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Dual spring force couples yield multifunctionality and ultrafast, precision rotation in tiny biomechanical systems

Citation

Patek, S. N. et al. (2022), Dual spring force couples yield multifunctionality and ultrafast, precision rotation in tiny biomechanical systems, Dryad, Dataset, https://doi.org/10.5061/dryad.c2fqz61bs

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 radians/sec (470,000 rpm) when powered by spring propulsion. Once spring propulsion ended, the mandibles moved with unconstrained and oscillatory rotation.  We term this mechanism “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-degree 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.

Methods

See associated publication for all Methods information.

Usage Notes

See associated publication for all modeling and analysis software information.  Matlab and Mathematica software may be needed to run the software, but all files can be read using any text reader and transferred to a different language if needed.

Funding

U.S. Army Research Office, Award: W911NF-15-1- 0358

Royal Society, Award: UF120507

NSF/CIHR/DFG/FRQ/UKRI-MRC Next Generation Networks for Neuroscience Program