Mixer mills grind and homogenize small sample volumes quickly and efficiently by impact and friction. These ball mills are suitable for dry, wet and cryogenic grinding as well as for cell disruption for DNA/RNA or protein recovery. For special applications such as mechanosynthesis, they offer unique solutions. Mixer mills are well known for their ease of use and small foot-print compared to other types of ball mills.
The grinding jars of mixer mills perform radial oscillations in a horizontal position. The inertia of the grinding balls causes them to impact with high energy on the sample material at the rounded ends of the jars and pulverize it. High energy milling is possible by operating at high frequencies up to 35 Hz. The movement of the jars and balls causes further size reduction effects through friction and additionally leads to effective mixing of the sample. The degree of mixing can be increased by using several smaller balls.
Mixer mills are used for the pulverization of soft, hard, brittle, and fibrous materials in dry and wet mode. With their small footprint, ease of use, and very short processing times, they are true allrounders in the laboratory.
Mixer mills are ideally suited for tasks in research like mechanochemistry (mechanosynthesis, mechanical alloying and mechanocatalysis), or ultrafine colloidal grinding on a nanometer scale, as well as for routine tasks such as mixing and homogenizing.
They are also widely used for cell disruption for DNA/RNA extraction via bead beating. Up to 240 ml of cell dispersions can be processed for protein extraction or metabolome analysis.
A crucial advantage of mixer mills is their great versatility – in some models combined with the capacity to actively cool or heat material, allowing for more controlled configurations than in other ball mills. In the field of mechanochemistry, the possibility to control the reactions inside the jar is very beneficial.
Depending on the models, temperatures down to -196°C or up to 100°C can be applied. Mixer mills are available with 1, 2 or 6 stations. Jars and balls are available in various sizes, designs and materials.
산화 티타늄
습식 분쇄
금속 합금
건식 분쇄
머리카락
건식 분쇄
타이어 고무
냉동 분쇄
The CryoMill is designed for cryogenic grinding at -196°C, whereas the MM 500 control covers a temperature from -100°C to +100°C, with a temperature regulation from -100°C to 0 °C.
Cooling is beneficial, e. g., for:
To find a jar and ball material with suitable hardness, the consideration is simple: The material must be harder than the sample. If the material is less hard, the grinding balls could be ground by the particles of the sample material.
It is not recommendable to use tools of different materials, e. g. a jar made of steel used with balls made of zirconium oxide. First, abrasion from both materials will influence the analytical result, and second, wear of the tools is increased.
Classic mixer mills work with screw-top jars which are designed for quick handling and pulverization of small sample amounts. The jars are available in hardened steel, stainless steel, tungsten carbide, agate, zirconium oxide, and PTFE.
The MM 500 nano and MM 500 control are operated with screw-lock jars. These jars are pressure-tight up to 5 bar, the integrated safety closure allows for convenient handling. The new jar design is very beneficial for wet grinding and pulverizing fibrous samples like hair.
Thanks to the flat lid, the nominal volume can be fully used, for instance when milling fibrous samples, or to ensure the optimum mixture of material, small balls and liquid for wet grinding.
Available materials include hardened steel, stainless steel, tungsten carbide and zirconium oxide ensuring contamination-free processing. Aeration lids for all mixer mill jar sizes and materials are available, e.g. for processing under inert atmosphere.
1. Screw-top jar
2. Screw-lock jar
3. Filling volume
| Screw-top jars MM 400, MM 500 vario, CryoMill | Screw-lock jars MM 500 nano, MM 500 control | |
| Different jar materials | 7 (4) | 4 |
| Jar sizes | 1.5 | 5 | 10 | 25 | 35 | 50 ml | 50 | 80 | 125 ml |
| Aeration lids | 아니오 | 네 |
| GrindControl | 아니오 | 네 |
| Integrated safety closure | 아니오 | 네 |
| Suitable for dry grinding | 네 | 네 |
| Suitable for wet grinding | Limited - jar design is not optimal for applying the 60% filling rule | Yes, designed to apply the 60% rule |
| Grinding of fibrous samples | 네 | Yes, very easy handling, as the lids are flat and the full volume of the jar can be used to fill in voluminous sample |
For dry grinding, the best results are usually obtained with the so-called one-third-rule. This means, that approximately one third of the jar volume should be filled with balls. Following this rule, the smaller the balls are, the more must be taken to fill a third of the jar. Another third of the jar volume should be filled with sample material. The remaining third is free space to allow the ball movement inside to achieve the required comminution energy for fast pulverization of the sample.
Following this rule, the required crushing energy is provided while at the same time sufficient sample material is in the jars to prevent wear.
1. One third free space
2. One third sample
3. One third grinding balls
For fibrous materials, or materials which lose their volume drastically when pulverized, a higher sample filling level is advisable. Sufficient material needs to be in the jar to minimize wear. If necessary, it is possible to add more material after some minutes to maintain the minimum required volume.
1. Two third sample
2. One third grinding balls
To produce particle sizes down to 100 nm or less, wet grinding and friction is required rather than impact. This is achieved by using many small balls with a large surface and many friction points. Consequently, the one third filling level, which is recommended for dry milling processes, is exchanged by the 60 % rule, meaning that 60 % of the jar are filled with small balls. The sample amount should be approx. 30 %. First, the small balls are added to the jars (by weight!) and then the material is added and mixed. Finally, the dispersant liquid is mixed carefully.
1. One sixth to one third sample + liquid
2. Two thirds grinding balls
Mixer mills belong to the family of ball mills and are characterized by their small footprint, fast processing times and great versatility.
They are used for mixing, pulverizing and homogenizing hard, medium-hard, brittle, soft, elastic and fibrous sample materials.
Size reduction is effected through impact and friction. Mixer mills from Retsch are available with one, two or six grinding stations.
Mixer mills are used for dry, wet and cryogenic pulverization of small sample volumes within seconds. They generate the required energy input for nanoscale grinding.
A typical field of application is cell disruption by bead beating for DNA/RNA and protein extraction.
Mixer mills are also frequently used in the field of mechanochemistry, particularly those models which provide cooling and heating options.
Sample material and grinding balls are filled into the jar which is clamped into the mill. The radial oscillations performed by the mill lead to the pulverization by impact and friction of the balls. The sample is also thoroughly mixed by the movements of jar and balls.
