低温液态水的太赫兹吸收特性研究

Terahertz Absorption Characteristics of Low Temperature Liquid Water

太赫兹波的光子能量只有毫电子伏特,远低于各种化学键的键能,因此不会和生物组织发生有害的电离反应;另一方面,由于大部分生物分子转动和振动所具有的特征能量都在太赫兹范围内,所以利用太赫兹波可以对生物分子进行识别。水是生物环境中最重要的液体,生物分子与液态水之间的相互作用决定了其生物活性,因此研究液态水的太赫兹特性就显得十分重要。水作为极性液体,其中的偶极分子-偶极分子间的相互作用和极性分子间的氢键会对太赫兹波产生较大的吸收作用,这就使利用太赫兹技术研究液体环境下的生物分子动力学特性变得相当困难。微流控技术通过改变微流控芯片中液体通道的深度来控制液体样品的厚度,以减少太赫兹波与液体样品的作用距离,从而使水对太赫兹波的吸收大幅减小。利用对太赫兹波的透过率高达95%的Zeonor 1420R材料和双面胶制作了可重复性使用的夹心式微流控芯片,芯片上液体通道的长度、宽度、深度分别为2 cm,5 mm和50μm。另外,设计制作了一个制冷系统,由制冷片、散热模块、温度传感器、保温箱和温度控制器构成,该制冷系统可以对保温箱的内部环境制冷并在一定程度上保持恒温。在实验过程中,将注满水的微流控芯片置于保温箱中,利用制冷系统对微流控芯片中的水进行制冷处理,从8~-3℃每隔1℃进行一次太赫兹透射测量,通过对实验数据的分析,发现随着温度降低,水的太赫兹透过率不断增大,说明水对太赫兹波的吸收随着温度的降低而降低。此结果为将来在不同低温环境下利用微流控技术研究液体样品的太赫兹吸收特性打下了基础,为太赫兹在生物领域的应用与发展提供了技术支持。

The photon energy of THz wave is only meV,which is much lower than the bond energy of various chemical bonds,so it will not cause harmful ionization reaction to biological tissues;on the other hand,because the characteristic energy of rotation and vibration of most biomolecules is in the THz range,THz wave can be used to identify the biomolecules.Water is the most important liquid in a biological medium,the interaction between biomolecules and liquid water determines its biological activity,so it is very important to study the terahertz characteristics of liquid water.As a polar liquid,the dipole-dipole interaction and the hydrogen bond between polar molecules in the liquid will have a great absorption effect on the THz wave,making it very difficult to study the characteristics of biomolecular dynamics in a liquid environment by using THz technology.Microfluidic technology controls the thickness of the liquid sample by changing the depth of the liquid channel in the microfluidic chip reduce the interaction distance between THz wave and liquid sample,thus greatly reducing the absorption of THz wave by water.In this study,a reusable sandwich microfluidic chip was fabricated using double-sided adhesive and Zeonor 1420 R material with a THz transmittance of 95%.The liquid channel’s length,width and depth are 2 cm,5 mm and 50μm,respectively.In addition,a refrigeration system is designed and manufactured,which is composed of a refrigeration chip,heat dissipation module,temperature sensor,incubator and temperature controller.The refrigeration system can cool the internal environment of the incubator and keep a constant temperature to a certain extent.During the experiment,the microfluidic chip filled with water is placed in the incubator,and the refrigeration system cools the water in the microfluidic chip.The THz transmission is measured every 1℃from 8 to-3℃.Through the analysis of the experimental data,it is found that the THz transmission of water increases with the decrease of temperature,it shows that the absorption of THz wave by water decreases with the decrease of temperature.The results lay a foundation for the future study of THz absorption characteristics of liquid samples by microfluidic technology in different low-temperature environments and provide technical support for the application and development of THz in the biological field.