Alternative Transparent Coating Lotus Suitable for Optics with Vacuum Deposition Layer

This durable, transparent, nano-textured coating can be applied via a wet chemistry process to variety of rigid and flexible surfaces by spin coating, brush application, or spray application, making it applicable for many purposes beyond space flight and aeronautical applications. The coatings unique nano-textured surface and overcoat reduces surface energy and contact surface area, giving the coating anti-contamination and self cleaning properties that minimize dust, liquid, and ice accumulation on its surface, similar to a leaf on the Lotus plant. The coating is low outgassing, stable in vacuum, and can survive harsh spaceflight environments. Depending on requirements, the Lotus Coating can be tailored to fit the specific needs of a project or customer. This customization makes the Lotus system far more adaptive, allowing for a more diverse range of applications.

The following methods can be used individually or in combination to generate superhydrophobic surfaces: Synthesis of novel copolyimide oxetanes with unique surface properties The technology is the synthesis of a polyimide coating or film with a modified surface chemistry shown in Figure 1. A minor amount of an oxetane reactant containing fluorine is added to the polyimide, and the oxetane preferentially migrates to the surface, enabling relatively high concentrations of fluorine at the surface, without compromising the functional performance of the bulk of the polymide coating/film. The copolymers exhibit mitigation of particle adhesion and fouling from exposure to various particulate and biological contaminants and exhibit reduced surface energy and increased surface fluorine content at extremely low oxetane loadings relative to the imide matrix (see Figure 2). Additionally, the short fluorinated carbon chains do not bioaccumulate, reducing the environmental impact of these materials. Modifying surface energy via laser ablative surface patterning This method uses a laser to create nanoscale patterns in the surface of a material to increase the hydrophobicity of the surface (see Figure 2). The benefits of hydrophobic surfaces include decreases in friction and increases in self-cleaning properties. This is an advantageous method of surface modification because it is fast and single-step, promises to be scalable, requires no chemicals, could be applied to a variety of materials, and does not require a planar surface for patterning.

Previous techniques for measuring dust accumulation, mostly de-pendent on solar cell output, were limited by their inability to distin-guish dust effects from other factors like incident radiation and radiation damage. These techniques were less effective in environ-ments with inconsistent solar flux and future missions, such as the Lunar South Pole, and lacked versatility in adapting to diverse envi-ronmental conditions. The PADS device embraces success over these challenges, and reflects enhanced features over prior iterations to also allow for space environments. Key design features begin with the customizable mechanical design of the PADS device for use in space environments, heaters with imbedded precision temperature sensors, a selected optical coating for the device coupons that are calibrated on high-fidelity thermal modeling and validated with ground-based testing to simulate the space environment of interest (including dusting with simulants representative of the planetary-body soil/regolith), and a control circuit for precision control/matching of the thermal inputs to the sensor via the heaters. Retainers with mount isolators are implemented to ensure the stacked layers within the device do not dislodge during high vibration or gravitational loads during launch. For operation, the PADS device is installed at the point of interest (e.g., space vehicle surface, extraterrestrial equipment) to quantify dust accumulation. Power and data transfer are done through cabling to the space vehicle system or can be provided standalone. A control circuit/algorithm adjusts the power to the heaters to precisely match the temperature setpoints. Ground testing in the simulated space environment conditions of interest creates a calibration plot of effec-tive emittance versus dust density, and allows determination of the degradation in emittance as the dust increases on the surface. Testing on the PADS device has been completed in a simulated lunar environment and data has been collected to enable sensor calibration for its use on the Moon. It is currently poised for integration into a lander for flight testing. Although the PADS device is intended for use in a burgeoning space industry and requisite environments – but given that the PADS device is partially comprised of programmable sensors in conjunction with optically coated coupons that can be tailored for custom use - it or its constituent components could be modified for terrestrial applications such as surface dust monitoring on photovoltaic panels or potentially combustible dust on various industrial surfaces.

The smart coating is based on the controlled release of corrosion inhibitors and indicators from specially formulated microcapsules and particles pioneered by NASA (patent allowed). The coating detects corrosion in its early stages, inhibits it, and/or repairs the coating. The onset of corrosion triggers the release of compounds that indicate and inhibit corrosion. Mechanical damage to the coating triggers the release of film-forming compounds to repair the damage. In practice, the corrosion-responsive microcapsules detect the chemical changes that occur when corrosion begins and respond by releasing their contents. A corrosion indicator will identify the affected region with a color change, and healing agents and corrosion inhibitors help mitigate the corrosion. The microcapsules can be tailored for incorporation into different coating systems. This multifunctional coating system will reduce maintenance cost and improve safety by preventing catastrophic corrosion failures. The coating can reduce infrastructure life cycle costs by extending the life of corrosion-susceptible structures and components, reduce inspection times of structures, and reduce the level of repair for corrosion-affected areas.

The new transparent EDS technology is lighter, easier to manufacture, and operates at a lower voltage than current transparent EDS technologies. The coating combines an optimized electrode pattern with a vapor deposited protective coating of SiO2 on top of the electrodes, which replaces either polymer layers or manually adhered cover glass (see figure on the right). The new technology has been shown to achieve similar performances (i.e., over 90% dust clearing efficiency) to previous technologies while being operated at half the voltage. The key improvement of the new EDS coating comes from an innovative method to successfully deposit a protective layer of SiO2 that is much thinner than typical cover glass. Using vapor deposition enables the new EDS to scale more successfully than other technologies that may require more manual manufacturing methods. The EDS here has been proven to reduce dust buildup well under vacuum and may be adapted for terrestrial uses where cleaning is done manually. The coatings could provide a significant improvement for dust removal of solar cells in regions (e.g., deserts) where dust buildup is inevitable, but water access is limited. The EDS may also be applicable for any transparent surface that must remain transparent in a harsh or dirty environment. The related patent is now available to license. Please note that NASA does not manufacturer products itself for commercial sale.