When cleaning our glasses, we often encounter problems, such as the inability to effectively remove oil stains and the difficulty in cleaning dirt from corners. Ultrasonic cleaners not only conveniently clean small items like glasses and jewelry, but also provide a thorough, all-around cleaning. But how do ultrasonic cleaners work? The History of Ultrasonic Cleaners The history of ultrasonic cleaners can be traced back to the early 20th century. Since the Curie brothers discovered the piezoelectric effect in 1880, piezoelectricity has become an important field of modern science and technology. However, the earliest application of piezoelectric transducers in engineering was as quartz crystal resonators, used only as filtering devices, and the application of the piezoelectric effect in engineering was limited to underwater acoustics and electroacoustic devices. During World War I, the famous French physicist Paul Langevin invented a sandwich piezoelectric transducer with a "steel-quartz-steel" structure and successfully conducted experiments on emitting and receiving ultrasonic waves in water. This marked the first research and application of ultrasonic technology. However, true research into ultrasonic cleaning technology began in the 1950s when H.B. Miller made significant improvements to transducers, developing pre-stressed composite transducers, laying the foundation for the industrial application of power ultrasonic technology. During this period, ultrasonic cleaning technology was primarily used in electronics, optics, and medicine. Due to its powerful practicality and wide range of applications, from cleaning large mechanical parts to small semiconductor devices, it has long been commonly known as "brushless cleaning." However, the widespread application of this technology has not been without its challenges. Although ultrasonic cleaners have been around for over 30 years, and Japan began using them 25 years ago, a misunderstanding has plagued this technology, leading to doubts about the effectiveness of ultrasonic cleaners. Traditional ultrasonic cleaner theory holds that air bubbles play a cleaning role. However, through repeated experiments, scientists have discovered that air bubbles are actually just simple gas bursts caused by the strong, dense waves of ultrasound. They actually inhibit or even eliminate the cleaning force of the ultrasonic cleaner; the real cleaning effect comes from vacuum cavitation. In 1987, Yoshihide Shibano, founder of the Japan Cleaning Engineering Research Association, publicly published the basic theory of ultrasonic cleaning and developed technologically advanced ultrasonic cleaning equipment based on this theory. With the expansion of its application scope and the advancement of technology, ultrasonic cleaning equipment is constantly developing and improving. Traditional ultrasonic cleaning equipment, due to its low degree of automation, struggles to ensure uniform cleaning of parts. In recent years, highly automated and flexible automated ultrasonic cleaning equipment has gradually emerged. Today, ultrasonic cleaning machines are further integrating into people's lives, helping to clean objects with complex structures that are difficult to clean. The Working Principle of Ultrasonic Cleaning Machines: In terms of working principle, ultrasonic cleaning machines mainly convert the acoustic energy of a high-power ultrasonic frequency source into mechanical vibration through a transducer. This ultrasonic wave is radiated through the cleaning tank wall into the cleaning liquid in the tank. Due to the radiation of the ultrasonic waves, microbubbles in the liquid in the tank can maintain vibration under the action of the sound waves. When these microbubbles burst, they generate a powerful impact force, thereby separating dirt and grease from the surface and interior of the object being cleaned. Simultaneously, when ultrasound propagates in the cleaning fluid, it generates alternating positive and negative sound pressure, forming a jet that impacts the parts being cleaned. Furthermore, due to nonlinear effects, acoustic flow and micro-flow are generated, and ultrasonic cavitation produces high-speed micro-jets at the solid-liquid interface. All these effects can break down contaminants, remove or weaken boundary contaminant layers, increase agitation and diffusion, accelerate the dissolution of soluble contaminants, and enhance the cleaning effect of chemical cleaning agents. Specifically, when the liquid is used, bubbles are generated, and when the liquid is compressed, these bubbles are compressed, shattered, and broken up—this is the well-known "ultrasonic cavitation effect." In cavitation, the instant the bubbles collapse generates shock waves, creating enormous pressure (10¹²-10¹³ Pa) and localized temperature regulation around the bubbles. This enormous pressure generated by ultrasonic cavitation can break down insoluble contaminants, causing them to disintegrate in the solution. Simultaneously, the direct and repeated impact of vapor-type cavitation on the dirt also facilitates stain removal. In addition, ultrasonic cleaning utilizes the cavitation, acceleration, and direct flow effects of ultrasound waves in liquids to directly or indirectly affect the liquid and contaminants. This disperses, emulsifies, and peels off the contaminant layer, thus achieving the cleaning purpose. It is worth mentioning that the transducer in an ultrasonic cleaner plays a crucial role; it is an energy conversion device. Its main function is to convert the input electrical power into mechanical power (i.e., ultrasound waves) and then transmit it, while consuming very little power itself (less than 10%). Specifically, the transducer converts the acoustic energy of the high-power ultrasonic source into mechanical vibrations, radiating the ultrasound waves through the cleaning tank walls into the cleaning fluid in the tank. Due to the radiation of the ultrasound waves, microbubbles in the liquid in the tank can maintain vibration under the action of the sound waves. When using an ultrasonic transducer, the most important consideration is the matching with the input and output terminals, followed by mechanical installation and fitting dimensions. Furthermore, the transducer generates high-frequency vibrations with extremely small amplitudes that propagate into the cleaning tank, removing contaminants from the product through mechanical energy action, improving product cleanliness. In summary, ultrasonic cleaners remove dirt through a principle known as the "cavitation effect," rather than using air bubbles. In the future, with continuous technological advancements and growing market demand, ultrasonic cleaners will be applied in more fields, becoming more environmentally friendly, efficient, and intelligent.
