A PMMA valveless micropump using electromagnetic actuation

We have fabricated and characterized a polymethylmethacrylate (PMMA) valveless micropump. The pump consists of two diffuser elements and a polydimethylsiloxane (PDMS) membrane with an integrated composite magnet made of NdFeB magnetic powder. A large-stroke membrane deflection (~200 µm) is obtained using external actuation by an electromagnet. We present a detailed analysis of the magnetic actuation force and the flow rate of the micropump. Water is pumped at flow rates of up to 400 µl/min and backpressures of up to 12 mbar. We study the frequency-dependent flow rate and determine a resonance frequency of 12 and 200 Hz for pumping of water and air, respectively. Our experiments show that the models for valveless micropumps of A. Olsson et al. (J Micromech Microeng 9:34, 1999) and L.S. Pan et al. (J Micromech Microeng 13:390, 2003) correctly predict the resonance frequency, although additional modeling of losses is necessary.

Magnetically actuated micropumps

Christophe Yamahata

"Lab-On-a-Chip" (LOC) systems are intended to transpose complete laboratory instrumentations on the few square centimetres of a single microfluidic chip. With such devices the objective is to minimize the time and cost associated with routine biological analysis while improving reproducibility. At the heart of these systems, a fluid delivery unit controls and transfers tiny quantities of liquids enabling the biological assays. This explains the need for robust integrated micropumps as a precondition for the development of many LOC devices. In this context, we have developed a rapid prototyping method for the fabrication of microfluidic chips in plastic and glass materials. The microfabrication principle, which is based on the powder blasting microstructuring process, was used to build devices in either polymethylmethacrylate (PMMA) or borosilicate glass. Various types of micropumps have been developed which were all based on external magnetic actuation. The use of ferrofluids (or magnetic liquids) has been the subject of the first part of the research. A piston pump using a ferrofluid plug moved by an external magnet has been studied. The integration of a rare-earth material (NdFeB) in a flexible polydimethylsiloxane (PDMS) membrane, in the form of a powder or as a classical permanent magnet, has then been proposed. An external electromagnet was used to actuate the magnet-containing diaphragm of a reciprocating micropump. Different types of valves, which constitute the critical element in reciprocating micropumps, have also been investigated. We have studied silicone membrane valves, nozzle-diffuser elements and ball valves. While nozzle-diffuser elements present the simplest valving solution from a manufacturing point of view, ball valves have been proposed as a very promising alternative due to their high efficiency. Together with the detailed characterization of the prototypes, we have proposed analytical models that predict the hydrodynamic behaviour of the micropumps. The performances of our micropumps indicate that magnetic actuation is well adapted for LOC microsystems. While we have demonstrated that our proposed microfabrication technique is an excellent rapid prototyping method for disposable plastic devices, our glass micropumps present a competitive low-cost alternative satisfying criteria of biocompatibility and high temperature (130 °C) resistance.

EPFL2005

Magnetic active-valve micropump actuated by a rotating magnetic assembly

Martinus Gijs, Meng Shen

We report on a high-efficiency and self-priming active-valve micropump consisting of a microfluidic chamber structure in glass that is assembled with a polydimethylsiloxane (PDMS) elastic sheet. The latter comprises two valving membranes and a central pumping chamber actuation membrane, having each an integrated permanent magnet that is magnetically actuated by arc-shaped NdFeB permanent magnets mounted on the rotation axis of a DC minimotor. The choice of this actuation principle allows very low-voltage (0.7 V) and low power (a few 10 mW) operation of the micropump. For the realisation, we use affordable powder blasting glass micropatterning and PDMS molding technologies. A flow rate of 2.4 mL/min and up to 70 mbar backpressure are obtained at the micropump resonance frequency of around 12 Hz, values that are much higher than reported so far for such type of micropump.

Elsevier2011

Magnetically actuated micropumps

Christophe Yamahata

EPFL2005