Research On The Composite Phonon Type High-Q Lamb Resonator

Thin-film acoustic wave sensors have expanded the application prospects and value of environmental monitoring,clinical diagnosis,and biological testing due to their high sensitivity.At present,the double-ended reflective Lamb wave piezoelectric sensor has high sensitivity,but the quality factor(Q factor)is too low,which restricts its application scenarios for fine sample detection.For this reason,this thesis proposes the use of phononic crystals that propagate elastic waves in steerable media instead of reflecting gratings to increase the resonant frequency of Lamb wave resonators.The following tasks were mainly completed:Using Comsol simulation to simulate a 10?m silicon-based device and a 2?m siliconbased device,the results show that in A0 and S0 modes using a silicon-based device with a thickness of 2?m,the particle movement inside the resonator is several times that of a 10?m silicon-based device.At the same time,after the material is selected,the width and spacing of the interdigital electrodes,the A0 mode and the S0 mode resonance frequency are calculated,and the basic Lamb wave resonator model is established to provide theoretical support for different types of Lamb wave resonators.Establish the model of the double-ended reflective Lamb wave resonator and optimize the process flow to characterize the device.The double-ended reflection Lamb wave resonator and QCM sensor are used to measure the concentration gradient of the carbon quantum dot solution.The measured Lamb wave resonator frequency shift caused by the concentration change is twice the order of magnitude of the QCM sensor frequency shift,establishing Lamb Advantages of wave resonators in liquid phase detection.The Lamb wave resonator was used to further test the finer sample solutions,and it was found that it was difficult to accurately distinguish the sample solutions with smaller concentration differences.The Q value of the Lamb wave resonator measured by the Agilent E5061 B network analyzer is only 39.304.After calculation,it is found that the reflectivity of the double-ended reflection Lamb wave resonator is only 0.09%,and the lateral propagation of elastic waves has become a restriction.A key factor in the resonant frequency of a resonator.In order to design a composite phononic high-Q Lamb wave resonator,the influencing factors of the band gap characteristics of the phononic crystal were studied.Using the finite element simulation Comsol steady-state solver,the full-scale band gap characteristics of gold,lead,aluminum,chromium,titanium,parylene,and epoxy resin scatterers were analyzed.When the thickness of the Si-based phononic crystal is 2?m and the unit cell length is 40?m,the first complete band gap width of Parylene C is the largest,which is 51.58 MHz.The first full band gap width of all scatterers increases with the increase of the filling rate,and decreases with the increase of the filling rate after reaching the peak.By studying the effects of other factors of the scatterers on the band gap characteristics under the same filling rate of each scatterer,it is found that the closer the density of the scatterer is to the density of the Si matrix,the wider the first complete band gap width of the scatterer,and vice versa.The smaller.Under the same conditions,the greater the difference in acoustic impedance between the scatterer and the Si matrix,the wider the first complete band gap width of the phononic crystal.Through the above research,the composite phonon Lamb wave resonator model is established,and the sound pressure field in the Comsol finite element simulation is used to verify the modulability of the phononic crystal to the elastic wave propagation.The elastic wave density at the interdigital electrode is 9 times to the lower part.This provides a theoretical basis for the phononic crystal to replace the reflection grid to increase the resonant frequency of the Lamb wave resonator.