Two-dimensional manipulation of microbubbles using standing leaky surface acoustic wave

In this paper, a microfluidic device is developed to transport the microbubbles on a two-dimensional plane. The microfluidic device consists of a polydimethylsiloxane (PDMS) microchannel and two pairs of perpendicular interdigital transducers (IDTs). When the surface acoustic wave (SAW) contacts the fluid medium inside the microchannel, some of SAW energy is coupled to the fluid and the SAW becomes the leaky surface wave (LSAW). The superposition of two series of planar LSAW with orthogonal wave vectors generates a two-dimensional standing LSAW and a planar pressure nodes with a periodic distribution. By modulating the relative phase between the IDTs, the pressure node plane changes linearly resulting in the transportation of the microbubbles continuously. Furthermore, the radiation force on the microbubbles can be acquired since the radiation force is balanced the drag force. These results demonstrate that the device may prove useful for many biochemical studies and applications.