Experimental Analysis of Temperature Dependent Ultrasound Microbeam Trapping Mechanism of Biocompatible Microdroplet by Dual Element Focused Ultrasonic Transducer
An experimental study is carried out by using a 20/40 MHz LiNbO3 dual element focused transducer to examine the quantitative relation between ambient temperature and transversely displaced distance (or displacement) of lipid droplets via a two-dimensional ultrasound microbeam trapping technique. 40 MHz burst ultrasound for trapping a droplet is emitted from the inner circular element of the transducer, while 20 MHz pulsed beam for sensing the speed of sound is sent out from its outer ring element. In the range of 25 °C to 30 °C, the sound speed in droplets decreases from 1440 m/s to 1429 m/s. The average displacement varies from 145.0 µm to 156.0 µm with an increasing rate of 2.2 µm/°C, and its standard deviation lies between 1.0 µm and 1.5 µm. The results suggest that the proposed trapping approach may also be controlled by adjusting the temperature surrounding the trap, rather than by varying the trapping system parameters such as input voltage amplitude or excitation frequency of transducers.