Tuning elastomer friction by hexagonal surface patterning

Murarash, Boris; Itovich, Yan; Varenberg, Michael

doi:10.1039/c1sm00015b

Cited by 87 publications

(56 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Upon shearing the interface, obtained by driving the translation stage at constant velocity v in the range [20 µm/s-120 µm/s], the micro-contacts size changes marginally from circular to slightly elliptic, still allowing local normal loads to be extracted within Hertz model's assumption. Contrary to the usual pillar geometry of asperities [6,[18][19][20], spherical asperities do not bend nor buckle. It is thus possible to locate unambiguously with sub-pixel accuracy (1/24 pixels, ∼ 400 nm) positions of the microcontacts centers and follow, using a custom made algorithm written in Matlab (MathWorks), their displacements with respect to their initial position, u c (Fig.…”

mentioning

confidence: 98%

Probing Locally the Onset of Slippage at a Model Multicontact Interface

et al. 2014

View full text Add to dashboard Cite

We report on the multi-contact frictional dynamics of model elastomer surfaces rubbed against bare glass slides. The surfaces consist of layers patterned with thousands spherical caps (radius of curvature 100 µm) distributed both spatially and in height, regularly or randomly. Use of spherical asperities yields circular micro-contacts whose radius is a direct measure of the contact pressure distribution. In addition, optical tracking of individual contacts provides the in-plane deformations of the tangentially loaded interface, yielding the shear force distribution. We then investigate the stick-slip frictional dynamics of a regular hexagonal array. For all stick phases including the initial one, slip precursors are evidenced. They are found to propagate quasi-statically, normally to the isopressure contours. A simple quasi-static model relying on the existence of interfacial stress gradients is derived and predicts qualitatively the position of slip precursors.PACS numbers: 46.55.+d, 68.35.Ct, 81.40.Pq In recent years, our understanding of the transition from static to dynamic friction has been markedly changed with the development of new imaging techniques to probe spatially the interfacial dynamics at the onset of sliding [1][2][3][4]. Slip phases were found to involve the propagation of a series of dynamical rupture fronts, far from the classical Amontons-Coulomb's picture. Using true contact area imaging with evanescent illumination of a 1D Plexiglas-Plexiglas plane contact, Fineberg and coauthors [1] measured in particular slow fronts with velocities orders of magnitude lower than the Rayleigh wave velocity, along with sub-Rayleigh and fast intersonic fronts. Slow fronts were also reported to propagate at soft elastomer-roughened glass spherical 2D contacts [5] by tracking optically markers positioned on the surface of the elastomer. Brörman et al.[6] extended such studies to micro-structured elastomer surfaces in the form of hexagonal arrays of cylindrical micro-pillars in contact with glass slides, and found again a similar phenomenology. During stick phases, slow slip precursors were also observed well before macroscopic slippage occurs [2]. In all these experiments, a single physical quantity is measured, either the real area of contact directly related to the local normal stress, or the local interfacial stress using displacement measurements. In a recent work [7], Ben-David and Fineberg provided both types of measurement in a system treated as a 1D interface. Using an array of strain gauges sensors distributed directly above the interfacial plane, these authors reported strong correlations between the characteristics of the fronts and the ratio of the measured tangential to normal local stresses. For an extended 2D contact, simultaneous measurements of both pressure and tangential interfacial fields is still lacking and out of reach using Ben-David and Fineberg's approach. In addition, it remains unclear what physical mechanism underlies the existence of slip precursors in the stick phase and thei...

show abstract

mentioning

confidence: 98%

Probing Locally the Onset of Slippage at a Model Multicontact Interface

et al. 2014

View full text Add to dashboard Cite

show abstract

“…Therefore, we will generate switchable adhesive performance parameters to provide metrics for comparison between the diverse approaches currently employed. [35][36][37][38] We exclude these active areas only to keep manuscript a reasonable size, not because we believe adhesion switching is not achieved in these scenarios or that these topics do not pose interesting questions. As these concepts are deeply intermingled with measurement, we attempt to provide some guidance toward "best practices" with respect to adhesion measurement.…”

mentioning

confidence: 99%

Switchable Adhesives for Multifunctional Interfaces

Croll

Hosseini

Bartlett

2019

Adv Materials Technologies

132

107

View full text Add to dashboard Cite

The reliable bonding or attachment of materials is critical in many industries, is a common necessity of daily life, and is key to functionality in numerous biological settings. [1][2][3][4][5][6][7][8][9][10][11] Adhesives Joining two materials with an adhesive is an extremely common activity, but is most often irreversible. However, emerging and current applications ranging from consumer and medical products to soft robotics and wearable bio-monitoring devices demand strong adhesives which can be easily removed on-demand and subsequently reused. This requires new paradigms in adhesive science and engineering, resulting in the emergence of new classes of multifunctional switchable adhesives. Here summarized is the current state of the art in switchable adhesive systems, focusing on how devices fit into the basic science of adhesion while providing performance metrics for comparison across current approaches. Using fracture mechanics as a guide, systems are classified as functioning under one of three basic mechanisms: near-interface, contact area, or mechanical. These mechanisms must be initiated or "triggered" by a specific input, which can include mechanical, electromagnetic, fluidic, or thermal stimuli. Triggers and adhesion switching performance are compared through the use of a "switching ratio," the interfacial energy release rate, and an estimate of mechanism timing. Finally, it is discussed that how the fundamental mechanisms relate to challenges and opportunities for switchable interfaces in future applications and adhesive systems.

show abstract

“…) and phylogeny (Green, , ; McAllister & Channing, ; Hertwig & Sinsch, ) of tree frogs, as well as to design bioinspired adhesives (Murarash et al. ; Drotlef et al. ; Tsipenyuk & Varenberg, ; Iturri et al.…”

Section: Introductionmentioning

confidence: 99%

“…Tree frogs possess adhesive digital pads that enable these animals to climb vertical substrates, hence allowing the exploration of arboreal habitats, the evasion of groundborne predators and the disclosure of otherwise unreachable food sources. Studying the morphology and functioning of these organs helps to unravel the ecology (Green & Simon, 1986;Emerson, 1991), evolution (Moen et al 2013;Sustaita et al 2013) and phylogeny (Green, 1979(Green, , 1980McAllister & Channing, 1983;Hertwig & Sinsch, 1995) of tree frogs, as well as to design bioinspired adhesives (Murarash et al 2011;Drotlef et al 2013;Tsipenyuk & Varenberg, 2014;Iturri et al 2015;Zhang et al 2016;Xue et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

View full text Add to dashboard Cite

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.

show abstract

Tuning elastomer friction by hexagonal surface patterning

Cited by 87 publications

References 20 publications

Probing Locally the Onset of Slippage at a Model Multicontact Interface

Probing Locally the Onset of Slippage at a Model Multicontact Interface

Switchable Adhesives for Multifunctional Interfaces

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

Contact Info

Product

Resources

About