Suitability of Silicone for Soft-Robotic Exploration of Terrestrial and Extraterrestrial Ocean Worlds

Abstract

This work revisits relevant mechanical and chemical properties of silicone rubber — Ecoflex in this study — to assess its suitability and viability for use in soft-robotic explorer construction and subsequent deployment and as a sealant for communication beacons, sensor pods, and other electronics in extreme planetary liquid environments, such as the depths of Earth’s oceans and extraterrestrial ocean worlds. Strain at a range of temperatures, as an indicator for operational durability, was tested under various endpoint clamp forces for several compound ratios. The temperature range at which silicone rubber remains pliable was assessed to determine its deployability. The re-binding property of cured silicone rubber samples with newly curing samples was investigated for its potential for additive manufacturing in soft robotics. Finally, the dissolution resistance, non-polarity, and electrical non-conductivity of silicone rubber were studied to assess its suitability for sealing electronics to be submerged in the salt water of both ocean and saturated salinity, as well as in hydrocarbon liquids. This work highlights critical aspects of silicone rubber for use in the construction, coating, and deployment of future soft robotic extraterrestrial liquid body explorers: The chosen silicone rubber Ecoflex is an electrically non-conducting sealant and pliable soft robotics material for temperatures above 50 °C, deployable in earthly extreme aqueous environments. Moreover, this work lays the foundation, albeit likely with different (silicone) rubbers/polymers due to much lower temperatures, for the robotic exploration of extraterrestrial liquid environments on ocean worlds, such as the hydrocarbon lakes on Titan and the putative subsurface oceans on Europa, Titan, and Enceladus.