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A Compact, Low-cost Microliter-range Liquid Dispenser based on Expandable Microspheres
KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).ORCID iD: 0000-0001-8248-6670
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2006 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 16, no 12, 2740-2746 p.Article in journal (Refereed) Published
Abstract [en]

This work presents a new low-cost liquid dispenser for the dispensing of microliters to milliliter volumes. The dispensing mechanism is based on a thermal actuator where highly expandable microspheres expand into a liquid reservoir consequently displacing any stored liquid. All device components are made out of low-cost materials and the fabrication process has the potential for high volume batch manufacturing. The device utilizes the property of the expandable microspheres to form a heat insulating layer between the heat source and the delivered liquid. Moreover, it does not require any feed back or complicated flow metering. The device was successfully tested showing a mean dispensed volume of 101 mu 1 with a standard deviation of 3.2% and with a maximum temperature of 59 degrees C in the liquid during actuation. It was shown that the dispenser is strong enough to deliver against counter pressures as high as 75 kPa. The device can also function as a low flow rate dispenser as demonstrated in a microfluidic dye laser application. The flow rate can be controlled between 1 mu 1 h(-1) and 2400 mu 1 h(-1) by adjusting the actuation power.

Place, publisher, year, edition, pages
2006. Vol. 16, no 12, 2740-2746 p.
Keyword [en]
FLOW-CONTROL; VALVE; Actuators; Dye lasers; Fluidics; Pressure effects; Reservoirs (water); Thermal insulating materials; Expandable microspheres; Heat insulating layers; Milliliter volumes; Volume batch manufacturing; Dispensers
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-7458DOI: 10.1088/0960-1317/16/12/030ISI: 000242475200030Scopus ID: 2-s2.0-33846117051OAI: oai:DiVA.org:kth-7458DiVA: diva2:12489
Note

QC 20100623

Available from: 2007-09-10 Created: 2007-09-10 Last updated: 2017-12-14Bibliographically approved
In thesis
1. A Fully Integrated Microneedle-based Transdermal Drug Delivery System
Open this publication in new window or tab >>A Fully Integrated Microneedle-based Transdermal Drug Delivery System
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Patch-based transdermal drug delivery offers a convenient way to administer drugs without the drawbacks of standard hypodermic injections relating to issues such as patient acceptability and injection safety. However, conventional transdermal drug delivery is limited to therapeutics where the drug can diffuse across the skin barrier. By using miniaturized needles, a pathway into the human body can be established which allow transport of macromolecular drugs such as insulins or vaccines. These microneedles only penetrate the outermost skin layers, superficial enough not to reach the nerve receptors of the lower skin. Thus, microneedle insertions are perceived as painless.

The thesis presents research in the field of microneedle-based drug delivery with the specific aim of investigating a microneedle-based transdermal patch concept. To enable controllable drug infusion and still maintain an unobtrusive and easy-to-use, patch-like design, the system includes a small active dispenser mechanism. The dispenser is based on a novel thermal actuator consisting of highly expandable microspheres. When actuated, the microspheres expand into a liquid reservoir and, subsequently, dispense stored liquid through outlet holes.

The microneedles are fabricated in monocrystalline silicon by Deep Reactive Ion Etching. The needles are organized in arrays situated on a chip. To allow active delivery, the microneedles are hollow with the needle bore-opening located on the side of the needle. This way, the needle can have a sharp and well-defined needle tip. A sharp needle is a further requirement to achieve microneedle insertion into skin by hand.

The thesis presents fabrication and evaluation of both the microneedle structure and the transdermal patch as such. Issues such as penetration reliability, liquid delivery into the skin and microneedle packaging are discussed. The microneedle patch was also tested and studied in vivo for insulin delivery. Results show that intradermal administration with microneedles give rise to similar insulin concentration as standard subcutaneous delivery with the same dose rate.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. x, 82 p.
Series
Trita-EE, ISSN 1653-5146 ; 2007:046
Keyword
Microneedle, Transdermal, Intradermal, Drug delivery, DRIE, MEMS, Microsystem
National Category
Biomedical Laboratory Science/Technology
Identifiers
urn:nbn:se:kth:diva-4484 (URN)978-91-7178-751-4 (ISBN)
Public defence
2007-09-28, F3, Lindstedsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100623Available from: 2007-09-10 Created: 2007-09-10 Last updated: 2010-06-28Bibliographically approved
2. 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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van der Wijngaart, WouterStemme, Göran

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