| Phononic crystals are a type of high-frequency elastic scattering material typically composed of two or more media distributed periodically.When elastic waves propagate in a phononic crystal,specific frequency bands of sound waves are attenuated and prohibited from propagating due to Bragg scattering or local resonance.This special property has been applied in many acoustic devices.In this article,a layered cylindrical phononic crystal sensor model based on 90 ST quartz as a piezoelectric substrate is proposed.The band gaps and transmission characteristics of the surface acoustic waves in the layered cylindrical phononic crystal are studied,and an optimized layered cylindrical phononic crystal sensor is used to detect HIV-1 virus particles.The main research results of this article are as follows:A layered phononic crystal model and a layered cylindrical phononic crystal model are constructed,and the dispersion curves of the layered phononic crystal model of different sizes and the layered cylindrical phononic crystal with a radius of 3μm are calculated.Two specific bending and one twisting modes and their corresponding characteristic frequencies are found to be 284.87 MHz,287.6 MHz,and 288.14 MHz,respectively.The transmission characteristics of the layered cylindrical phononic crystal with a radius of 3 μm are studied,and it is proved that specific bending and twisting transmission modes can be excited by coupling between Love waves and layered cylindrical phononic crystals.The resonance peak of the twisting mode is sharper and the calculated quality factor is higher than that of the bending mode.Its Q value for the twisting mode is 5851.A defect is introduced into the bottom layer of the layered cylindrical phononic crystal with a radius of 3μm,and by adjusting the height of the defect layer,it is found that the characteristic frequencies of specific bending and twisting modes decrease as the height of the defect layer increases.The coupling between the layered cylindrical phononic crystal and Love waves is studied,and the Q value of the T mode resonance peak for different defect layers is calculated.It is found that the Q value is highest when the defect layer is 2.4 μm,and the corresponding Q value is 6499.This proves that the introduction of defects improves the Q value of the device.Using perturbation and finite element theory to calculate the frequency shift caused by virus particles acting on the r=3μm phononic crystal biosensor,the maximum frequency shift caused by a single virus particle is around 4400 Hz,and the mass sensitivity is about 1.11 k Hz/(ng.cm^-2).The frequency shift caused by 0-1×10^5 randomly distributed virus particles on the surface of the phononic crystal is also calculated.When the number of virus particles is between 0 and 2×10^4,the results obtained by the two methods are the same.When the number of virus particles reaches 2×10^4,the frequency shift reaches 25 MHz,and the mass sensitivity is about 318.5 Hz/(ng.cm^-2).The linear formula derived from firstorder perturbation theory is no longer valid for N above 2×10^4,so higher orders must be considered to fit the numerical curve.Finally,the size of the phononic crystal biosensor is optimized,and a sensor with a radius of 0.4 μm and a defect height of 0.43 μm is chosen to detect virus particles.The maximum frequency shift caused by a single virus particle on this sensor is 2.55 MHz,and the maximum mass sensitivity is 11.82 k Hz/(ng.cm^-2). |
PDF Full Text Request