What makes a pipette an ergonomic device?On the one hand, ergonomics refers to the pipette itself. It is important to be able to hold it in different ways in the hand and use different grip patterns throughout the day so that the muscles do not stiffen and fatigue is avoided, Schmidt explains: "This is why pipettes tend to be round and the user can grip them with different grip patterns - from the front, the finger hook between the index finger and middle finger, and in different positions." The many different hand positions allow for long, fatigue-free work. But the forces required for operation and the accessibility of the operating elements are part of the pipetting ergonomics as well." The operating forces are adjusted to achieve an optimum balance between ease of movement and sensory feedback. Furthermore, the joints should not be angled more than necessary. And small hands must be able to reach the button while large hands should be able to work with it just as well as small hands - this determines, for example, the optimum circumference of the pipette." On the other hand, an optimization for certain hand sizes would not be an appropriate solution, as several researchers, especially at universities, usually work with the same pipette sets. Color-coded pipette tips or haptic feedback when adjusting the volume are examples of cognitive ergonomics that support work processes and avoid both uncertainty and unnecessary stress in laboratory work.
Fatigue-free working is not the only motive of ergonomics - in extreme cases, it can even determine life and death, for example when working with highly pathogenic viruses in the BSL-4 laboratory: "We absolutely have to make sure that gloves do not get caught or pinched and tear. This is also part of the pipetting ergonomics," explains Peter Schmidt: "The gloves themselves have relatively little effect on usability. But under no circumstances may they be destroyed during work. When adjusting the volume, the edges should therefore be slightly rounded everywhere, as sharp edges could rub through the glove in the long run. And when you press and release the eject button, the glove must not get caught and torn apart.” In addition, there must not be any edges or pinch points on the pipette in which the glove could get stuck. Neglecting this aspect when setting up a laboratory can be life-threatening. "We have competitors who use a wheel for volume adjustment below the finger hook in the middle of the handle. This is where the glove can get stuck between the housing and the wheel. If you pull it, the glove can rip," warns the pipette expert. And this would be just one example of pipettes that are less suitable for special operating conditions. Metal ejectors that can be pulled off could also pose a safety risk due to sharp corners, edges or corrosion. "Therefore, in our pipettes, almost all parts touched by the user are made of plastic to prevent corrosion and injury from sharp metal edges. Any metal parts are rounded and made of a special stainless steel highly resistant to chemicals."
When a pipette's ergonomics are a matter of life and death
While in single channel pipettes the center of gravity is usually relatively high up in the handle, balancing is not critical here. Due to their large head, electronic pipettes also have an inherently high center of gravity. But, things are completely different with mechanical multichannel and special pipettes, such as the new Move It® pipette, explains Schmidt: "Some of these pipettes have a rather heavy lower part, which is really unpleasant when working for long periods of time, because the user has to hold against the pipette all the time. This is why we counterbalanced the Move It® with stainless steel elements in the control knob and in the volume adjustment wheel." The adjustable Move It® pipette is a perfect example illustrating the pipetting ergonomic optimization of new products at Eppendorf. For perfect counterbalancing, stimulation current tests were even carried out on users' upper and lower arms. In order to make the knob for adjusting the distances between the cones as large and easy to use as possible, it was attached to the front of the pipette. The lower part has been designed to rotate so that users can grip and hold the pipette in a way that is particularly comfortable for them and can also change their hand position regularly.
Keeping the balance
"There was a great reluctance among users of mechanical pipettes to get involved with electronic pipettes," reports Peter Schmidt: "Many feel that they are losing control over the pipetting process. That's why we have equipped the electronic Xplorer® series with a tilt mechanism: To aspirate liquid, press the upper part of the tilt, to release the lower part. With this system, the piston movement can be stopped, reversed, or continued at any time. Thus, a click of the button does not mean that the pipette unstoppably carries out the dosage. However, for a new pipette which we are currently designing, we are still considering whether to install a tilt mechanism again or switch to a single button operation, as it is common in the market. The single-knob operation is not as flexible as the tilt mechanism, because it only allows a fixed sequence of pick-up, delivery and blow-out and the user cannot repeat individual steps. But both concepts have their supporters - and you can see that intuition somewhat happens in the eye of the beholder.” When developing new pipettes, Eppendorf works a lot with prototypes that are handed over to customers for testing. "Ideally, they will ask whether they really have to return the prototype. Then we've been very successful," says Schmidt. In any case, the feedback from customers helps to identify potential for improvement and to use it for further development.