A Theoretical Characterization of Curvature Controlled Adhesive Properties of Bio-Inspired Membranes

Afferante, L.; Heepe, Lars; Casdorff, Kirstin; Gorb, Stanislav N.; Carbone, Giuseppe

doi:10.3390/biomimetics1010003

Cited by 7 publications

(6 citation statements)

References 40 publications

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“…Although we do not provide conclusive evidence, we propose that curvature is a programmed cell wall-determined biophysical effect that is synergistic with the wellunderstood effects of HG dissolution in middle lamellae. There is evidence from particle physics and biological systems that curvature can promote separation by reducing contact surface area (Derjaguin et al, 1975;Afferante et al, 2016). Indeed, the everyday process of pinching contact lenses to remove them is based on this principle.…”

Section: Discussionmentioning

confidence: 99%

Pea Border Cell Maturation and Release Involve Complex Cell Wall Structural Dynamics

et al. 2017

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The adhesion of plant cells is vital for support and protection of the plant body and is maintained by a variety of molecular associations between cell wall components. In some specialized cases, though, plant cells are programmed to detach, and root cap-derived border cells are examples of this. Border cells (in some species known as border-like cells) provide an expendable barrier between roots and the environment. Their maturation and release is an important but poorly characterized cell separation event. To gain a deeper insight into the complex cellular dynamics underlying this process, we undertook a systematic, detailed analysis of pea (Pisum sativum) root tip cell walls. Our study included immunocarbohydrate microarray profiling, monosaccharide composition determination, Fourier-transformed infrared microspectroscopy, quantitative reverse transcription-PCR of cell wall biosynthetic genes, analysis of hydrolytic activities, transmission electron microscopy, and immunolocalization of cell wall components. Using this integrated glycobiology approach, we identified multiple novel modes of cell wall structural and compositional rearrangement during root cap growth and the release of border cells. Our findings provide a new level of detail about border cell maturation and enable us to develop a model of the separation process. We propose that loss of adhesion by the dissolution of homogalacturonan in the middle lamellae is augmented by an active biophysical process of cell curvature driven by the polarized distribution of xyloglucan and extensin epitopes.

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Section: Discussionmentioning

confidence: 99%

Pea Border Cell Maturation and Release Involve Complex Cell Wall Structural Dynamics

et al. 2017

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“…The dermal tissue between the terminal phalanx and the ventral epidermis is heavily vascularised (Fig. 1 B 2; [ 44 ]), which might allow an active modification of pad curvature [ 64 ] and pad stiffness [ 47 ] by varying blood pressure.…”

Section: Morphology and Materials Properties Of 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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“…Additionally, contraction of the fibres in the lymph space might allow for the active modification of the stiffness and hence the contact area (Afferante et al. ), or of the viscoelasticity of the lymph space, which could act as macroscopic shock absorber with muscle‐modulated dampening properties.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, contraction of the thin muscle fibre bundles might alleviate the mechanical stresses in the two thick muscle fibre bundles and the septum, hence avoiding peeling via septum-loading as discussed above. Additionally, contraction of the fibres in the lymph space might allow for the active modification of the stiffness and hence the contact area (Afferante et al 2016), or of the viscoelasticity of the lymph space, which could act as macroscopic shock absorber with muscle-modulated dampening properties.…”

Section: Attachment-related Functions Of the Smooth Musculaturementioning

confidence: 99%

Force‐transmitting structures in the digital pads of the tree frog Hyla cinerea: a functional interpretation

et al. 2018

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The morphology of the digital pads of tree frogs is adapted towards attachment, allowing these animals to attach to various substrates and to explore their arboreal habitat. Previous descriptions and functional interpretations of the pad morphology mostly focussed on the surface of the ventral epidermis, and little is known about the internal pad morphology and its functional relevance in attachment. In this study, we combine histology and synchrotron micro‐computer‐tomography to obtain a comprehensive 3‐D morphological characterisation of the digital pads (in particular of the internal structures involved in the transmission of attachment forces from the ventral pad surface towards the phalanges) of the tree frog Hyla cinerea. A collagenous septum runs from the distal tip of the distal phalanx to the ventral cutis and compartmentalises the subcutaneous pad volume into a distal lymph space and a proximal space, which contains mucus glands opening via long ducts to the ventral pad surface. A collagen layer connects the ventral basement membrane via interphalangeal ligaments with the middle phalanx. The collagen fibres forming this layer curve around the transverse pad‐axis and form laterally separated ridges below the gland space. The topological optimisation of a shear‐loaded pad model using finite element analysis (FEA) shows that the curved collagen fibres are oriented along the trajectories of the maximum principal stresses, and the optimisation also results in ridge‐formation, suggesting that the collagen layer is adapted towards a high stiffness during shear loading. We also show that the collagen layer is strong, with an estimated tensile strength of 2.0–6.5 N. Together with longitudinally skewed tonofibrils in the superficial epidermis, these features support our hypothesis that the digital pads of tree frogs are primarily adapted towards the generation and transmission of friction rather than adhesion forces. Moreover, we generate (based on a simplified FEA model and predictions from analytical models) the hypothesis that dorsodistal pulling on the collagen septum facilitates proximal peeling of the pad and that the septum is an adaptation towards detachment rather than attachment. Lastly, by using immunohistochemistry, we (re‐)discovered bundles of smooth muscle fibres in the digital pads of tree frogs. We hypothesise that these fibres allow the control of (i) contact stresses at the pad–substrate interface and peeling, (ii) mucus secretion, (iii) shock‐absorbing properties of the pad, and (iv) the macroscopic contact geometry of the ventral pad surface. Further work is needed to conclude on the role of the muscular structures in tree frog attachment. Overall, our study contributes to the functional understanding of tree frog attachment, hence offering novel perspectives on the ecology, phylogeny and evolution of anurans, as well as the design of tree‐frog‐inspired adhesives for technological applications.

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A Theoretical Characterization of Curvature Controlled Adhesive Properties of Bio-Inspired Membranes

Cited by 7 publications

References 40 publications

Pea Border Cell Maturation and Release Involve Complex Cell Wall Structural Dynamics

Pea Border Cell Maturation and Release Involve Complex Cell Wall Structural Dynamics

Tree frog attachment: mechanisms, challenges, and perspectives

Force‐transmitting structures in the digital pads of the tree frog Hyla cinerea: a functional interpretation

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