Dust-Repellent Coating for Spacecraft Inspired by the Lotus Leaf

Innovation: Industry

NASA

2015

Image: Irakli Kvaratskhelia / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Protect From Dirt/solids

When dirt and other small solids adhere to living systems, they can slow them down, create blockages, reduce their ability to carry out vital functions, or cause surface wear and tear. Due to electrostatic forces, it’s easy for dirt and other solids to adhere to surfaces, so living systems must overcome those forces. An earthworm, for example, uses a small electric current to keep soil particles from adhering to its body as it moves through the soil. This enables it to move more efficiently by reducing drag.

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Protect From Nuclear Radiation

Nuclear radiation is a threat that some living systems can survive. Most survival strategies help living systems survive other kinds of extreme threats, although in situations where there has been human-caused exposure to nuclear radiation, some quickly reproducing organisms (such as bacteria) might develop new strategies. The tardigrade (also called a water bear) survives extreme conditions by undergoing a suspended metabolic state called cryptobiosis. Going into this state helps it survive nuclear radiation, dehydration, and low temperatures.

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Protect From Temperature

Many living systems function best within specific temperature ranges. Temperatures higher or lower than that range can negatively impact a living system’s physiological or chemical processes, and damage its exterior or interior. Living systems must manage high or low temperatures using minimal energy, which often requires controlling responses along incremental temperature changes. To do so, living systems use a variety of strategies, such as avoiding high or low temperatures, removing excess heat, and holding heat in. Insulation is a well-known example of managing low temperatures by retaining heat using thick layers of hair, fur, or feathers to hold warm air next to the skin.

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Manage Turbulence

A turbulent force occurs when air or water creates a chaotic or irregular motion. The source can be such things as wind, waves, and eddies caused by obstructions to air or water flow (such as that created by a rock in a stream). Because the force is irregular, it acts in unpredictable ways on multiple parts of a living system at any given time, decreasing the living system’s efficiency. Strategies used to manage turbulence include dampening the amount of turbulence, having flexibility to handle sudden changes, and making quick adjustments. An example is the mucus on aquatic organisms, such as barracuda sharks, that can reduce turbulent friction of seawater by 66%. In doing so, it decreases drag and increases the sharks’ swimming efficiency.

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Lotus coating from NASA repels dirt and dust to protect space equipment.

Benefits

Dust and dirt resistant
Flexible
Durable

Applications

Spacecraft
Space equipment

UN Sustainable Development Goals Addressed

Goal 9: Industry Innovation & Infrastructure

The Challenge

Dust is prevalent on lunar surfaces and can be incredibly damaging to spacecraft and other equipment. It adheres to every surface, including skin and metal, creating a restrictive, friction-like action. Highly abrasive lunar dust has also been known to adhere to astronauts’ spacesuits, causing damage.

Innovation Details

The coating is made from silica, zinc oxide and other oxides, and was originally developed to reduce the need for window cleaning on spacecraft. It is now being developed and tested to perform under multiple conditions, including extreme temperatures, ultraviolet radiation, solar wind, and electrostatic charging. Different variations of the coating may also be developed depending on different needs. For example, a coating that’s applied to spacesuits would need to adhere to a flexible surface, while a coating developed to protect moving parts of the spaceship or lunar equipment needs to be exceptionally durable to resist wear and tear. The team is also looking to add a biocide to the coating, which would kill bacteria that thrive and produce foul odors wherever people are confined to a small space for long periods, like the space station. NASA could also apply the same biocide-infused coating on a planetary lander to prevent Earth-borne bacteria from adhering and potentially contaminating the surface of an extraterrestrial object.

Biological Model

Lotus plants stay dirt-free, an obvious advantage for an aquatic plant living in typically muddy habitats. The surface of the lotus leaf contains microscopic bumps that prevent water molecules from adhering to the surface. Instead, the water rolls right off, and picks up any dirt or oil on the surface of the lotus leaf along the way.

See Related Strategy

Biological Strategy

Surface Allows Self-Cleaning

Sacred lotus

Leaves of the sacred lotus are self-cleaning thanks to hydrophobic microscale bumps.

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