Study On Ultrasound Transducer Based On Lateral Vibrating Mode

Piezoelectric elements vibrating in thickness mode may be converted to vibrate in lateral mode by taking advantage of the characteristics of piezoelectric materials with various vibrating modes,in this process,the electrode surface area reduces and electrode thickness increases which allow higher clamped capacitance and lower electrical impedance.The multi-layer structure,lateral model piezoelectric elements used to make ultrasound needle transducer,using the characteristics of needle transducer of small volume,light quality and the advantages of multi-layer structure,lateral model piezoelectric elements of low frequency,low impedance,high strength,can be used to design and manufacture the ultrasound transducer for nerve stimulation for small animals.In this paper,the theoretical design,manufacture and tests of a low-frequency piezoelectric ultrasound transducer based on multi-layer structure and lateral mode are studied.(1)A multi-layer structure,lateral mode piezoelectric element configuration method is proposed.The improved multi-layer structure configuration method is adopted and magnetron sputtering method is used to prepare the surface electrodes,which makes the multi-layer structure electrode extraction more convenient and can effectively export the inner surface electrode without extra intermediate sandwich structure.(2)The impedance characteristics of a piezoelectric element with a double-layer structure and lateral mode are studied.When other condition is constant,increasing the length of the piezoelectric element(l)and thickness(t),reducing the piezoelectric element width(w)can reduce the electrical impedance at the resonant frequency.We demonstrated the double-layer structure,lateral model fabrication method can effectively reduce the electrical impedance of piezoelectric element at the resonance frequency from two aspects of experiment and simulation.(3)An ultrasound needle transducer with a diameter of 1.6mm,a mass of about 0.2g,a working frequency of 820 kHz and a ultrasound pressure amplitude of 0.3Mpa in the target area is designed and fabricated.The size(length,width and height)of the piezoelectric element is 0.6mm,0.6mm and 1.65 mm,respectively.It adopts 8-layer structure and vibrats in lateral mode.Compared withsingle-layer structure and thickness mode,the electrical impedance of the piezoelectric element is greatly reduced,showing excellent electrical performance.When the frequency is 820 kHz,the input voltage amplitude is 150 V,and the number of input sinusoidal signal cycles is 20 of the ultrasound needle transducer,the ultrasound pressure amplitude at the axial distance of 3mm is 240 kPa,4.7 times of the ultrasound pressure amplitude of 51 kPa of the control group,showing excellent acoustic performance.Transcranial performance using an ex-vivo mice skull was measured.The ultrasound beam had almost no attenuation and displacement through the skull of mice,and the transcranial performance of the transducer was good,which could be used as ultrasound nerve stimulation in small animals.Moreover,its advantages of small size,light weight and strong ultrasound pressure amplitude could be applied to multi-point nerve stimulation in mice.