As labor-saving devices go, laboratory rockers and shakers are up there with the best. Step into almost any lab and you’re likely to find one whirring away, saving untold hours of manual mixing time. But for such a seemingly simple process, there’s a considerable degree of choice on the market, and one size does not fit all. If you want the best fit, you’ll need to answer a few fundamental questions. Then make your choice based on price point and/or additional features.
Shake, rattle and rock
First things first: rocker vs. shaker. This basically concerns the mixing action you need for your sample. “Generally, rockers are mostly for gentle agitation and washing of molecular, cell-culture and biochemistry applications,” explains Robert Skehens of lab equipment manufacturer Bibby Scientific. “Shakers are employed where more vigorous agitation is required.”
Although many labs swap between rockers and shakers at will, picking a device with motions and speeds specific to your application will optimize your results, says Faye Annis, online marketing specialist at Universal Medical, which supplies equipment for the medical industry. “For example, successful gel staining requires a wave effect to ensure that the staining agent evenly penetrates all pores within a given gel. Similar results can be achieved with both a 2D (see-saw) and 3D (nutating) rocker by adjusting speed and tilt angle.” A rocker would also be the best option for gel de-staining, blotting and film development.
Shakers are most appropriate for medium-speed applications, like cell culture and suspension, and general reagent mixing.
Selecting a model
After you’ve established which type of machine is most appropriate for your specific process, several factors will help you select a particular model. These include the speed and orbit/tilt you need, the size or capacity you want to accommodate and whether you need built-in temperature control (for example, if the machine is to be used in a cold room or incubator). “As shakers are more advanced than rockers, other features such as programmability or [stackability] may be factors when deciding [on] an appropriate unit,” adds Kris Fairfield, global business manager for rockers and shakers at Thermo Fisher Scientific.
Rockers are available with a 2D (see-saw) or 3D (nutating) motion. 2D rockers (like Benchmark Scientific’s BenchRocker 2D) tip back and forth in a see-saw movement and operate at lower speeds that are good for staining, blotting and gentle mixing. 3D rockers (such as Bibby Scientific’s SSM3 gyratory rocker) move in a circular up and down motion, so that the wave generated moves around the vessel from corner to corner. These rockers often are used when trying to avoid the formation of foam, and they are also capable of stronger agitation, if needed.
Rockers come with speed and tilt controls that can be adjusted for different applications, but as a representative for instrument manufacturer Benchmark Scientific points out, if you know the instrument will only be used for one purpose (e.g. blotting), a good deal of money can be saved by going for a fixed-speed, fixed-angle rocker optimized for the application (such as the Benchmark’s BlotBoy™).
If opting for a shaker, you need to consider the speed and shaking orbit you require. Reciprocal shakers move back and forth on a horizontal plane, but orbital shakers move with a swirling, circular motion, which is good for aerating samples.
It’s also worth considering flask capacity and the attachment system when looking at particular models. “While capacity is widely based on the size of the platform, few researchers consider the attachment mechanism for clamps,” explains Annis. “Many traditional shakers utilize a pre-drilled universal platform which requires each individual clamp to be screwed down. If a lab must shake a large number of small flasks, followed by a few larger flasks, they may spend upwards of an hour each day simply exchanging clamps.”
Some manufacturers use a sticky mat for low-speed applications, though there are other options, such as Benchmark Scientific’s MAGic Clamp system, which uses a magnetic clamping mechanism so flasks can be switched more quickly. The system also allows clamps to be placed anywhere on the platform, which increases capacity by 20% compared with other platforms of similar size.
A question of dollars and space
Whatever product you pick, there is one basic thing you should remember to account for: “A consideration we often see that is overlooked is laboratory space,” says Thermo Fisher Scientific’s Fairfield. “Generally, someone working in a commercial lab will have access to a larger space in the laboratory to house the unit vs. a researcher working in a smaller-scale lab.”
The most popular products tend to be those that give as much capacity and functionality as possible on a reduced footprint. Thermo Scientific’s MaxQ™ 4000 series is the firm’s most popular, says Fairfield. “This series of shaker has a wide temperature range for culturing samples, [from] 15°C below ambient to 80°C, depending on model. [It] also combines a large interior chamber capable of holding six 2-L flasks, while minimizing the exterior footprint.” Universal Medical’s most popular product is the temperature-controlled Incu-Shaker Mini from Benchmark Scientific, which Universal says is the most compact incubated shaker on the market, with a footprint of 40 cm x 28 cm.
Finally, there is cost to consider. Rockers generally come in under $1,000. A small, fixed-speed, fixed-angle model will set you back about $400, and a medium-sized adjustable benchtop rocker will be $700 to $800.
Shakers carry a heftier price tag, typically $1,500–$25,000+, depending on the model and functionality required, says Fairfield. “For example, a shaker in the $4,000 [to] $5,000 range will provide incubation, platform, timer, alarm and accommodate a variety of vessel types and sizes.”
Be sure to check what you get for your money; many rockers come with a platform as standard, whereas more sophisticated shakers (such as the Corning® LSE™ Orbital Shaker) may not to accommodate a wider variety of applications. But Fairfield notes that many companies offer promotional packages that include platform and clamps with the purchase of a shaker.