Medical ultrasonic transducer is a device that converts ultrasonic frequency electric energy into ultrasonic energy in ultrasonic processing equipment. Currently, there are two types of ultrasonic transducers that are widely used. The types of ultrasonic transducers are as follows:
The first type of the medical ultrasonic transducer is the magnetostrictive transducer, which can be divided into two types according to the material. One is made by stacking sheets of metal materials with magnetostrictive properties (such as nickel, iron-cobalt alloys and aluminum-iron alloys, etc.). It is characterized by high mechanical strength, large emission power, stable performance, medium electroacoustic efficiency, and the working frequency range is generally below 50KHZ. It includes two structural types, window type and annular ultrasonic transducer. The other one is made of ferrite powder material by press molding and sintering. It is characterized by easy molding, high material resistivity, and higher electro-acoustic conversion efficiency than the former. Its working frequency can reach 100KHZ, but its mechanical strength is lower than the former, and its transmitting power is smaller. Magnetostrictive transducers also have the characteristics of high Curie point, low power supply voltage and easy cooling.
The piezo ultrasonic transducer can also be divided into two categories according to the type of material. One type is made by cutting and grinding a single crystal material with piezoelectric properties (such as quartz crystal) in a certain direction. It is characterized by high transmitting power and high electroacoustic efficiency, and is suitable for working in the high frequency range (up to several gigahertz). However, due to the high impedance, the supply voltage is relatively high and inconvenient to use. The other type is piezoelectric ceramics formed by pressing, sintering, and polarizing powdered materials. It is characterized by easy molding, high electroacoustic efficiency, low impedance, and lower power supply voltage than the former, and it is also suitable for high-frequency range work. In addition, a large number of sandwich structures are currently used in the low frequency range (several kilohertz to tens of kilohertz). The piezo ultrasonic transducer utilizes different polarizations and combinations to easily implement various vibration modes to meet the needs of different ultrasonic processing. The disadvantage of this type is low tensile strength. However, due to abundant material sources and low prices, applications are gradually increasing.