Biological shakers are used to Cool Thermal Mixer agitate a collection of biological samples simultaneously. Shakers consist of a motor attached to a flat surface, with fasteners for securing labware whose contents require mixing. All points on the surface move in the same fashion, either back and forth (reciprocal shakers) or in a circular motion (orbital shakers). Shaker flasks are similar in design to Erlenmeyer flasks but may have a baffled bottom to promote mixing.
The principal application of shakers is for growing yeast, bacteria, or mammalian cells in specialized containers known as shaker bottles. Shaking promotes the growth of cells and microorganisms by improving aeration and oxygen transfer and by promoting more efficient mixing of cells with food and nutrients. Biological shakers generally operate at temperatures between ambient and 37ºC, but some models offer refrigeration, and hightemperature instruments operate at up to 100ºC.
“Orbital shakers can accept vessels of almost any size or shape, from Erlenmeyer flasks to test tubes and vials, as well as trays for staining and destaining electrophoresis gels,” notes Janet O’Bryan, product manager at Thermo Fisher Scientific (Vernon Hills, Ill.)
Choosing a shaker comes down to such features as heating/cooling capability, capacity, shaking speed, orbital vs. reciprocating motion, ease of use, programmability and footprint. With research budgets tight and lab space even tighter, groups or departments are increasingly sharing shakers. “Customers frequently choose models based on how much space they require. It’s highly desirable to be able to stack shakers, pizza oven style, and keep them in a shared equipment room,” O’Bryan said. Customers also value ease of use—the ability to utilize shakers fully, out of the box, with labware of any shape and size. Labware flexibility is particularly critical for shared instruments.
Microplate shakers facilitate chemical and mechanical cell lysis and the homogenization of inert samples, cells, or cell components; they also help emulsify liquid-liquid and solid-liquid mixtures. An efficient shaker can also reduce the time by half for assays that depend on rapid agitation.
Like their large-scale counterparts, microplate shakers operate at variable, user-specified speeds and employ mechanical agitation—rocking or circular (orbital) movement—to mix components within microplate wells. A typical microplate shaker handles all common plate densities, rotates at up to 1,500 rpm, and accommodates sample volumes of up to 250 microliters.
Engineering issues come into play for mixing very small samples. As sample volume decreases, mixing efficiently becomes an engineering problem, as the fluid’s low mass causes it to adhere to surfaces, says Sriram Kumaraswamy, Ph.D., product manager at ForteBio (Menlo Park, Calif.). Plate shakers become the “slow step” in high-throughput workflows unless they are interoperable within a larger microtiter plate-handling environment, which generally includes a microplate handler. Essential integration features include a spring lock to retain the plate against the shaking surface and a robotfriendly lock/unlock mechanism. “Plate shakers, like other components in a microplate-handling system, should be automation-friendly,” notes Dr. Kumaraswamy.
• Feature programmable changes to multiple parameters on a timed basis
• Temperature is regulated ±0.1°C from 30°C to 40°C in incubated models
• Features acceleration-deceleration circuit to prevent sudden starts and stops
• Temperature-controlled models include thermostat fail-safe, shutting off heaters if high limit is exceeded
New Brunswick Scientific
Digital Magnetic Stirrers
• Two sizes: 6.25” plate with a 4-liter load capacity; 8.25” plate with a 5-liter load capacity
• Supplied with two non-slip silicon plate pads
• Wide speed range of 30 to 2,000 rpms
• Large, bright VFD readout allows easy monitoring of stirring speed
• Can be programmed to provide orbital, reciprocation and vibration mixing functions
• Three functions can be set for continuous or timed operation in a single function mode or any combination of all three
• A variety of interchangeable platforms accommodate different sized flasks, beakers, Petri dishes and other vessels
Zero Torque Overhead Stirrer
•Redesign of the BDC1850, BDC3030 and BDC6015 hightorque stirrers includes the addition of a zero torque button
• Allows the user to zero the torque at any stage of mixing, or zero out any additional overhead torque created by the mixing paddle and chuck before mixing starts