Non-destructive, non-contact handling method for biomaterials in micro-chamber by ultrasound

We investigated the non-contact handling of micrometer-sized samples in the micro-chamber using acoustic radiation force for lining up the microparticles and for mixing solutions. The chamber for handling samples consists of a fused quartz cell attaching a pair of 3.5 MHz lead zirconate titanate (PZT) transducers both sides. For lining up the particles, pure water containing 7-μm polystyrene spheres was introduced into the chamber. When 3.5 MHz ultrasound was irradiated into the chamber, the particles lined up at the pressure node of ultrasound less than 0.3 μm of the spatial distribution. For mixing, samples such as erythrocytes and fluorescent dye were introduced into the chamber from the inlet which arranged at the side wall of the chamber and the laminar flow of the two different kinds of solutions keeping their boundaries is observed. When the 3.5 MHz ultrasound irradiation into the chamber started, the boundaries of the two sample's flow were broken and the erythrocytes spread and mixed into all the span of the chamber. The possible damage caused by the 3.5 MHz ultrasound during the mixing process was also measured, and no significant release of the erythrocyte's component was detected even without the degas process, which was pre-processed for preventing cavitation generation. The results suggested the potential use of acoustic radiation force for non-contact, non-destructive and time-resolved handling method for micro-chamber as the sample preparation process.