Two-dimensional manipulation of micro particles by acoustic radiation pressure in a heptagon cell

Abstract

An acoustic particle manipulation system is presented, using a flexible printed circuit board formed into a regular heptagon. It is operated at 4 MHz and has a side dimension of 10 mm. The heptagonal geometry was selected for its asymmetry, which tends to reduce standing wave behavior. This leads to the possibility of having fine control over the acoustic field by varying the output phases of the transducer elements. Configurations with two and three active transducers are demonstrated experimentally. It is shown that with two transducers, the particles align along straight lines, the position of which can be moved by varying the relative excitation phases of the two transducers. With three active transducers, hexagonal-shaped patterns are obtained that can also be moved, again according to the phase of the excitation signals. Huygens' principle-based simulations were used to investigate the resultant pressure distributions. Good agreement was achieved between these simulations and both Schlieren imaging and particle manipulation observations.

Counterpropagating wave acoustic particle manipulation device for the effective manufacture of composite materials

“…10 (b) shows a staggered offset of small particle agglomerates that was formed by combining two pairs of opposed transducers at an angle of 45 to each other, with the horizontally aligned elements driven at an advancing phase of ⇡/2. A more detailed discussion on the particle assembly patterns that can be generated using an octagonal acoustic particle manipulation device was previously given by Bernassau et al [8], [7]. Importantly here, the broadband frequency characteristics of the two transducer model are maintained and the build time of the eight transducer device remains comparable.…”

“…The most common of these devices produce a standing wave between a transducer and a reflector (see reviews by Laurell et al [1] and Evander et al [2]) and have seen application, particularly in the biomedical field to, for example, tissue engineering [3], [4]. Devices with additional transducers have also been explored and shown to be able to create a wide range of patterns [5], [6], [7] and allow these patterns to be translated [8], [9], [10], [11].…”

Manipulation of microspheres and microbubbles in an octagonal sonotweezers

“…Exciting six transducers (Fig. 2d and 3c) with transducers are arranged with two pairs (3,7) and (1,5) arranged at 45 o either side of the central pair (2,6), gives more complicated patterns. The pattern is periodic perpendicular to the common axis of the central pair, and has a period of λ/√2.…”

“…However, due to the low number of degrees of freedom, pattern shapes and displacement are limited. Trapping, patterning, and displacement of microspheres and cells have also been demonstrated in a heptagonal sonotweezer [3,4]. In these devices, streaming effects due to the asymmetry of the manipulation chamber and the transducers were generated.…”

Direct patterning of mammalian cells in an ultrasonic heptagon stencil

“…The influence and combination of two and three simultaneously excited transducers was investigated and discussed in detail elsewhere (Bernassau et al 2011). In this paper, each excited transducer was separated by at least one inactive transducer.…”