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Wedge transducer design for two-dimensional ultrasonic manipulation in a microfluidic chip
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. (Biomedical & X-Ray Physics)ORCID iD: 0000-0002-4720-2756
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. (Biomedical & X-Ray Physics)
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. (Biomedical & X-Ray Physics)ORCID iD: 0000-0003-2723-6622
KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics. (Biomedical & X-Ray Physics)
2008 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 18, 095025- p.Article in journal (Refereed) Published
Abstract [en]

We analyze and optimize the design of wedge transducers used for the excitation of resonances in the channel of a microfluidic chip in order to efficiently manipulate particles or cells in more than one dimension. The design procedure is based on (1) theoretical modeling of acoustic resonances in the transducer-chip system and calculation of the force fields in the fluid channel, (2) full-system resonance characterization by impedance spectroscopy and (3) image analysis of the particle distribution after ultrasonic manipulation. We optimize the transducer design in terms of actuation frequency, wedge angle and placement on top of the chip, and we characterize and compare the coupling effects in orthogonal directions between single- and dual-frequency ultrasonic actuation. The design results are verified by demonstrating arraying and alignment of particles in two dimensions. Since the device is compatible with high-resolution optical microscopy, the target application is dynamic cell characterization combined with improved microfluidic sample transport.

Place, publisher, year, edition, pages
2008. Vol. 18, 095025- p.
Keyword [en]
standing-wave; separation; particles; channels; bioassays; cells
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-10915DOI: 10.1088/0960-1317/18/9/095025ISI: 000259590700025Scopus ID: 2-s2.0-54749116541OAI: oai:DiVA.org:kth-10915DiVA: diva2:231811
Note
QC 20100730Available from: 2009-08-18 Created: 2009-08-18 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Multidimensional Ultrasonic Standing Wave Manipulation in Microfluidic Chips
Open this publication in new window or tab >>Multidimensional Ultrasonic Standing Wave Manipulation in Microfluidic Chips
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of ultrasonic standing waves for contactless manipulation of microparticles in microfluidic systems is a field with potential to become a new standard tool in lab-on-chip systems. Compared to other contactless manipulation methods ultrasonic standing wave manipulation shows promises of gentle cell handling, low cost, and precise temperature control. The technology can be used both for batch handling, such as sorting and aggregation, and handling of single particles.

This doctoral Thesis presents multi-dimensional ultrasonic manipulation, i.e., manipulation in both two and three spatial dimensions as well as time-dependent manipulation of living cells and microbeads in microfluidic systems. The lab-on-chip structures used allow for high-quality optical microscopy, which is central to many bio-applications. It is demonstrated how the ultrasonic force fields can be spatially confined to predefined regions in the system, enabling sequential manipulation functions. Furthermore, it is shown how frequency-modulated signals can be used both for spatial stabilization of the force fields as well as for flow-free transport of particles in a microchannel. Design parameters of the chip-transducer systems employed are investigated experimentally as well as by numerical simulations. It is shown that three-dimensional resonances in the solid structure of the chip strongly influences the resonance shaping in the channel.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. ix, 83 p.
Series
Trita-FYS, ISSN 0280-316X ; 2009:44
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-10919 (URN)978-91-7415-398-9 (ISBN)
Public defence
2009-09-11, FD5, Roslagstullsbacken 21, Stockholm, 14:00 (English)
Opponent
Supervisors
Note
QC 20100730Available from: 2009-09-01 Created: 2009-08-18 Last updated: 2010-07-30Bibliographically approved
2. Ultrasonic Handling of Living Cells in Microfluidic Systems
Open this publication in new window or tab >>Ultrasonic Handling of Living Cells in Microfluidic Systems
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Microfluidic chips have become a powerful tool in research where biological cells are processed and/or analyzed. One method for contactless cell manipulation in microfluidic chips that has gained an increasing amount of attention the last decade is ultrasonic standing wave (USW) technology. This Thesis explores the biocompatibility of USW technology applied to microfluidic chips, and presents a novel USW-based method for serial processing and accurate characterization of living cells.

The biocompatibility has been investigated by measuring the proliferation rate of cells after they had been trapped and aggregated inside a chip by ultrasound. No negative influence was observed after continuous exposure to 0.85 MPa pressure amplitudes for up to 75 min. Furthermore, the heat generation in the fluid channel caused by the ultrasound has been measured and used in a regulation scheme where the temperature can be controlled around any relevant temperature (e.g. 37‰) with ±0.1‰ accuracy for more than 12 hours. The proliferation rate and temperature investigations suggest that USW technology applied to microfluidic chips is a biocompatiblemethod useful for long-term handling of living cells.

We have introduced a new concept of contactless ultrasonic ”caging” of single cells or small aggregates of cells. These cages are channel segments in the microfluidic chips that are geometrically designed to resonate at one or several actuation frequencies. The actuation is performed remotely by up to five external frequency specific wedge transducers, where each transducer produces a localized and spatially confined standing wave with a specific orientation of its corresponding radiation force field. By multi-frequency actuation, sophisticated and flexible force fields are realized by both overlapping and separated single fields. The Thesis describes two different cages: A sub-mm ”micro-cage” for tree-dimensional manipulationof single cells, and a 5-mm ”mini-cage” for selective retention of small cell aggregates (up to approx. 10^3 cells) from a continuously feeding sample flow. Finally,our microfluidic chips were also designed to be compatible with high-resolution optical microscopy. We have demonstrated sub-μm-resolution confocal fluorescence and trans-illumination microscopy imaging of ultrasonically caged living cells.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. xi, 53 p.
Series
Trita-FYS, ISSN 0280-316X ; 2009:56
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:kth:diva-11500 (URN)978-91-7415-466-5 (ISBN)
Public defence
2009-11-27, FB42, Roslagstullsbacken 21, AlbaNova Universitetscentrum, Kungliga Tekniska Högskolan., Stockholm., 10:00 (English)
Opponent
Supervisors
Note
QC 20100811Available from: 2009-11-17 Created: 2009-11-17 Last updated: 2011-10-04Bibliographically approved

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Publisher's full textScopushttp://www.iop.org/EJ/abstract/0960-1317/18/9/095025/

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Manneberg, OttoHertz, Hans M.

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