Microfluidics and Macrofluidics in Space: ISS-Proven Fluidic Transport and Handling Concepts

Abstract

Fluid transport and handling in extraterrestrial conditions, i.e. microgravity, require significantly different system engineering than here on Earth. On Earth, a notable part of fluid processing units inherently relies on buoyancy to transport and handle fluids. In space, however, buoyancy effects are negligible due to the strong diminishment of gravity, resulting in the domination of surface tension forces. Surface tension forces are also dominating micro-scale processes in gravity, making microfluidics a promising technology for fluidic transport and handling in microgravity. Recently, three different microfluidics-suitable fluid behavior phenomena have been studied on the ISS that might further facilitate the manipulation of fluids in space: capillary-driven flow, thermocapillary Marangoni forces, and electrolytic gas evolution-driven flow. Furthermore, attention is drawn for strategies to eliminate unwanted bubbles from liquid bodies in space, as they can damage sensitive equipment: Mesh-screen capillarity and open wedge channels have been identified as promising approaches. Finally, the relevance of fluid handling in space is illustrated with everyday activities during space missions, such as drinking, plant watering, and gathering biometric data.

Effects of gravity modulation on the dynamics of a radial A+B→C reaction front

“…In addition to the decoupling of buoyancy-driven effects from other phenomena, experimenting on reduced or increased gravity gives us a first glimpse of how fundamental chemical processes might behave in the absence of gravity, revealing their potential use for in situ in-space manufacturing (Makaya et al, 2022). Microscale processes as in our study might provide solutions to problems that arise when transferring chemical technology to space (Hessel et al, 2020;Nijhuis et al, 2022). They further appear promising for process intensification in environments with reduced or increased gravity levels (Hessel et al, 2020).…”

Space Medicines for Space Health

“…In microgravity, however, molecular processes that on Earth support the matter distribution such as natural convection are absent, e.g., facilitated by buoyancy or density convection . This absence actually is ideal for crystal formation, as it leaves diffusion as the only driving force, which is a theoretically very well understood physical process with uniform mass-transfer settings .…”

Nanomaterials for Cortisol Sensing

“…To improve the binding kinetics of aptamers for cortisol, the authors applied this sensing strategy without surface immobilization within a nanoslit ( Figure 9 ) geometry, locating the sensing electrode in the vicinity of the electroactive species released by the aptamers. The microfluidic nature of this system precludes the possibility to use it in the absence of gravity, but it is open to the practicability for analysis in real life [ 66 ]. In fact, fluid motion and handling microgravity or the absence of gravity require different system engineering with respect to those used on Earth.…”