Random Positioning Machine - microgravity-simulator
The "Random Positioning Machine" (RPM) is used to expose biological samples to simulated weightlessness. To produce microgravity the samples are in constant motion. The rotational movement is controlled through algorithms so that the gravitational vector is equal in all directions. This averages out the gravitational force that acts on the sample over a long period of time.
With the dawn of manned space flight, it soon became clear that weightlessness (also known as microgravity) had some drastic effects on the human body and individual organs. The significant muscle and bone atrophy seen on astronauts during long space flights in particular can also be observed in older people. Therefore, space is the ideal place for a mechanobiological laboratory in order to study such changes. Amazingly, microgravity not only affects organs but also individual cells.
Experiments that require conditions of microgravity for only a few seconds can be conducted in drop towers or parabolic flights. However, space flights are necessary in order to carry out longer-term experiments involving weightless conditions. As access to space remains very limited and the preparations for such experiments are extremely demanding, science has to rely on simulation models. These enable in-depth pre-studies and post-studies, plus hardware tests.
Random Positioning Machines (RPMs) are used to simulate weightless conditions. These RPMs are comprised of two gimbal-mounted frames, in the middle of which the biological samples are positioned. The frames are driven by two independent motors. This means that the samples can be freely adjusted in relation to the gravitational vector. It is assumed that the gravitational vector has to have an effect on biological systems (e.g. cells) for a short time in order for it to be recognized by them. If the gravitational vector is reoriented fast enough (by rotating the samples), then it is no longer possible for the cells to react to gravity. This in turn leads to reactions that are also seen in weightless conditions. With the help of a random walk algorithm, the gravitational vector is distributed so that the gravity converges at around zero when measured over time.
Random Positioning Incubator
The CC Bioscience and Medical Engineering [BAH1] initiated a redesign of the classical RPM, which had been developed by T. Hoson in Japan and manufactured by Dutch Space (formerly Fokker Space). Prof. Jörg Sekler, Institute of Automation at the University of Applied Sciences Northwestern Switzerland (FHNW) implemented the redesign.
The new RPM had following properties:
- CO2-Incubator (constant temperature and CO2 - concentration)
- Several operation modes (random walk, swinging, partial gravity, cyclic operation)
- Programmable start and stop times of different sequences
- G-sensor verification of the generated zero-gravity field
- Automatic data registration
- Rotary joints for liquids and gases
- Wireless monitoring of various parameters
Microgravity Incubator
Another RPM design is being developed at the Lucerne University of Applied Sciences and Arts. It is called the “Microgravity Incubator” (MGI). This RPM is characterized by several internal rotation axes. This means that all samples are rotated exactly around the center of rotation and are thus treated equally. Thanks to the compact design, the MGI can be operated in incubators without any problems.
Digital Holographic Microscope
The Digital Holographic Microscope (DHM) is a new and innovative imaging technique, especially suited to study the surface of microscopic objects. Quantitative "phase images" are produced by this method, which can be directly correlated to the "optical path length" (OPL) of the object. This also allows analysis of cell morphology.
The DHM technology has been linked to the "Random Position Machine" to follow morphological changes of cells in real time in simulated weightlessness over a longer period of time The scientists can thus explore in detail how changes triggered by overriding gravity affect living cells.
The new technology was used extensively to demonstrate the changes on a mouse muscle cell line (C2C12) in simulated weightlessness. The big advantage here is that the cells can be examined without any special treatment
