Biomechanics of the stick insect antenna: Damping properties and structural correlates of the cuticle

Self Cite

101

124

SUMMARYInsect cuticle is one of the most common biological materials, yet very little is known about its mechanical properties. Many parts of the insect exoskeleton, such as the jumping legs of locusts, have to withstand high and repeated loading without failure. This paper presents the first measurements of fracture toughness for insect cuticle using a standard engineering approach. Our results show that the fracture toughness of cuticle in locust hind legs is 4.12MPam 1/2 and decreases with desiccation of the cuticle. Stiffness and strength of the tibia cuticle were measured using buckling and cantilever bending and increased with desiccation. A combination of the cuticleʼs high toughness with a relatively low stiffness of 3.05GPa results in a work of fracture of 5.56kJm -2 , which is amongst the highest of any biological material, giving the insect leg an exceptional ability to tolerate defects such as cracks and damage. Interestingly, insect cuticle achieves these unique properties without using reinforcement by a mineral phase, which is often found in other biological composite materials. These findings thus might inspire the development of new biomimetic composite materials.

Section: Effect Of Water Content On Mechanical Propertiessupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Fracture toughness of locust cuticle

Dirks

Taylor

2012

Self Cite

101

124

“…The dynamic response showed no signs of directional anisotropy when comparing dorsal, ventral, lateral and medial planes. This directional isotropy corroborates findings in stick insect antennae (Dirks and Dürr, 2011) and is consistent with our static bending results. The variance in frequencies observed in the present study can mainly be attributed to different initial deflection angles.…”

Section: The Antenna Rapidly Damps Oscillationssupporting

confidence: 93%

Mechanical processing via passive dynamic properties of the cockroach antenna can facilitate control during rapid running

Mongeau

Demir

Dallmann

et al. 2014

The integration of information from dynamic sensory structures operating on a moving body is a challenge for locomoting animals and engineers seeking to design agile robots. As a tactile sensor is a physical linkage mediating mechanical interactions between body and environment, mechanical tuning of the sensor is critical for effective control. We determined the open-loop dynamics of a tactile sensor, specifically the antenna of the American cockroach, Periplaneta americana, an animal that escapes predators by using its antennae during rapid closed-loop tactilely mediated course control. Geometrical measurements and static bending experiments revealed an exponentially decreasing flexural stiffness (EI) from base to tip. Quasi-static experiments with a physical model support the hypothesis that a proximodistally decreasing EI can simplify control by increasing preview distance and allowing effective mapping to a putative control variable -body-to-wall distance -compared with an antenna with constant EI. We measured the free response at the tip of the antenna following step deflections and determined that the antenna rapidly damps large deflections: over 90% of the perturbation is rejected within the first cycle, corresponding to almost one stride period during high-speed running (~50 ms). An impulse-like perturbation near the tip revealed dynamics that were characteristic of an inelastic collision, keeping the antenna in contact with an object after impact. We contend that proximodistally decreasing stiffness, high damping and inelasticity simplify control during high-speed tactile tasks by increasing preview distance, providing a one-dimensional map between antennal bending and body-to-wall distance, and increasing the reliability of tactile information.

“…a decreasing stiffness profile -can help resolve finer details (higher spatial frequencies) during a contour extraction task (Demir et al, 2010). Studies on the biomechanics of arthropod antennae such as in crayfish (Sandeman, 1989) and stick insects (Dirks and Dürr, 2011) are consistent with a decreasing flexural stiffness from base to tip. While from geometry we expect similar mechanical properties in P. americana (Kapitskii, 1984), further mechanical testing will be necessary.…”

Section: Physical Model Of Antenna Provides Insight On Preview Distancementioning

confidence: 94%

Locomotion- and mechanics-mediated tactile sensing: antenna reconfiguration simplifies control during high-speed navigation in cockroaches

Mongeau

Demir

Lee

et al. 2013

SUMMARYAnimals can expend energy to acquire sensory information by emitting signals and/or moving sensory structures. We propose that the energy from locomotion itself could permit control of a sensor, whereby animals use the energy from movement to reconfigure a passive sensor. We investigated high-speed, antenna-mediated tactile navigation in the cockroach Periplaneta americana. We discovered that the passive antennal flagellum can assume two principal mechanical states, such that the tip is either projecting backward or forward. Using a combination of behavioral and robotic experiments, we demonstrate that a switch in the antenna's state is mediated via the passive interactions between the sensor and its environment, and this switch strongly influences wall-tracking control. When the tip of the antenna is projected backward, the animals maintain greater body-to-wall distance with fewer body collisions and less leg-wall contact than when the tip is projecting forward. We hypothesized that distally pointing mechanosensory hairs at the tip of the antenna mediate the switch in state by interlocking with asperities in the wall surface. To test this hypothesis, we performed laser ablation of chemo-mechanosensory hairs and added artificial hairs to a robotic antenna. In both the natural and artificial systems, the presence of hairs categorically increased an antenna's probability of switching state. Antennal hairs, once thought to only play a role in sensing, are sufficient for mechanically reconfiguring the state of the entire antenna when coupled with forward motion. We show that the synergy between antennal mechanics, locomotion and the environment simplifies tactile sensing.