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Contactless microfluidics “on tracks”: A fundamental study of acoustic levitation allowing the controlled motion and mixing of droplets

English title Contactless microfluidics “on tracks”: A fundamental study of acoustic levitation allowing the controlled motion and mixing of droplets
Applicant Poulikakos Dimos
Number 122169
Funding scheme Project funding (Div. I-III)
Research institution Institut für Energietechnik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Mechanical Engineering
Start/End 01.10.2008 - 31.12.2011
Approved amount 355'450.00
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All Disciplines (2)

Discipline
Mechanical Engineering
Fluid Dynamics

Keywords (8)

acoustic levitation; fluid dynamics; microfluidics; contactless transfer; dielectrophoresis; mixing processes; acoustic streaming; diagnostics

Lay Summary (English)

Lead
Lay summary
The goal of the project is the development of a novel concept in which ultrasonically generated pressure nodes are one dimensional (lines) instead of zero dimensional (points). This is achieved by creating a channel-shaped acoustic resonance cavity. It is a significant advancement for it allows for the contactless translation of levitated particles and droplets along tracks, which can initiate a next generation of fluidic devices, e.g. for medical or other diagnostic applications. A number of open basic scientific questions related to the novel levitation concept, allowing for motion and possible application scenarios deserve careful investigation and constitute the main goals of this project:a)Experimental and theoretical/numerical investigation of the levitation force and the Bernoulli forces that suspend the droplet on the nodal line. b)Experimental and theoretical/numerical investigation of the translation of droplets along the nodal line "tracks" (acoustic or dielectrophoretic (DEP) translation). The translation force will be determined as a function of droplet size and other system parameters. The drag force from the air is expected to be influenced markedly by the presence of acoustic streaming.c)Experimental investigation of droplet dynamics. Dispensing of aqueous droplets onto levitation tracks and mixing of colliding droplets will be studied. Because merged droplets can be brought to a halt after collision, the mixing process can be carefully observed. The ultrasonic excitation is expected to enhance mixing. Finally, the possibility of dividing a droplet into two parts by ultrasonically excited resonance will be investigated.In summary, the results of the research will piece together a fundamental knowledge base for contactless, acoustically levitated, controlled droplet motion and mixing. In addition to its merit from the fundamental standpoint, this research is a necessary step toward the future development of novel technologies based on ultrasonic levitation.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Investigation of a line-focused acoustic levitation for contactless transport of particles
Foresti Daniele, Bjelobrk Nada, Nabavi Majid, Poulikakos Dimos (2011), Investigation of a line-focused acoustic levitation for contactless transport of particles, in Journal of Applied Physics, 109, 093503-1-093503-11.
Contactless transport of acoustically levitated particles
Bjelobrk Nada, Foresti Daniele, Dorrestijn Marko, Nabavi Majid, Poulikakos Dimos (2010), Contactless transport of acoustically levitated particles, in Applied Physics Letters, 97, 161904-1-161904-3.
An acoustic manipulator device for contactless transport and mixing of droplets in air
Bjelobrk Nada, Nabavi Majid, Poulikakos Dimos, An acoustic manipulator device for contactless transport and mixing of droplets in air, Proceeding of 162nd Acoustical Society of America Meeting, USA.
Contactless transport of matter in the first five resonance modes of a line-focused acoustic manipulator
Foresti Daniele, Nabavi Majid, Poulikakos Dimos, Contactless transport of matter in the first five resonance modes of a line-focused acoustic manipulator, in Journal of the Acoustical Society of America, 131.
Simultaneous contactless levitation and transport of matter in the third resonance mode of a line-focused acoustic manipulator
Foresti Daniele, Nabavi Majid, Poulikakos Dimos, Simultaneous contactless levitation and transport of matter in the third resonance mode of a line-focused acoustic manipulator, Proceeding of 161st Acoustical Society of America Meeting, USA.
Time-averaged acoustic forces acting on a rigid sphere within a wide range of radii in an axisymmetric levitator
Foresti Daniele, Nabavi Majid, Poulikakos Dimos, Time-averaged acoustic forces acting on a rigid sphere within a wide range of radii in an axisymmetric levitator, Proceeding of ICU 2011, Gdansk, Poland.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
162nd MEETING OF THE ACOUSTICAL SOCIETY OF AMERICA 31.10.2011 San Diego, California, USA
International Congress on Ultrasonics 05.09.2011 Gdańsk, Poland
161st Acoustical Society of America Meeting 23.05.2011 Seatlle, USA


Associated projects

Number Title Start Funding scheme
107450 Fundamental thermofluidic and interfacial phenomena in "fountain pen" based micro/nano-writing and curing of nanopartilce inks 01.05.2005 Project funding (Div. I-III)
144397 “Digitized” Acoustic Actuation for Precise Contactless Transport of Droplets in Air 01.01.2013 Project funding (Div. I-III)

Abstract

Ultrasonic levitators have been used for contactless elevation and support of small amounts of matter at a fixed point since 1933[Bue33]. Droplets and particles could be held at the pressure nodes of standing acoustic waves in a gaseous or liquid environment, e.g. for studying crystallization or evaporation without the intrusive effect of support objects. We propose herein a novel concept in which pressure nodes are one dimensional (lines) instead of zero dimensional (points). This is achieved by creating a channel-shaped acoustic resonance cavity. It is a significant advancement for it allows for the contactless translation of levitated particles and droplets along tracks, which can initiate a next generation of fluidic devices, e.g. for medical or other diagnostic applications. A number of open basic scientific questions related to the novel levitation concept, allowing for motion and possible application scenarios deserve careful investigation and will constitute the main goals of this proposal. To this end, the main research tasks of the proposed work are:a)Experimental and theoretical/numerical investigation of the levitation force and the Bernoulli forces that suspend the droplet on the nodal line. b)Experimental and theoretical/numerical investigation of dielectrophoretic (DEP) translation of droplets along the nodal line “tracks”. The translation force will be determined as a function of droplet size and electrode geometry. The drag force from the air is expected to be influenced markedly by the presence of acoustic streaming. To the best of our knowledge, dielectrophoresis has not yet been investigated as a means to translate levitated objects, nor has the influence of the acoustic streaming on the drag force been determined.c)Experimental investigation of droplet dynamics. Dispensing of aqueous droplets onto levitation tracks and mixing of colliding droplets will be studied. Because merged droplets can be brought to a halt after collision, the mixing process can be carefully observed for the first time. The ultrasonic excitation is expected to enhance mixing. Finally, the possibility of dividing a droplet into two parts by ultrasonically excited resonance will be investigated.In summary, the results of the research proposed herein will piece together a fundamental knowledge base for contactless, acoustically levitated, controlled droplet motion and mixing. In addition to its merit from the fundamental standpoint, this research is a necessary step toward the future development of novel technologies based on the proposed concept.
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