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
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
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
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
Figure 3 - The user simply matches the color of the pipet with the corresponding
Matrix ClipTips rack label.
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.
- McGlothlin, J.D.; Hales, T.R. Health Hazard Evaluation Report Aug 1996, 95-0294-2594, iv-12.
- Mannonen, S.; Mieminen, P.; Kaasinen, J.; Andersin, K. Multichannel pipetting: how to choose the correct pipettor. Am. Biotech. Lab. 2004, 22(13), 12–14.
- McGlothlin, J.D.; Hales, T.R. Health Hazard Evaluation Report Aug 1996, 95-0294-2594, iv-12.
- 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;