Microfluidics is an upcoming technology in a wide variety of fields including biology, chemistry and medicine. In these small channels the Reynolds number is very low (Re < 1). At these low Re values, viscosity dominates over inertia ensuring predictable laminar flows, which provides an exceptional control over the handled fluid streams. This makes it possible to continuously produce highly uniform droplets and particles. Continuous and high throughput production of micron size particles is becoming more and more relevant even in the industry. Particle maturation is often one of the limiting factor. For the production of poly(lactic-co-glycolic acid) (PLGA) microparticles for example, the rate limiting step is the solvent extraction from the produced droplet to yield the final particle. The use of standing acoustic waves in microfluidic devices gives the possibility to enhance the mass transfer rate far beyond the rate of diffusion. Acoustic streaming is a flow phenomenon occurring when an acoustic wave propagates through an enclosed fluid. These streaming flows take the form of vortices transverse to the microfluidic channel. However, when particles are suspended in a liquid a second phenomenon occurs, namely acoustic radiation. Acoustic radiation arises from the scattering of the soundwave on the particle, this pushes it towards the pressure node. Both phenomena, radiation and streaming, have been investigated in this contribution. For large particles (5µm) radiation dominates, while for small particles (0.5µm) streaming dominates. CFD simulations have been performed to get insight in the streaming velocity fields inside a half wavelength channel for a channel depth of 100 µm. Depending on the applied energy to the channel, velocities of approximately 50 µm/s could be reached, showing a very fast mixing of two streams. This has also been shown experimentally with fluorescence experiments. Tracking of small particles revealed that the vortex flows behave as predicted and conform that the boundary conditions are realistic. Large particle displacement distances and velocities have also been investigated experimentally as a function of the applied energy and frequency. Very fast focussing of particles on the pressure node has been shown. The use of both these phenomena is of great relevance in the production on microparticles. Streaming can be used to enhance the formation of the particles while radiation enables to focus and further concentrate the desired particles.
Original languageEnglish
Title of host publication23rd National Symposium on Applied Biological Sciences - Abstract book
Place of PublicationGhent, Belgium
PublisherGhent University
Number of pages1
ISBN (Print)ISSN 1379-1176
StatePublished - 8 Feb 2018
EventNational Symposium for Applied Biological Sciences - Vrije Universiteit Brussel, Brussel, Belgium
Duration: 8 Feb 20188 Feb 2018


ConferenceNational Symposium for Applied Biological Sciences
Abbreviated titleNSABS
Internet address

ID: 36652374