Friction of partially embedded vertically aligned carbon nanofibers inside elastomers

Aksak, Burak; Sitti, Metin; Cassell, Alan M.; Li, Jun; Meyyappan, M.; Callen, Phillip

doi:10.1063/1.2767997

Cited by 47 publications

(40 citation statements)

References 12 publications

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“…Three different sizes of microfibres with tip diameters, B, of 20, 30 and 95 mm (figure 2) were fabricated along with a flat unstructured reference sample. The polyurethane (ST-1060, BJB Enterprises) had a Young's modulus E f of 2.9 MPa and a work of adhesion W pf (to glass) of 93 mJ m 22 . The adhesive samples, including the reference sample, were cut into square patches of 500 Â 500 mm and affixed to a clear acrylic sheet with a double-sided adhesive tape.…”

Section: Methodsmentioning

confidence: 99%

“…During the past decades, engineers and scientists successfully uncovered the principles of the gecko's impressive adhesive capabilities [1][2][3][4][5][6], but there are only a few studies on their self-cleaning abilities [7,8]. Although, gecko-inspired adhesives have been demonstrated to compare favourably with the gecko in attachment strength on smooth dry surfaces [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], no synthetic gecko adhesive [24 -27] has matched its natural counterpart in the ability to regain adhesion after contamination. Consequently, the development of gecko-inspired adhesives with self-cleaning capability is the critical next step to successfully produce biomimetic solutions such as strong and reusable adhesive tapes, power-efficient and robust climbing robots [28,29], and robotic pick-and-place manipulators for tiny parts and large fragile devices [30,31].…”

Section: Introductionmentioning

confidence: 99%

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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: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

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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“…By sliding a gold tip with apex radii of (4.5-30 mm) on a 6 mm thick VACNT film, Kinoshita et al (2004) found m = 1.0-2.2. Aksak et al (2007) have found that m ranges from 0.8 to 1 for VACNT fibres (3, 25 mm average lengths) on a compliant polyurethane (PU) backing. The same *Author for correspondence (ajeet@aem.umn.edu).…”

Section: Introductionmentioning

confidence: 99%

“…Many of these man-made surfaces use stiff materials such as carbon-nanotube (CNT) as fibres (e.g. Kinoshita et al 2004;Dickrell et al 2005;Majidi et al 2006;Aksak et al 2007;Ge et al 2007;Schubert et al 2008;Qu et al 2008;Maeno & Nakayama 2009). Although most stiff fibre arrays show poor normal adhesion, the friction coefficients of these arrays, m, are found to be much greater than flat surfaces of the same material.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of shearing of a microfibre during friction testing of a microfibre array

Kumar

Hui

2010

Proc. R. Soc. A.

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Friction testing of microfibre arrays is typically conducted under displacement boundary conditions. For example, after the application of a compressive preload, the translation stage is fixed in the vertical direction while a shear displacement is applied by translating the stage laterally. A nonlinear rod model is used to compute the normal and shear forces acting on a typical microfibre during such a test. The normal load acting on a typical fibre is found to switch from compression to tension as the shear displacement increases. The critical shear force to detach a fibre is found to depend linearly on the compressive preload. The fibre is also found to become more stable as it is sheared, hence it never buckles. On the other hand, instead of fixing the vertical displacement, when a fibre is subjected to constant normal load, it becomes unstable upon shearing. We show that the buckling load (the applied normal load to make a fibre unstable) of a microfibril is reduced by the application of a shear displacement.

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“…Inspired by these micro-and nanostructures, many research groups have fabricated synthetic mimics using various polymers or carbon nanotubes to create arrays of microfibrils. Typically, fibrils in these arrays are terminated with either a thin film or a spatula to enhance contact and adhesion (Gorb et al 2006;Kim & Sitti 2006;Aksak et al 2007;del Campo et al 2007;Greiner et al 2007;Reddy et al 2007;Schubert et al 2007). These fibrils are part of a backing layer that is made up of the same material, typically a soft elastomer such as poly(dimethylsiloxane) or polyurethane.…”

Section: Introductionmentioning

confidence: 99%

Buckling of sheared and compressed microfibrils

Nadermann

Kumar

Goyal

et al. 2010

J. R. Soc. Interface.

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In this paper, we study the stability of an initially straight elastic fibril clamped at one end, while the other end is subjected to a constant normal compressive force and a prescribed shear displacement. We found the buckling load of a sheared fibril to be always less than the Euler buckling load. Furthermore, if the end of the fibril loses adhesion, then the buckling load can be considerably less. Our result suggests that the static friction of microfibre arrays can decrease with increasing normal compressive load and, in some cases, friction force can actually become negative.

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Friction of partially embedded vertically aligned carbon nanofibers inside elastomers

Cited by 47 publications

References 12 publications

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

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

Numerical study of shearing of a microfibre during friction testing of a microfibre array

Buckling of sheared and compressed microfibrils

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