The design and modeling of a lateral acoustic particle manipulator exhibiting quarter-wave operation

Prior work [Petersson et al., 2004] has demonstrated the operation of a half-wave acoustic particle manipulator, whose forces act in the plane of a silicon substrate. In a half-wave device particles are directed to the centre of a channel. Devices acting in plane have manufacturing advantages, and lend themselves to many microfluidic applications. We demonstrate, for the first time, such a device with a quarter-wave mode that is able to manipulate particles to the side of a channel in addition to a near half wave mode. The design utilises resonant “islands” to create the necessary pressure release boundary condition. The device is conventionally milled in brass, permitting cheaper and quicker fabrication than in silicon. Finite element modelling is presented to elucidate the operation of both half and quarter-wave devices. In contrast to essentially one-dimensional planar devices, the two-dimensional distribution of the velocity and pressure fields result in particles being constrained to a line within the channel.