Search for: All records

Ultrafast organisms exemplify how biological systems manipulate and control energy to generate spectacularly diverse movements. Across the tree of life, repeateduse, ultrafastmovements are driven by springs and controlled by opposing, latch-like forces. We focus on the biomechanical processes that sequentially reduce the duration of each energetic event to yield intense mechanical power density - often external to the organism to reduce self-damage.We leverage a new model system of young, transparent mantis shrimp (Stomatopoda) to quantify the timing and dynamics of muscle contraction, storage of elastic potential energy, latch engagement and release, and the levers and linkages that transform elastic potential to kinetic energy of their ultrafast strikes. We examine how the convergence of physical limits and inherent evolutionary integration of biomechanical structures yield generalizable features of energy storage and energy delivery, such that these mechanisms occur exclusively in small systems.While ultrafast organisms have historically been invisibly fast to science, today’s technology and new model systems have unveiled effective experimental approaches to quantifying energetic control and manipulation in these intriguing biomechanical systems. 

ABSTRACT Small organisms use propulsive springs rather than muscles to repeatedly actuate high acceleration movements, even when constrained to tiny displacements and limited by inertial forces. Through integration of a large kinematic dataset, measurements of elastic recoil, energetic math modeling and dynamic math modeling, we tested how trap-jaw ants (Odontomachus brunneus) utilize multiple elastic structures to develop ultrafast and precise mandible rotations at small scales. We found that O. brunneus develops torque on each mandible using an intriguing configuration of two springs: their elastic head capsule recoils to push and the recoiling muscle–apodeme unit tugs on each mandible. Mandibles achieved precise, planar, circular trajectories up to 49,100 rad s−1 (470,000 rpm) when powered by spring propulsion. Once spring propulsion ended, the mandibles moved with unconstrained and oscillatory rotation. We term this mechanism a ‘dual spring force couple’, meaning that two springs deliver energy at two locations to develop torque. Dynamic modeling revealed that dual spring force couples reduce the need for joint constraints and thereby reduce dissipative joint losses, which is essential to the repeated use of ultrafast, small systems. Dual spring force couples enable multifunctionality: trap-jaw ants use the same mechanical system to produce ultrafast, planar strikes driven by propulsive springs and for generating slow, multi-degrees of freedom mandible manipulations using muscles, rather than springs, to directly actuate the movement. Dual spring force couples are found in other systems and are likely widespread in biology. These principles can be incorporated into microrobotics to improve multifunctionality, precision and longevity of ultrafast systems.