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November 2020 − Inspiring Science
During their mission, astronauts are on their own. They must be able to perform every single task themselves – while strictly following consistent steps when conducting their research. This is particularly true for pipetting.
On board the International Space Station (ISS), astronauts participate in long-term missions during which they conduct experiments and operate the systems of the station. They install, activate and test station components; they conduct research, and even act as test subjects for life science experiments. Every team member must at all times be able to perform the tasks of every other member.
Training and retraining all members of the team in the exact same manner is also a good idea for laboratories on planet Earth: this process significantly strengthens the flexibility of the team as a whole while simultaneously improving the quality of results.
Particularly during laboratory work, it is crucial that everyone be trained on the same SOPs – especially when it comes to handling liquids, as different pipetting techniques and pipetting habits may influence the series of results to a significant extent. In addition, since conventional balances are of no use under zero gravity conditions, astronauts must instead rely on volumetric data instead of weighing mass. They must also learn how to select the right pipette for handling difficult liquids as well as carry out maintenance work independently.
One of the recurring activities in research is pipetting. Those who are used to working in a terrestrial laboratory may be asking themselves whether it is indeed possible to work with an air cushion pipette under zero gravity conditions. The surprising answer: the differences are not that serious; in the absence of gravity, or in free fall, liquids respond directly to any and all forces applied to them. For these reasons, only two factors are relevant: the atmosphere within the space station and the surface tension of the liquid to be pipetted.
Outside, in the vacuum of space, pipetting with air cushion pipettes would not be possible as pipettes must generate a vacuum in order to aspirate liquid. This is achieved by moving air inside the pipette tip. Since the atmospheric pressure on board the ISS is the same as on Earth at sea level (101.3 kPa; 1.0 atm), this does not present a problem. The surface tension between the liquid and the inside wall of the pipette tip holds the liquid together inside the pipette. For these reasons, the mechanism of aspiration is basically the same as it is on Earth. Whereas on Earth, gravity facilitates dispensing of liquids into the desired receptacles, astronauts must work even more diligently and always dispense the liquid directly against the wall to build the surface tension between the receptacle and the liquid. The rule of holding the pipette tip against the inner wall of the vessels during dosing of course also applies on Earth.
Even though it is not quite as important on Earth as it is in space, dispensing the liquid directly against the vessel wall does minimize the risk of error.
In principle, reverse pipetting is employed when working with air cushion pipettes in space – exactly as it is done on Earth for liquids of high viscosity, as well as for strong detergents and solvents which exhibit high vapor pressure.This means that during liquid aspiration, the button of the pipette is pressed down to the second stop, followed by pressing down to the first stop only when subsequently dispensing the liquid. In this way, residual liquid will remain inside the pipette tip following dispensing of the correct volume. There are of course other techniques which make sense on Earth only, such as, for example, pre-wetting of the air cushion to prevent dripping when working with liquids that generate high vapor pressure.
In order to achieve the best results possible independent of the pipetting technique, care should also be taken to keep the air cushion between piston and liquid as small as possible. For the purpose of certain experiments, especially when working with non-aqueous liquids, direct displacement pipettes are often the better choice. Direct displacement pipettes have been shown to generate better pipetting results than air cushion pipettes with respect to both accuracy and precision.
Astronauts who conduct research always consider carefully which pipetting technique they will employ for any particular experiment – and they ensure that it executed in the exact same manner by everyone involved.
Inside the ISS, everything that is not secured will float through the air, and even the most minute impulse can influence its direction. For example, pipette tips kept in a regular box as it is used on Earth would be able to leave the box and float through the laboratory. Even more dangerous: after dislodging from the pipette, used pipette tips could easily turn into contaminated projectiles. Thus, care and attention – whether in space or firmly on the ground – will guide you to success.
Did you know?
Professional training in three steps
During the course of their one-year-long basic training, which prepares them for their mission in space, astronauts become acquainted with space agencies and their respective programs. Astronauts also receive basic knowledge of space and electronic technologies, as well as multiple scientific disciplines. At the end of their basic training, they will complete a scuba-diving course – the buoyancy of the body during scuba diving resembles that in zero gravity. Last, but not least, astronauts receive Russian language instruction, and they complete courses in behavior and performance.
The second phase comprises additional training over the course of one year. This phase concentrates on capabilities that are required during every ISS mission: operation and maintenance of ISS modules and systems, load capacity and transporters; handling of resources and data, as well as robotics and navigation, where operation and maintenance on board as well as outside the craft are critical. In addition, astronauts receive medical training to the level of certified paramedics.
The final training phase provides the crew with the comprehensive knowledge that is required for their mission. This 18-month period will also strengthen the team spirit and the bond between the crew members.
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