A random positioning machine, or RPM, rotates biological samples along two independent axes to change their orientation in space in complex ways and so eliminate the effect of
gravity
In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...
.
[Jack J.W.A. van Loon (2007). Some history and use of the random positioning machine, RPM, in gravity related research. Advances in Space Research 39: 1161-1165] RPMs are often used as an alternative to
sub-orbital flights or
drop towers in research studying the effects of
weightlessness
Weightlessness is the complete or near-complete absence of the sensation of weight, i.e., zero apparent weight. It is also termed zero g-force, or zero-g (named after the g-force) or, incorrectly, zero gravity.
Weight is a measurement of the fo ...
or microgravity on biological systems.
Description
The RPM is a more sophisticated development of the single-axis
clinostat
A clinostat is a device which uses rotation to negate the effects of gravitational pull on plant growth (gravitropism) and development (gravimorphism). It has also been used to study the effects of microgravity on cell cultures, animal embryos and ...
. RPMs usually consist of two independently rotating frames. One frame is positioned inside the other giving a very complex net change of orientation to a biological sample mounted in the middle. The RPM is sometimes wrongly referred to as the "3-D clinostat" (which rotates both axis in the same direction, i.e. both clockwise). It is a microweight ('
micro-gravity
Weightlessness is the complete or near-complete absence of the sensation of weight, i.e., zero apparent weight. It is also termed zero g-force, or zero-g (named after the g-force) or, incorrectly, zero gravity.
Weight is a measurement of the fo ...
') simulator that is based on the principle of 'gravity-vector-averaging'. RPM provides a functional volume which is 'exposed' to simulated microweight.
[A. G. Borst, J.J.W. A. van Loon. Technology and Developments for the Random Positioning Machine, RPM. Microgravity Sci. Technol., 2008. DOI 10.1007/s12217-008-9043-2]
Simulated micro-, partial, and hyper gravity
The concept of 'random' positioning has been used to simulate a micro-gravity environment through the nullification of gravity. This is accomplished by disorientating the target model, or as "vector-averaging". Through the use of a centrifuge, a '
hyper-gravity' gravity can be simulated, as the model will get exposed to a continued accelerated force. In the circumstances of hyper-gravity within a micro-gravity environment, a partial 'Earth' gravity is created. Hyper-gravity simulation is also achieved through the use of larger centrifuges, such as the
Large diameter Centrifuge (LDC) at the European Space Agency. The LDC is able to simulate up to twenty times the Earth's gravitational strength. A system developed by Airbus uses an algorithm to simulate partial-gravity through a not fully randomly vector-averaging. The vector-averaging by Airbus' algorithm doesn't average out the vector to null but to a percentage representing simulated partial-gravity.
Disadvantages
The simulated microgravity environment attained inside the RPM is not perfect. A secondary effect part of this is the shear forces created by the fluid dynamics of the cell culture medium. They have been mathematically modeled by Wüest, and according to the research by Hauslage, they are of a magnitude enough to have biological implications. Also, Cortés-Sánchez showed these effects in mammalian cells cultured in the RPM.
[{{cite journal , last1=Cortés-Sánchez , first1=José Luis , last2=Melnik , first2=Daniela , last3=Sandt , first3=Viviann , last4=Kahlert , first4=Stefan , last5=Marchal , first5=Shannon , last6=Johnson , first6=Ian R. D. , last7=Calvaruso , first7=Marco , last8=Liemersdorf , first8=Christian , last9=Wuest , first9=Simon L. , last10=Grimm , first10=Daniela , last11=Krüger , first11=Marcus , title=Fluid and Bubble Flow Detach Adherent Cancer Cells to Form Spheroids on a Random Positioning Machine , journal=Cells , date=January 2023 , volume=12 , issue=22 , pages=2665 , doi=10.3390/cells12222665 , doi-access=free , pmid=37998400 , pmc=10670461 , language=en , issn=2073-4409]
See also
*
Gravitropism
Gravitropism (also known as geotropism) is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either "artificial gravity" or natural gravity. It is a general feat ...
*
Sub-orbital flights
*
Weightlessness
Weightlessness is the complete or near-complete absence of the sensation of weight, i.e., zero apparent weight. It is also termed zero g-force, or zero-g (named after the g-force) or, incorrectly, zero gravity.
Weight is a measurement of the fo ...
*
Drop tubes
References
External links
* ETH Space Biolog
''Random Positioning Machine''* DESC VU Amsterda
*Manufacturer's Website
yuri GmbH
Laboratory equipment
Gravitational instruments
Positioning instruments