Ultrasonic transducers emit ultrasonic waves, a type of mechanical wave. They feature good directivity and strong penetration, and can travel through water and air. Common applications include distance measurement, speed measurement, cleaning, welding, lithotripsy, sterilization and disinfection. According to excitation modes, mainstream ultrasonic transducers are divided into magnetostrictive transducers and electrostrictive transducers.
In the early 20th century, advances in electronics made it possible to fabricate electromechanical transducers using piezoelectric and magnetostrictive effects of certain materials. In 1917, French physicist Langevin built a sandwiched ultrasonic transducer with natural piezoelectric quartz to detect submarines underwater. As ultrasound technology developed for military and civilian use, high-power magnetostrictive transducers and many specialized types (piezoelectric, electromagnetic, electrostatic transducers) were developed.
Medical applications of ultrasonic transducers fall into two categories: medical imaging detection and clinical treatment.
Medical instruments such as B-scan ultrasound, color Doppler ultrasound, ultrasonic holography systems, ultrasonic scalpels and ultrasonic lithotripters all rely on ultrasonic transducers.
Medical ultrasound works similarly to sonar. The transducer sends ultrasound waves into human tissue. When the waves hit tissue boundaries, reflection and refraction occur. Ultrasound will be absorbed and attenuated inside the human body, and will not harm tissues under normal operation.
Different medical devices adopt customized ultrasonic transducers for different functions. Thanks to its safety, ultrasound is widely adopted in clinical medicine.