High frequency focused ultrasound transducer

The propagation of vibration sensor in the medium is referred to as wave. There are two conditions for generating wave: vibration (generated by the wave source) and propagation (need to propagate the medium). According to the generation of fluctuations, it can be divided into mechanical waves and electromagnetic waves. Mechanical waves are generated by the propagation of mechanical vibrations in the medium. Ultrasonic waves are mechanical waves, and their propagation requires the media. The human body as a medium of sound waves has different acoustic properties in the different tissues, piezoceramic materials piezos discs can be used medically to diagnose the physiological characteristics of organs in the body.

In 1917, the French scientist Paul Langevin discovered the inverse piezoelectric effect, which is along the surface of the piezoelectric material.A certain voltage is applied in the direction of the electric axis, and due to the action of the electric field, the center of the positive and negative charges inside the piezo pickup tube amp is displaced.Therefore, stress is generated inside the material, which causes deformation of the material and the first practical one is successfully developed. The Langevin transducer is relatively simple, using PZT material piezos discs quartz crystals as piezoelectric material and formed by clamping two steel plates. Due to its poor stability, low strength and low power capacity.The shortcomings were replaced by laminated magnetostrictive transducers that appeared after 1933.In the later stage,it is electrostriction with ferroelectric materials (ceramic acid ), piezoelectric ceramics (lead acid, lead PZT).The development of materials and the maturity of the polarization process have led to the study of sandwich piezoelectric ultrasonic transducers.

In the 1970s, piezoelectric ceramic composites were developed by using PvDF as a substrate and PZT attached to a substrate.The material has better performance than the pure piezoelectric ceramic and can better improve the matching characteristics of the material. Until now, most of the piezoelectric materials of medical ultrasonic transducers have used composite materials as piezoelectric materials.Compared with single-phase piezoelectric composites, piezoelectric composites have higher thickness direction electromechanical coefficient, low acoustic impedance, low lateral electromechanical cohesion coefficient, low dielectric constant, low mechanical quality factor, and good flexibility and controllability make it easy to make a variety of high-performance PZT-52 piezo tube for high-performance clinical diagnosis.Such as ultra high frequency, broadband, miniature transducers. With the development of piezoelectric materials, there are improvements in the manufacturing processes, The processing power is improved, and the frequency for ultrasonic diagnosis is also getting higher and higher. High frequency ultrasonic transducer is heart frequency >20MHZ, especially high frequency focused ultrasound transducers can improve the imaging resolution of the target area,Ultrasonic Biological Microscope (UBM), photo acoustic imaging,(photo acoustic imaging, PAI),Ultrasound (IVUS) And small animal experiments and other fields have broad application prospects, and this topic is based on this background.