Figure 6.

Mixing of fluids using knots of flexible tubing. (a) Schematic showing the experimental setup for observation of the spatial distribution of fluorescent nanoparticles after mixing. (b) Photograph of a microchannel for the infusion of two types of fluids to assess the mixing efficiency (one with 100 nm fluorescent nanoparticles and the other one without the particles). The outlet is directly connected to the flexible tubing with serial knots without premixing. (c) Photograph of knots in the tubing, which induce abrupt changes in a flow direction. (d) Fluorescence images after the mixing of the buffer solution (no fluorescent nanoparticles) and the solution containing 100-nm green-fluorescent nanoparticles. (e) The degree of mixing efficiency can be obtained from the standard deviation of the fluorescent intensity across the channel. The 100-nm fluorescent particles in laminar flows were completely mixed when flowing through 10 serial knots of tubing, even at low Reynolds numbers, in comparison to the tubing with 3 knots. (scale bars: 1 mm)