72
5 Designing Meanders
Fig. 5.4 Overall design for generating mixing ratios
resistances of both meanders have to be equal (e.g., 20 mbar/(μl/min) for both
meanders). In contrast, to realize a mixing ratio of 2:1, the resistances of the two
meanders have to relate accordingly (e.g., 40 mbar/(μl/min) for one meander and
20 mbar/(μl/min) for the other). For this case study, mixing ratios of 20:20, 40:20,
30:10, and 40:10 were realized. These values in the mixing ratios also represent the
used fluidic resistances in mbar/(μl/min) of the two meanders.
Figure 5.4 shows the design for two mixing structures allowing to generate a
ratio of 30:10 and 40:10. Here, e.g., the left structure connects the two meanders to
inputs In1 and In2 and merges the outputs of both meanders into a wide channel.
This channel allows to observe the mixing ratio and ends in output Out1. This is
similar for the structure on the right-hand side of Fig. 5.4.
For measuring the mixing ratios, dyed water with two different colors was used,
i.e. water colored with blue and red ink. A pressure pump drove both fluids, which
entered the device via In1 and In2, respectively. The respective fluidic resistances
of the meanders determined the amount of flow (i.e., the flow rate) passing them.
These flow rate ratio eventually realized the mixing ratio.
For observing the mixing ratio, images were taken using a microscope and a
CCD camera. The width of the blue colored stream and the width of the red colored
stream in the channel where the two meanders merge were measured pixel-wise
with the image processing software ImageJ. The mixing ratio was determined by
the ratio of two pixel values. The obtained results are discussed in Sect. 5.4.2.
5.4 Results of Case Studies
This section presents and discusses the results which are obtained in the two case
studies.
5.4.1 Results for Dedicated Resistances
For the evaluation of the first case study, the resistances of generated and fabricated
meanders were measured and compared. The used meanders realized different
5 Designing Meanders
Fig. 5.4 Overall design for generating mixing ratios
resistances of both meanders have to be equal (e.g., 20 mbar/(μl/min) for both
meanders). In contrast, to realize a mixing ratio of 2:1, the resistances of the two
meanders have to relate accordingly (e.g., 40 mbar/(μl/min) for one meander and
20 mbar/(μl/min) for the other). For this case study, mixing ratios of 20:20, 40:20,
30:10, and 40:10 were realized. These values in the mixing ratios also represent the
used fluidic resistances in mbar/(μl/min) of the two meanders.
Figure 5.4 shows the design for two mixing structures allowing to generate a
ratio of 30:10 and 40:10. Here, e.g., the left structure connects the two meanders to
inputs In1 and In2 and merges the outputs of both meanders into a wide channel.
This channel allows to observe the mixing ratio and ends in output Out1. This is
similar for the structure on the right-hand side of Fig. 5.4.
For measuring the mixing ratios, dyed water with two different colors was used,
i.e. water colored with blue and red ink. A pressure pump drove both fluids, which
entered the device via In1 and In2, respectively. The respective fluidic resistances
of the meanders determined the amount of flow (i.e., the flow rate) passing them.
These flow rate ratio eventually realized the mixing ratio.
For observing the mixing ratio, images were taken using a microscope and a
CCD camera. The width of the blue colored stream and the width of the red colored
stream in the channel where the two meanders merge were measured pixel-wise
with the image processing software ImageJ. The mixing ratio was determined by
the ratio of two pixel values. The obtained results are discussed in Sect. 5.4.2.
5.4 Results of Case Studies
This section presents and discusses the results which are obtained in the two case
studies.
5.4.1 Results for Dedicated Resistances
For the evaluation of the first case study, the resistances of generated and fabricated
meanders were measured and compared. The used meanders realized different