adhesive with a thickness of 50 μm is used to replace the polydimethylsiloxane (PDMS) film in the traditional sandwich microfluidic chip, so that there is no leakage phenomenon in the heating process of the microfluidic chip. In addition, we design a temperature control system, which is composed of a heating plate, a temperature sensor and a temperature controller. The temperature control system can control the temperature with the precision of 0.1 ℃. The deionized water in the microfluidic chip was heated by this system, and the terahertz transmission was measured every 5 ℃ from 20 to 90 ℃. Through the analysis of the experimental data, it was found that the terahertz transmittance of water decreased with the increase of temperature, indicating that the absorption of water to terahertz waves increased with the increase of temperature.The results provide a precondition for the study of THz absorption characteristics of liquid samples by microfluidic technology at different ambient temperatures in the future and provide technical support for the application and development of THz in the future.
王国阳，白志晨，王佳慧，苏 波，张存林. 基于微流控技术的水的太赫兹吸收特性研究[J]. 光谱学与光谱分析, 2021, 41(06): 1678-1682.
WANG Guo-yang, BAI Zhi-chen, WANG Jia-hui, SU Bo, ZHANG Cun-lin. Study on Terahertz Absorption Characteristics of Water Based on Microfluidic Technology. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2021, 41(06): 1678-1682.
