The vibrational and rotational energy levels of many biological macromolecules fall in the THz band, so terahertz spectroscopy can be used to identify the species of substances and detect the structure of substances. Due to the strong absorption of THz wave by water, it is difficult to study liquid biological samples by THz spectroscopy. Microfluidic technology is a kind of micro scale fluid control technology, which has the advantages of light volume, less sample usage and fast reaction speed. The combination of terahertz technology and microfluidic technology can increase the accuracy of liquid sample measurement and reduce the amount of sample. In this paper, COC5013 material with high terahertz transmittance was used to prepare microfluidic chip, and then the terahertz transmittance of two kinds of food additives sodium carboxymethyl cellulose solution and guar gum solution was studied. The results show that the terahertz transmittance of sodium carboxymethyl cellulose solution and guar gum solution with different mass fraction are different.
The rotational mode and vibrational mode of many biomolecules are all located in terahertz band, and the photon energy of terahertz wave is low, which is only millivolt level, and will not damage the internal structure of molecules, so terahertz time-domain spectroscopy technology has a good application prospect in biological detection. In addition, most biomolecules can only exert their biological activity under liquid conditions, so it is necessary to study the interaction between biomolecules in liquid environment. In the study of the interaction between biomolecules and terahertz wave in solution, minimizing the absorption of terahertz waves by water molecules has become a research hotspot in recent years. The microfluidic chip reduces the absorption of terahertz waves by reducing the distance between the measured sample and the terahertz waves, and has important application value in the detection of biological samples. By changing the concentration of hydrogen ions in the aqueous solution, different pH values can be obtained. In this paper, Zeonor 1420rs, which has high transmission rate to terahertz wave, is selected as the material of microfluidic chip, and the microchannel depth is 50 μm. Then we combine terahertz technology and microfluidic technology, and prepare three kinds of strong acid solutions with different pH values. By analyzing the terahertz time-domain and frequency-domain spectra of strong acid solutions, we can explore the influence of different pH solutions on terahertz wave absorption, and provide necessary reference for the application of terahertz technology in the field of biochemistry.
Water molecules are polar molecules, and intermolecular hydrogen bonds interact strongly with terahertz waves, which makes it very difficult to study the dynamic characteristics of biological samples in aqueous solutions by using terahertz technology. Microfluidic technology is famous for its ability to accurately control micro scale fluid, and its channel depth can reach 50 μm or even smaller. Because microfluidic technology reduces the propagation distance of terahertz wave in the fluid, it greatly reduces the absorption of water to terahertz wave. In addition, pH value also has a certain impact on biological activity. In this study, different pH values are generated by changing the concentration of hydrogen ions and hydroxyl ions in aqueous solution. THz technology and microfluidic technology are combined to explore the THz spectrum characteristics in different pH value of strong acid and alkali solution, and analyze the influence of pH value on the absorption characteristics .
Terahertz (THz) technology has become popular worldwide as a new approach to detecting biomolecules because the vibrational and rotational energy levels of many biomolecules fall in the THz band and because the THz wave has the characteristics of low electronic energy, which will not damage the samples to be measured. Many biomolecules need to maintain their biological activity in liquid environment. However, as a polar molecule, water has a strong absorption of THz wave, which is mainly because the vibration frequency of hydrogen bond in aqueous solution is within the THz frequency range. Therefore, the best solution is to reduce the action distance between the aqueous solution and THz wave and control it within 100 μm. Microfluidic chips can meet such requirements. Therefore, the combination of THz technology and microfluidic technology can study the dynamic characteristics of biomolecules in an aqueous solution. The microfluidic chip was fabricated using ZEONOR 1420Rs. The THz transmittance of the material can exceed 95%. The depth of the microchannel in the microfluidic chip is 50 μm. In addition, the chip has the characteristics of good airtightness, portability, convenient disassembling, and reusability. Seventeen kinds of electrolytes were tested with the chip. The results show that the THz spectral intensity of electrolyte composed of different anions and cations, so the spectral characteristics of other electrolyte solutions can be obtained according to the spectral information of these detected ions.
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