ICU2015/77
Focusing microparticles inside droplets using acoustics
A. Fornella, H. N. Joenssonb, M. Antfolka, J. Nilssona and M. Tenjec
aDept Biomedical Engineering Lund University, Box 118, S-22100 Lund, Sweden
bDiv of Nanobiotechnology and Proteomics KTH Royal Institute of Technology, Science for Life Laboratory, Box 1031, S-17121 Solna, Sweden
cDept Engineering Sciences Uppsala University, Box 753, S-75121 Uppsala, Sweden anna.fornell@bme.lth.se
Motivation
Droplet-based microfluidics has emerged as an exciting tool with applications for single-cell analysis.
One obstacle has been the lack of precise methods to control the position of particles or cells inside the droplets. The challenge is to overcome the drag force from the internal fluid streams in the droplets.
Recently, acoustics have been combined with droplet microfluidics, to control the position of aqueous droplets in microfluidic channels. Here, a method is introduced that uses integrated bulk acoustic standing waves to reproducibly position microparticles inside moving droplets.
Methods
An isotropically wet-etched glass chip with a glued piezoelectric element was used to generate aqueous droplets containing polystyrene microparticles (7 µm) in an organic phase. The channel depth and top- width were 150 µm and 435 µm, respectively, corresponding to a resonance frequency of around 1.9 MHz in water. The total flow rates were set between 3-18 µl/min, and different flow rate ratios were evaluated.
At resonance, the microparticles will be moved towards the centre of the microchannel, due to gradients of the acoustic pressure field.
Results
The microparticles were acoustically positioned to the centre of the nanoliter-sized droplets at the res- onance frequency, at total flow rates between 3-12 µl/min (water:oil ratio 1:2). At higher flow rates reduced focusing was seen due to insufficient time for the primary acoustic radiation force to act.
This new method to control the position of microparticles inside droplets by bulk acoustophoresis opens up for a range of on-chip droplet-based assays that are not possible to perform today.
Number of words in abstract: 250
Keywords: Acoustics - Droplets - Microfluidics
Technical area: Standing waves, resonating and actuating ultrasonics
Presentation: Oral preferred, but poster accepted Special equipement:
Registration: 129014514 - Fornell Anna - 0 0 not paid
ICU 2015 Metz
Email: submissions icu2015@conforg.fr, Web: http://2015-icu-metz.gatech.edu/
