Various aspects of the present invention relate to the control and manipulation of fluidic species, for example, in microfluidic systems. In one set of embodiments, droplets may be sorted using surface acoustic
waves. The droplets may contain cells or other species. In some cases, the surface acoustic
waves may be created using a
surface acoustic wave generator such as an interdigitated
transducer, and / or a material such as a
piezoelectric substrate. The
piezoelectric substrate may be isolated from the microfluidic substrate except at or
proximate the location where the droplets are sorted, e.g., into first or second microfluidic channels. At such locations, the microfluidic substrate may be coupled to the
piezoelectric substrate (or other material) by one or more
coupling regions. In some cases, relatively high sorting rates may be achieved, e.g., at rates of at least about 1,000 Hz, at least about 10,000 Hz, or at least about 100,000 Hz, and in some embodiments, with
high cell viability after sorting.