Acoustofluidic particle steering

Zaid Shaglwf, Bjorn Hammarström, Dina Shona Laila, Martyn Hill, Peter Glynne-Jones
2019 Journal of the Acoustical Society of America  
12 Steering micro objects using acoustic radiation forces is challenging for several reasons: 13 resonators tend to create fixed force distributions that depend primarily on device geometry, 14 and even when using switching schemes, the forces are hard to predict a-priori. In this paper 15 an active approach is developed that measures forces from a range of acoustic resonances 16 during manipulation using a computer controlled feedback loop based in MATLAB, with a 17 microscope camera for
more » ... pe camera for particle imaging. The arrangement uses a planar resonator where the 18 axial radiation force is used to hold particles within a levitation plane. Manipulation is 19 achieved by summing the levitation frequency with an algorithmically chosen second 20 resonance frequency, which creates lateral forces derived from gradients in the kinetic energy 21 density of the acoustic field. Apart from identifying likely resonances, the system does not 22 3 devices for research assays, configurable diagnostic devices, and the tissue engineering. Early 35 devices typically trapped or focussed particles towards locations that were fixed, and dictated 36 by the modes dependent on device geometry 3,4 . A number of approaches have been 37 explored to create flexible manipulation devices that are able to dynamically modulate 38 trapping positions. One option is to switch between resonant modes to create trapping 39 positions that form a continuum of positions, to either translate particles through a range of 40 positions 5-8 or to create a new fixed manipulation position 9 . An alternative, analogous to 41 optical tweezing, is to use higher frequency systems that form a localised focus and translate 42 the manipulation chamber relative to the transducer 10-12 . 43 The standing wave pattern that determines trapping locations can be considered a 44 superposition of two counter propagating waves. By aligning transducers at an oblique angle 45 13,14 , utilising transducers that minimise reflections 15 , or relying on absorption 16 , systems can 46 be created that allow each of these components to be independently created with arbitrary 47
doi:10.1121/1.5090499 fatcat:jccixurpjfbvvaq24a2eizec7u