Particle trapping for acoustic tweezers

The optical tweezers has been found to have many biomedical applications in trapping macromolecules and cells. A recent theoretical study has shown that under appropriate conditions acoustic trapping is also possible [1]. Compared to the optical tweezers, the acoustic tweezers is more useful in light opaque media. In this paper, first we present the range where a particle can be trapped in single focused field along the axial direction from a 100MHz concave circular transducer on various sizes of particles. Secondly, we also proposed a multitrap model of acoustic tweezers which can trap 4 particles simultaneously. A 100MHz 2-D phased array with each line composed of 80 elements was used to generate and control the multiple-focus acoustic field. Both of the two fields generated by concave circular and phased array transducer were evaluated based on finite-element model. The radiation force was computed by the momentum transfer occurs between the mediums inside and outside the particle according to the law of conservation. The result demonstrates that the acoustic tweezers not only can manipulate larger particles, but also owns the feasibility of multitrap.