How Microgravity is Reshaping Materials Science

Introduction

From jet engines to fiber optic cables, microgravity is liberating materials science from familiar constraints. It is making way for improvements and innovations by unshackling manufacturing processes from earthly limitations. 

As one might expect, materials science deals with the properties and structures of materials. The field straddles the shrinking spaces between chemistry, physics, engineering, and manufacturing. Progress here is especially crucial for nanotechnology, drug delivery systems, energy storage systems, and quantum computing (University of Oxford, n.d.).

Surface tension's abundance in microgravity discourages void formation, allowing materials with different properties to more seamlessly bond. The absence of buoyancy and sedimentation further facilitates the casting of quality alloys and unique material compositions. Without convection—the transfer of heat through the movement of fluids—materials form in a stable, undisturbed environment, minimizing defects to yield superior finished products (ISS, n.d.).

Fiber Optics in Microgravity

Fiber optics allow for higher bandwidth data transmission over greater distances than electrical cables. Suborbital research from NASA’s Marshall Space Flight Center showed that optical fibers fashioned in microgravity have fewer imperfections than their earth-bound counterparts. 

Some fiber optics are extremely efficient but difficult to assemble under ordinary conditions. In the past decade interest in the advantages of engineering fiber optics in space and space-like conditions has ramped up, paving the way for better telecommunications, lasers, semiconductors, spectroscopy and more (NASA, 2023).  

ZBLAN is a type of fluoride-based optical fiber glass that is 100 times more efficient than traditional silica-based fibers. However, the hindrances of gravity cause impurities to form, drastically reducing performance. ZBLAN optical fibers on the International Space Station are created with greater facility and fewer flaws (ISS, 2020).

ZBLAN is a fluoride-based optical fiber glass known for transmitting data with minimal loss, up to 100 times more effectively than its common silica-based cousins. However, gravity causes impurities to form during ZBLAN production, reducing performance. In the microgravity environment of the ISS, ZBLAN fibers can be manufactured with fewer imperfections and greater precision, improving performance (ISS, 2020).

Alloys and Metals 

Enhanced distribution in solid-liquid mixtures can enhance strength and uniformity. In an ISS experiment, solid tin particles were mixed with a lead-tin liquid. Under normal gravitational conditions, heavier particles sink while lighter ones rise, disrupting even distribution. Microgravity lets them remain more evenly suspended, blazing the path to more desirable properties and more precise measurements. 

Initial investigations revealed that the particles increased in size—a phenomenon known as coarsening—through a process called Ostwald Ripening. This stabilized the material's thermodynamic state in the absence of gravitational interference, enabling scientists to more precisely gauge particle growth. The experiment also illuminated the ways dendritic structures evolve, broadening our knowledge of material behavior in space conditions (NASA, 2015).

An investigation focused on how alloys form solid structures during casting helped solidify our understanding of how microgravity can give us better metals. Comparison of Structure and Segregation (CSS) studies by NASA 

In 2010 and 2011, samples were processed in space. After returning to earth for analysis, it was discovered they consist of a network of pristine tree-like metallic branches that favorably influence the strength and other properties of the material.

Convection is minimized in microgravity, leading to a more uniform solidification. This is vital for forming quality parts, like those required by jet engines (NASA, 2015).

Crystal Growth

Microgravity’s benefits for crystal growth are already well-substantiated. In one review, researchers combed through 507 different crystallization experiments. They analyzed the results to see how well crystals grew based on factors like size, structural quality, clarity, and uniformity.

The review compared results from microgravity experiments in space with those actuated on earth. Crystals grown in microgravity consistently performed better across all aforementioned factors. Even more exciting, is that later experiments consistently saw rising success rates (Jackson, 2024).

More controlled and uniform crystal growth is invaluable for making complex molecules when achieving high purity and consistency is critical and difficult (ISS National Lab, n.d.).

Crystals with fewer defects have far reaching implications for the semiconductor and pharmaceutical industries. Microgravity crystallization is leading to enhanced performance in electronic devices and drug formulations. These augmentations are primarily due to a reduction in convective forces (Sierra Space, 2023).

The benefits to the pharmaceutical realm are especially welcome as the global population continues to grow older, with median age and life expectancies continuing to climb (Statistica, 2023).

Over 60% of all pharmaceutical drugs have crystalline structures. Alterations to the shape, structure, size and uniformity change drug performance and manufacturing ease. Uniformity can ensure effective products which leads to improved outcomes for patient health and economic considerations (ISS National Lab, n.d.).

3D Printing

Additive manufacturing, otherwise known as 3D printing, can glean massive advantages from microgravity. The absence of various gravitational conditions, like buoyancy, allows for the creation of more intricate and complex structures (Innovation News Network, 2023).

This synergy was first demonstrated in 2018 when a 3D printer was brought aboard the ISS as a collaborative enterprise between NASA and Made In Space. This printer can produce tools, plastics, and medical supplies. This can grant astronauts greater autonomy with supply issues (Innovation News Network, 2023).

Conclusion

Microgravity research continues to extend its reach. Its full range of applications, and their implications, are only beginning to be explored. Microgravity is assisting in advanced materials production in a variety of domains, and companies like Litegrav are making this profoundly transformative universe of possibilities accessible to all. 

References and Suggested Reading

Innovation News Network. (2023, October 2). Materials science in microgravity: Unlocking new frontiers in innovation. Innovation News Network. https://www.innovationnewsnetwork.com/materials-science-microgravity-unlocking-new-frontiers-innovation/31491/

International Space Station National Laboratory. (n.d.). Advanced manufacturing and materials. https://issnationallab.org/research-and-science/space-research-overview/research-areas/in-space-production-applications/advanced-manufacturing-and-materials

International Space Station National Laboratory. (2020, October 5). Taking ZBLAN optical fiber production to space. https://issnationallab.org/iss360/taking-zblan-optical-fiber-production-to-space

International Space Station National Laboratory. (n.d.). Crystal growth: In-space production applications. ISS National Lab. https://issnationallab.org/research-and-science/space-research-overview/research-areas/in-space-production-applications/crystal-growth/

Jackson, K.; Brewer, F.; Wilkinson, A.; Williams, A.; Whiteside, B.; Wright, H.; Harper, L.; Wilson, A.M. Microgravity Crystal Formation. Crystals 2024, 14, 12. https://doi.org/10.3390/cryst14010012

Lecture 9: Particle Coarsening: Ostwald Ripening, my.eng.utah.edu/~lzang/images/lecture-9.pdf. Accessed 2 Nov. 2024.

NASA. (2015). Microgravity materials: International Space Station research in materials science (NP-2015-09-030-JSC). NASA. https://www.nasa.gov/wp-content/uploads/2016/05/np-2015-09-030-jsc_microgravity_materials-iss-mini-book-508c2.pdf

NASA. (2023, October 11). NASA-supported optical fiber manufacturing arrives at space station. NASA. https://www.nasa.gov/centers-and-facilities/armstrong/nasa-supported-optical-fiber-manufacturing-arrives-at-space-station

Sierra Space. (2023, April 14). The potential of microgravity in advanced materials and therapeutics. Sierra Space. https://www.sierraspace.com/blog/the-potential-of-microgravity-in-advanced-materials-and-therapeutics/

Statista. (2023). Projected global median age 2022-2100. Statista. https://www.statista.com/statistics/672669/projected-global-median-age/

University of Oxford. (n.d.). Materials science. https://www.ox.ac.uk/admissions/undergraduate/courses/course-listing/materials-science

Voorhees, Peter W. "The theory of Ostwald ripening." Journal of Statistical Physics 38 (1985): 231-252.

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