Optimal roughness for minimal adhesion

Abstract:In order to understand the contact phenomena of micron-sized particles, which have a tremendous impact on a variety of applications in industry and technology, direct access to the loads as well as the displacements accompanying such contacts are mandatory. Typical particle ensembles show a size variation ranging from the nanometer to the tenths of micron scale. Especially the contact behavior of particles featuring radii of several up to several tenths of microns is scarcely studied as these particles are typically too large for atomic force microscopy (AFM) based approaches and too small for conventional macroscopic testing setups. In this work a nanoindenter based approach is introduced to gain insight into the contact mechanics of micron-sized glass beads sliding on rough silicon surfaces at various constant low normal loads. The results are analyzed by a simple modified Coulomb friction law, as well as Hertz, JKR, and DMT contact theory.

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“…The adhesion, however, decreases with increasing surface roughness. The latter agrees well with results reported by Liu et al [20].…”

Section: Characterization Of Particle Probes and Si Surfacessupporting

confidence: 83%

Effect of surface roughness on sliding friction of micron-sized glass beads

et al. 2014

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“…In the fi rst and second categories, computational or purely theoretical models of contact mechanics are proposed or used, and thus an input value is needed for range of adhesion. As shown in Table 1 , the majority of these studies [ 4,27,31,34,44,45,[48][49][50] estimate the range of adhesion as equal to the interatomic spacing of atoms in the contacting material. While it seems a reasonable ballpark estimate, there is little direct justifi cation provided for this claim.…”

Section: Comparing Range Of Adhesion To Previously Proposed Valuesmentioning

confidence: 99%

“…This quantity is the correct one for use in continuum contact models [4][5][6]8,27,28 ] as well as in roughness models. [ 26,29,30 ] The investigations in this second category have employed the atomic force microscope (AFM), [ 8,12,[31][32][33][34] the related interfacial force microscope (IFM), [ 35 ] and the surface forces apparatus (SFA) [ 36,37 ] to conduct adhesion tests with high-force resolution using a single-asperity contact, typically on the nanometer length scale. Since these are not fl at surfaces, a value for work of adhesion requires using a contact mechanics model to fi t the data.…”

Section: Introductionmentioning

confidence: 99%

“…Other researchers [ 12,32,33 ] applied similar techniques with silicon-and/or carbon-based interfaces. Burnham [ 34 ] carried out extensive pull-off force measurements between silicon AFM tips and silicon substrates and analyzed results using a related approach. In another study, the IFM was used to study a silicon/silicon interface under a variety of conditions.…”

Section: Introductionmentioning

confidence: 99%

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Measurement of the Length and Strength of Adhesive Interactions in a Nanoscale Silicon–Diamond Interface

Jacobs¹,

Lefever²,

Carpick³

2015

Adv Materials Inter

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the interaction (characterized by the range of adhesion z 0 ).The intrinsic work of adhesion W adh is the energy per unit area required to separate two planar surfaces from equilibrium contact to infi nite separation. In terms of surface energy (γ i of surface i ) and interfacial energy (γ ij between surfaces i and j ), the work of adhesion is calculated as follows:In accordance with prior literature on adhesion and roughness, [ 9 ] the intrinsic work of adhesion W adh,int is defi ned as the work of adhesion between two perfectly fl at, planar surfaces. While W adh,int is a continuum concept, it can be robustly mapped onto an atomistic description of two atomically fl at, single-crystal surfaces in contact. The effective work of adhesion, W adh,eff , is defi ned as the work of adhesion for the same material pair and the same global geometry (planar), but with the addition of local surface roughness on one or both surfaces. The distinction between W adh,int and W adh,eff is shown schematically in Figure 1 . The W adh,int is determined by the identity of the materials in contact, and the environment, whereas W adh,eff is a function of W adh,int and the local surface topography. For hard, non-conforming materials, W adh,eff is typically much smaller than W adh,int . The primary reason for this is that the roughness increases the effective separation between the two materials, and therefore signifi cantly increases γ ij between the materials as they can no longer make intimate contact. Roughness can also increase the surface energies γ i and γ j , but this effect is typically overwhelmed by the change in γ ij . This distinction is drawn because many experimental techniques exist to measure W adh,eff (for example, using microfabricated beam tests [ 10 ] ), but generally applicable techniques to deduce from this the W adh,int are not well established.Physically, z 0 describes the equilibrium separation distance between perfectly fl at surfaces, i.e., the separation distance at which their interaction force is zero. However, in many mathematical descriptions of adhesion (for instance, refs. [ 5,7,8,11 ] ) z 0 also scales the distance over which adhesion acts for a particular material. Therefore, the parameter z 0 is referred to in this paper as the "range of adhesion," (in accordance with Greenwood, [ 5 ] who calls it the "range of action of the surface forces").The adhesive interactions between nanoscale silicon atomic force microscope (AFM) probes and a diamond substrate are characterized using in situ adhesion tests inside of a transmission electron microscope (TEM). In particular, measurements are presented both for the strength of the adhesion acting between the two materials (characterized by the intrinsic work of adhesion W adh,int ) and for the length scale of the interaction (described by the range of adhesion z 0 ). These values are calculated using a novel analysis technique that requires measurement of the AFM probe geometry, the adhesive force, and the position where the snap-in instability occurs. Values ...

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“…It has been shown that the adhesion force between two surfaces in ambient atmosphere is reduced by two orders of magnitude when the combined surface roughness increases from 1 nm to 10 nm for several different counter-surfaces on gold. 13,29,30 The combined surface roughness of the matrix region of the piezocomposite and wafer is almost 6 nm, which already yields relatively low adhesion forces between silicon and gold. 13 After actuation, the wafer rests solely on the protruding PZT fibers.…”

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confidence: 99%

Switchable static friction of piezoelectric composite—silicon wafer contacts

Ende

Fischer

Groen

et al. 2013

Applied Physics Letters

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The meso-scale surface roughness of piezoelectric fiber composites can be manipulated by applying an electric field to a piezocomposite with a polished surface. In the absence of an applied voltage, the tips of the embedded piezoelectric ceramic fibers are below the surface of the piezocomposite and a silicon wafer counter surface rests solely on the matrix region of the piezocomposite surface. When actuated, the piezoelectric ceramic fibers protrude from the surface and the wafer rests solely on these protrusions. A threefold decrease in engineering static friction coefficient upon actuation of the piezocomposite was observed: from l* ¼ 1.65 to l* ¼ 0.50. These experimental results could be linked to the change in contact surface area and roughness using capillary adhesion theory, which relates the adhesive force to the number and size of the contacting asperities for the different surface states. The manipulation of friction and adhesion of surfaces is interesting for many applications, such as precision manufacturing processes, where tolerances are becoming ever tighter and components are becoming smaller and more delicate.

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Optimal roughness for minimal adhesion

Cited by 49 publications

References 14 publications

Effect of surface roughness on sliding friction of micron-sized glass beads

Effect of surface roughness on sliding friction of micron-sized glass beads

Measurement of the Length and Strength of Adhesive Interactions in a Nanoscale Silicon–Diamond Interface

Switchable static friction of piezoelectric composite—silicon wafer contacts

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