Rate-dependent adhesion together with limb collaborations facilitate grasshoppers reliable attachment under highly dynamic conditions

Published: 28 October 2023| Version 2 | DOI: 10.17632/fyh8b96g2b.2
Contributor:
yi song

Description

Dynamic attachment is indispensable for animals to cope with unexpected disturbances. Minor attention has been paid to the dynamic performance of insects’ adhesive pads. Through experiments pulling whole grasshoppers off a glass rod at varying speeds, surprising findings emerged. The feet did not always maintain contact but released and then reconnected to the substrate rapidly during leg extension, potentially reducing the shock damage to pads. As the pulling speeds increased from 1 to 400 mm/s, the maximum forces of single front tarsus insects and entire tarsi insects were nearly proportional to the 1/3 power of pulling speeds by 0.11 and 0.29 times, respectively. The force of some individuals could be even 800 times greater than their weight, which is unexpectedly high for smooth insect pads. This work not only helps us to understand the attachment intelligence of animals but is also informative for artificial attachment in extreme situations.

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Steps to reproduce

Grasshoppers (Oxya chinensis, body mass 0.1-1.0g, snout-event length LSV: 2-4cm) captured at Purple Mountain (Nanjing, China) were glued with their dorsal thorax surface to a thin stem, which was subsequently linked to a multi-axis force transducer19. A glass rod (diameter 6mm) was used to mimic convex substrates typical for the habitat of this animal. The substrate was attached to a two-dimensional mobile platform to control its displacement and velocity (Fig.1). The glass rod was first brought towards the animal until its thorax came into contact with it. The stem connecting the insects and the force sensor has a high respect ratio (300), resulting in a low radial stiffness. After touching the glass rod, the insects could freely move their limbs and modify their positions. After several seconds given for the insects to establish an initial contact, we moved the rod away from the animal at different speeds (1mm/s, 10mm/s, 50mm/s, 100mm/s, 200mm/s, 300mm/s or 400mm/s), then collected the force signals through an NI DAQ model (NI 9237, USA) at a rate of 1662 - 5000 Hz and monitored the motion by a high-speed camera (BFS-U3-16S2M-CS, FLIR Systems Inc., USA) at 500fps. At first, eighteen grasshoppers with intact tarsi and 12 grasshoppers with a single front tarsus were tested. Notably, four individuals were tested in both cases. The insects with a single tarsus were allowed to rest for at least 48 hours after the surgery. The rod was cleaned using 75% alcohol before each test to minimise the effects of secretion stains from the insect’s pads.

Institutions

Zhejiang University of Technology

Categories

Biomechanics

Funding

National Natural Science Foundation of China

32101119

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