Continuous flow ultrasonic particle trapping in a glass capillary

Ultrasonic manipulation devices frequently exploit ultrasonic standing waves to trap particles in locations across the width of a fluidic channel or chamber. In contrast, this work describes a device, which traps particles along the length of the channel and hence at different locations along the direction of fluid flow. Actuation is achieved using a single piezoelectric transducer bonded to a borosilicate glass capillary, which defines the fluidic channel. Modes of operation have been found experimentally and through use of finite element simulation methods in which the particles can be trapped at locations away from the piezoelectric transducer allowing optimal visual access to the clumps of particles. These locations are separated by distances significantly greater than half the acoustic wavelength. When flow is introduced, a single clump is formed and optical access is unhindered by the opaque transducer allowing a method of capturing particles for multi-axial optical analysis. Applications could include determination of sample concentration or creation of concentrated samples for subsequent batch operations. (c) 2014 AIP Publishing LLC.