A working centrifuge can now be 3-D printed for about 25 dollars
Open-source designers have published a hand-powered centrifuge that spins at more than 1,732 revolutions per minute and can be printed entirely on a 3-D printer for roughly 25 dollars. Another low-cost design, the Dremelfuge, borrows its motor from a Dremel power tool.
Spin a container of fluid fast enough and denser material is flung outward while lighter material is pushed toward the centre. In a lab tube, that means heavy particles pack into a pellet at the bottom. The same principle separates cream from milk, liquids from solids, and immiscible liquids from one another, and the fastest ultracentrifuges can sort particles down to the nanoscale and molecules by mass.
The idea has roots in eighteenth-century ballistics, when the English military engineer Benjamin Robins built a whirling arm to measure drag. In 1864 Antonin Prandtl proposed a dairy centrifuge for skimming cream, and his brother Alexander refined the design and exhibited a working butterfat extractor in 1875. Later, the Swedish chemist Theodor Svedberg devised the principles behind the analytical ultracentrifuge, which studies how large molecules settle.
Rotor design matters. Fixed-angle rotors hold tubes at a constant tilt, while swinging-bucket rotors let the tubes swing out horizontally as they spin; continuous tubular machines skip individual tubes altogether for high volumes. Industrial machines split into two families: filtration centrifuges with perforated drums lined with cloth or mesh that trap solids as liquid passes through, and sedimentation machines with solid walls, such as decanters, which simply accelerate settling.
The uses are wide. Haematocrit centrifuges measure what share of blood is red cells, and labs spin samples repeatedly with buffers to purify DNA. Huge centrifuges subject test pilots to high g-forces, washing machines and some swimming pools use modest ones to wring water out of fabric, and a hand-powered model inspired by the whirligig toy has been developed for clinics in developing countries. Gas centrifuges, starting with the Zippe type, separate isotopes and are used in both nuclear power and nuclear weapons programmes.
Source: Centrifuge
