The «Lab-On-a-Chip» Concept

1. A Glass Valveless Micropumpwith Electromagnetic Actuation C. Yamahata, F. Lacharme, and M. A. M. Gijs Institute of Microelectronics and Microsystems, EPFL, Swiss Federal Institute of Technology Lausanne, CH – 1015 Lausanne, Switzerland Abstract: We present a low-cost glass micropump targeted to Lab-On-a-Chip applications. The developed microchip is fabricated by powder blasting, a rapid prototyping method which appears to be very suitable for the development of microfluidic structures. Nozzle/diffuser elements are used to obtain the valving effect. An external electromagnet is employed to actuate the membrane of the reciprocating pump. With a sinusoidal current of 100 mA, a water flow rate of up to 1 mL/min is obtained up to a backpressure of 50 mbar. The «Lab-On-a-Chip» Concept • Schematic diagram • The diffuser micropump is constituted • of 3 glass layers and a flexible • silicone membrane : • the central glass layer contains the fluidic network; • the top glass layer has the fluidic connections; • the membrane is attached to the bottom glass layer. • The micropump is actuated with an external electromagnet placed below. Initiated in the 1990’s, Lab-On-a-Chip (LOC) technology represents a revolution in laboratory experimentation. The main benefits of this technology are miniaturization, integration and automation which have a large potential to improve and lower the costs of many biochemical analysis. Microfabrication Technique1 Magnetic membrane A Neodymium magnet (Ø 3 mm  3 mm) was integrated in the membrane during polymerization of the polydimethylsiloxane (PDMS) elastomer. Air plasma treatment was used for the bonding of PDMS membrane on glass. • Due to its chemical inertness, glass material is undeniably the favourite material for LOC devices fabrication. • Our microfabrication technique • is based on : • Microstructuration of fluidic • channels by powder blasting. • Multi-layered microchip • assembly by glass bonding. Glass microchip Accelerated alumina particles (30 mm) are used to erode the surface of thin (300 mm) borosilicate glass plates. The fluidic microchip is obtained by fusion bonding of the glass plates (see figure on the right). Micro- and Nano-Engineering 2004 • 19-22 September 2004 • Rotterdam, The Netherlands Diffuser Micropump2 As a major part of the fluid delivery system, the micropump is a key element of fluidic devices. Pumps of the « reciprocating type » that contain a flexible membrane are the most commonly used among micropumps. The nozzle/diffuser element is a fluidic channel constriction that has a different fluidic resistance in the diffuser (direct) and nozzle (reverse) direction. A diffuser micropump uses two nozzle/diffuser elements instead of valves. It is very attractive for its ease of fabrication. Nozzle/diffuser element characterization The ratio between the flow rate in the diffuser and in the nozzle direction determines the efficiency of the diffuser. This characteristic was determined on a separate device. • Micropump characterization • The resonance frequency was theoretically estimated with a low order damped oscillator model. The two main parameters that determine the resonance are : • the Membrane stiffness • Fluid inertia in the diffusers 1. D. Solignac, “Glass microchips for bio.chemical analysis: technologies and applications,” Ph.D. thesis, EPFL, Lausanne, Switzerland, 2003. 2. A. Olsson, “Valve-less Diffuser Micropumps,” Ph.D. thesis, KTH, Stockholm, Sweden, 1998. • Christophe.Yamahata@epfl.chhttp://lmis2.epfl.ch • Frederic.Lacharme@epfl.ch • Christophe.Yamahata@epfl.chhttp://lmis2.epfl.ch • Frederic.Lacharme@epfl.ch