Passive Nano-and Micro-Textured Dust-Mitigation Surfaces in Space-Grade Materials Made with a Highly-Scalable Fabrication Process

With the imminent return of humans and infrastructure to the Moon through Artemis, the challenges posed by lunar dust have returned to the forefront. During the Apollo missions, dust clogged chamber seals, damaged spacesuits, degraded mechanical gears, and limited the range of the lunar rover. The issue remains critical for both manned and unmanned lunar or planetary missions, where key infrastructures can be degraded over time by highly abrasive dust. While active dust-mitigation approaches consume energy to remove dust from a surface, passive approaches typically aim to reduce surface energy to make dust less prone to sticking. In this project, a passive approach will be developed to add a nanotexture to critical components using scalable processes, thereby reducing contact area and adhesion force. The Phase I research demonstrated a highly effective nanotexture that reduced coverage of a lunar dust simulant on a polycarbonate substrate by 93%. Fabrication of these surfaces was based on thermal embossing using metal molds created with our patented Nanocoining technology. During Phase II, Nanocoining and tangential processes including high-throughput roll-to-roll embossing will be used to create an optimized surface texture at scale in relevant space-grade materials. In addition, a team at the UT, Austin will further develop a simulated lunar environment to study particle adhesion physics. Their goal will be to understand how texture geometries, surface energy, low-energy monolayer coatings, vacuum, and humidity affect dust mitigation and to test the surfaces durability to thermal, abrasive, and repeated dust loading. Deliverables will include 1 m2 of nanotextured polycarbonate, along with batch-scale samples of textured polyimide, PET, and FEP. Further, the best-performing textures will be applied to relevant applications, including a radiator strip, visible camera optic, and solar-panel coating, for demonstration and testing. Passive dust-mitigating surfaces offer a means to reduce dust adhesion on key surfaces, without consuming any power. Certain nanotextures have been shown to significantly reduce adhesion forces, but they are extremely difficult to fabricate. The key innovation in this work is not only an optimized dust-mitigating texture; it’s also the highly scalable process to create it. This SBIR project leverages an innovative method to make large metal micro and nanotextured drum molds for roll-to-roll nanoimprint lithography processes. This method, called Nanocoining, can rapidly create textures with individual features that are smaller than the wavelength of light, enabling the creation of highly textured surfaces that maintain or even enhance optical transparency. These robust metal molds are capable of withstanding high pressure and temperature, allowing the processing of space-grade materials like polyimide and PET. Further, the same metal drum can be used to imprint resists that can be used to transfer the pattern into almost any material via etching. The primary goals of this SBIR project are to demonstrate that nanotextured surfaces can reduce dust adhesion on critical spacecraft components and that these surfaces can be created at the scale and in the form factors needed for use on the Moon. These passive surfaces require no energy and add negligible mass to the payload, but they can be combined with active dust-mitigating strategies to improve the efficacy of those systems. At the end of Phase II, Smart Material Solutions, Inc. (SMS) will show side-by-side comparisons of several space-grade materials with and without an engineered nanotextured surface. All the samples will be tested for dust mitigation and durability by a team at the UT, Austin in a specially designed vacuum- and humidity-controlled chamber that simulates the lunar environment. In addition, SMS will partner with MicroContinuum Inc. to texture more than 1 m2 of optically clear polycarbonate using roll-to-roll imprinting. SMS will also develop methods to transfer the textures to other space-grade materials that are notoriously difficult to imprint, including polyimide (Kapton), FEP, PTFE, and PET. These surfaces will be applied to several commercially motivated applications: radiator strips, solar-panel cover glass, and curved camera optics, and then sent to NASA and partner companies for evaluation.
Benefits: Solar-panel cover glass coatings Radiator strips Camera optics Drag-reduction surfaces Metamaterials for sensing and energy harvesting Micro optics for augmented and virtual reality Light extraction films for LED/OLED displays and lighting Tuned spectral absorbers for camouflage Anti-microbial surfaces