Ultracentrifuge
While
high speed centrifuges such as ultracentrifuges may be applied in a number of industries, they are most commonly used in polymer science, biochemistry, molecular biology, medical and other research fields. There are two distinct kinds of
laboratory centrifuges that may be employed, each producing different avenues for research. Analytical centrifuges are for more inquisitive applications as they allow scientists, engineers and researchers to perform sedimentation velocity experiments and sedimentation equilibrium experiments which ultimately provide information such as the molecular behavior, size, shape and mass of individual particles. Optical detection systems are in place and often digitized to provide real time data of solutes under extreme centrifugal forces. The alternative type is the preparative centrifuge which may be differential or density based. These mechanisms separate, sort and isolate materials based on specific densities. Larger particulates separate out first creating a gradient that can be removed in tact from the
centrifuge for further study.
Both preparative and analytical ultracentrifuges operate in largely similar fashion. An enclosure or arm-like apparatus is attached to a fixed central axis about which it can move in a rotary motion. This component, which houses the materials to be studied, is most commonly made of metal or plastic and must be able to withstand the forces generated by the attached motor. The type of enclosure or rotor set up determines the capacity and capabilities of the machine. Swinging bucket or
basket centrifuges are largely popular as they allow the tubes of materials to hang on hinges allowing for horizontal spinning. Fixed angle rotors are common in hospital or medical settings in which several samples are placed in a perforated block which holds them in place securely. Zonal rotors are for large capacity ultracentrifuge use as they hold a single central cavity rather than smaller vials or test tubes. In any design, the motor applies force to the axis perpendicular to the central line in order to facilitate spinning. The centrifugal force generated by this motion causes heavier or more dense particles to separate out in a radial motion first, followed by progressively lighter materials. As with all centrifuges, balanced design and loading are of utmost importance when working with these machines as their operation requires a tremendous amount of rotational kinetic energy. At such high speeds even a slight imbalance can throw off the equilibrium of the spin cycle and lead to potentially catastrophic mechanical failure.
