Dynamics of rapid vertical climbing in cockroaches reveals a template

Fibrillar, or ''hairy,'' adhesives have evolved multiple times independently within arthropods and reptiles. These adhesives exhibit highly desirable properties for dynamic attachment, including orientation dependence, wear resistance, and self-cleaning. Our understanding of how these properties are related to their fibrillar structure is limited, although theoretical models from the literature have generated useful hypotheses. We survey the morphology of 81 species with fibrillar adhesives to test the hypothesis that packing density of contact elements should increase with body size, whereas the size of the contact elements should decrease. We test this hypothesis in a phylogenetic context to avoid treating historically related species as statistically independent data points. We find that fiber morphology is better predicted by evolutionary history and adhesive mechanism than by body size. As we attempt to identify which morphological parameters are most responsible for the performance of fibrillar adhesives, it will be important to take advantage of the natural variation in morphology and the potentially suboptimal outcomes it encompasses, rather than assuming evolution to be an inherently optimizing process.contact splitting ͉ fibrillar adhesion ͉ setae ͉ phylogeny ͉ independent contrasts

Section: Resultsmentioning

confidence: 99%

Phylogenetic analysis of the scaling of wet and dry biological fibrillar adhesives

Peattie

Full

2007

“…We proposed more broadly that the appropriate modulation of the two waves was in fact a control "template," defined as a behavior that contains the smallest number of variables and parameters that exhibits a behavior of interest (12). Templates provide relatively simple targets for motion control and feedback responses (13) and have proved useful to understand locomotion of legged runners (14), climbers (15), and undulatory swimmers (16).…”

Section: Significancementioning

confidence: 99%

Modulation of orthogonal body waves enables high maneuverability in sidewinding locomotion

Astley

Gong

Dai

et al. 2015

Self Cite

110

Many organisms move using traveling waves of body undulation, and most work has focused on single-plane undulations in fluids. Less attention has been paid to multiplane undulations, which are particularly important in terrestrial environments where vertical undulations can regulate substrate contact. A seemingly complex mode of snake locomotion, sidewinding, can be described by the superposition of two waves: horizontal and vertical body waves with a phase difference of ±90°. We demonstrate that the high maneuverability displayed by sidewinder rattlesnakes (Crotalus cerastes) emerges from the animal's ability to independently modulate these waves. Sidewinder rattlesnakes used two distinct turning methods, which we term differential turning (26°change in orientation per wave cycle) and reversal turning (89°). Observations of the snakes suggested that during differential turning the animals imposed an amplitude modulation in the horizontal wave whereas in reversal turning they shifted the phase of the vertical wave by 180°. We tested these mechanisms using a multimodule snake robot as a physical model, successfully generating differential and reversal turning with performance comparable to that of the organisms. Further manipulations of the two-wave system revealed a third turning mode, frequency turning, not observed in biological snakes, which produced large (127°) in-place turns. The two-wave system thus functions as a template (a targeted motor pattern) that enables complex behaviors in a high-degree-offreedom system to emerge from relatively simple modulations to a basic pattern. Our study reveals the utility of templates in understanding the control of biological movement as well as in developing control schemes for limbless robots.sidewinder | biomechanics | robotics | template | control P ropagating waves of flexion along the axis of a long, slender body (henceforth "axial waves") to produce propulsion is common in biological locomotion in aquatic and terrestrial environments. The majority of biological studies of axial wave propulsion at different scales have occurred in aquatic environments (1, 2). Understanding the efficacy of given wave patternswhich are often assumed to act in a single plane (e.g., mediolateral axial bending)-can be gained through full solution of the equations of hydrodynamics (3) or approximations (4). Terrestrial environments such as sand, mud, and cluttered heterogeneous substrates encountered by limbless axial undulators such as snakes can display similar (if not greater) complexity, yet far less attention has been paid to such locomotion (5, 6).Snake axial propulsion in terrestrial environments differs from fluid locomotion in two key ways. First, most substrates are not yet described at the level of fluids (7), making it a challenge to understand how substrate-body interactions affect locomotor performance, and therefore requiring robotic physical models. Second, the body may be both laterally and/or dorsoventrally flexed (5) to allow different elements of the body to contact ...

“…Cockroaches use rigid, jointed exoskeletons to run rapidly at speeds approaching 1.5 m·s −1 (31), climb up walls (11,32), race along ceilings (33), and swing stealthily under ledges out of sight (34). However, materials science has revealed that the stiffness of exoskeletal tissue can differ by eight orders of magnitude (35)(36)(37)(38), permitting the possibility that cockroaches with powerful propulsive appendages might also retain the advantages of soft-bodied animals capable of conforming to their environment (39).…”

mentioning

confidence: 99%

Cockroaches traverse crevices, crawl rapidly in confined spaces, and inspire a soft, legged robot

Jayaram

Full

2016

Self Cite

153

112

Jointed exoskeletons permit rapid appendage-driven locomotion but retain the soft-bodied, shape-changing ability to explore confined environments. We challenged cockroaches with horizontal crevices smaller than a quarter of their standing body height. Cockroaches rapidly traversed crevices in 300-800 ms by compressing their body 40-60%. High-speed videography revealed crevice negotiation to be a complex, discontinuous maneuver. After traversing horizontal crevices to enter a vertically confined space, cockroaches crawled at velocities approaching 60 cm·s −1 , despite body compression and postural changes. Running velocity, stride length, and stride period only decreased at the smallest crevice height (4 mm), whereas slipping and the probability of zigzag paths increased. To explain confined-space running performance limits, we altered ceiling and ground friction. Increased ceiling friction decreased velocity by decreasing stride length and increasing slipping. Increased ground friction resulted in velocity and stride length attaining a maximum at intermediate friction levels. These data support a model of an unexplored mode of locomotion-"body-friction legged crawling" with body drag, friction-dominated leg thrust, but no media flow as in air, water, or sand. To define the limits of body compression in confined spaces, we conducted dynamic compressive cycle tests on living animals. Exoskeletal strength allowed cockroaches to withstand forces 300 times body weight when traversing the smallest crevices and up to nearly 900 times body weight without injury. Cockroach exoskeletons provided biological inspiration for the manufacture of an origami-style, soft, legged robot that can locomote rapidly in both open and confined spaces.T he emergence of terradynamics (1) has advanced the study of terrestrial locomotion by further focusing attention on the quantification of complex and diverse animal-environment interactions (2). Studies of locomotion over rough terrain (3), compliant surfaces (4), mesh-like networks (5), and sand (6-8), and through cluttered, 3D terrain (9) have resulted in the discovery of new behaviors and novel theory characterizing environments (10). The study of climbing has led to undiscovered templates (11) that define physical interactions through frictional van der Waals adhesion (12, 13) and interlocking with claws (14) and spines (5). Burrowing (15, 16), sand swimming (17), and locomotion in tunnels (18) have yielded new findings determining the interaction of bodies, appendages, and substrata.Locomotion in confined environments offers several challenges for animals (18) that include limitations due to body shape changes (19,20), restricted limb mobility (21), increased body drag, and reduced thrust development (22). Examining the motion repertoire of soft-bodied animals (23), such as annelids (19), insect larvae (24), and molluscs (25), has offered insight into a range of strategies used to move in confined spaces. Inspiration from softbodied animals has fueled the explosive growth in soft robo...