Beyond mass measurement for single microparticles via bimodal operation of microchannel resonators

Abstract

This paper reports bimodal operation of microchannel resonators towards measurements of properties associated with energy dissipation resulting from travelling particles along with their buoyant masses. Two independent actuation methods are applied for simultaneous operation of the first and second flexural bending modes of cantilever-type microchannel resonators. The first mode is operated in closed loop feedback and the second mode is operated in open loop. During a single microparticle transit inside a microchannel resonator, resonance frequency of the first mode is measured via a heterodyne frequency down-mixer and amplitude and phase of the second mode are measured via a lock-in technique. While a 5-μm diameter single polystyrene particle is dynamically trapped by alternating pneumatic pressure gradient, frequency shift of the first mode and amplitude change and phase shift of the second mode are measured, analyzed, and then statistically compared. Bimodal operation of microchannel resonators demonstrated herein can be applicable to arbitrary modes and will be useful to provide information associated with energy dissipation in addition to buoyant mass for particles of interest.