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A Thermally Responsive PDMS Composite and its Microfluidic Applications
KTH, School of Electrical Engineering (EES), Microsystem Technology.
KTH, School of Electrical Engineering (EES), Microsystem Technology.
KTH, School of Electrical Engineering (EES), Microsystem Technology.ORCID iD: 0000-0001-9552-4234
2007 (English)In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 16, no 1, 50-57 p.Article in journal (Refereed) Published
Abstract [en]

This paper describes a novel composite actuator for controlled liquid actuation in microsystems which is based on a thermally responsive elastomer. The composite actuator consists of expandable microspheres incorporated in a polydimethylsiloxane (PDMS) matrix and entails the merits of both PDMS and expandable microspheres. The main characteristic of the composite actuator is to expand upon heat. The expansion is irreversible and the relative volume increase is measured up to 270% of its original volume after heating to 80 degrees C. The composite was used to fabricate single-use microfluidic pumps and valves. We show the displacement of liquids in the range of nanoliters even against counter pressures up to 100 kPa. Moreover, liquid flow in microchannels was entirely blocked by means of the integrated valves. The valves can withstand pressures up to 140 kPa. The devices are fabricated using low-cost materials only, and the composite actuator allows using wafer-level processing. The fluidic components based on the novel composite are highly integrable and do not require external actuators.

Place, publisher, year, edition, pages
2007. Vol. 16, no 1, 50-57 p.
Keyword [en]
Fluidics; Microactuators; Micropumps; Channel flow; Microactuators; Microchannels; Microfluidics; Microspheres; Thermal expansion; Valves (mechanical); Integrated valves; Micropumps; Polydimethylsiloxane
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-7397DOI: 10.1109/JMEMS.2006.886025ISI: 000244434300008Scopus ID: 2-s2.0-33947208945OAI: oai:DiVA.org:kth-7397DiVA: diva2:12413
Note
QC 20100817Available from: 2007-08-21 Created: 2007-08-21 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Novel Microfluidic Devices Based on a Thermally Responsive PDMS Composite
Open this publication in new window or tab >>Novel Microfluidic Devices Based on a Thermally Responsive PDMS Composite
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The field of micro total analysis systems (μTAS) aims at developments toward miniaturized and fully integrated lab-on-a-chip systems for applications, such as drug screening, drug delivery, cellular assays, protein analysis, genomic analysis and handheld point-of-care diagnostics. Such systems offer to dramatically reduce liquid sample and reagent quantities, increase sensitivity as well as speed of analysis and facilitate portable systems via the integration of components such as pumps, valves, mixers, separation units, reactors and detectors.

Precise microfluidic control for such systems has long been considered one of the most difficult technical barriers due to integration of on-chip fluidic handling components and complicated off-chip liquid control as well as fluidic interconnections. Actuation principles and materials with the advantages of low cost, easy fabrication, easy integration, high reliability, and compact size are required to promote the development of such systems.

Within this thesis, liquid displacement in microfluidic applications, by means of expandable microspheres, is presented as an innovative approach addressing some of the previously mentioned issues. Furthermore, these expandable microspheres are embedded into a PDMS matrix, which composes a novel thermally responsive silicone elastomer composite actuator for liquid handling. Due to the merits of PDMS and expandable microspheres, the composite actuator's main characteristic to expand irreversibly upon generated heat makes it possible to locally alter its surface topography. The composite actuator concept, along with a novel adhesive PDMS bonding technique, is used to design and fabricate liquid handling components such as pumps and valves, which operate at work-ranges from nanoliters to microliters. The integration of several such microfluidic components promotes the development of disposable lab-on-a-chip platforms for precise sample volume control addressing, e.g. active dosing, transportation, merging and mixing of nanoliter liquid volumes. Moreover, microfluidic pumps based on the composite actuator have been incorporated with sharp and hollow microneedles to realize a microneedle-based transdermal patch which exhibits on-board liquid storage and active dispensing functionality. Such a system represents a first step toward painless, minimally invasive and transdermal administration of macromolecular drugs such as insulin or vaccines.

The presented on-chip liquid handling concept does not require external actuators for pumping and valving, uses low-cost materials and wafer-level processes only, is highly integrable and potentially enables controlled and cost-effective transdermal microfluidic applications, as well as large-scale integrated fluidic networks for point-of care diagnostics, disposable biochips or lab-on-a-chip applications.

This thesis discusses several design concepts for a large variety of microfluidic components, which are promoted by the use of the novel composite actuator. Results on the successful fabrication and evaluation of prototype devices are reported herein along with comprehensive process parameters on a novel full-wafer adhesive bonding technique for the fabrication of PDMS based microfluidic devices.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. xii, 68 p.
Series
Trita-EE, ISSN 1653-5146 ; 2007:31
Keyword
MEMS, microsystem technology, micro total analysis system, lab-on-a-chip, microfluidics, composite actuator, expandable microspheres, PDMS, poly dimethylsiloxane, disposable, wafer bonding, adhesive bonding, PDMS bonding, adhesive PDMS bonding, selective PDMS bonding, microcontact printing
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4470 (URN)978-91-7178-732-3 (ISBN)
Public defence
2007-09-07, F3, Lindstedtsvägen 26, KTH, 10:00
Opponent
Supervisors
Note
QC 20100817Available from: 2007-08-21 Created: 2007-08-21 Last updated: 2010-08-17Bibliographically approved

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