Continuous flow ultrasonic particle trapping in a glass capillary

Abstract

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.

Three-Dimensional Numerical Modeling of Acoustic Trapping in Glass Capillaries

“…[7,9]), C2 from Lei et al [29], C3 from Mishra et al [27], and C4 from Gralinski et al [28]. We also characterize a lowaspect-ratio version of C1 denoted C5.…”

“…In the original work on the circular capillary C4 [28], effects due to reflections at the end of the capillary were discussed. Therefore, we study numerically the frequency response with PML absorption (perfect absorption of all outgoing waves) and without it (reflection of all outgoing waves at the end wall without absorption).…”

“…Capillary geometries modeled in this work: C1 from Hammarström et al [8], C2 from Lei et al [29], C3 from Mishra et al [27], C4 from Gralinski et al [28], and C5 a capillary design proposed in this work. Besides the symbols defined in Fig.…”

“…Examples of recent advances in modeling include Lei et al [29], who modeled the three-dimensional (3D) fluid domain without taking the solid domain into account; Muller and Bruus [32,39], who made detailed models in 2D of the thermoviscous and transient effects in the fluid domain; Gralinski et al [28], who modeled circular capillaries in 3D with fluid and glass domains without taking absorption and outgoing waves into account; Hahn and Dual [33], who calculated the acoustic field in a 3D model for a glass-silicon device (not a capillary system) and characterized the various loss mechanisms; and Garofalo et al [40], who studied a coupled transducer-silicon-glass-water system in 2D.…”

“…However, the ultrasound capillary system remains an active research topic, as cell-handling applications have become more numerous and refined over the years. Recent examples include cardiac myoblast viability in ultrasonic fields [25], sonoporation [26], the squeezing of red blood cells [27], and the trapping and retention of particles against an external flow [28].…”