Acoustic levitation and manipulation by a high-frequency focused ring ultrasonic transducer

Recently, acoustic levitation for non-contact micro-particle manipulation has been attracting great interest in physical, biological, and medical applications. Among the state-of-the-art manipulation technologies, single beam acoustic tweezing exhibits advantages of providing stronger trapping force and deeper penetration depth in tissues, inducing less tissue damage, and a simple configuration involving only one device. However, particle trapping by the single beam acoustic tweezer could only be operated on a smooth two-dimensional substrate, which limits the potential for real applications. Here, we report an initial attempt to acoustically levitate an individual micro-particle stably in water and manipulate the levitated micro-particle arbitrarily two-dimensionally by simply employing a 60-MHz focused ring ultrasonic transducer. The proposed working mechanism agrees well with the phenomenon. This approach could not only acoustically levitate and manipulate a micro-particle on a culture dish and on a mylar film, but could also work properly in levitating and manipulating a micro-particle placed inside the polyimide tube. This simple and low-cost approach is extremely useful for effective non-contact micro-particle manipulation without having critical concerns on the substrate properties.