Particle trapping in suspended microchannel resonator

Suspended microchannel resonators (SMRs) embed a microfluidic channel inside a nanomechanical resonator. This facilitates high-throughput measurements of analytes immersed in liquid, that independently characterize analyte volume, mass, and mechanical properties. While it has been assumed that particles travel unhindered through these devices, we show that they become trapped under certain conditions. This phenomenon arises from nonlinear (acoustic streaming) fluid forces, for which an analytical theory is developed. This theory elucidates the conditions when trapping occurs, which are in agreement with experiment. These findings enable the active control of analytes in SMRs, based on their buoyant mass, oscillation amplitude, and resonator mode-shape.