Towards Arbitrary Acoustic Force Fields

  • Luke Cox

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

The use of acoustic radiation forces as a tool for micro-manipulation is an area of growing interest. In-air levitation has proven useful for contactless containment of scientific samples (among other things), whilst in-water manipulation has gained particular attention as a tool for moving and patterning biological cells. However, to date most applications of acoustic forces have relied upon relatively simple force fields. Increasing the complexity of the obtainable fields would increase their applicability and as such is the primary aim of this thesis. This will be balanced against maintaining the other attractive, and related, qualities of low cost and simplicity of the device. Cross seeding developed approaches between the two commonly used media of water and air is also an area of interest here (noting that these can also be translated to other liquids or gases).

The first investigation in this thesis was the levitation of non-spherical objects in air. This adapted an existing low-cost standing wave levitator (the TinyLev) to multiplex between a standing wave, for vertical forces, and a twin trap, for lateral forces. Stable levitation was achieved experimentally for a range of sub-wavelength objects and this stability was characterised and explained with the help of simulations.

The second approach for complex fields combined in-water 3D printed acoustic holograms, capable of producing complex static fields, with phased arrays, capable of producing simple dynamic fields. It showed that the phase outputs from each of these could be linearly added and used this effect to produce complex manipulation by combining a 64-element linear phased array with printed holograms. It also demonstrated that simple 1D manipulation could be achieved with a two element amplitude controlled array combined with holograms on each element.

This thesis has explored multiple techniques to produce arbitrary acoustic force fields.
Date of Award2 Dec 2021
Original languageEnglish
Awarding Institution
  • University of Bristol
SponsorsUltraleap
SupervisorAnthony J Croxford (Supervisor) & Bruce W Drinkwater (Supervisor)

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