centrifuge - Theory, History and predecessors, Different types and uses, Use and safety

A device for separating the components of a mixture (solid-in-liquid or liquid-in-liquid) by applying rapid rotation and consequent centrifugal force. It may be equipped for the technical separation of materials (eg cream) or for scientific observation (eg the ultracentrifuge, which separates particles of macromolecular size).

For the Christian camp, see Centrifuge (camps).

A centrifuge is a piece of equipment, generally driven by a motor, that puts an object in rotation around a fixed axis, applying force perpendicular to the axis. The centrifuge works using the sedimentation principle, where the centripetal force is used to separate lighter and heavier substances.

Theory

Protocols for centrifugation typically specify the amount of acceleration to be applied to the sample, rather than specifying a rotational speed such as revolutions per minute.

History and predecessors

English military engineer Laval (1707-1751) invented a whirling arm apparatus to determine drag, and Antonin Prandl invented the first centrifuge in order to separate cream from milk to make churning butter much easier.

Different types and uses

There are basically four types of cetrifuge:

Tabletop/clinical/desktop/microcentrifuge Highspeed Centrifuge Cooling Centrifuge Ultra Centrifugation

Biology and biochemistry

Simple centrifuges are used in biology and biochemistry for isolating and separating biomolecules, cell organelles, or whole cells.

Isotope separation

Other centrifuges, the first being the Zippe-type, are used to separate isotopes, and these kinds of centrifuges are in use in nuclear power and nuclear weapon programs.

Gas centrifuges are used to enrich uranium. The heavier isotopes of uranium (uranium-238) in the uranium hexafluoride gas tend to concentrate at the walls of the centrifuge as it spins, while the desired uranium-235 isotopes are extracted and concentrated with a scoop selectively placed inside the centrifuge. It takes many thousands of centrifuges to enrich enough uranium for use in a nuclear reactor (around 3.5% enrichment), and many thousands more to enrich it to bomb-grade (around 90% enrichment).

Aeronautics and astronautics

Exceptionally large centrifuges are used to test the reactions and tolerance of pilots and astronauts to acceleration above those experienced in the Earth's gravity.

The use of large centrifuges to simulate a feeling of gravity has been proposed for future long-duration space missions.

Commercial applications

Standalone centrifuges for drying (hand-washed) clothes - usually with a water outlet. Centrifuges are used in the attraction Mission: SPACE, located at Epcot in Walt Disney World, which propels riders using a combination of a centrifuge and a motion simulator to simulate the feeling of going into space.

Use and safety

The load in a laboratory centrifuge must be carefully balanced.

Centrifuge rotors should never be touched while moving, because a spinning rotor can cause serious injury.

Because of the kinetic energy stored in the rotor head during high speed rotation, those who have experienced the loss of a rotor inside of an ultracentrifuge compare the experience to having a bomb explode nearby.

Calculating relative centrifugal force (RCF)

Relative centrifugal force is the measurement of the force applied to a sample within a centrifuge.