Nature-inspired micro-fluidic manipulation using artificial cilia

December 2006 - November 2010




Pres. & Pub.





Project objectives

Micro-Fluidics is the science and technology of manipulating and analysing fluid flow in structures of sub-millimetre dimensions. The availability of micro-fluidics technology is essential for the development of advanced products in a variety of application areas, the most important of which is the biomedical field. Examples are micro-channel cooling for micro-electronics, inkjet printing for display and biosensor manufacturing, controlled drug delivery systems, pharmaceutical and chemical high-throughput analysis, and, in particular, micro-fluidic systems for biosensors.

 In the latter application, biochemical analyses of body fluids such as saliva, urine and blood are carried out to obtain information about health and disease. A biosensor is small cartridge-based micro-fluidic device, typically of the size of a credit card, in which the complex body fluids must be transported, mixed, routed, or manipulated in other ways in microscopic channels or flow chambers.

                  Schematic of a biosensor cartridge, showing the micro-channels and flow 
                  chambers in which biological fluids must be manipulated.


Many (industrial) research groups are studying ways of micro-fluidic manipulation. Often these are based on downscaling of existing flow devices, such as pumps, valves, or mixers. Others use techniques based on physical principles that are advantageous at small scales, such as surface tension, surface energy patterning, or electro-osmosis. These techniques have various limitations: some are still relatively large, hampering true integration in a micro-fluidic device, whereas for most it is impossible to achieve local manipulation of the fluid or the generation of complex fluid patterns. The latter would be advantageous for example in many biosensor applications. The recently started European research project ARTIC deals with a completely novel method of fluid manipulation technology in micro-fluidics systems, inspired by nature, namely by the mechanisms found in ciliates. This approach enables effective local fluid manipulation, and the possibility to generate complex flow patterns.

One particular micro-fluidics manipulation process “designed” by nature is that due to a covering of oscillating cilia over the external surface of micro-organisms. A cilium can be viewed as a small hair or flexible rod (in protozoa: typical length 10 mm and diameter smaller than 100 nm) attached to the surface (see Figure 2). The movement of the individual cilia is asymmetric, i.e. a deformation cycle consists of an effective or power stroke and a recovery stroke, so that fluid transport in one direction is induced. This asymmetric movement is essential for so-called low-Reynolds number propulsion. Also, the cilia move back and forth collectively in a particular concerted manner, and are in this way quite effective in generating flow: the swimming speed of Paramecium, for example, can be more than 1 mm/s. Apart from propelling micro-organisms, other functions of cilia are in cleansing of gills, feeding, excretion, and in reproduction. The human trachea, for instance, is covered with cilia that transport mucus upwards and out of the lungs.



Two micro-organisms that use cilia for propulsion, (a) Paramecium, (b) Pleurobrachia; (c) schematic of the asymmetric stroke of an individual cilium.

Our aim in the ARTIC project is to develop artificial cilia, on the basis of polymer micro-actuators, that can be integrated in micro-fluidic systems, and that can be used for fluid manipulation, in particular pumping. The movement of the artificial cilia can be actively controlled, preferably using a magnetic field or an electrical field. To achieve this, we will start by studying the natural cilia in terms of underlying mechanisms, energy consumption, and effectiveness. The knowledge obtained will be translated into advanced mechanical, electro-magnetic, and fluid flow models, which will be used to generate optimum designs and specifications for the artificial cilia to be made. Based on these specifications, (composite) materials will be synthesized that can be used as a basis to fabricate the artificial cilia. To validate the effectiveness of fluid manipulation using artificial cilia, we will design and set up a basic experiment.  

The project consortium reflects the range of activities that are required to reach the goals of the project. Philips Research and Applied Technologies (The Netherlands) is project co-ordinator and brings in the application and the technology know-how. The Centre for Biomimetics and Natural Technologies, University of Bath (UK), will look at the biological ciliated systems and study underlying mechanisms, energy consumption and effectiveness. This knowledge serves as an inspiration and a reference for the technical, artificial cilia processes and technology. A team of modeling groups will develop and use models to simulate the magneto-mechanical or electro-mechanical deformation behavior of the artificial cilia and the fluid-cilia interaction, in order to extract design rules for the materials, geometries, and driving mechanisms to be developed: University of Groningen (The Netherlands) for mechanical modeling, Polytechnic University of Bucharest (Romania) for magnetic modeling and design, and Eindhoven University of Technology (The Netherlands) for fluid flow modeling. The synthesis of tailor-made polymer-based electromagnetic materials, as well as the microstructuring into cilia-geometries will be done by the University of Freiburg – IMTEK (Germany) and Liquids Research Ltd. (UK). The micro-channel device manufacturing and integration of the artificial cilia is the task of Philips Research and Applied Technologies. The micro-fluidic flow characterization, finally, will be carried out by  Delft University of Technology (The Netherlands).

First results:  movie of Cilia: Flaps were fabricated with the Dual Purpose Layer Technique shown in Delft 2008 (internal presentation). copyright �


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