School of Life Sciences , University of Lincoln, Lincoln LN6 7TS, UK.
Department of Mechanical and Aerospace Engineering, University at Buffalo, Buffalo, NY 14260, USA.
J Exp Biol. 2022 Jul 15;225(14). doi: 10.1242/jeb.244077. Epub 2022 Jul 21.
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.
小型生物利用推进弹簧而不是肌肉来反复驱动高加速度运动，即使它们受到微小位移的限制和惯性力的限制。通过整合一个大型运动学数据集、弹性回弹测量、能量数学建模和动态数学建模，我们测试了捕蝇草蚂蚁（Odontomachus brunneus）如何利用多个弹性结构在小尺度上实现超快速和精确的下颚旋转。我们发现，O. brunneus 通过使用两个弹簧的有趣配置在上颚上产生扭矩：它们的弹性头壳回弹以推动，而回弹的肌肉-小翼单元则拉动每一个下颚。当下颚由弹簧推进提供动力时，它们可以实现精确的、平面的、圆形的轨迹，最高速度可达 49100 rad s-1（470000 rpm）。一旦弹簧推进结束，下颚就会以不受约束和振荡的方式旋转。我们将这种机制称为“双弹簧力偶”，即两个弹簧在两个位置提供能量以产生扭矩。动态建模表明，双弹簧力偶减少了对关节约束的需求，从而减少了耗散关节损失，这对于重复使用超快速、小系统至关重要。双弹簧力偶使多功能性成为可能：捕蝇草蚂蚁使用相同的机械系统，通过推进弹簧产生超快速、平面的打击，并且使用肌肉而不是弹簧直接驱动运动，从而产生缓慢的、多自由度的下颚操纵。双弹簧力偶在其他系统中也有发现，并且可能在生物学中广泛存在。这些原则可以被纳入微机器人中，以提高超快速系统的多功能性、精度和寿命。
