Gravity Directional Position Control of a Micro-particle through Frequency Variation of a Single Ultrasonic Transducer

As a promising untethered actuator, an ultrasound has been researched for several applications such as drug delivery, cell manipulation, and microrobot actuation. When micro objects are located in the standing wave field, the particles are trapped at the low acoustic potential position by the generated acoustic radiation force. Based on this principle, the ultrasound can move, trap, sort, and align a single micro device or particles without physical wiring onto the target object. In this study, we present a micro particle position control method by using ultrasound wave frequency control through an ultrasonic transducer, especially for the gravity directional movement. The acoustic potential of the medium was changed with respect to the standing wave position by controlling the excitation voltage frequency to the ultrasound transducer. In experiments, a single transducer with a resonance frequency of 950 kHz was used in the medium (water) to manipulate a micro particle. It was carried out to characterize the controllability of manipulation, and capture the micro particle in the medium. The results showed that the proposed system can successfully move up and down the micro particle by using the suggested ultrasound frequency control method.