Rolling and Spinning Friction Characterization of Fine Particles Using Lateral Force Microscopy Based Contact Pushing

Sümer, Bilsay; Sitti, Metin

doi:10.1163/156856108x295527

Cited by 74 publications

(75 citation statements)

References 29 publications

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“…Based on experimental and theoretical values of reported shear strength at different scales of contact radii, Sumer & Sitti [43] have shown that t decreases as the contact size increases, except for very small contact radii (less than 20 nm) and large contact radii (larger than 40 mm), and is given as G 2 ), G 1 and G 2 are the shear moduli of the materials, and…”

Section: Effect Of Normal and Shear Loadingmentioning

confidence: 99%

Staying sticky: contact self-cleaning of gecko-inspired adhesives

Mengüç

Röhrig

Abusomwan

et al. 2014

J. R. Soc. Interface.

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The exceptionally adhesive foot of the gecko remains clean in dirty environments by shedding contaminants with each step. Synthetic gecko-inspired adhesives have achieved similar attachment strengths to the gecko on smooth surfaces, but the process of contact self-cleaning has yet to be effectively demonstrated. Here, we present the first gecko-inspired adhesive that has matched both the attachment strength and the contact self-cleaning performance of the gecko's foot on a smooth surface. Contact self-cleaning experiments were performed with three different sizes of mushroom-shaped elastomer microfibres and five different sizes of spherical silica contaminants. Using a load-drag-unload dry contact cleaning process similar to the loads acting on the gecko foot during locomotion, our fully contaminated synthetic gecko adhesives could recover lost adhesion at a rate comparable to that of the gecko. We observed that the relative size of contaminants to the characteristic size of the microfibres in the synthetic adhesive strongly determined how and to what degree the adhesive recovered from contamination. Our approximate model and experimental results show that the dominant mechanism of contact self-cleaning is particle rolling during the drag process. Embedding of particles between adjacent fibres was observed for particles with diameter smaller than the fibre tips, and further studied as a temporary cleaning mechanism. By incorporating contact self-cleaning capabilities, real-world applications of synthetic gecko adhesives, such as reusable tapes, clothing closures and medical adhesives, would become feasible.

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Section: Effect Of Normal and Shear Loadingmentioning

confidence: 99%

Staying sticky: contact self-cleaning of gecko-inspired adhesives

Mengüç

Röhrig

Abusomwan

et al. 2014

J. R. Soc. Interface.

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“…Constant-velocity rolling. For PSL, [8] have measured the rolling force using an AFM for 5, 10 and 15 µm. The spheres were pushed across a glass substrate at a constant velocity of 0.1 µm s −1 .…”

Section: Polystyrene Microspheresmentioning

confidence: 99%

“…As care was taken to apply the pushing force a height R from the substrate, we can relate this force to a rolling torque via F ext = M ext /R. Figure 3 shows the results of [8] in comparison to (11), for various values of ( γ /γ ). The theory of [14], i.e.…”

Section: Polystyrene Microspheresmentioning

confidence: 99%

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Rolling friction of adhesive microspheres

Krijt¹,

Dominik²,

Tielens³

2014

J. Phys. D: Appl. Phys.

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The rolling friction of adhesive microspheres is an important quantity as it determines the strength and stability of larger aggregates. Current models predict rolling forces that are 1 to 2 orders of magnitude smaller than observed experimentally. Starting from the well-known Johnson-Kendall-Roberts (JKR) contact description, we derive an analytical theory for the rolling friction based on the concept of adhesion hysteresis, e.g. a difference in apparent surface energies for opening/closing cracks. We show how adhesion hysteresis causes the pressure distribution within the contact to become asymmetrical, leading to an opposing torque. Analytical expressions are derived relating the size of the hysteresis, the rolling torque, and the rolling displacement, ξ . We confirm the existence of a critical rolling displacement for the onset of rolling, the size of which is set by the amount of adhesion hysteresis and the size of the contact area. We demonstrate how the developed theory is able to explain the large rolling forces and particle-size dependence observed experimentally. Good agreement with experimental results is achieved for adhesion hysteresis values of ( γ /γ ) 3 for polystyrene, and ( γ /γ ) 0.5 for silicates, at crack propagation rates of 0.1 µm s −1 and 1-10 µm s −1 , respectively.

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“…Here, R is the effective radius between two contacting particles (1/R = 1/r p1 + 1/r p2 ), a is the radius of the contact area with a 0 at equilibrium in the JKR model. The values or ranges of µ f , Θ crit and F C are selected according to the data from atomic force microscopy measurements [25][26][27].…”

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Adhesive loose packings of small dry particles

Liu

Baule

et al. 2015

Soft Matter

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We explore adhesive loose packings of dry small spherical particles of micrometer size using 3D discrete-element simulations with adhesive contact mechanics. A dimensionless adhesion parameter (Ad) successfully combines the effects of particle velocities, sizes and the work of adhesion, identifying a universal regime of adhesive packings for Ad > 1. The structural properties of the packings in this regime are well described by an ensemble approach based on a coarse-grained volume function that includes correlations between bulk and contact spheres. Our theoretical and numerical results predict: (i) An equation of state for adhesive loose packings that appears as a continuation from the frictionless random close packing (RCP) point in the jamming phase diagram; (ii) The existence of a maximal loose packing point at the coordination number Z = 2 and packing fraction φ = 1/2 3 . Our results highlight that adhesion leads to a universal packing regime at packing fractions much smaller than the random loose packing, which can be described within a statistical mechanical framework. We present a general phase diagram of jammed matter comprising frictionless, frictional, adhesive as well as non-spherical particles, providing a classification of packings in terms of their continuation from the spherical frictionless RCP.Jammed particle packings have been studied to understand the microstructure and bulk properties of liquids, glasses and crystals [1, 2] and frictional granular materials [3,4]. Two packing limits have been identified for disordered uniform spheres: The random close packing (RCP) and random loose packing (RLP) limits [1,[5][6][7][8][9][10][11]. The upper RCP limit is reproduced for frictionless spheres at volume fractions φ ≈ 0.64 and has been associated with a freezing point of a 1st order phase transition [12][13][14][15], among other interpretations [2,16]. In the presence of friction, packings reach lower volume fraction up to the RLP limit φ RLP ≈ 0.55 for mechanically stable packings [6,8,11]. However, most packings of dry small micrometer-sized particles in nature are not only subject to friction, but also adhesion forces. In fact, van der Waals forces generally dominate interactions between particles with diameters of around 10µm or smaller. In this case, the adhesive forces begin to overcome the gravitational and elastic contact forces acting on the particles and change macroscopic structural properties [17,18].Despite the ubiquity of adhesive particle packings in almost all areas of engineering, biology, agriculture and physical sciences [18][19][20][21], these packings have so far not been systematically investigated. The multi-coupling of adhesion, elastic contact forces and friction within the short-range particle-particle interaction zone and their further couplings with fluid forces (e.g., buoyancy, drag and lubrication) across long-range scales make it highly difficult to single out the effect of the adhesion forces * lishuiqing@tsinghua.edu.cn † hmakse@lev.ccny.cuny.edu alone. Previous stud...

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Rolling and Spinning Friction Characterization of Fine Particles Using Lateral Force Microscopy Based Contact Pushing

Cited by 74 publications

References 29 publications

Staying sticky: contact self-cleaning of gecko-inspired adhesives

Staying sticky: contact self-cleaning of gecko-inspired adhesives

Rolling friction of adhesive microspheres

Adhesive loose packings of small dry particles

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