Vortex mixer

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A vortex mixer is a simple device used most commonly in cell culture and microbiology laboratories to suspend cells, although it can be used to mix many other substances. It consists of an electric motor with the drive shaft oriented vertically and attached to a cupped rubber piece mounted slightly off-center. As the motor runs the rubber piece oscillates rapidly in a circular motion. When a test tube or other appropriate container is pressed into the rubber cup (or touched to its edge) the motion is transmitted to the liquid inside and a vortex is created. Most vortex mixers have variable speed settings and can be set to run continuously, or to run only when downward pressure is applied to the rubber piece.

An alternative to the electric vortex mixer is the "finger vortex" technique in which a vortex is created manually by striking a test tube in a forward and downward motion with one's finger or thumb. This generally takes longer and often results in inadequate suspension, although it may be suitable in some cases when a vortex mixer is unavailable. The technique is better suited to accelerate the mixture of solutions which do not require the kinetic energy input needed to create suspensions.