Achieving enhanced and tunable adhesion via composite posts

Minsky, Helen; Turner, Kevin T.

doi:10.1063/1.4921423

Cited by 63 publications

(78 citation statements)

References 29 publications

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“…(45,46) As the thickness of the PDMS layer on top of the stiff core is decreased, the maximum stress shifts to the center and the detachment force increases. (45) Considering the strong interfacial bonding between the PS nanopillars and PDMS matrix (Comp+) in the structures investigated here, the PS/PDMS composite effectively acts as a stiff core, similar to the previous work discussed above. However, the discrete nature of the PS nanopillars may affect the stress distribution, thus we investigated our structure using finite element analysis ( Figure 6).…”

Section: Resultsmentioning

confidence: 99%

Hybrid Surface Patterns Mimicking the Design of the Adhesive Toe Pad of Tree Frog

et al. 2017

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Biological materials achieve directional reinforcement with oriented assemblies of anisotropic building blocks. One such example is the nanocomposite structure of keratinized epithelium on the toe pad of tree frogs, in which hexagonal arrays of (soft) epithelial cells are crossed by densely packed and oriented (hard) keratin nanofibrils. Here, a method is established to fabricate arrays of tree-frog-inspired composite micropatterns composed of polydimethylsiloxane (PDMS) micropillars embedded with polystyrene (PS) nanopillars. Adhesive and frictional studies of these synthetic materials reveal a benefit of the hierarchical and anisotropic design for both adhesion and friction, in particular, at high matrix–fiber interfacial strengths. The presence of PS nanopillars alters the stress distribution at the contact interface of micropillars and therefore enhances the adhesion and friction of the composite micropattern. The results suggest a design principle for bioinspired structural adhesives, especially for wet environments.

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Section: Resultsmentioning

confidence: 99%

Hybrid Surface Patterns Mimicking the Design of the Adhesive Toe Pad of Tree Frog

et al. 2017

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“…30 In addition, numerical simulations revealed that the stress distribution along the pillar–substrate interface dramatically varied with the soft layer thickness, Young’s modulus ratio, and materials interface curvature as shown in Supporting Information Figure S1. Particularly, the stresses at the center of the fibril increased with decreasing soft layer thickness, i.e., increasing confinement.…”

Section: Discussionmentioning

confidence: 99%

“…29 Recently, first experimental and numerical studies have been performed for fibrils with axial variations of the Young’s modulus adhering to smooth surfaces. 30 It was found that very thin soft tip layers promise the best adhesion enhancements for smooth substrates. Interestingly, Bae et al demonstrated that a soft tip coating added to a micropatterned fibrillar array improved adhesion to skin, i.e.…”

Section: Introductionmentioning

confidence: 99%

Composite Pillars with a Tunable Interface for Adhesion to Rough Substrates

Fischer

Arzt

Hensel

2016

ACS Appl. Mater. Interfaces

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The benefits of synthetic fibrillar dry adhesives for temporary and reversible attachment to hard objects with smooth surfaces have been successfully demonstrated in previous studies. However, surface roughness induces a dramatic reduction in pull-off stresses and necessarily requires revised design concepts. Toward this aim, we introduce cylindrical two-phase single pillars, which are composed of a mechanically stiff stalk and a soft tip layer. Adhesion to smooth and rough substrates is shown to exceed that of conventional pillar structures. The adhesion characteristics can be tuned by varying the thickness of the soft tip layer, the ratio of the Young’s moduli and the curvature of the interface between the two phases. For rough substrates, adhesion values similar to those obtained on smooth substrates were achieved. Our concept of composite pillars overcomes current practical limitations caused by surface roughness and opens up fields of application where roughness is omnipresent.

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“…Inspired by the unique properties of adhesive surfaces found in nature, micropatterned adhesives are currently under intense research for handling fragile and miniaturized objects, even in demanding environments such as vacuum . Among the various designs, microstructures with mushroom‐shaped tips have an exceptionally high adhesion . It was demonstrated that their pull‐off force, i.e., the force necessary for detaching the adhesive from a substrate, was up to an order of magnitude higher than with nonoptimized flat punch pillars .…”

Section: Introductionmentioning

confidence: 99%

In Situ Observation Reveals Local Detachment Mechanisms and Suction Effects in Micropatterned Adhesives

Tinnemann

Hernández

Fischer

et al. 2019

Adv Funct Materials

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Fibrillar adhesion pads of insects and geckoes have inspired the design of highperformance adhesives enabling a new generation of handling devices. Despite much progress over the last decade, the current understanding of these adhesives is limited to single contact pillars and the behavior of whole arrays is largely unexplored. In the study reported here, a novel approach is taken to gain insight into the detachment mechanisms of whole micropatterned arrays. Individual contacts are imaged by frustrated total internal reflection, allowing in situ observation of contact formation and separation during adhesion tests. The detachment of arrays is found to be governed by the distributed adhesion strength of individual pillars, but no collaborative effect mediated by elastic interactions can be detected. At the maximal force, about 30% of the mushroom structures are already detached. The adhesive forces decrease with reduced air pressure by 20% for the smooth and by 6% for the rough specimen. These contributions are attributed to a suction effect, whose strength depends critically on interfacial defects controlling the sealing quality of the contact. This dominates the detachment process and the resulting adhesion strength.

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Achieving enhanced and tunable adhesion via composite posts

Cited by 63 publications

References 29 publications

Hybrid Surface Patterns Mimicking the Design of the Adhesive Toe Pad of Tree Frog

Hybrid Surface Patterns Mimicking the Design of the Adhesive Toe Pad of Tree Frog

Composite Pillars with a Tunable Interface for Adhesion to Rough Substrates

In Situ Observation Reveals Local Detachment Mechanisms and Suction Effects in Micropatterned Adhesives

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