Silver Coated Ionic Liquids for Liquid Phase Space Optics

Origami inspired deployment of space telescope mirrors is a complex approach to increasing the aperture size of these orbital science assets with potential multi single point failures, see the James Webb Space Telescope (JWST). The size, mass, and general handling issues of these mirrors have been a cost, time, and energy-intensive challenge to space agencies like NASA. To address these challenges, a novel approach is needed. Herein we report the development of an alternative multiwavelength reflecting-based mirror that in theory is geometrically independent from these orbital assets.

Our research demonstrated the successful coating of an ionic liquid with silver nanoparticles under UV light exposure to form a reflective, mirroring surface. Ionic liquids are salts with extremely low melting points and negligible vapor pressure. These properties render them ideal candidates for liquid deployment in space without mass loss in vacuum or freezing in ultra-low temperatures. The general procedure includes using candidate ionic liquids such as 1-ethyl-3-methylimidazolium ethyl sulfate ([EMIM][ESO₄]) and dissolving a silver containing salt, silver tetrafluoroborate (AgBF₄), with a photoinitiator diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) followed by UV light exposure. This resulted in the self-assembly of silver nanoparticles at the surface of the ionic liquid caused by the photoreduction of Ag⁺ cations by free radicals from the homolytic cleavage of the photoinitiator, forming a smooth and reflective surface. The liquid mirror exhibits reflective and self-healing properties while maintaining stability in vacuum conditions. Additionally, there is potential for the introduction of polymeric chemistry to enable the tunability of the mirror viscosity. The outcome of this research demonstrates alternatives to conventionally used space telescope mirrors applicable to the next generation observatory.