Viscous–poroelastic interaction as mechanism to create adhesion in frogs’ toe pads

Tulchinsky, Arie; Gat, Amir D.

doi:10.1017/jfm.2015.293

Cited by 10 publications

(7 citation statements)

References 25 publications

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“…6 does not hold anymore, particularly with an increasing sliding distance. Alternatively, viscous-poroelastic effects have been proposed to contribute to tree frog attachment [ 93 ].…”

Section: Basic Theory Of Potential Attachment Mechanisms In a Toe Padmentioning

confidence: 99%

Tree frog attachment: mechanisms, challenges, and perspectives

et al. 2018

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Tree frogs have the remarkable ability to attach to smooth, rough, dry, and wet surfaces using their versatile toe pads. Tree frog attachment involves the secretion of mucus into the pad-substrate gap, requiring adaptations towards mucus drainage and pad lubrication. Here, we present an overview of tree frog attachment, with focus on (i) the morphology and material of the toe pad; (ii) the functional demands on the toe pad arising from ecology, lifestyle, and phylogenetics; (iii) experimental data of attachment performance such as adhesion and friction forces; and (iv) potential perspectives on future developments in the field. By revisiting reported data and observations, we discuss the involved mechanisms of attachment and propose new hypotheses for further research. Among others, we address the following questions: Do capillary and hydrodynamic forces explain the strong friction of the toe pads directly, or indirectly by promoting dry attachment mechanisms? If friction primarily relies on van der Waals (vdW) forces instead, how much do these forces contribute to adhesion in the wet environment tree frogs live in and what role does the mucus play? We show that both pad morphology and measured attachment performance suggest the coaction of several attachment mechanisms (e.g. capillary and hydrodynamic adhesion, mechanical interlocking, and vdW forces) with situation-dependent relative importance. Current analytical models of capillary and hydrodynamic adhesion, caused by the secreted mucus and by environmental liquids, do not capture the contributions of these mechanisms in a comprehensive and accurate way. We argue that the soft pad material and a hierarchical surface pattern on the ventral pad surface enhance the effective contact area and facilitate gap-closure by macro- to nanoscopic drainage of interstitial liquids, which may give rise to a significant contribution of vdW interactions to tree frog attachment. Increasing the comprehension of the complex mechanism of tree frog attachment contributes to a better understanding of other biological attachment systems (e.g. in geckos and insects) and is expected to stimulate the development of a wide array of bioinspired adhesive applications.Electronic supplementary materialThe online version of this article (10.1186/s12983-018-0273-x) contains supplementary material, which is available to authorized users.

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“…6 does not hold anymore, particularly with an increasing sliding distance. Alternatively, viscous-poroelastic effects have been proposed to contribute to tree frog attachment [ 93 ].…”

Section: Basic Theory Of Potential Attachment Mechanisms In a Toe Padmentioning

confidence: 99%

Tree frog attachment: mechanisms, challenges, and perspectives

et al. 2018

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“…Duchemin & Vandenberghe (2014) examined the dynamics due to impact of a rigid body on a thin elastic sheet laying over a liquid. Tulchinsky & Gat (2015) studied externally forced deformation of a saturated poroelastic medium laying on rough wet surface in the context of adhesion.…”

Section: Introductionmentioning

confidence: 99%

Transient dynamics of an elastic Hele-Shaw cell due to external forces with application to impact mitigation

Tulchinsky¹,

Gat²

2016

J. Fluid Mech.

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We study the transient dynamics of a viscous liquid contained in a narrow gap between a rigid surface and a parallel elastic plate. The elastic plate is deformed due to an externally applied time-varying pressure-field. We model the flow-field via the lubrication approximation, and the plate deformation by the Kirchhoff-Love plate theory. We obtain a self-similarity solution for the case of an external point force acting on the elastic plate. The pressure and deformation field during and after the application of the external force are derived and presented by closed form expressions. We examine a uniform external pressure acting on the elastic plate over a finite region and during a finite time period, similar to the viscous-elastic interaction time-scale. The interaction between elasticity and viscosity is shown to reduce by order of magnitude the pressure within the Hele-Shaw cell compared with the externally applied pressure, thus suggesting such configurations may be used for impact mitigation.

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“…In recent years, the quest for functional structures inspired by nature raised great interest in the relation between function (e.g., light harvesting, impact‐resistance, adhesion) and properties (e.g., strength, toughness, stiffness) by means of varying structural rather than material properties . Indeed, to meet the natural equilibrium between material formation and degradation, biological materials are limited in both number and performance (e.g., natural materials are typically soft or brittle), and exceptional properties originate from geometric complexity, rather than from the used materials.…”

Section: Introductionmentioning

confidence: 99%

Nanostructure and Microstructure Fabrication: From Desired Properties to Suitable Processes

Assenbergh

Meinders²,

Geraedts

et al. 2018

Small

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When designing a new nanostructure or microstructure, one can follow a processing-based manufacturing pathway, in which the structure properties are defined based on the processing capabilities of the fabrication method at hand. Alternatively, a performance-based pathway can be followed, where the envisioned performance is first defined, and then suitable fabrication methods are sought. To support the latter pathway, fabrication methods are here reviewed based on the geometric and material complexity, resolution, total size, geometric and material diversity, and throughput they can achieve, independently from processing capabilities. Ten groups of fabrication methods are identified and compared in terms of these seven moderators. The highest resolution is obtained with electron beam lithography, with feature sizes below 5 nm. The highest geometric complexity is attained with vat photopolymerization. For high throughput, parallel methods, such as photolithography (≈10 m h ), are needed. This review offers a decision-making tool for identifying which method to use for fabricating a structure with predefined properties.

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Viscous–poroelastic interaction as mechanism to create adhesion in frogs’ toe pads

Cited by 10 publications

References 25 publications

Tree frog attachment: mechanisms, challenges, and perspectives

Tree frog attachment: mechanisms, challenges, and perspectives

Transient dynamics of an elastic Hele-Shaw cell due to external forces with application to impact mitigation

Nanostructure and Microstructure Fabrication: From Desired Properties to Suitable Processes

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