Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801;
Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA 24061.
Proc Natl Acad Sci U S A. 2021 Feb 2;118(5). doi: 10.1073/pnas.2014569118.
Many small animals use springs and latches to overcome the mechanical power output limitations of their muscles. Click beetles use springs and latches to bend their bodies at the thoracic hinge and then unbend extremely quickly, resulting in a clicking motion. When unconstrained, this quick clicking motion results in a jump. While the jumping motion has been studied in depth, the physical mechanisms enabling fast unbending have not. Here, we first identify and quantify the phases of the clicking motion: latching, loading, and energy release. We detail the motion kinematics and investigate the governing dynamics (forces) of the energy release. We use high-speed synchrotron X-ray imaging to observe and analyze the motion of the hinge's internal structures of four specimens. We show evidence that soft cuticle in the hinge contributes to the spring mechanism through rapid recoil. Using spectral analysis and nonlinear system identification, we determine the equation of motion and model the beetle as a nonlinear single-degree-of-freedom oscillator. Quadratic damping and snap-through buckling are identified to be the dominant damping and elastic forces, respectively, driving the angular position during the energy release phase. The methods used in this study provide experimental and analytical guidelines for the analysis of extreme motion, starting from motion observation to identifying the forces causing the movement. The tools demonstrated here can be applied to other organisms to enhance our understanding of the energy storage and release strategies small animals use to achieve extreme accelerations repeatedly.
许多小动物利用弹簧和闩锁来克服肌肉的机械功率输出限制。叩头虫利用弹簧和闩锁在胸铰链处弯曲身体，然后极快地伸直，从而产生咔嗒声。在不受约束的情况下，这种快速的咔嗒声会导致跳跃。虽然跳跃运动已经被深入研究，但使快速伸直的物理机制尚未被研究。在这里，我们首先确定并量化了咔嗒声运动的阶段：闩锁、加载和能量释放。我们详细描述了运动运动学，并研究了能量释放的控制动力学（力）。我们使用高速同步加速器 X 射线成像来观察和分析四个样本的铰链内部结构的运动。我们提供了软壳在铰链中通过快速回弹有助于弹簧机制的证据。通过频谱分析和非线性系统识别，我们确定了运动方程，并将甲虫模型化为非线性单自由度振荡器。二次阻尼和突跳屈曲被确定为主要的阻尼力和弹性力，分别在能量释放阶段驱动角位置。本研究中使用的方法为从运动观察到确定引起运动的力的极端运动分析提供了实验和分析指南。这里展示的工具可以应用于其他生物体，以增强我们对小动物用于实现反复极端加速度的能量存储和释放策略的理解。
