Some insects and plants are what are termed “power-amplified organisms.” That is, they have found creative ways to slowly store elastic energy and release it quickly to create extremely fast motion that is not possible with muscle power alone. Examples of this include the trap-jaw ant that can store elastic energy in its jaw for 400 milliseconds (ms) and then close it in just 0.6 ms, 600 times faster. The Venus flytrap plant stores energy and snaps its jaw shut in about 100 ms. Amazingly fast motion for an organism without muscles! Another insect in this extreme motion category is the click beetle. This beetle stores energy in its thoracic hinge and then unbends with a click and a release of energy that causes it to jump extremely quickly. Although the kinetic aspects of the click beetle’s jump have been studied, the dynamics of how the ultra-fast clicking or bending movement is generated are less well understood because it has been difficult to capture the details of the super-fast action. Now, with data generated thanks to extreme-brightness x-rays from the U.S. Department of Energy’s Advanced Photon Source (APS), researchers used high-speed synchrotron x-ray imaging to analyze the dynamics of the click beetle’s unique spring and latch system. The work, published in the Proceedings of the National Academy of Sciences of the United States of America, provides tools for others interested in studying extreme motion in natural systems and also offers insights into how these systems work that may be used for the design of insect-inspired robots.
The work started with collection of four candidate click beetles from the University of Illinois Urbana-Champaign natural area and preparation of the motion capture set-up. The team of researchers from the University of Illinois at Urbana–Champaign, Virginia Tech, and Argonne National Laboratory used visible-light imaging to monitor the beetles and make sure the observed movements were clicks. High-speed synchrotron x-ray imaging at the Argonne X-ray Science Division Imaging Group’s 32-ID x-ray beamline at the APS allowed for viewing and recording of the internal structures of the insect (see Fig. 1, panels A and B). (The APS is an Office of Science user facility at Argonne.) Analysis of the high-speed synchrotron x-ray images allowed the researchers to identify and categorize the click beetles’ motion into three phases: latching, loading, and energy release.
The latching phase involves the beetle rotating its head around a hinge, leaving the head angled upward compared to the back part of its body and deforming an area of soft cuticle while in this braced position (see A in the figure). This position is held because the peg in the hinge (see B in the figure) moves out of the cavity where it normally rests and latches onto what is called the mesosternal lip. Once latched, the beetle stays in this braced position to “load” the elastic energy in the latch. The beetles in the experiment did this for 33 ms to 243 ms.
Next, the soft cuticle displaces in less than 1 ms and the peg slips, causing rapid release of the stored energy through an elastic recoil that provides the energy for the fast-motion jump (see C in the figure). This release causes the beetle’s head to move back to its normal position, and generates the click sound associated with the jump. The peg swings back into the cavity and then oscillates, very much like a spring that is tethered at one end, for a total energy release phase lasting ~10 ms.
Analysis of the kinematics of the elastic recoil in the first part of the energy release stage showed that the velocity of the release is 1.8 meters per second or 1,000 peg lengths per second with an acceleration that is 530 times the natural acceleration due to gravity. That is very fast indeed! In addition, analysis of the energy release (through the peg oscillations) as a one-degree-of-freedom system allowed the team to calculate the damping and elastic forces associated with the release. These results demonstrate how effective these power-amplified organisms are at using elastic energy storage to provide the speed and force to overcome the limitations of their muscles.
Understanding the forces governing these complex natural systems will enable the creation of insect-inspired robots capable of super-fast motion that can be used for various tasks or as research platforms to understand more about how nature achieves these amazing feats.
― Sandy Field
See: Ophelia Bolmin1, John J. Socha2, Marianne Alleyne1, Alison C. Dunn1, Kamel Fezzaa3, and Aimy A. Wissa1, “Nonlinear elasticity and damping govern ultrafast dynamics in click beetles,” Proc. Natl. Acad. Sci. U.S.A. 118(5), e2014569118 (2021). DOI: 10.1073/pnas.2014569118
Author affiliations: 1University of Illinois at Urbana–Champaign, 2Virginia Tech, 3Argonne National Laboratory
Correspondence: * obolmin2@illinois.edu, ** awissa@illinois.edu
We thank Alex L. Deriy for his help with the experimental setup at Argonne National Laboratory. The use of the APS was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract DE-AC02-06CH11357. This research used resources of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. DOE Office of Science by the Argonne National Laboratory under contract no. DE-AC02-06CH11357.
Click beetle photo on home page: Click beetle photo: Katja Schulz https://bit.ly/3t71s6j
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