Critical Components in Microfluidic Systems for Drug Delivery

Lennart Bitsch

    Research output: Book/ReportPh.D. thesis

    2189 Downloads (Pure)

    Abstract

    The goal of this thesis has been to evaluate microfluidic systems for applications in drug delivery. In particular, we have focused on safety in reciprocating pumps, for continuous insulin delivery, and identified the microvalves, as being critical components.

    We have investigated a technology for engineering of microfluidic components which promises good sealing properties. A good sealing property is a mean to ensure a high safety level for applications in drug delivery, and we have used the technology to fabricate a turning microvalve, which provides a significantly higher safety level compared to delivery systems using prestressed check valves.

    The technology is based on construction with soft incompressible rubber materials and hard surfaces. By basic studies on sliding friction between rubber and a hard substrate we show that friction force scales with contact area, and depends linearly on the contact pressure. Therefore, energy savings are obtained by down-scaling. Similar basic flow studies show that sealing properties depend on contact pressure, and how well the rubber-incompressibility is utilized in the actual geometry. In addition to the basic studies, scaling properties and dependency on contact pressure for turning valves are illustrated by construction and test of a large and a small turning valve. Therefore, low-energy, turning microvalves with high-pressure seals are feasible.

    The major benefits of down-scaling mechanical systems are the more compact and less energy consuming devices. We show the feasibility of a low-energy, turning microvalve with a high pressure seal by construction and test of a demonstrator with a rod diameter of 250 µm, the actuation energy of opening and closing is 0.15 mJ, and it withstand a pressure above 0.7 MPa.

    We have also used the studied technology to suggest the design and construction of a pump in an unexplored branch of micropumps, namely, the reciprocating piston pump. The pump utilizes turning microvalves to rectify the fluid flow, and it appears feasible to construct true micro-scale demonstrators of this pump. Further optimization and understanding of the friction processes could therefore provide a pump which is attractive for drug delivery.
    Original languageEnglish
    Place of PublicationKgs. Lyngby
    PublisherTechnical University of Denmark
    Number of pages120
    ISBN (Print)87-89935-86-1
    Publication statusPublished - Sep 2006

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