Research On Microfluidic Biosensor Based On Reflective Terahertz Time Domain Spectroscopy

Terahertz(THz)wave refers to the electromagnetic wave whose frequency is 0.1-10 THz and wavelength is 0.03-3 mm.In the past 30 years,with the emergence of femtosecond laser,many unique properties of terahertz wave have been discovered,such as low photon energy,strong penetration,transient,broadband and coherence.In addition,terahertz wave can interact with many new materials,such as graphene,liquid crystal and so on.These characteristics of terahertz wave make it have great potential in national defense,communication technology and medical diagnosis.Based on the application of Terahertz Science in biomedical detection,a high performance terahertz microfluidic chip which can be used in reflective terahertz time-domain spectroscopy system is developed by combining Terahertz Science with microfluidic technology and graphene materials.In this paper,we introduced terahertz science and terahertz time-domain spectroscopy(THz-TDS).Next,the optical parameters extraction algorithm of sandwich structure in transmission and reflective THz-TDS is discussed.Then,a kind of sandwich structure Terahertz biosensor for reflective THz-TDS is designed and studied.The negative film of the biosensor is made of silicon,which is suitable for reflective THz-TDS with silicon prism.Then,in order to improve the sensitivity of the biosensor,we transfer a layer of graphene to enhance the terahertz signal through the interaction between graphene and terahertz wave,so as to further improve the performance of biosensor.After the design and fabrication,we tested the performance of the biosensor by detecting pure water,alcohol,absolute ethanol,and human epidermal growth factor receptor-2 antigen protein(HER2 protein).Then,in order to meet the demand of real-time detection,we further improved the material of the cover plate and replaced it with polydimethylsiloxane(PDMS)material which is easier to process and package.The microchannel structure can be made thinner to save sample consumption.The material of biosensor negative film is quartz material which has higher transmission to terahertz wave because there is no silicon prism in the reflective THz-TDS.Finally,we use this new biosensor to detect the coagulation process of human plasma,and find out the optical law of the coagulation process of human plasma in terahertz frequency band,that is,the amplitude of time domain signal,frequency domain signal and real refractive index gradually decreases with time.