The preserved shell serves as a flexible bending actuator. When combined with synthetic components, it creates a durable, high-performance robot capable of rapid movement (up to 8 Hz) and load-bearing strength of up to 680 g - more than 200 times the weight of the exoskeleton itself.
Background
This work sits within the field of bio-hybrid robotics, which combines biological materials with synthetic systems to overcome the limitations of fully artificial designs. While past efforts have explored living tissues, plants, and even entire animals, those approaches face challenges like ethical concerns, environmental fragility, and limited agility or speed.
More recently, a subfield called "necrobotics," which uses non-living biological components such as spider legs or beetle shells, has gained traction. But necrobotic systems to date have tended to be limited in function, offering low force output, short lifespans, and restricted motion, making them impractical for many real-world applications.
This study takes a different approach. Instead of delicate tissues or limited necrobotic elements, the researchers used crustacean exoskeletons (specifically, langoustine abdomens) as a sustainable and structurally robust alternative. These joints maintain flexibility even after death and offer a naturally optimized form for actuation.
The team developed three augmentation methods to expand the shell’s capabilities:
- Passive base excitation for propulsion in water,
- Tendon-driven actuation using integrated elastomers,
- Protective silicone coatings for durability.
Together, these approaches enabled the creation of versatile, long-lasting robots that can perform heavy lifting, adaptive grasping, and efficient swimming (up to 11 cm/s), pushing necrobotics from proof-of-concept into practical territory.
Material and Methods
The process begins with cleaning and preparing the langoustine’s abdominal exoskeleton. After thawing and boiling to remove soft tissue, the shell is stored in a humid, refrigerated environment to retain flexibility.
To turn the shell into a robotic actuator, researchers added synthetic components. A thermoplastic polyurethane (TPU) elastomer band was sewn along the dorsal side, segmenting the joint into spring-like elements. A braided fishing line was then threaded through the ventral side to act as a tendon, which, when pulled, bends the structure. Adhesives anchor the tendon in place. For enhanced durability and waterproofing, the entire assembly can be coated in silicone.
To guide the design, the team developed a detailed kinematic model treating the abdomen as a series of seven rigid segments (six plus the tail) connected by flexible joints. This model allowed them to simulate how tendon tension alters joint angles and optimize tendon paths before building physical prototypes.
They also constructed full robotic systems to demonstrate real-world applications. One key example was an untethered swimming robot powered by two augmented exoskeletons functioning as fins. These were driven by waterproof servo motors controlled by a microcontroller, and the motion pattern was modeled on aquatic animals. Motion analysis was carried out using video, high-speed photography, and microscopic imaging.
Experimental Findings and Applications
The researchers began by surveying various arthropod joints to find the most suitable structure for robotic actuation.
The langoustine’s abdominal joint stood out for its combination of strength, flexibility, and accessibility as food waste. Its anisotropic stiffness (easy to bend, hard to stretch) and segmented structure allowed for a wide range of motion and impressive load-bearing capacity.
They applied three primary augmentation strategies:
- Base Excitation: By oscillating the base of the shell in a resistive medium like water, the exoskeleton's asymmetric stiffness generated thrust, which is perfect for swimming robots.
- Tendon-Driven Actuation: With the added elastomer and tendon, the joint could perform controlled, high-speed motions up to 8 Hz.
- Silicone Coating: Sealing the shell with silicone dramatically increased operational life from just a few hours to over 38 hours, preventing dehydration and mechanical failure.
Demonstrated prototypes included:
- A swimming robot using two exoskeletons as flapping fins,
- A single-arm manipulator for object handling,
- A two-fingered adaptive gripper capable of grasping irregular shapes.
Each robot highlighted the value of combining biodegradable biological parts with reusable synthetic components. The synthetic actuators and electronics can be removed and reused, while the bio-waste components naturally decompose - supporting a circular, eco-conscious design model.
Conclusion
This study presents a novel and sustainable approach to robotics, where food waste is turned into high-performance, biodegradable actuators. By combining biological materials with synthetic enhancements, the research team addressed key limitations of earlier necrobotic systems.
These bio-hybrid robots show strong potential for real-world use, demonstrating forceful lifting, adaptive manipulation, and efficient aquatic locomotion. The ability to extend lifespan from under five hours to nearly 39 hours, and reuse synthetic parts, adds another layer of sustainability.
This research not only advances the field of bio-hybrid robotics but also offers a compelling example of how waste materials can become part of a circular design strategy for eco-friendly machines.
Journal Reference
Kim, S., Gilday, K., & Hughes, J. (2025). Dead Matter, Living Machines: Repurposing Crustaceans’ Abdomen Exoskeleton for Bio-Hybrid Robots. Advanced Science. DOI:10.1002/advs.202517712. https://advanced.onlinelibrary.wiley.com/doi/10.1002/advs.202517712
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