Newsletter 2015.12 Index
Theme : "Mechanical Engineering Congress, 2015 Japan (MECJ-15) Part 2"
Electro-conjugate fluid is a kind of functional fluid, which generates an active flow when subjected to a high DC voltage. Since it only requires a tiny electrode pair in sub-millimeter scale, the electro-conjugate fluid flow can be a possible candidate for fluid power source of micro fluidic systems. On the other hand, micro fluidic systems are gathering attentions in the field of bioengineering, to realize a micro total analysis system or μTAS, which may reduce the volume of samples and regents, analysis time and cost compared with general biochemical analyses. This paper introduces a novel approach for droplets mixing procedure using the electro-conjugate fluid, since mixing droplets are quite often required in the process of biochemical analyses. In the developed droplets mixing device, swirl flow is generated in a chamber by using the electro-conjugate fluid flow generation. Then, droplets whose density is lower than that of electro-conjugate fluid are dripped into the chamber. Due to the density difference, the droplets are subjected to centripetal forces, which make them move to and mix at the center of the chamber. Experimental results confirmed this concept and showed a possibility of the device. In addition, biocompatibility of the electro-conjugate fluid is also tested by using L929 cells. The cells are subjected to the electro-conjugate fluid for up to 25 min, and the number of cells is counted by every 5 min. As a result, the number of cells decreases as the explosion time becomes longer. This may suggest that the cells are dead or detached from a cultivation substrate. For further investigation, the proliferation of cells is experimentally confirmed. The result suggests that the proliferation of cells dose not decrease at least with 5-min explosion of electro-conjugate fluid or shorter.
Electro-conjugate fluid, Functional fluid, μTAS, Droplet, Mixing
Fig. 1 Centripetal force induced in the swirl flow.
Fig. 2 Configuration of electrode substrate.
Fig. 3 Actual view of the mixing experiment: A red droplet moves spirally to the center and becomes in contact with a blue droplet at t = 2.60 s. Afterwards, two droplets keep rolling together and mix at t = 3.96 s. Droplets stay at the center of the chamber until applied voltage is off.
Fig. 4 Number of cells remained on the culture substrate after the ECF exposure.