The centrifuge demonstrates strong capabilities in diverse application fields.

　　 Centrifuge The key to centrifugation technology lies in determining the appropriate settings for centrifugal force, rotational speed, and centrifugation time based on the properties of the sample particles and the medium, as well as the technical parameters of the rotor. The sedimentation or separation rate of particles (a collective term encompassing cells, organelles, and macromolecules) depends on the centrifugal force, the size, shape, and density of the particles, as well as the density and viscosity of the sedimentation medium.

　　The rotor of a centrifuge can only rotate smoothly if its operating speed is not at the critical speed. For low-speed centrifuges with relatively low operating speeds, the critical speed is generally raised as much as possible, enabling the centrifuge to operate below its critical speed. Such centrifuges have thick shafts with high rigidity, and these shafts are referred to as rigid shafts. When very high rotational speeds are required, the critical speed is minimized as much as possible, and the shaft is made thinner with lower rigidity—these are called flexible shafts. Modern ultracentrifuges all employ flexible shafts.

　　During daily use of the centrifuge, the horizontal alignment of the main unit should be checked and adjusted every three months. Vacuum pump oil should be replaced after every 500 million revolutions of operation. After every 500 hours of work, the carbon brushes of the drive motor should be inspected; any carbon dust generated by friction should be removed using a vacuum cleaner. If necessary, the carbon brushes should be replaced or the commutator should be polished with fine sandpaper. Every approximately 1,500 hours of operation, the bearings in the drive section should be cleaned and lubricated with high-speed grease. The joint between the spindle and the rotor should be regularly coated with grease to prevent rusting. When the centrifuge is not used for an extended period, it should be wrapped in oil-paper and coated with anti-rust oil. During regular periods of non-use, the centrifuge should be started at low speed once or twice each month for about 0.5 hour each time to ensure that all components remain in good working order.

　　A centrifuge is a specialized device that uses centrifugal force to rapidly separate mixed solutions. It has a wide range of applications, such as in biochemical research, where it is used to separate, concentrate, and extract samples—including biological cells, viruses, serums, organic and inorganic solutions, suspensions, and colloids—from the objects under study. Among these, ordinary centrifuges (with rotational speeds ranging from 4,000 to 5,000 r/min) are the most commonly encountered.

　　The critical speed is related to both the centrifuge itself and the rotor it is equipped with. A single centrifuge can be fitted with several different types of rotors; therefore, when designing a centrifuge, it’s essential to take into account the vibration-damping design’s compatibility with various rotors. Centrifuges operate over a wide range of speeds—from several thousand to tens of thousands of revolutions per minute. The higher the rotational speed at which vibration occurs in a centrifuge, the greater the associated risk.

　　Centrifuges rotate at high speeds, so special attention must be paid to safety. Therefore, please pay attention to the following points:

　　1. The bottom of the centrifuge’s tube sleeve should be padded with cotton or a test-tube pad.

　　2. If an electric centrifuge makes noise or the machine body vibrates, the power should be immediately cut off to promptly troubleshoot the issue.

　　3. Centrifuge tubes must be placed symmetrically in the rotor to prevent vibration of the machine. If you insist on using one sample tube while leaving another empty, the empty tube should be replaced with an equal mass of water.

　　4. When starting the centrifuge, you must first close the top cover before slowly starting it up.

　　5. After the separation is complete, first turn off the centrifuge. Only after the centrifuge has come to a complete stop can you open the centrifuge lid and remove the sample. Do not use external force to forcibly stop the centrifuge from rotating.

　　6. The centrifugation time is generally 1 to 2 minutes; during this period, the experimenter must not leave to attend to other tasks.

　　Once vibration occurs at high rotational speed, the centrifuge should be brought to a stop as quickly as possible by engaging the fastest deceleration gear. All personnel must promptly evacuate the area to avoid injury in case of accidents such as rotor breakage. Under no circumstances should the power be cut off—once the power is interrupted, the braking mechanism (which provides rapid deceleration) will fail, and the rotor will come to a halt very slowly. Such accidents are typically caused by improper operation of the centrifuge—for example, if the rotor is not properly seated on the spindle, the rotor lid is not securely closed, or the basket for swinging out the rotor is not positioned correctly. These accidents are often accompanied by a loud bang; a centrifuge weighing 300–400 kg may suddenly spin over 270 degrees. Upon opening the lid, you’ll find the rotor lying inside the chamber. When the rotor is removed and examined, its outer surface will show severe scratches and discoloration. The inner walls of the centrifuge chamber will also be damaged, and in some cases, refrigerant may even leak out. Sometimes, the rotor and rotor lid separate, causing liquid from the tubes to spill into the chamber, and the spindle may break or bend severely. Because these accidents are frequently caused by operator error, modern centrifuges are generally equipped with an imbalance protection feature. That is, when the centrifuge starts up, if the rotor’s vibration exceeds a certain threshold, the machine automatically slows down and shuts down. However, centrifuges with this feature can sometimes fail to trigger the alarm, leaving the risk of accidents unmitigated.

　　Modern centrifuges are generally compact, made of either plastic or metal, and visually appealing. They typically sit atop countertops on rubber feet to prevent them from shifting during operation. The bottom is weighted to ensure stability while in use. The size of the centrifuge determines how many glass tubes or vials it can hold at one time. These machines are controlled by a timer and offer at least two speed settings—low and high. There are also medical centrifuges designed for a wide range of biomedical applications, including the study of viruses, proteins, polymers, nucleic acids, and blood. They can separate serum from plasma as well as extract solids from liquids.