1. Gun body (hand grip part)
It is easy to understand that this part needs to be resistant to corrosion and wear, but it is easy to overlook that this part needs to have low thermal conductivity: if the hand holds the pipette for a long time, it is possible to conduct the hand temperature through the gun body. to the internal parts, so that the temperature of the inner cavity of the pipette increases and the air pressure increases, thus affecting the accuracy of the pipette. The part is basically made of plastics, of which PVDF (polyvinylidene fluoride) is the best;
2. Sleeve handle (or sleeve, refers to the lower half of the pipette, usually white plastic)
In addition to corrosion resistance, it is necessary to:
One is wear resistance. The lower end of the sleeve needs to constantly rub against the tip;
The second is impact resistance. In China, due to the use of poor quality tips in most cases, a larger force is required when loading the tips. In order to solve these two problems, some brands use metal material at the lower end of the handle or even the entire handle; some brands make great efforts in the design to reduce the friction between the handle and the suction head and reduce the force of installing the suction head. In this way, the requirements for the handle material are reduced;
3. Piston (located in the handle of the lower half of the pipette)
Currently, there are three most commonly used materials:
① Stainless steel:
Stainless steel has good machining performance, is easy to achieve sealing, has high strength, is not easy to deform, and can ensure very high precision. It is a common choice for high-end pipettes. But stainless steel also has disadvantages, that is, poor corrosion resistance. Therefore, stainless steel pistons have higher requirements for daily use and maintenance;
② Plastic:
Plastics are easy to form and inexpensive, and are commonly used on low-end pipettes. At the same time, plastic also has a big disadvantage, that is, it is easy to deform, and it is difficult to maintain a high sealing performance, thereby reducing the accuracy of the pipette.
③Ceramic:
The outstanding feature of ceramics is corrosion resistance, but it is difficult to process, and the surface of the piston cannot be as smooth as stainless steel. Therefore, it is necessary to maintain the seal without the help of lubricants, and if it is used as a small-scale pipette piston, the diameter is too large. Small, poor mechanical strength; in addition to the above two, there are still some special materials on the market:
For example, glass. Glass is corrosion-resistant and has a smooth surface, but the surface is not wear-resistant, prone to scratches, and extremely difficult to repair after damage. In general, stainless steel pistons have the highest accuracy and plastic pistons have the lowest.
④Sealing ring (installed on the piston):
Because the sealing ring may be "attacked" by various chemical media, and has a great influence on the sealing performance, it needs to maintain a long youth, so it is best to use PTFE (polytetrafluoroethylene) and other corrosion-resistant, not easy to deform material.
⑤Design: