Preparation And Performance Study Of Multilayer Film Saw Carcinoembryonic Antigen Sensor

The surface acoustic wave device is a new type of sensor with merits such as low-cost,small size,easy portability,and multiple functions.It is developed based on the mature semiconductor micromachining technology.With the unique advantages,it has shown great potential for the applications in the fields of communication and microfluidics.Love mode surface acoustic wave sensors have been demonstrated that they are capable of stable and normal operation in liquid environments with high sensitivity and low detection limit.They have been gradually applied to many fields such as materials science,molecular biology,medicine,and food analysis.Combining surface acoustic wave devices with the detection of carcinoembryonic antigen is expected to obtain a marker-free and highly sensitive early tumor diagnosis system.This study contains the following contents:(1)Design and simulation of the Love mode surface acoustic device for carcinoembryonic antigen detection.It was found that as the thickness of the waveguide layer increases,the energy of the acoustic wave is increasingly confined to the surface of the device.The effect of different thicknesses of the SiO₂ waveguide on the mass sensitivity of the device was explored,and the results showed that when the normalized thickness of SiO₂ was 0.14,the mass sensitivity reached the optimal value.(2)A surface acoustic wave device using ST-90° quartz as the substrate and Au as the interdigitaltransducer was prepared through a conventional photolithographic lift-off process,and the Love wave was excited by depositing a SiO₂ film on the surface acoustic wave device.A multilayer thin film surface acoustic wave sensor for liquid phase biological testing was developed.The effects of sputtering pressure and sputtering power on the deposition rate of SiO₂ films were discussed.The results showed that the sputtering rate was proportional to the sputtering power,and the film deposition rate reached the maximum value when the sputtering gas pressure was 0.5 Pa.With the sputtering power of 150 W and the sputtering pressure of 0.5 Pa,the effects of different thicknesses of the SiO₂ films varying from 100 nm to 1000 nm on the insertion loss and the operating frequency were investigated by controlling the sputtering time.The final experimental results showed that the insertion loss of the device with 1?m-thick waveguide layer has increased to 6 dB,which has reduced the center frequency of the device about 6 MHz.The results of the finite element simulation have also been verified.(3)Thesurface acoustic wave device with 1 ?m SiO₂ waveguide layer was selected as a biosensor,on which a detachable microfluidic channel and a test platform were designed,to detect the concentration of the carcinoembryonic antigen.A simple,easy-to-operate aldehyde-based method of immobilizing antibody probes to prepare specific bio-functional membranes was used to achieve a multilayer thin film surface acoustic wave sensor capable of detecting carcinoembryonic antigen.The compound prepared by bonding nano-gold particles to the detection antibody successfully amplified the biological detection signal,which increased the detection sensitivity and the detection limit.The detection limit of carcinoembryonic antigen was reduced to 291.6 pg/m L,which can meet the requirements of low-concentration CEA detection.Besides,the sensor also showed good linearity in the range of 0.2 ng/m L-5 ng/m L.In addition,other non-specific interferences have been tested accordingly,and the results show that the sensor has good biological selectivity.