Controlling Polymer Adhesion with “Pancakes”

Crosby, Alfred J.; Hageman, Mark; Duncan, Andrew J.

doi:10.1021/la051721k

Cited by 164 publications

(153 citation statements)

References 27 publications

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“…Failure by void nucleation represents the maximum enhancement possible by the mechanism proposed here and is limited by individual fibril detachments, a situation that has been studied in detail elsewhere (21,30). Before concluding, it should be noted that crack arrest and re-initiation have been observed to enhance adhesion, even in nonfibrillar systems (40)(41)(42)(43). These cases involve incisions in thin confined films (40,41), discontinuity of film thickness (42,43), and the discontinuity of the elastic modulii of adjoining films (42).…”

Section: Resultsmentioning

confidence: 73%

“…Before concluding, it should be noted that crack arrest and re-initiation have been observed to enhance adhesion, even in nonfibrillar systems (40)(41)(42)(43). These cases involve incisions in thin confined films (40,41), discontinuity of film thickness (42,43), and the discontinuity of the elastic modulii of adjoining films (42). It may be possible to develop a unifying description of the enhancement of fracture toughness in these related systems by using the picture of crack trapping developed in this article.…”

Section: Resultsmentioning

confidence: 99%

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Biologically inspired crack trapping for enhanced adhesion

Glassmaker

Jagota

Hui

et al. 2007

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

245

270

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We present a synthetic adaptation of the fibrillar adhesion surfaces found in nature. The structure consists of protruding fibrils topped by a thin plate and shows an experimentally measured enhancement in adhesion energy of up to a factor of 9 over a flat control. Additionally, this structure solves the robustness problems of previous mimic structures and has preferred contact properties (i.e., a large surface area and a highly compliant structure). We show that this geometry enhances adhesion because of its ability to trap interfacial cracks in highly compliant contact regimes between successive fibril detachments. This results in the requirement that the externally supplied energy release rate for interfacial separation be greater than the intrinsic work of adhesion, in a manner analogous to lattice trapping of cracks in crystalline solids.interface ͉ fracture ͉ fibrillar ͉ lattice trapping ͉ biomechanics T he ability to adhere two surfaces strongly together and then reversibly separate them, repeatedly, is a desirable capability that is rarely achievable using conventional fabrication techniques and materials. Nevertheless, fibrillar surfaces with these properties have evolved in nature on the adhesive surfaces of the feet of many lizards and insects. With such natural surfaces as inspiration, we have developed a fibrillar structure that produces a robust, reusable material with strongly enhanced adhesion compared with a flat control of the same material, with the enhancement resulting only from the modification of surface geometry.The essential feature that our surfaces borrow from biology is the seta, a hair-like bristle having a diameter of 0.5-10 m and terminating in one or more flattened, expanded tips (''spatulas'') at its contacting end. A number of biological studies (1-16) have found that arrays of setae are a common feature on the adhesion surfaces of many lizards and insects. In the biological literature, the shape, dimensions, and composition of setae from various species are described (1-5, 9-16). Also, the mechanical properties and adhesion force of a single gecko seta (7) and even a single spatula (17,18) were the subjects of recent investigations. An important conclusion to emerge from these two studies is that setal arrays use noncovalent surface forces to achieve adhesion, and evidence suggests that geckos rely primarily on van der Waals and capillary forces (8, 18). As a result, the surface architecture is the primary design variable that has been adjusted in biological systems by evolution.Because of the extraordinary adhesion ability of animals that possess setal arrays, several researchers have recently made an effort to mimic the biological setal geometry by using synthetic materials (19)(20)(21)(22)(23)(24)(25)(26). It has been established theoretically that a fibrillar interface can increase both strength and interfacial toughness, compared with a flat control (21, 27-30). However, simple arrays of micropillars (19-21) have not exhibited stronger adhesion than flat control surfaces o...

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Section: Resultsmentioning

confidence: 73%

Section: Resultsmentioning

confidence: 99%

Biologically inspired crack trapping for enhanced adhesion

Glassmaker

Jagota

Hui

et al. 2007

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

245

270

View full text Add to dashboard Cite

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“…The elastic modulus, E, of the gel is determined by E ¼ 3kd 4 , where k is the slope of the measured force-displacement relationship, and d is the diameter of the cylidrical probe. 16 …”

Section: Contact Mechanics Measurementsmentioning

confidence: 99%

Cavity growth in a triblock copolymer polymer gel

et al. 2012

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Cavitation rheology is a recently developed measurement method for studying the mechanical properties of polymer gels from sub-micron to millimeter length scales at arbitrary locations within the network material. Current knowledge has focused on understanding the relationship between materials properties, such as modulus or fracture strength, and the maximum pressure for initiating cavitation. After the maximum pressure is reached, the growth of the bubble and the associated pressure drop is sudden and uncontrolled. We develop methods to control the growth of the bubble and to understand the relationship between cavity growth, pressure drop, and the material properties of the surrounding polymer network. We conduct these measurements on swollen networks of a triblock copolymer of poly(methyl methacrylate)-poly(n-butyl acrylate)-poly(methyl methacrylate) (PMMA-PnBA-PMMA).

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“…Therefore, contact mechanical tests 16 were performed to determine E independently and allow G c to be quantified. In these tests, the gels were compressed using a cylindrical probe of 2 mm diameter and the corresponding force vs. displacement curve was recorded.…”

Section: 11mentioning

confidence: 99%

Cavitation and fracture behavior of polyacrylamide hydrogels

2009

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The mechanical properties of gels present qualitatively contradictory behavior; they are commonly soft but also notoriously brittle. We investigate the elasticity and fracture behavior of swollen polymer networks using a simple experimental method to induce cavitation within a gel and adapt scaling theories to capture the observed transition from reversible to irreversible deformations as a function of polymer volume fraction. It is shown quantitatively that the transition from reversible cavitation to irreversible fracture depends on the polymer volume fraction and an initial defect length scale. The use of cavitation experiments permits characterization of network properties across length scales ranging from mm to mm. We anticipate that these results may significantly enhance the understanding of mechanical properties of soft materials, both synthetic and biological.

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Controlling Polymer Adhesion with “Pancakes”

Cited by 164 publications

References 27 publications

Biologically inspired crack trapping for enhanced adhesion

Biologically inspired crack trapping for enhanced adhesion

Cavity growth in a triblock copolymer polymer gel

Cavitation and fracture behavior of polyacrylamide hydrogels

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