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Continuous flow switching by pneumatic actuation of the air lubrication layer on superhydrophobic microchannel walls
KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.ORCID iD: 0000-0003-2830-0454
KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).ORCID iD: 0000-0001-9552-4234
KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.ORCID iD: 0000-0003-3336-1462
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2008 (English)In: 21st IEEE International Conference on Micro Electro Mechanical Systems (IEEE MEMS 2008), IEEE conference proceedings, 2008, 599-602 p.Conference paper (Refereed)
Abstract [en]

This paper introduces and experimentally verifies a method for robust, active control of friction reduction in microchannels, enabling new flow control applications and overcoming previous limitations with regard to sustainable liquid pressure. The air pockets trapped at a

superhydrophobic micrograting during liquid priming are coupled to an actively controlled pressure source, allowing the pressure difference over the air/liquid interface to be dynamically adjusted. This allows for manipulating the friction reduction properties of the surface, enabling active control of liquid mass flow through the channel. It also permits for sustainable air lubrication at theoretically unlimited liquid pressures, without loss of superhydrophobic properties. With the non-optimized grating used in the experiment, a difference in liquid mass flow of 4.8 % is obtained by alternatively collapsing and recreating the air pockets using the coupled pressure source, which is in line with a FE analysis of the same geometry. A FE analysis of a more optimized geometry predicts a mass flow change of over 30%, which would make possible new microfluidic devices based on local friction control. It is also experimentally shown that our method allows for sustainable liquid pressure 3 times higher than the Laplace pressure of a passive device.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2008. 599-602 p.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:kth:diva-24758DOI: 10.1109/MEMSYS.2008.4443727ISI: 000253356900150ScopusID: 2-s2.0-50149113512ISBN: 978-1-4244-1792-6OAI: diva2:356140
21st IEEE International Conference on Micro Electro Mechanical Systems (IEEE MEMS 2008), Tucson, AZ, USA, 13-17 Jan, 2008

QC 20101011

Available from: 2010-10-11 Created: 2010-09-27 Last updated: 2015-06-04Bibliographically approved
In thesis
1. Development of materials, surfaces and manufacturing methods for microfluidic applications
Open this publication in new window or tab >>Development of materials, surfaces and manufacturing methods for microfluidic applications
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents technological advancements in microfluidics. The overall goals of the work are to develop new miniaturized tests for point-of-care diagnostics and robust super-lubricating surfaces for friction reduction. To achieve these goals, novel materials, surfaces and manufacturing methods in microfluidics have been developed.

Point-of-care diagnostic tests are portable miniaturized instruments that downscale and automate medical tests previously performed in the central laboratories of hospitals. The instruments are used in the doctor’s office, in the emergency room or at home as self-tests. By bringing the analysis closer to the patient, the likelihood of an accurate diagnosis, or a quick therapy adjustment is increased. Already today, there are point-of-care tests available on the market, for example blood glucose tests, rapid streptococcus tests and pregnancy tests. However, for more advanced diagnostic tests, such as DNA-tests or antibody analysis, integration of microfluidic functions for mass transport and sample preparation is required. The problem is that the polymer materials used in academic development are not always suited for prototyping microfluidic components for sensitive biosensors. Despite the enormous work that has gone into the field, very few technical solutions have been implemented commercially.

The first part of the work deals with the development of prototype point of-care tests. The research has focused on two major areas: developing new manufacturing methods to leverage the performance of existing materials and developing a novel polymer material platform, adapted for the extreme demands on surfaces and materials in miniaturized laboratories. The novel manufacturing methods allow complex 3D channel networks and the integration of materials with different surface properties. The novel material platform is based on a novel off-stoichiometry formulation of thiol-enes (OSTE) and has very attractive material and manufacturing properties from a lab-on-chip perspective, such as, chemically stable surfaces, low absorption of small molecules, facile and inexpensive manufacturing process and a biocompatible bonding method. As the OSTE-platform can mirror many of the properties of commercially used polymers, while at the same time having an inexpensive and facile manufacturing method, it has potential to bridge the gap between research and commercial production.

Friction in liquid flows is a critical limiting factor in microfluidics, where friction is the dominant force, but also in marine applications where frictional losses are responsible for a large part of the total energy consumption of sea vessels. Microstructured surfaces can drastically reduce the frictional losses by trapping a layer of air bubbles on the surface that can act as an air bearing for the liquid flow. The problem is that these trapped air bubbles collapse at the liquid pressures encountered in practical applications.

The last part of the thesis is devoted to the development of novel low fluidfriction surfaces with increased robustness but also with active control of the surface friction. The results show that the novel surfaces can resist up to three times higher liquid pressure than previous designs, while keeping the same friction reducing capacity. The novel designs represent the first step towards practical implementation of micro-structured surfaces for friction reduction.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. xiii, 87 p.
Trita-EE, ISSN 1653-5146 ; 2011:058
microsystem technology, MEMS, microfluidics, polymers, off-stoichiometry thiol-ene, point-of-care, lab-on-chip
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:kth:diva-38605 (URN)978-91-7501-086-1 (ISBN)
Public defence
2011-09-23, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20110907

Available from: 2011-09-02 Created: 2011-08-30 Last updated: 2012-09-03Bibliographically approved

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Carlborg, Carl FredrikDo-Quang, MinhStemme, GöranAmberg, Gustavvan der Wijngaart, Wouter
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