Flow oscillating-droplet mixing

These droplets are then mixed with more air to dry the particles. The rate of droplet formation is equal to the oscillation frequency (/) of the piezoelectric crystal. From the volumetric flow rate of the liquid and the frequency /, the volume of the individual drops and particle diameter can be calculated. 

M 14] [P 14] In order to combine the effect of efficient oscillation of the extended linear arrays and the avoidance of flow reversibility of the circular arrays, an extended circular array (2 x 4) of electrodes was developed [29], This has three possible pivot points with up to two translations. This enhances the number of possible paths for the droplet which may result in enhanced mixing. 

A micromixer in which the fluid can be stirred by periodically pumping through the side channels is shown in Figure 3.45 [481]. The periodic perturbation applied via the side channel allows liquids A and B to be mixed. Other mixers based on oscillating pressure-pumped flow have also been reported [482,483]. Two droplets (600 pL) were merged and mixed by a push-pull (shuttling) method in a PDMS device consisting of a hydrophobic microcapillary vent (HMCV) [364]. 

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