Micropump | EPFL Graph Search

Micropumps are devices that can control and manipulate small fluid volumes. Although any kind of small pump is often referred to as micropump, a more accurate definition restricts this term to pumps with functional dimensions in the micrometer range. Such pumps are of special interest in microfluidic research, and have become available for industrial product integration in recent years. Their miniaturized overall size, potential cost and improved dosing accuracy compared to existing miniature pumps fuel the growing interest for this innovative kind of pump. Note that the below text is very incomplete in terms of providing a good overview of the different micropump types and applications, and therefore please refer to good review articles on the topic. Introduction and history First true micropumps were reported in the mid-1970s, but attracted interest only in the 1980s, when Jan Smits and Harald Van Lintel developed MEMS micropumps. Most of the fundamen

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

Bi-directional AC electrothermal micropump for on-chip biological applications

Jürgen Brugger, Reza Hadjiaghaie Vafaie, Philippe Renaud, Harald Van Lintel

The ability to control and pump high ionic strength fluids inside microchannels forms a major advantage for clinical diagnostics and drug screening processes, where high conductive biological and physiological buffers are used. Despite the known potential of AC electro-thermal (ACET) effect in different biomedical applications, comparatively little is known about controlling the velocity and direction of fluid inside the chip. Here, we proposed to discretize the conventional electrodes to form various asymmetric electrode structures in order to control the fluid direction by simple switching the appropriate electric potential applied to the discretized electrodes. The ACET pumping effect was numerically studied by solving electrical, thermal and hydrodynamic multi-physic coupled equations to optimize the geometrical dimensions of the discretized system. PBS solutions with different ionic strength were seeded with 1 μm sized fluorescent particles and electrothermally driven fluid motion was observed inside the channel for different electrode structures. Experimental analyses confirm that the proposed micropump is efficient for a conductivity range between 0.1 and 1 S/m and the efficiency improves by increasing the voltage amplitude. Behavior of the proposed electrode–electrolyte system is discussed by lumped circuit model. Frequency response of system illustrated that the optimal frequency range increases by increasing the conductivity of medium. For 0.18 S/m PBS solution, the constant pumping effect was observed at frequency range between 100 kHz and 1 MHz, while frequency range of 100 kHz to 5 MHZ was observed for 0.42 S/m. The characteristics of experimental results were in good agreement with the theoretical model.

Wiley-Blackwell2016

Microfabricated All-Around-Electrode AC Electro-osmotic Micropump

Luca Ribetto

This thesis presents the fabrication and characterisation of AC electro-osmotic micropumps with a simple design and velocity generation enhanced by about four times with respect to devices with simpler designs. Electro-osmosis is a convenient and effective method to pump liquids without the need for moving components. The implementation of valveless micropumps is important for the realisation of safe and robust biomedical devices, which require long-term reliability. AC electro-osmosis has the advantage, over other kinds of pumping strategies, of being implementable with relatively simple geometries and fabrication processes. Moreover, it uses low voltages and avoids undesired phenomena such as electrolysis, thus being suitable for the implementation in implantable devices that should operate in a closed environment. Whereas AC electro-osmotic pumps presented in the literature exploit planar electrode designs and fail to generate good values of velocity and pressure, the prototypes presented in this work have electrodes patterned all around the pumping channel and can generate much larger values. Moreover, with respect to other improved prototypes based on 3D electrode geometries, our devices are simpler to fabricate and give comparable enhancements of the performances. In this work, we present the development of the all-around-electrode devices and give a theoretical explanation for the measured improvements in velocity generation. The fabrication process is carried out in the cleanroom by depositing Ti/Pt electrodes on pre-structured Pyrex substrates and requires only three lithographic steps. The performances of the fabricated devices are characterised as a function of the applied voltage and frequency, and the dynamic behaviour of the prototypes is studied using the Fourier transform. In order to evaluate the suitability of the pumps for biomedical fluids, the dependence of velocity generation on the concentration of the pumped solution is also addressed. Finally, we show that the fabrication process can be adapted to an industrial batch manufacture requiring lower costs by substituting the Pyrex substrates with thin plastic foils. All-around-electrode micropumps can be successfully fabricated by patterning metal electrodes onto 12-µm-thick plastic foils and the costs might be further reduced by substituting the metal structures with inkjet-printed conductive-polymer electrodes.