Pipettes and syringes - good design and safe use
Pipetting work demands concentration, accuracy and precision. There is often a time restraint to achieve optimal test results.
A wide range of makes and models is available on the market. The features of each vary in terms of ease of use, technical specification and price.
The features of the pipette will influence comfort and ease of use and may affect the risk of upper limb problems. The design of the plunger, the weight and length of the pipette, the force needed to operate the pipette and how the pipette fits into the hand are all-important factors.
Research shows that using a pipette for long periods is associated with an increased risk of hand and shoulder ailments.
This page contains guidance on the ergonomic aspects of pipette design and use and also highlights points to assess when procuring new equipment.
The following are some of the main ergonomic points to consider when selecting a pipette:
- Light in weight
- Comfortable to hold
- Good grip
- No sharp edges or ridges
- Suitable for right or left handed use
- Easy tip ejection and fitting
- Convenient plunger or main button position, avoiding over-stretching the thumb
- Minimal force to push plunger (including the second push on manual pipettes)
- Easy to set and read dosage
- Positive feedback from button operation
The way in which a pipette is used will influence the comfort and safety of the operation. The following are some of the key points to consider when using pipettes:
- Always select the most appropriate pipette or syringe for the task
- Avoid using pipettes or syringes continuously for long periods
- Organise the work to allow regular short breaks or changes in activity
- Try to keep your wrists straight and don’t over-stretch your thumb when using the plunger
- Arrange your workplace to allow a good working posture, avoiding outstretched and unsupported arms
A well-designed product that has considered ergonomics should be safe, comfortable and efficient to use. A pipette must be accurate and reliable for repetitive usage.
The design process must take account of users, the tasks they perform, and the environment in which they work and the equipment they use. The design of pipettes should allow a neutral position of the user’s hand and wrist, it should not require excessive force for operating the pipette and it should minimise any contact stresses incurred to the hand.
User satisfaction may be measured by such features as the texture of the handle, the shape of the hilt, the force and distance required for plunging and the overall weight of the pipette. Consideration also needs to be given to ease of tip ejection.
Performance and usability features should be considered when purchasing pipettes.
It is important that there is minimal strain on the soft tissues (e.g. muscles, ligaments, tendons) of the upper body whilst pipetting.
Standing or sitting at the wrong height will put additional strain onto the upper limbs. If the working height is too low, the person will stoop over their work and put strain on their back and neck. If the working height is too high, the person’s shoulders and arms will be working in an elevated position and this will put tension on the muscles.
A suitable chair or stool should be provided for longer periods of pipetting. There should be leg space under the work surface to enable the person to sit close to the work they are doing.
Seating should be comfortable and with sufficient lumbar support. The seat should be height-adjustable to ensure a good working posture is achieved.
Footrests may be required if the feet do not comfortably touch the floor with the seat at the correct height. A foot ring on the chair does not offer sufficient support.
If the arms are held unsupported away from the body, then the muscles in the upper arms and shoulder work statically to maintain this position and therefore tire quickly.
The wrist should be maintained in a relaxed, neutral position, not flexed, extended or rotated. The shape of the pipette hilt will have some bearing on the posture of the wrist, but the person may be using the pipette in such a way that the wrist is not relaxed.
The thumb should not have to apply significant force, or work in isolation from the hand. It may be under strain to depress the plunger, particularly for the second, final press.
Tip ejection is carried out either by the thumb only, or by a power grip involving the fingers. The latter is preferable, as it is less stressful to the hand. On the Anachem model, there is a lever which may be pushed or pulled to eject tips. It makes the task easy to carry out with little effort.
Equipment on the work surface should be positioned to allow a good working posture. The height and position of sample holders, solution containers and the waste receptacle should reduce the need for twisting, bending or awkward stretching.
Research shows that the more repetitive the task of pipetting, the higher the chances of developing upper limb problems.
Means of reducing the effects of excessive pipette use include varying the work routine to introduce tasks that involve different postures and taking regular breaks. Short, frequent breaks are more effective than working for a longer duration and taking a longer break. It is advisable to vary the work routine to alternate between a number of different tasks.
Other methods of reducing the effects of repetition are to use an electronic pipette, or use a multipipette in place of a single pipette, or programme a robot to carry out the task.
Task sharing may be another alternative to divide the workload amongst a team of operators.
Excessive force to operate a pipette should not be necessary. One of the reasons for force to be applied is if the plunger is not easy to operate and the thumb has to apply significant effort to press it. Another reason for a forceful action is when the liquid viscosity is greater.
The greater the distance the plunger has to be depressed, the more effort is required. Pipette designs with a shorter plunger are preferred. The movement of pressing the plunger should be smooth and easy to control. Any damaged or faulty pipettes should be fixed or replaced. This is beneficial in terms of effort and accuracy.
The shaft of the pipette should be easy to grip. Small ridges or a textured material will reduce the effort required to grip the pipette.
The most effective way to reduce the amount of force to be applied is to use an electronic pipette. Electronic pipettes require less effort in terms of operating, but the weight of these is greater and may cause strain when holding for longer periods.
Discomfort may be felt in areas of the hand which are in contact with the pipette. Any sharp edges or areas which are in constant contact with the hand should be considered. Pressure should be diffused across the hand as much as possible.
In preference to the thumb alone operating tip ejection, the whole hand should be involved in a power grip (where practicable).
Sample tubes are the most widely known and used tubes and the name is commonly used as a generic term for all tubes.
The ergonomics issues concerned with the use of these tubes include the force required to open and close them, contact stresses, the posture of the hand and repetition.
The fastenings on sample tubes vary between models. Some have a simple 'snap' lid which have a tight fitting seal and can be difficult to open and close. Others have a small button which is clasped to fix the lid to the tube. The latter type requires less effort but can be fiddly to operate.
The thumb applies the majority of the force which puts excessive strain on the one digit and significantly increases the risk of a strain.
The wrist should be maintained in a relaxed, neutral position. The upper arm should be in a comfortable position to avoid unnecessary strain.
The use of sample tubes is generally of a repetitive nature. This may be avoided by mechanising the process (using a robotic machine, for example) or reducing the effects by taking frequent breaks and rotating tasks.
Labelling of the tubes is a fiddly process and can be avoided by using coloured tubes.
Some ergonomic concerns regarding syringe use include the force required, the posture of the thumb and wrist and the contact stresses.
Syringes are often used to transfer large quantities of liquid which may require additional force to depress the plunger. The top of the plunger could create contact stress to the thumb if the surface area is small.
Syringes are often used to pierce sealed airtight bottles, as shown in this photograph. The thumb is held at full stretch in this example which increases the strain on the joints of the thumb.
When syringing a large quantity of liquid, the hand may be fully extended (outstretched) which increases the risk of a wrist strain. The wrist should preferably be in a relaxed, straight posture.
Where the syringe is not specifically required, an electronic pipette suitable for handling larger quantities should be used. This enables a good wrist posture, minimal effort to operate and virtually no strain to the thumb.
The shaft of some models is angled to improve the wrist position.