Summary: Engineers developed a compact robot that reproduces the mechanics behind the mantis shrimp’s exceptionally powerful and rapid strike.
Source: US Army Research Laboratory
Researchers, supported by U.S. Army funding, have built a robotic model that reproduces the mantis shrimp’s punch mechanics. This work reveals how small devices can achieve extreme accelerations and could influence future lightweight, high-power actuators for defense and robotic applications.
Teams at Harvard University and Duke University report their findings in Proceedings of the National Academy of Sciences. Their experiments and modeling illuminate how mantis shrimp use spring-like structures and geometry to generate strikes that accelerate faster than a fired bullet at very small scales.
A single mantis shrimp blow can dismember a crab’s limb or crack a snail’s shell; these crustaceans have even bested octopuses in encounters. Understanding the mechanics behind such extreme, repeated impacts could help engineers design compact actuators that deliver impulsive forces efficiently.
“A latch-released spring is a common engineering motif, but natural systems like the mantis shrimp achieve performance levels that engineered Latch-Mediated Spring Actuators have not matched,” said Dr. Dean Culver, program manager, U.S. Army Combat Capabilities Development Command Army Research Laboratory. “By more closely mimicking the mantis shrimp’s geometry, the team exceeded typical limb accelerations in comparable robotic systems by over tenfold.”
Biologists have long been intrigued by how mantis shrimp produce these ultra-fast strikes. Advances in ultra-high-speed imaging have revealed timing and motion details, yet some aspects of the underlying mechanics remained unclear.
Many small animals and even some plants produce rapid movements by storing elastic energy and releasing it suddenly through a latch mechanism, similar to a mousetrap. In mantis shrimp, two small sclerites embedded in tendon tissue act as the initial latch. But high-speed recordings show a brief delay between sclerite release and the arm’s firing, implying an additional mechanism controls the timing of energy release.
“On ultra-high-speed video, there’s a distinct pause after the sclerites release and before the appendage accelerates,” said Nak-seung Hyun, a postdoctoral fellow at Harvard John A. Paulson School of Engineering and Applied Sciences and co-first author. “It’s like triggering a mousetrap that doesn’t snap immediately—something else is holding the system until a secondary release condition is reached.”
Scientists hypothesized that the appendage’s geometry functions as a secondary, or geometric, latch: after the sclerites initiate unlatching, linkage geometry continues to constrain motion while the spring stores energy, and then releases once the mechanism passes an over-center point. To test this, the research team analyzed the linkage kinematics, built a physical robotic model, and developed a mathematical description of the dynamics.
Their analysis identified four distinct temporal phases during the strike: the latched state with sclerites engaged; the initiation of unlatching; a geometrically constrained phase where linkage geometry maintains the appendage position while energy remains stored; and the final release when the linkage passes the over-center point and the appendage accelerates. This geometric latching both regulates energy flow and amplifies mechanical output.
“The geometric latching process controls how stored elastic energy is released and actually enhances the mechanical performance,” explained Emma Steinhardt, a graduate student at Harvard SEAS and first author. “This explains how organisms generate extremely high acceleration during very short movements like punches.”
The resulting robotic mechanism outperforms previously reported devices at comparable scales. The physically realized mantis shrimp model enabled the team to validate a dynamic mathematical model and to derive a nondimensional performance metric that quantifies potential energy transfer in these systems.
Dr. Sheila Patek, a co-author and biology professor at Duke University, added: “Combining biological observation, a physical prototype, and mathematical modeling pushed us to revise our view of mantis shrimp strike mechanics. More broadly, we discovered how linkage geometry can be used in both living and engineered systems to control extreme, repeatable energy releases.”
This combined experimental and analytical approach offers a template for studying other ultrafast biological mechanisms—such as trap-jaw ants’ rapid mandible closure or frogs’ explosive jumps—and for translating those principles into compact, high-performance actuators for robotics and defense.
“This actuator architecture provides impressive capability for small, lightweight mechanisms that must deliver impulsive forces,” Culver said. “The engineering community and defense research programs still have much to learn from biological systems. Even familiar concepts like spring-loaded actuators can yield new insights when studied across scales and contexts.”
About this robotics research news
Author: Lisa Bistreich-Wolfe
Source: US Army Research Laboratory
Contact: Lisa Bistreich-Wolfe – US Army Research Laboratory
Image credit: Second Bay Studios and Roy Caldwell/Harvard SEAS
Original Research: Closed access. “A physical model of mantis shrimp for exploring the dynamics of ultrafast systems” by Dean Culver et al., PNAS
Abstract
A physical model of mantis shrimp for exploring the dynamics of ultrafast systems
Efficient generation of extremely high-acceleration movement in biology depends on mechanisms that control energy flow and amplify muscle-limited power. Historically, these capabilities were attributed to small elastic recoil systems. The new work shows that linkages can undergo distinct dynamic phases and that geometric latching — where linkage geometry constrains motion until an over-center condition — mediates the release of stored elastic energy and enhances mechanical power output.
Using synchronized biological observations, a synthetic mantis shrimp robot, and a dynamic mathematical model, the researchers identify how linkage dynamics govern energy transfer during ultrafast movements. They demonstrate a 1.5-gram mantis shrimp–scale mechanism that achieves peak velocities over 26 m s−1 in air and 5 m s−1 in water, and they introduce a nondimensional performance metric to compare potential energy transfer across systems.
These findings show that linkage geometry and temporal phase control can be tuned in robotic and mathematical designs, offering a unified framework to understand and replicate fast, repeatable movements in both biological and engineered systems.