Pipettes: Ergonomics and Electronics
Pipetting is part of nearly every laboratory’s workflow. Yet this established technology continues to undergo improvements, most related to usability and consistency.
Ergonomics, Electronics Dominate Instrument Trends
Pipetting is part of nearly every laboratory’s workflow. Yet this established technology continues to undergo improvements, most related to usability and consistency.
At the top of every manufacturer’s priorities, says Raymond Mercier, business director for liquid handling at Thermo Fisher Scientific (Waltham, MA), is ergonomics, which affects nearly every aspect of pipetting. Larger companies with serious health and safety initiatives lead the demand for pipettes that reduce repetitive strain while providing a high degree of reproducibility.
Today’s microplate-based assays would never have emerged without multichannel pipettes incorporating eight, 12, or 16 dispensers. Multichannel pipettes provide parallelism but require many multiples of the force needed to operate single-channel pipettes. Most of the strain falls on the operator’s thumb. A parallel and related trend, arising from the high cost of samples and reagents, is the desire to operate at lower and lower volumes.
Traditionally, operators combat repetitive strain by sitting properly, taking regular breaks, and following training.
Pipette design also goes a long way toward reducing strain. Examples of design changes include ultralight pipettes, positioning plungers in more user-friendly configurations, using electronic pipetting, and reducing frictional forces that translate to strain.
The latter idea is one of the advantages of Thermo Fisher’s Clip Tip design, which significantly alters the mechanical relationship between pipette and dispensing tip. Instead of using friction to hold tips in place, Clip Tip employs hinges, similar to those found on luggage, that fit over a flange on the pipette. “You can’t pull the tip off unless you unlock the clips,” Mercier says. “If the pipette picks up a tip, it’s definitely sealed.”
Electronic pipettes
Electronic pipettes represent the most serious attempt to provide consistency and improve ergonomics. From a design standpoint, electronic models provide great leeway in how the operator activates the plunger. Instead of manually pressing and releasing a plunger, the user actuates it by pressing a button. This has the effect of relieving the thumb of actuation forces, positioning the actuator button more conveniently and more ergonomically, within easy reach of the forefinger, for example. Tip ejection is mechanized as well and is under control of fingers instead of the thumb.
The downside of electronic designs is they’re heavier, which adds to user fatigue. But the main reason many users have difficulty getting used to non-mechanical pipettes is that, along with the loss of repetitive thumb movements, users miss the tactile feedback that indicates the pipette is working correctly.
This was exactly the complaint oldtime drivers had with power steering, a fact Mercier picks up on. “The analogy with driving is you’re still steering, but a motor does all the work.”
Some experts view the trend toward electronic pipetting as a kind of low-risk intermediate step between fully manual and fully automated liquid dispensing. On the basis of cost, learning curve, and throughput, electronic models are more closely related to manual devices than to automated liquid handlers. But they resemble automated systems to a greater degree in terms of accuracy, programmability, and reproducibility
Melinda Sheehan, product manager for liquid handling at Eppendorf North America (Hauppauge, NY), views electronic pipettes as a smart value addition to many laboratory workflows. “Although you pay a premium for their functionality, electronic models streamline processes and make them more mistake-proof.” The cost of pipetting aside, labs can potentially reduce the number of replicates in analyses or processes based on the superior reproducibility of electronic pipettes.
“Everyone is guaranteed to follow the same protocol and to do pipetting in exactly the same manner,” Sheehan adds.
Workflow considerations
The question “to automate or not to automate” brings a variety of responses from experts. The most common answer is, “It depends.” Lab managers decide based on a complex assessment of throughput, the value of consistency, and the importance of walkaway time. In regulated industries one can add documentation and the ease with which methods are validated.
Regardless, for many labs an affirmative answer is that it’s easier to reach for electronic pipettes than for complex robotics and their steep learning curves.
“If you have a lot of people using the exact same kit, say, RNA or DNA extraction or ELISA, following a protocol might involve dispensing 250 microliters of one buffer, 100 microliters of another, 125 microliters of a reagent, etcetera,” Sheehan explains. “Users have to go through each step over and over.”
Manual pipetting requires that operators adjust volumes at each step. Expert users also adjust draw/dispense speeds when viscosity changes significantly, for example, between a high-salt aqueous solution and alcohol or a detergent. “But if two people set out to pipette manually at a specific speed, you’ll get two different results,” Sheehan warns. Electronic pipettes can store protocols and execute each step, including speed changes, by pressing buttons. “This ensures that experiments are conducted the same way, no matter who is running them.”
The industry is not yet at the stage where users can design protocols on a computer or download them from a kit on the manufacturer’s site, then upload to the pipette. Sheehan says that “some customers have inquired about that feature, which is common in fully robotic systems.”
But as Alex Spector, President of Pipette.com, comments, “I would be surprised if every major manufacturer is not looking into this capability.”
“Rumors of my death …”
Tides of technology aside, Spector believes the demise of manual pipettes has been greatly exaggerated. “Ten years ago everyone thought that electronic pipettes would take over the market, but today, mechanical units make up 80 percent of sales.”
Early electronic designs, he explains, were too bulky, not as reliable as today’s models, and two to three times as expensive as manual pipettes. “Many scientists felt that they were more in control with manual designs, especially with tricky liquids that they could not control dispensing as accurately as by hand.” He describes preferences for one pipette type to another as a personal decision, “like a knife to a sculptor or a writer’s favorite pen. People get attached to their preferred tools.”
For additional resources on pipettes, including useful articles and a list of manufacturers, visit www.labmanager.com/pipettes