Pipets and Ergonomics: What Matters Most

The handheld pipet is perhaps the most ubiquitous piece of equipment in any laboratory. These instruments have been in use for decades, but only recently has the scientific community begun to realize the ergonomic implications of prolonged pipet use. Increased reports of repetitive stress injuries (RSI), such as carpal tunnel syndrome, have forced many laboratories to examine the ergonomics of their handheld pipets.

While all manufacturers claim that their pipets are ergonomic, many users continue to have problems with comfort and ease-of-use of these instruments. These difficulties are usually related to the stresses placed on the hand (primarily the thumb) due to tip application, tip ejection, and plunger operation or to poor posture adopted for extended periods of pipetting.1 Pipets that require a user to engage in multiple arm and hand movements, excessive reaching or stretching, and unnatural gripping of the pipet can also cause injury. How can a user relieve some of these stresses? Outlined below are a few criteria that should be considered when selecting a pipet.

Repetitive use of thumb

Even though the thumb is the weakest part of the hand, the majority of pipets on the market today still rely on it to operate. With this in mind, particular attention needs to be paid to the forces required for the thumb to work these pipets. The Thermo Scientific Matrix Hybrid pipet and ClipTips system (Thermo Fisher Scientific, Hudson, NH) addresses this by minimizing the forces needed for the two primary uses of the thumb in pipetting—plunger actuation and tip ejection.

If a user is pipetting hundreds of times per day, it can be no surprise that serious fatigue can occur in the muscles involved in thumb depressions. Reducing the amount of force necessary to actuate the pipet can significantly reduce the strain placed on the thumb. Generally the force needed to depress the plunger varies from 2 to 10 lb, depending on the manufacturer.2 However, the Matrix Hybrid pipet requires just 1 lb of force to actuate the plunger (Table 1), ensuring more comfortable pipetting over a longer period of time.

Tip ejection can also demand a great deal of force in pipetting and is directly related to the fit and seal of the tips on the pipet. Typically, to ensure a good fit, only tips recommended by the pipet manufacturer should be used. Using an inappropriate tip not only can result in the use of high forces to apply the tips, but in poor pipet performance as well. Matrix Hybrid pipets have solved this problem by creating the Matrix ClipTips system (Figure 1) (patent U.S. 6,923,938 B2 and patents pending pub. no. U.S. 2005/02 62951 A1; U.S. 2005/0175511 A1; U.S. 2006/0027033 A1). The Matrix ClipTips “lock” into place via a clasp or clip with minimal application force to provide an effective seal. This type of seal requires only 1.1 lb of force to remove it from the tip fitting, in comparison with the 10–15 lb of force required by other tip attachment systems, and has the added benefit of a tip that locks on and will not come off until ejected. When combined with the ease of plunger actuation, the Matrix Hybrid pipet requires only a minimal amount of work, and thus force, by the thumb.

Figure 1 - The Thermo Scientific Matrix ClipTips interface provides an effective seal without the need to apply excessive force.

Hand and shoulder strain

Strains can be placed on the entire hand and also the shoulder while pipetting. These strains are caused both by exertion of excessive forces on those body parts, as well as unnatural postures being maintained for long periods of time.3 The hand is also often used for volume selection in micrometer-based pipets, and the hand with the shoulder are used when seating a tip on the tip fitting. Additionally, the shoulder is used to hold the pipet over the work surface, oftentimes in a cramped environment such as a laminar flow hood. In response, there are pipet design options that can help relieve these strains.

The majority of pipets in the laboratory are micrometer based, meaning volumes are adjusted via the twisting of a knob. Throughout the day, a user may change pipet volume settings hundreds of times, resulting in excessive torque on the hand and wrist. The Matrix Hybrid pipet is essentially a manual pipet that, while it has no knobs, manages to offer multiple means of intelligent, electronic-controlled volume adjustment. On the instrument, tedious manual adjustments have been replaced with an increment adjustment option, where the user is able to select a volume using up and down scroll buttons. For users with more frequent but predictable volume changes, the QUIK-set mode allows the user to toggle between six user-defined, preset volumes that are stored in the microprocessor memory. Additionally, state-of-the-art voice recognition technology permits the user to speak to the pipet and have the volume adjust accordingly. Voice recognition is an example of an adaptive technology, much like special computer keyboards or mouse replacements, often recommended for people suffering from RSI, since it enables partial or complete cessation of hand activity.4

Tip attachment can also be troublesome, even when tips of an original manufacturer are being used. In order to achieve a good seal and ensure that tips will not fall off, users may bang the tips onto the fitting or rock the pipet over the tip rack. These actions put undue stress on the hand, arm, and shoulder. Often these extreme measures create the additional problem of hard-to-eject tips. In contrast, the Matrix Hybrid/ClipTips system requires a mere 1.4 lb of force to apply the tips, essentially just touching the pipet to the tips. Even with such a light force, the user need not worry about the seal since Matrix ClipTips are either on or off. With no wiggle room, once a ClipTip is seated on the tip fitting, it will not come off until the tip ejection button is pressed.

Tip attachment does not just end with the design of the tip and the design of the tip fitting. The tip rack is equally important, especially when attaching tips to a multichannel pipet. A tip rack that is not sturdy will flex as pressure is applied to attach tips. This transfer of energy into the tip rack is counterproductive, and only compounds the previously mentioned problems associated with tip attachment. Matrix ClipTips racks are extremely rigid to provide stable, even tip seating.

Figure 2 - The large, easy-to-read display makes it simple to identify the volume programmed.

It is typically recommended that users work with their arms close to their body since working with arms in an elevated position for an extended period of time can cause fatigue.5 One way to achieve this objective is to use a pipet that allows the hand to be as close to the work surface as possible. The Matrix Hybrid is compact in design and is an average of 231 mm in length. The weight is also quite low, affecting the stability and fit of the pipet in the user’s hand. In fact, the device has a contoured grip and finger support to fit the pipet comfortably and naturally in the hand and to reduce strain on the muscles of the hand.6

Eye strain and accessibility

As with any pipet with a digital readout, the display is only valuable if it is easy to read. There are a handful of manufacturers who utilize a digital display, but it is often placed in an inconvenient spot, such as on the front of the pipet. To read the display with such an instrument, a user would need to either turn the pipet (wrist action) or twist his or her head (neck action). On the Matrix Hybrid pipet, the user only needs to look near the plunger at the top of the pipet (Figure 2). In addition, the pipet offers true one-handed operation, all controls being within easy reach with the thumb while holding the pipet in its natural position. This allows the user to adjust the volume, while keeping hand motions to a minimum during labware handling.

Almost all the pipets on the market are color coded in some fashion for volumetric identification. The pipet is only half of the equation, however; a user also needs to know what tips to use on the pipet and how to quickly identify them. To help with this, the Matrix Hybrid/ClipTips system uses a series of color codes on both the pipet and the tip racks to ensure quick and easy identification of the comparable tip for the pipet and the application (Figure 3). Additionally, tips are supplied in three sizes to provide the full volume range necessary for the five different pipet volume ranges.

Figure 3 - The user simply matches the color of the pipet with the corresponding Matrix ClipTips rack label.

Conclusion

With so many pipet choices on the market today, it is easy to be overwhelmed with product information. By concentrating on the key ergonomic factors involved in pipetting—stressors on the thumb, excessive arm and hand movements, reaching or stretching positions, and unnatural gripping—a pipet can be selected that relieves or eliminates problems in each of those areas. Addressing the factors frequently linked with fatigue can result in greater productivity and more consistent results.

References

  1. McGlothlin, J.D.; Hales, T.R. Health Hazard Evaluation Report Aug 1996, 95-0294-2594, iv-12.
  2. Mannonen, S.; Mieminen, P.; Kaasinen, J.; Andersin, K. Multichannel pipetting: how to choose the correct pipettor. Am. Biotech. Lab. 2004, 22(13), 12–14.
  3. McGlothlin, J.D.; Hales, T.R. Health Hazard Evaluation Report Aug 1996, 95-0294-2594, iv-12.
  4. http://en.wikipedia.org/wiki/Repetitive_strain_injury.
  5. http://dohs.ors.od.nih.gov/lab1.html.
  6. Buckle, D.G. A questionnaire survey of the ergonomic problems associated with pipets and their usage with specific reference to work-related upper limb disorders. Appl. Ergonom. 1997, 28(4), 257–62.

Mr. Weiss is a Director of Marketing, Thermo Fisher Scientific, 22 Friars Dr., Hudson, NH 03051, U.S.A.; tel.: 603-595-0505; fax: 603-595-0106; e-mail: craig.weiss@thermofisher.com.

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