Mixing liquids in microseconds

An instrument is described in which two solutions can be homogeneously mixed within several microseconds. The liquids flow separately through two coaxial capillaries with conical tips and then simultaneously around a sphere (50–100 μ in diameter) which has been positioned close to the end of the outer tip. The liquids flow with velocities of ∼100 m/s through the small passages (∼5 μ wide) separating the sphere and the wall of the outer capillary and mix in the turbulent liquid flow behind the sphere. The mixed liquids are then ejected as a narrow liquid jet for observation. Design characteristics and construction techniques are presented along with a discussion of the properties of the turbulent flow field and estimates of the expected practically realizable mixing times. The experimentally determined speed of mixing indicates that we have nearly achieved the proposed lower limits of the mixing time.