Followability in Transportation of Droplet by Using Counter-Faced Focused Ultrasound

Abstract

Contactless liquid manipulation is important for applications in analytical chemistry, biotechnology and material science. The manipulation technology can prevent the wall effect, such as contamination, absorption, and heterogeneous nucleation for the wall. This study focuses on an ultrasonic phased array system based on the acoustic levitation method. Although the ultrasonic phased array system is promising for sample manipulation in mid-air, this method has not been fully investigated. This paper aims to demonstrate the contactless droplet levitation and three-dimensional (3D) transportation in mid-air via an ultrasonic phased array system. We have developed an opposing device with a face-to-face ultrasonic phased array system and demonstrated the transportation of the droplet. First, the droplet can be transported one-dimensionally (1D). Then, the followability of the droplet was shown with transport speed and droplet diameter. The sound field analysis showed the potential of the levitated point. Based on the experiments, it was found that oscillation amplitude of the droplet increased with the increase of the transport speed and the droplet diameter. For developing the contactless liquid manipulation, we demonstrated the 2D and 3D transportation. Our findings promote the feasibility of contactless droplet manipulation with a phased array for potential applications.