Properly mixing solutions ensures uniformity of mixture components, temperature and pH throughout a sample container. Mixing also helps to dissolve solids in liquids and speeds up enzymatic reactions. As important as mixing might be in any assay, it is a step that is often overlooked or shortened by laboratories in the interest of time.
While many labs use magnetic stirrers and orbital shakers for mixing large volumes of liquids, mixing is particularly challenging for users of microplates due to the possibility of splashing, especially with samples so close to each other. Moreover, the dynamics of working with small volumes is an issue within itself. Subtle variations are magnified and may cause misleading data. As such, many microplate users are paying closer attention to these details and understand that mixing can improve assay results.
Microplate mixers employ traditional mixing technologies such as magnetic stirrers and orbital shakers. VP Scientific offers several magnetic mixing mechanisms including a levitation system that moves a stainless steel ball in the microplate well. The company also sells the Burt Lancaster Trapeze, which is a miniature mechanical mixer that can fit into each well without touching the bottom. Because these mixing technologies are invasive, they are more likely to be more useful in non-life science applications.
Orbital shakers such as Eppendorf’s MixMate employ a noninvasive mixing method. It moves standard microplates in a circular motion at up to 3,000 rpms. The MixMate uses a two dimensional axis control to adjust the orbit path and prevent spilling and lid wetting. Orbital microplate shakers are gentler on the sample and are often used in biotechnology and pharmaceutical research. Other companies such as Tecan and Thermo Fisher Scientific offer orbital microplate shakers with heating and controlled environment options.
While mechanical microplate mixers are finding a niche in the market, alternative approaches are fast moving into the mainstream. Advalytix’s system utilizes surface acoustic wave technology, to gently agitate the sample. Because the technology is vibration free, it does not produce any foam or cause spillage. Covaris’ L8 Acoustic Plate Mixer technology is based on adaptive focused acoustics, which concentrates acoustic energy wave packets from a dish-shaped transducer to the sample. Another mixing technology employed is sonication. MatriCal offers the SonicMan system that can be used for resuspending stored compounds.
The market for microplate mixers is a small yet burgeoning part of the sample preparation market. Traditional mechanical methods are relatively inexpensive, but are more prone to contamination and spillage. New acoustic wave technologies show significant potential, but may be too expensive for labs to afford. Nonetheless, for many microplate users, this could be the answer to inconsistent results.
Microplate Mixers at a Glance:
• Eppendorf AG
• Thermo Fisher Scientific
• VP Scientific