Research On The Biosensing Technology Based On Metamaterials In Terahertz Bands

Biosensor is an analytical device that converts biological response into electrical signals.It has been used in many fields,such as food industry,medical treatment and so on.Since biosensor owns better stability and sensitivity,it becomes an indispensable tool to study biological phenomena.Combining the local near-field enhancement on metamaterials with the natural advantages of terahertz(THz)waves in biological fields,THz metamaterial biosensor shows a great potential in the trace detection of biological macromolecules.Focusing on the research of THz metamaterial biosensors,this thesis includes three main contents:(1)Based on the summary of electromagnetically induced transparency(EIT)phenomena in existing works,the geometric structure of EIT-like metamaterial biosensor in THz bands is designed by using simulation software CST.The physical mechanism of the transparency peak is originated from the electromagnetically destructive interference between the bright mode and the dark mode;In addition,the sensing characteristics of the metasurfaces with different analyte thickness,covering area and dielectric constant are simulated,respectively.As a result,the limit thickness of the detection is measured approaching 17 ?m,and the detection area is mainly concentrated between the inner opening ring and the outer square ring.The calculated sensitivity is 162 GHz/RIU.(2)The EIT-like metamaterial biosensor operating in THz bands is prepared.The frequency shift of the EIT transmission peak was used as one of the indicators to detect the midkine factor(MDK)concentration.By performing Fourier transform on the full spectral magnitude difference(FSAD),a set of pseudo spectra was obtained.The results show that the limit of detection(LOD)of the metamaterial biosensor reaches at least 0.5 ?g/mL.The measurement time was shortened to less than 5 minutes.Finally,we also use continuous wavelet transform(CWT)to establish two-dimensional time-frequency mappings(TFMs)spectra with different solutions and different MK concentrations.These TFMs derived from CWT clearly identify different solutions without introducing confusion.The maps similar with conventional fluorescence images of ELISA can serve as effective visual outputs for MDK concentration levels.By comparing with ELISA method,the biosensor platform provides a uniform measurement standard,which makes the MDK expression level of each measurement comparable,showing the great potential of EIT-like metamaterial biosensors in cancer disease labeling detection.(3)The metamaterials composed of different SRRs are designed for biosensing platform.The TFMs processed by CWT shows the difference between normal epithelial keratinized cell HaCaT and oral cancer cell HSC3,further demonstrating CWT great potential in label-free recognition of cell types.In addition,the TFMs corresponding to the concentration of HSC3 cells ranging from 1 × 105 cells/mL to 7×105 cells/mL are measured,which provides a new way for sensitive detection to related cancer biomolecules.After comparing the TFMs of different metamaterials,it is found that the coupling between biological cells and localized field can be controlled by designing different SRRs structures.Also,it means that different near-field distributions on metasurface have different effects on biological cells.This property provides a reference for the bio-electromagnetic interaction in localized fields.