Hybrid optical and acoustic trapping

  • Graham Brodie

    Student thesis: Doctoral ThesisDoctor of Philosophy


    The need for non-contact micromanipulation methods is apparent for a number
    of different applications. Optical tweezers, a technique which uses highly focused laser beams to trap and move microscopic objects, has become an important tool for many applications owing to its incredible precision and dexterity. Optical trapping is, however, limited in several ways. It often struggles with particles larger than 10 micrometers, agglomerates and large numbers of particles.

    Complimentary technologies such as acoustic trapping, aim to overcome some
    of these limitations. This technique, also termed as Sonotweezers, uses ultrasonic fields to manipulate particles and can manipulate large particles with ease and manipulate large numbers of polydisperse particles and agglomerations, although they currently lack the dexterity of optical tweezers. Combining these two trapping modalities overcomes the some of the limitations of both of them and opens up a new range of useful applications.

    Three main types of hybrid optical and acoustic traps have been devised and
    are presented here. The first is an acoustic Bessel beam trap which is used to
    arrange a large number of polydisperse particles into concentric rings whereupon the smaller particles can then be further manipulated using a single beam optical tweezer.

    A rudimentary optical sorting system, which pushes particles in a flow laterally using an optical trap, has been combined with an acoustic levitator, which moves all particles away from the edges of the microfluidic channel reducing on sticking and other negative effects.

    A novel optically transparent ultrasonic device has been developed for easier integration into optical traps without the need for modication. This transparent trap has also been used in combination with a multibeam interference optical
    sorter to improve the separation between 5 and 10 micron particles.
    Date of Award2014
    Original languageEnglish
    SupervisorMichael MacDonald (Supervisor)


    • Optical
    • Acoustic
    • Trapping
    • Tweezers
    • Ultrasound
    • Sorting
    • Hybrid
    • Sonotweezers
    • Transparent
    • Bessel

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