Experimental investigation of the flow induced by artificial cilia

The fluid transport produced by rectangular shaped, magnetically actuated artificial cilia of 70 mu m length and 20 mu m width was determined by means of phase-locked Micro Particle Image Velocimetry (mu PIV) measurements in a closed microfluidic chamber. The phase-averaged flow produced by the artificial cilia reached up to 130 mu m s(-1) with an actuation cycle frequency of 10 Hz. Analysis of the measured flow data indicate that the present system is capable of achieving volume flow rates of (V) over dot(cilia) 14 +/- 4 mu l min(-1) in a micro channel of 0.5 x 5 mm(2) cross-sectional area when no back pressure is built up. This corresponds to an effective pressure gradient of 6 +/- 1 Pa m(-1), which equals a pressure difference of 0.6 +/- 0.1 mPa over a distance of 100 mu m between two rows of cilia. These results were derived analytically from the measured velocity profile by treating the cilia as a thin boundary layer. While the cilia produce phase-averaged velocities of the order of O(10(2) mu m s(-1)), time-resolved measurements showed that the flow field reverses two times during one actuation cycle inducing instantaneous velocities of up to approximately 2 mm s(-1). This shows that the flow field is dominated by fluid oscillations and flow rates are expected to increase if the beating motion of the cilia is further improved.