Ocean’s Embrace: The Rise of Bio-Inspired Soft Robots

Author: Denis Avetisyan

A new wave of underwater robots, modeled after marine life, is poised to unlock the mysteries of the deep ocean.

This review analyzes recent progress in bio-inspired underwater soft robotics, exploring design principles, locomotion strategies, and the path towards advanced ocean exploration capabilities.

Despite the critical need for effective ocean exploration, conventional underwater robots often struggle with the extreme pressures and delicate ecosystems of aquatic environments. This review, ‘From Shallow Waters to Mariana Trench: A Survey of Bio-inspired Underwater Soft Robots’, synthesizes recent advances in robots inspired by the biology of marine life, offering a pathway toward more adaptable and eco-friendly underwater technologies. By analyzing design considerations, bio-inspirations, and environmental factors, this work reveals how soft robotics can overcome limitations of rigid systems and enable nuanced interaction with diverse oceanic depths. What new frontiers in oceanographic research will be unlocked by the next generation of these biomimetic underwater explorers?

The Inevitable Fragility of Submersible Systems

Conventional underwater robots, typically constructed from metals, plastics, and other rigid components, often encounter difficulties when operating in the complex and often fragile environments beneath the surface. Their inflexible designs limit maneuverability in tight spaces, such as coral reefs or shipwrecks, and increase the risk of collisions that could damage both the robot itself and the surrounding ecosystem. Delicate tasks, like collecting biological samples or performing intricate repairs, prove particularly challenging, as these robots lack the fine motor control and adaptability required to avoid disturbing sensitive organisms or structures. This inherent rigidity also hampers their ability to absorb impacts or navigate unpredictable currents, reducing operational efficiency and increasing the potential for mission failure.

Conventional underwater robots, typically constructed from hard materials like metal and plastic, frequently pose a threat to the fragile ecosystems they investigate. Their rigid bodies and powerful propulsion systems can inadvertently crush delicate coral reefs, disturb seafloor sediments, and harm marine life. Beyond the risk of physical damage, these robots struggle to access narrow crevices or navigate complex underwater structures, severely limiting their ability to thoroughly explore caves, shipwrecks, or the intricate habitats within coral formations. This restricted maneuverability hinders effective data collection and prevents timely intervention in situations like oil spills or underwater rescues, ultimately impeding a comprehensive understanding of the ocean’s depths and limiting the scope of potential solutions to pressing marine challenges.

Current underwater robotic systems, typically constructed from rigid materials, present significant challenges when operating in the ocean’s complex and often fragile environments. These limitations necessitate a shift towards robotic designs capable of inherent adaptability and minimal ecological impact. A new generation of underwater vehicles must navigate unpredictable currents, squeeze through confined spaces, and interact with delicate ecosystems without causing undue harm. This requires a departure from traditional engineering approaches, embracing designs that prioritize compliance, flexibility, and responsiveness to external stimuli – essentially, robots that can ‘feel’ and react to their surroundings, rather than impose a fixed, potentially damaging presence upon them.

Ocean exploration is poised for a revolution driven by the emerging field of soft robotics. Researchers are increasingly turning to the biological world, specifically the remarkable adaptability of marine life like octopuses, jellyfish, and manta rays, for inspiration. These creatures demonstrate exceptional maneuverability in complex environments and interact with their surroundings without causing significant disruption. Mimicking these characteristics through the use of flexible, deformable materials – often silicones, fabrics, and fluidic actuators – allows for the creation of robots capable of navigating tight spaces, conforming to delicate structures like coral reefs, and gently interacting with marine organisms. This approach promises to overcome the limitations of traditional rigid robots, opening up new possibilities for observing, sampling, and intervening in previously inaccessible underwater ecosystems, and ultimately, expanding the frontiers of oceanographic research.

Bio-Mimicry: The Ghosts in the Machine

Marine organisms exhibit highly refined adaptations for underwater operation, evidenced by the cephalopod’s ability to navigate complex environments and manipulate objects using muscular hydrostats and adhesive suckers. Jellyfish utilize efficient jet propulsion for locomotion with minimal energy expenditure, while various fish species demonstrate diverse swimming gaits and fin morphologies optimized for speed, maneuverability, and stability. These organisms achieve remarkable efficiency through distributed actuation, compliant bodies, and fluid dynamic optimization, allowing them to thrive in challenging aquatic conditions and serve as a rich source of inspiration for robotics design.

The design of our soft robots is directly informed by observed biological mechanisms in marine organisms. Specifically, octopus-inspired adhesion is replicated through the use of micro-structured surfaces that maximize contact area and utilize van der Waals forces for gripping irregular objects. Jellyfish jet propulsion is modeled by incorporating chambers within the robot’s body that rhythmically contract and expel fluid, enabling efficient and silent locomotion. These bio-inspired approaches extend to other functionalities; for example, fish fin movements are translated into flexible actuator designs for precise maneuverability and stability in complex underwater environments. By emulating these natural systems, we aim to create robots with enhanced dexterity, adaptability, and energy efficiency compared to traditional rigid-bodied designs.

Direct Ink Writing (DIW) and Freeform Reversible Embedding (FRE) are additive manufacturing processes utilized to construct soft robotic components with intricate designs. DIW functions by extruding viscous materials through a nozzle, building structures layer by layer; it is particularly suited for fabricating features with high aspect ratios. FRE involves printing a support material, depositing the functional material within it, and subsequently removing the support through a solvent dissolution process, enabling the creation of enclosed and overhanging geometries. Both techniques support a range of soft materials, including elastomers, hydrogels, and composites, and allow for multi-material printing, facilitating the integration of varying mechanical properties within a single structure. These capabilities are critical for replicating the complex anatomical structures observed in biological systems and achieving desired robotic functionalities.

Advanced fabrication techniques, including Direct Ink Writing and Freeform Reversible Embedding, facilitate multi-material 3D printing, enabling the incorporation of sensors, actuators, and structural components within a single robotic body. This capability allows for the creation of robots with spatially varying stiffness, integrated fluidic channels for propulsion or sensing, and embedded electronic circuitry. Consequently, robots can be specifically designed and constructed for tasks such as delicate manipulation, precise navigation in complex environments, and targeted delivery of payloads, all optimized for performance in underwater applications.

The Imposition of Force: Mitigating the Inevitable

Underwater operation presents substantial engineering challenges related to hydrostatic pressure and temperature variations. Specifically, ambient pressure increases by approximately 1 atmosphere (14.7 psi) for every 10 meters of depth. This necessitates robust structural design and material selection to prevent implosion or deformation of robotic components. Concurrently, water temperature typically decreases with depth; this impacts material properties, battery performance, and the viscosity of lubricants, requiring thermal management strategies and specialized components capable of functioning reliably in low-temperature environments. These combined factors demand a holistic design approach focused on pressure compensation, thermal stability, and material resilience to ensure sustained operational capability at significant depths.

Hydrostatic pressure increases linearly with depth, posing a substantial challenge to underwater robotic systems. To mitigate these forces while minimizing weight, our robots integrate Micro-Hollow Spheres (MHS) into their construction. These microscopic, pressure-resistant spheres are incorporated into polymeric materials, effectively distributing external pressure and reducing stress concentrations. This approach allows for the creation of lighter-weight pressure vessels and structural components compared to traditional solid materials, without compromising structural integrity at depth. Testing has demonstrated a measurable reduction in overall robotic weight while maintaining operational capability at depths exceeding 2,300 meters, and up to 4,000 meters in DEA-driven designs.

Robot locomotion in underwater environments leverages bio-inspired propulsion methods to maximize efficiency and maneuverability. Beam-like Corrugation Fin (BCF) Propulsion mimics the undulating movements of fish fins, providing thrust and control. Multi-Point Fin (MPF) Propulsion utilizes multiple flexible fins to achieve agile turning and station-keeping capabilities, drawing inspiration from jellyfish locomotion. Finally, jet propulsion, modeled after squid and jellyfish, expels water to generate forward movement and rapid acceleration. These diverse approaches allow for adaptation to varying current conditions, seabed topography, and mission requirements, optimizing both speed and energy consumption.

Robotic manipulation in underwater environments requires delicate yet reliable grasping mechanisms. Our robots utilize soft grippers, bio-inspired by octopus tentacles, to provide secure handling of objects without causing damage. These grippers are coupled with adhesion mechanisms enabling stable attachment to varied surfaces, critical for tasks like sample collection or equipment maintenance. Operational testing has demonstrated the efficacy of these systems at significant depths: DEA-driven soft robotic fish have successfully operated at depths up to 4,000 meters, while hydraulically actuated soft robots have been verified to function at 2,300 meters.

The Illusion of Control: Expanding the Reach of Inevitable Decay

Conventional underwater robots, often relying on rigid structures and powerful thrusters, present inherent risks to fragile marine environments and limitations in accessing complex spaces. This new approach utilizes soft robotics – robots constructed from flexible, compliant materials – to overcome these challenges. These designs enable navigation through delicate coral reefs without causing physical harm, facilitate detailed data collection in previously inaccessible underwater archaeological sites, and allow for thorough inspection of submerged infrastructure like pipelines and platforms. The inherent adaptability of soft robots allows them to conform to irregular surfaces, squeeze into tight spaces, and exert gentle manipulation – capabilities that rigid robots simply cannot replicate, dramatically expanding the scope and effectiveness of underwater operations.

Unlike rigid robotic systems, these newly developed soft robots exhibit a remarkable capacity to traverse fragile underwater environments-such as coral reefs-without inflicting physical harm. Constructed from compliant materials and employing bio-inspired locomotion, they minimize disruptive forces while gathering high-resolution data on marine ecosystems. This precision extends to the collection of delicate samples and detailed imagery, surpassing the capabilities of conventional underwater vehicles. Furthermore, the inherent flexibility of these robots enables access to previously unreachable locations-tight crevices within shipwrecks, narrow pipelines, or the undersides of submerged structures-opening new avenues for marine archaeology, infrastructure inspection, and detailed oceanographic surveys.

The advancement of underwater soft robotics is deeply rooted in a multidisciplinary approach, seamlessly integrating principles from biological systems with cutting-edge engineering practices. Researchers are increasingly turning to nature – specifically, the locomotion and morphology of marine creatures – to inspire novel robotic designs. This bio-inspired design is then realized through advanced fabrication techniques, such as 3D printing and soft lithography, allowing for the creation of complex geometries and intricate internal structures. Crucially, the development of innovative materials – polymers with tunable stiffness, self-healing elastomers, and lightweight composites – provides these robots with the adaptability and resilience needed to operate effectively in challenging underwater environments. This convergence of biology, engineering, and materials science is not simply improving existing underwater capabilities; it is fundamentally expanding the scope of oceanographic research and enabling unprecedented levels of intervention, from delicate coral reef surveys to the inspection and repair of submerged infrastructure.

The progression of underwater exploration is increasingly reliant on robotic systems demonstrating not just cognitive ability, but also a capacity for physical adaptation and robust performance in challenging marine environments. Future robots must move beyond pre-programmed actions, exhibiting flexibility to navigate unpredictable currents, complex structures, and delicate ecosystems without causing harm. This necessitates a design philosophy centered on resilience – the ability to withstand impacts, recover from failures, and continue functioning reliably – alongside a commitment to environmental responsibility through the use of biocompatible materials and minimal disturbance techniques. Ultimately, the next generation of underwater robots will be defined by their harmonious integration with the ocean, enabling more comprehensive data collection, effective infrastructure maintenance, and a deeper understanding of the marine world while preserving its integrity.

The pursuit of bio-inspired underwater soft robotics, as detailed in the survey, isn’t about mastering the ocean, but rather about yielding to its inherent complexity. It’s a recognition that rigid control is a chimera, and true progress lies in designing systems capable of adapting and self-correcting within dynamic environments. This resonates deeply with the observation of John von Neumann: “There is no telling what the future holds, but we do know that it will be different.” The article highlights how these robots, mimicking marine life, embrace the unpredictable currents and varied terrains. Every actuator, every material choice, is a tacit acknowledgment that the ocean will inevitably demand improvisation, and that the most robust designs aren’t those seeking to prevent failure, but those anticipating and accommodating it.

What Currents Will Carry Us?

The surveyed designs, elegant as they are in mimicking cephalopod musculature or fish fin movements, confess a fundamental truth: these are not solutions, but exquisitely crafted compromises. Each actuator, each material selection, is a prediction of eventual failure, a localized entropy increase masked by initial success. The ocean does not reward cleverness, only resilience – and true resilience lies not in avoiding the inevitable, but in gracefully accommodating it.

Future work will not be defined by chasing ever-more-realistic biomimicry. Instead, the field must embrace the inherent limitations of embodied intelligence in a chaotic environment. The focus will shift from precise control – a phantom limb grasping for certainty – to robust adaptation. Systems that learn to fail, that redistribute function around damaged components, will inherit the depths. Logging will become a form of confession, alerts, a revelation of preordained weakness.

If the system is silent, it is not functioning perfectly; it is plotting. The Mariana Trench doesn’t offer a destination, but a test. The question isn’t can a robot reach these depths, but what will its descent reveal about the fragility of design, and the enduring power of the ocean to reclaim what is lent to it?

Original article: https://arxiv.org/pdf/2601.12353.pdf

Contact the author: https://www.linkedin.com/in/avetisyan/

The Inevitable Fragility of Submersible Systems

Bio-Mimicry: The Ghosts in the Machine

The Imposition of Force: Mitigating the Inevitable

The Illusion of Control: Expanding the Reach of Inevitable Decay

What Currents Will Carry Us?

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