Understanding of Water Molecule Dynamics in Terahertz Region and Development of Near-field Array Sensor

Abstract

Water molecules are well known to have extremely important functions in various biological reactions caused by their unique properties. Especially interactions between molecules via hydrogen bonds are observed in many situations, but direct measurement methods for finding themselves are limited. In this report, I present a method to determine the complex dielectric constant of a cell monolayer using terahertz time-domain attenuated total reflection spectroscopy combined with a two interface model. The complex dielectric constants of distilled water and HeLa cell monolayer between 0.25 and 3.5 THz come from Debye-type relaxation and Lorentz-type vibration dynamics of the water molecules and can be expressed as a superposition of the complex susceptibilities of slow relaxation, fast relaxation and intermolecular stretching vibration. This result also indicated the difference of such dynamics between distilled water and intracellular water clearly. Furthermore, I introduce a CMOS biosensor integrated circuit focusing on dielectric relaxations of biological water. Since this sensor can work as a near-field sensor, I demonstrated the measurement of intracellular water of cultured cell. I believe such a compact and easy sensor has a potential to open up the bio application in sub-THz region.