Multisensory Soft Robotic Explorer With a Biologically Inspired, Shape-Memory Alloy-Driven, Dual-Action Propulsion System for Extreme Aqueous Environments

Abstract

The final frontier of extraterrestrial planetary exploration is the exploration of subsurface environments, such as caves and oceans. Inparticular, the existence of subsurface oceans on celestial bodies – e.g., Europa and Enceladus – known as ocean worlds has been backed by varying levels of evidence since the 1980s, but there has been no direct confirmation as of yet. Such environments are largely shielded from radiation, and in combination with the hypothesized presence of water, are prime candidate environments for finding extant or extinct life. However, the in-situ exploration of these subsurface oceans at hypothesized depths ranging anywhere from 1km to 100km (including terrestrial oceans up to 11km) necessitates disruptive advances in the design of robotic subsurface explorers capable of operating in such extreme aqueous environments, i.e., at such depths/pressures and temperatures. The field of underwater exploration systems is currently dominated by rigidly framed robots whose designs convey a philosophy of having widearenas in which to move about without interruption. However, such a design ideology is less suitable for confined environments, which might limit a rigid explorer’s ability to navigate, and for extreme environments characterized by high pressures and low temperatures, i.e., extreme aqueous environments, such as Titan’s hydrocarbon lakes. Limited efforts have gone towards designing underwater exploration systems with a soft robotics philosophy, which overcomes the limitations of stiff robotic systems and permits more flexibility in underwater exploration. It is in this soft robotics underwater exploration context that the research of this Ph.D.-Thesis takes root: The design of a multisensory soft robotic explorer with a biologically inspired propulsion system for extreme aqueous environments using silicone rubber, thereby reframing its flexibility in a space which physically hinders the use of commonly employed pneumatic or hydraulic drivers. Taking inspiration from various biological sources including jellyfish, squid, octopus, and even the chambers of the human heart, this work presentsthe prototype for an autonomous underwater soft robotic exploration system featuring a novel propulsion system for navigation that is devoid of any (electric) motors or actuators and thus well-suited for extreme aqueous environments. The soft robotic explorer features onboard sensors for depth/pressure and temperature, and an onboard computer in charge of data recording, navigation, and propulsion control. Silicone rubber, widely used in other soft robotics applications due to its flexibility, forms the overall shell of the soft robot and its thrusters, and encases the onboard electronics. In addition, its electric inertness to permit direct electronics enclosure, resistance to saltwater degradation, maintained flexibility in low temperatures, and suitability for an additive manufacturing process were reconfirmed. The resulting soft robotic explorer system is fully sealed for all electrical components and fully open in its propulsion design.