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Because the vibrational and rotational energy levels of many biomolecules are in the terahertz range, they can interact with terahertz. In addition, the photon energy of terahertz wave is very low, only meV level, which will not cause damage to the material, so terahertz technology can be used for non-destructive detection of biological molecules. As we all know, many biomolecules need to maintain their biological activity in aqueous solution, so it is of practical significance to study the biological characteristics in aqueous solution. The combination of terahertz and microfluidic technology can greatly reduce the absorption of liquid samples to terahertz, so it can detect more accurate signals. Therefore, terahertz time domain spectroscopy technology has a good application prospect in biological detection. The terahertz transmission characteristics of different sodium salts standing in electric field for different time are studied. Double layer terahertz microfluidic chips were prepared by using cycloolefin copolymer (COC) materials with high transmission rate for terahertz wave. The terahertz transmission characteristics of four kinds of sodium salts under the action of electric field were tested by using microfluidic chips with strong sealing performance. In order to avoid the influence of ionic impurities in aqueous solution, deionized water was used to prepare the solution. NaCl, CH3COONa, NaHCO3 and Na2CO3 electrolyte solutions with concentration of 0.9 mol/L are selected. The four solutions were injected into the microfluidic chip in turn, and then put into the external electric field device. The electric field treatment time is 0 min, 5 min, 10 min, 15 min and 20 min respectively. The transmission intensity is measured by terahertz time domain spectroscopy system every five minutes, and the corresponding spectrum can be obtained. The results show that with the increase of electric field time, the THz transmission intensity of the four sodium salt solutions increases.
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