Active micromixers - Micromixers Fundamentals Design and Fabrication - page 290

FIGURE 7.42

Active micromixers based on thermally induced convection.

(Reprinted with permission from [57] .)

7.8 THERMAL DISTURBANCE
Because molecular diffusion depends on the kinetic energy of the molecules, the diffusion coefficient
highly depends on the temperature. Thus, thermal energy can be used to enhance mixing. Darhuber
et al. [57] proposed and numerically analyzed the thermocapillary advection induced by transverse
temperature gradient. In Fig. 7.42 , two liquids are following along a hydrophilic stripe. The stripe is
500 mm wide. The liquid column is 20 4 C/

mm. The lines in Fig. 7.42 are experimental results of the tractories of two tracing particles. Figs.
7.42 (a)-(c) show the concentration distribution of the two liquids ( D

m m high. The temperature gradient in use was d T /d y ¼

0). The transverse motion is
achieved by the thermal gradient d T /d y . According to the simulation results [57] , the interfacial area
between the two liquids increases 150 times in 30 seconds.

¼

References
[1] F.M. White, Viscous Fluid Flow, second ed., McGraw-Hill, New York, 1991.
[2] J. Ducr´e, S. Haeberle, T. Brenner, T. Glatzel, R. Zengerle, Patterning of flow and mixing in rotating
radical microchannels, Microfluidics and Nanofluidics 2 (2006) 97-105.
[3] C.H. Berg, The rotary motor of bacterial flagella, Annual Review of Biochemistry 72 (2003) 19-54.