Cassie-Wenzel–like transition in patterned soft elastomer adhesive contacts

Degrandi-Contraires, Élise; Beaumont, Audrey; Restagno, Frédéric; Weil, Raphaël; Poulard, Christophe; Léger, Liliane

doi:10.1209/0295-5075/101/14001

Cited by 16 publications

(20 citation statements)

References 25 publications

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“…the load on each pillar is assumed to be the same. As pads with mixed full and partial contact did not show any consistent position of the full contact within the contact zone (unlike in comparable experiments for PDMS spheres in contact with PDMS microstructures [ 45 , 46 ]), the latter assumption appears justified. Third, we assume that full contact (i.e.…”

Section: Contact Model For Smooth Pads On Pillar Substratesmentioning

confidence: 66%

Insect adhesion on rough surfaces: analysis of adhesive contact of smooth and hairy pads on transparent microstructured substrates

Zhou

Robinson

Steiner

et al. 2014

J. R. Soc. Interface.

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Insect climbing footpads are able to adhere to rough surfaces, but the details of this capability are still unclear. To overcome experimental limitations of randomly rough, opaque surfaces, we fabricated transparent test substrates containing square arrays of 1.4 µm diameter pillars, with variable height (0.5 and 1.4 µm) and spacing (from 3 to 22 µm). Smooth pads of cockroaches (Nauphoeta cinerea) made partial contact (limited to the tops of the structures) for the two densest arrays of tall pillars, but full contact (touching the substrate in between pillars) for larger spacings. The transition from partial to full contact was accompanied by a sharp increase in shear forces. Tests on hairy pads of dock beetles (Gastrophysa viridula) showed that setae adhered between pillars for larger spacings, but pads were equally unable to make full contact on the densest arrays. The beetles' shear forces similarly decreased for denser arrays, but also for short pillars and with a more gradual transition. These observations can be explained by simple contact models derived for soft uniform materials (smooth pads) or thin flat plates (hairy-pad spatulae). Our results show that microstructured substrates are powerful tools to reveal adaptations of natural adhesives for rough surfaces.

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Section: Contact Model For Smooth Pads On Pillar Substratesmentioning

confidence: 66%

Insect adhesion on rough surfaces: analysis of adhesive contact of smooth and hairy pads on transparent microstructured substrates

Zhou

Robinson

Steiner

et al. 2014

J. R. Soc. Interface.

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show abstract

“…12), and w 0 (PDMS/cross-linked) = 65 ± 3 mJ/m 2 (larger than in ref. 55). The shear strengths of the various interface types were obtained as in Fig.…”

Section: Substrate Preparationmentioning

confidence: 99%

Evolution of real contact area under shear and the value of static friction of soft materials

Sahli

Pallares

Ducottet

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

156

206

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The frictional properties of a rough contact interface are controlled by its area of real contact, the dynamical variations of which underlie our modern understanding of the ubiquitous rate-and-state friction law. In particular, the real contact area is proportional to the normal load, slowly increases at rest through aging, and drops at slip inception. Here, through direct measurements on various contacts involving elastomers or human fingertips, we show that the real contact area also decreases under shear, with reductions as large as 30[Formula: see text], starting well before macroscopic sliding. All data are captured by a single reduction law enabling excellent predictions of the static friction force. In elastomers, the area-reduction rate of individual contacts obeys a scaling law valid from micrometer-sized junctions in rough contacts to millimeter-sized smooth sphere/plane contacts. For the class of soft materials used here, our results should motivate first-order improvements of current contact mechanics models and prompt reinterpretation of the rate-and-state parameters.

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“…9 with the example of P = 8 mN, deviations between theory and experiments are clearly evidenced. Recently, Degrandi-Contraires and coworkers [18] have studied the adhesive contact between a flat PDMS decorated with cylindrical pillars of equal heights and a spherical indenter. In their analysis, they measured the apparent contact area as a function of the normal load.…”

Section: B Microcontact Radius and Contact Pressure Distributionsmentioning

confidence: 99%

Adhesive Contact of Model Randomly Rough Rubber Surfaces

et al. 2019

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We study experimentally and theoretically the equilibrium adhesive contact between a smooth glass lens and a rough rubber surface textured with spherical microasperities with controlled height and spatial distributions. Measurements of the real contact area A versus load P are performed under compression by imaging the light transmitted at the microcontacts. A(P ) is found to be non-linear and to strongly depend on the standard deviation of the asperity height distribution. Experimental results are discussed in the light of a discrete version of Fuller and Tabor's (FT) original model (Proceedings of the Royal Society A 345 (1975) 327), which allows to take into account the elastic coupling arising from both microasperities interactions and curvature of the glass lens. Our experimental data on microcontact size distributions are well captured by our discrete extended model. We show that the elastic coupling arising from the lens curvature has a significant contribution to the A(P ) relationship. Our discrete model also clearly shows that the adhesioninduced effect on A remains significant even for vanishingly small pull-off forces. Last, at the local asperity length scale, our measurements show that the pressure dependence of the microcontacts density can be simply described by the original FT model.

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Cassie-Wenzel–like transition in patterned soft elastomer adhesive contacts

Cited by 16 publications

References 25 publications

Insect adhesion on rough surfaces: analysis of adhesive contact of smooth and hairy pads on transparent microstructured substrates

Insect adhesion on rough surfaces: analysis of adhesive contact of smooth and hairy pads on transparent microstructured substrates

Evolution of real contact area under shear and the value of static friction of soft materials

Adhesive Contact of Model Randomly Rough Rubber Surfaces

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