Theory of acoustics in microfluidics: frequency modulation of acoustic resonances

Contacts:

Henrik Bruus, DTU Nanotech, 4525-6399 (bruus@nanotech.dtu.dk)

Rune Barnkob, DTU Nanotech, 4525-6868 (Rune.Barnkob@nanotech.dtu.dk)

Web: http://www.nanotech.dtu.dk/microfluidics

(a) Experiment from KTH, Manneberg et. al., Lab Chip 9, 833 (2009): microbeads (black spots) are focused to pressure-resonance nodes inside a microchannel with (bottom) and with¬out (the rest) frequency modu¬lation. (b) COMSOL mesh for the model system. (c) COMSOL solution for the pressure (color) and displacement field (vectors) of the model system.

Acoustofluidics deals with ultrasound handling of liquids, microparticles and cells in microfluidic lab-on-a-chip systems. During the past five years this new research field has undergone a very rapid development resulting in the appearance of a number of new biotechnological devices. As this progress has been mainly application-driven, a number of questions regarding the basic physical aspects of acoustofluidics remains open.

The controlled and predictable establishment of acoustic resonances is one of the main challenges in the field. A new, very promising technique is to frequency-modulate the piezo-transducers delivering the acoustic power, whereby un-wanted mode-specific structures are averaged out, leaving only the desired, general features, as illustrated in Fig. (a).

During this theoretical and numerical project you will be part of the Teoretical Microfluidics Group and join our collaboration with our experiemental colleagues at KTH Royal Instute of Technology, Stockholm.

In the project you will be introduced to the basic acoustofluidic theory through simplified analytical models. Later you will learn to use the finite element software COMSOL for full numerical simulation of the model systems, as illustrated by the examples from our research shown in Fig. (b) and (c).           

The overall goal of the project is to provide a basic theoretical physics analysis of the system and to help us find designs for optimal frequency modulation.