Role of microfluidics in accelerating new space missions

Abstract

Numerous revolutionary space missions have been initiated and planned for the following decades, including plans for novel spacecraft, exploration of the deep universe, and long duration manned space trips. Compared with space missions conducted over the past 50 years, current missions have features of spacecraft miniaturization, a faster task cycle, farther destinations, braver goals, and higher levels of precision. Tasks are becoming technically more complex and challenging, but also more accessible via commercial space activities. Remarkably, microfluidics has proven impactful in newly conceived space missions. In this review, we focus on recent advances in space microfluidic technologies and their impact on the state-of-the-art space missions. We discuss how micro-sized fluid and microfluidic instruments behave in space conditions, based on hydrodynamic theories. We draw on analyses outlining the reasons why microfluidic components and operations have become crucial in recent missions by categorically investigating a series of successful space missions integrated with microfluidic technologies. We present a comprehensive technical analysis on the recently developed in-space microfluidic applications such as the lab-on-a-CubeSat, healthcare for manned space missions, evaluation and reconstruction of the environment on celestial bodies, in-space manufacturing of microfluidic devices, and development of fluid-based micro-thrusters. The discussions in this review provide insights on microfluidic technologies that hold considerable promise for the upcoming space missions, and also outline how in-space conditions present a new perspective to the microfluidics field.

FIG. 1.

Recently developed in-space microfluidic applications. (i) Microfluidics in space pharmaceutics and biology; (ii) Tests in a space trip or on another planet; (iii) 3D printing and bio-printing in space; (iv) Micro-propulsion technologies.

FIG. 2.

Microfluidics applications in space biology. (a) Bioreactor: (i) photograph of the bioreactor. Distributed under a Creative Commons Attribution License 4.0 (CCBY). (ii) cross-section of bioreactor chamber. Reproduced with permission from Enzyme Microb. Technol. 27, 778 (2000). Copyright 2000 Elsevier Science Inc. (iii) photograph of flow sensor and micropump in bioreactor. Distributed under a Creative Commons Attribution License 4.0 (CCBY). (b) Space Shuttle missions, STS-65 in 1994 and STS-76 in 1996. Reproduced with permission from NASA. (c) Percentage of randomly located bud scars vs normal bipolar positioning, F: Flight, G: Ground. Distributed under a Creative Commons Attribution License 4.0 (CCBY).

FIG. 3.

Microfluidics-enabled lab-on-a-chip technology within CubeSats for space pharmaceutics, and biology. (a) CubeSat “Genesat-1.” Reproduced with permission from NASA. (b) Payload optical detector system on CubeSat “Genesat-1.” Reproduced with permission from IEEE. (c) Modified microfluidic, optical, and thermal cross-section of one of 48 wells, each containing 100 μl with an integral 1.2 μm filter membrane at the inlet and outlet to confine the yeast. Reproduced with permission from NASA. (d) Schematic of fluidic system showing flow directions through valve board on CubeSat “EcAMSat.” Reproduced with permission from Life Sciences in Space Research 24, 18 (2020). Copyright 2020 Elsevier. (e) Average reduction of alamarBlue over time for wildtype uropathogenic E. coli and its isogenic $\mathrm{\Delta }rpoS$ mutant on CubeSat “EcAMSat.” Reproduced with permission from Life Sciences in Space Research 24, 18 (2020). Copyright 2020 Elsevier.

FIG. 4.

Biological tests in a space trip or on another planet. (a) Photograph of microfluidic cytometer system. (Left) portable optical reader, and (Right) microfluidic cartridge. Reproduced with permission from IEEE. (b) Measured intensities of all leukocyte cells displayed as a scatter plot, each point representing a counted leukocyte. The scatter plot shows four distinct clusters. Reproduced with permission from IEEE. (c) Fluorescence image of C. elegans: (i) original fluorescence image, (ii) converted grayscale image, (iii) image after filtering process, (iv) image after corrosion process. Reproduced with permission from Electrophoresis 40, 922 (2019). Copyright 2018 WILEY-VCH. (d) Wearable sensor array monitoring human health by analyzing sweat. Reproduced with permission from Nature 529, 509 (2016). Copyright 2016 Macmillan Publishers Limited. (e) Microfluidic systems as the water-quality microanalyzer in a living ecosystem for long-term space trips or planet immigration. Reproduced with permission from Acta 995, 77 (2017). Copyright 2017 Elsevier B.V.

FIG. 5.

In-space manufacturing for microfluidics. (a) First 3D printing task in space. Reproduced with permission from NASA. (b) SEM images of a 3D-printed channel before (i) and after (ii) removing supporting material. Reproduced with permission from Anal. Methods 8, 6005 (2016). Copyright 2016 The Royal Society of Chemistry. (c) First 3D bio-printing task in space. Distributed under a Creative Commons Attribution License 4.0 (CCBY). (d) Bio-printing process recorded by a video. Distributed under a Creative Commons Attribution License 4.0 (CCBY). (e) Macro photography of printed 3D construct returned to Earth. Distributed under a Creative Commons Attribution License 4.0 (CCBY).

FIG. 6.

Handling fluids in micro-scales promotes new thrusters for satellite. (a) and (b) Electrospray of conductive liquids or liquid metals. Reproduced with permission from Rep. Prog. Phys. 71, 0 36 601 (2008). Copyright 2018 IOP Publishing Ltd. Reproduced with permission from J. Aerosol Sci. 25, 1065 (1997). Copyright 1994 Elsevier Science Ltd. (c) Application of electrospray thruster technology in space gravitational wave detection missions. Distributed under the terms of the Creative Commons Attribution 3.0 License. (d) and (e) Fabrication of micro capillary, porous emitters, and emitters array for higher flow impedance. Reproduced with permission from J. Micromech. Microeng 24, 0 75 011 (2014). Copyright 2014 IOP Publishing Ltd. Reproduced with permission from J. Nanomech. Micromech. 7, 0 40 17 006 (2017). Copyright American Society of Civil Engineers. (f) Actively controlled proportional valve based on MEMS technology for changing the flow impedance. Reproduced with permission from Sens. Actuators, A 83, 188 (2000). Copyright Elsevier Science S.A.