How does tack depend on time of contact and contact pressure?

Creton, Costantino; Leibler, Ludwik

doi:10.1002/(sici)1099-0488(199602)34:3<545::aid-polb13>3.0.co;2-i

Cited by 198 publications

(186 citation statements)

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“…For very soft surfaces, adhesion may even increase with increasing roughness [568,569]. This happens if deformations become large enough to induce an intimate contact between surfaces.…”

Section: Influence Of Roughness On Adhesionsupporting

confidence: 78%

Force measurements with the atomic force microscope: Technique, interpretation and applications

Butt

Cappella

Kappl

2005

Surface Science Reports

3,246

2,949

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“…For very soft surfaces, adhesion may even increase with increasing roughness [568,569]. This happens if deformations become large enough to induce an intimate contact between surfaces.…”

Section: Influence Of Roughness On Adhesionsupporting

confidence: 78%

Force measurements with the atomic force microscope: Technique, interpretation and applications

Butt

Cappella

Kappl

2005

Surface Science Reports

3,246

2,949

View full text Add to dashboard Cite

“…10 MPa, which is common for soft rubbers and elastomers, whereas paper is much stiffer (> 1GPa). Tapes are normally designed to have moduli below 0.1 MPa, which is known as the Dahlquist criterion (41). Taking h ′ rms ∼ 1 and Δr ∼ 0:5 nm, one finds adhesion for d rep .…”

Section: Discussionmentioning

confidence: 99%

Contact between rough surfaces and a criterion for macroscopic adhesion

Pastewka

Robbins

2014

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

275

238

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At the molecular scale, there are strong attractive interactions between surfaces, yet few macroscopic surfaces are sticky. Extensive simulations of contact by adhesive surfaces with roughness on nanometer to micrometer scales are used to determine how roughness reduces the area where atoms contact and thus weakens adhesion. The material properties, adhesive strength, and roughness parameters are varied by orders of magnitude. In all cases, the area of atomic contact is initially proportional to the load. The prefactor rises linearly with adhesive strength for weak attractions. Above a threshold adhesive strength, the prefactor changes sign, the surfaces become sticky, and a finite force is required to separate them. A parameter-free analytic theory is presented that describes changes in these numerical results over up to five orders of magnitude in load. It relates the threshold adhesive strength to roughness and material properties, explaining why most macroscopic surfaces do not stick. The numerical results are qualitatively and quantitatively inconsistent with classical theories based on the Greenwood−Williamson approach that neglect the range of adhesion and do not include asperity interactions.surface roughness | contact mechanics S urfaces are adhesive or "sticky" if breaking contact requires a finite force. At the atomic scale, surfaces are pulled together by van der Waals interactions that produce forces per unit area that are orders of magnitude larger than atmospheric pressure (1). This leads to strong adhesion of small objects, such as Gecko setae (2, 3) [capillary forces may also contribute to Gecko adhesion in humid environments (4, 5)] and engineered mimics (6), and unwanted adhesion is the main failure mechanism in microelectromechanical systems with moving parts (7). Although tape and gecko feet maintain this strong adhesion at macroscopic scales, few of the objects we encounter are sticky. Indeed, our world would come to a halt if macroscopic objects adhered with an average pressure equal to that from van der Waals interactions.The discrepancy between atomic and macroscopic forces has been dubbed the adhesion paradox (8). Experiments show that a key factor underlying this paradox is surface roughness, which reduces the fraction of surface atoms that are close enough to adhere (8-11). Quantitative calculations of this reduction are extremely challenging because of the complex topography of typical surfaces, which have bumps on top of bumps on a wide range of scales (12, 13). In many cases, they can be described as self-affine fractals from a lower wavelength λ s of order nanometers to an upper wavelength λ L in the micrometer to millimeter range (10,14).The traditional Greenwood−Williamson (GW) (15) approach for calculating nonadhesive contact of rough surfaces approximates their complex topography by a set of spherical asperities of radius R. The distribution of asperity heights is assumed to be either exponential or Gaussian, and the long-range elastic interactions between different asperities...

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“…Tacky materials are those that exhibit spontaneous plastic deformation that increases the true area of contact with the surface at the molecular scale. Theoretical considerations (Creton and Leibler, 1996) agree with Dahlquist's empirical observation (Dahlquist, 1969;Pocius, 2002) that a Young's modulus (E) below 100·kPa (at 1·Hz) is needed to achieve a high contact fraction with the substrate. PSAs such as masking tape or sticky notes are capable of repeated attachment and detachment cycles without residue because the dominant mechanism of adhesion is weak intermolecular forces.…”

Section: Discussionmentioning

confidence: 99%