Nonangled anisotropic elastomeric dry adhesives with tailorable normal adhesion strength and high directionality

Sameoto, Dan; Sharif, Helia; Téllez, Juan; Ferguson, Brendan; Menon, Carlo

doi:10.1080/01694243.2012.693809

Cited by 22 publications

(25 citation statements)

References 29 publications

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“…Interestingly, while a few individual fibers near the perimeter of the contact area fail earlier for PDMS A, the core group of fibers that experience lower torques during pull off remain in contact for a longer period -showing a secondary stable fiber arrangement after the initial contact area is reduced. This is consistent with the findings in our other submitted work [48] that the larger overhangs primarily affect the resistance to nonaxial forces on fibers, and are therefore most apparent when observing adhesion loss near the perimeter of hemispherical indenters. …”

Section: Discussionsupporting

confidence: 92%

“…These adhesives have already demonstrated some of the highest adhesion pressures (based on the measured pull-off force divided by contact area) to date for elastomer dry adhesives [48] and it has been shown that the reason they are so effective is that the amount of overhang of their cap is high enough to withstand significant tangential loads during normal pull off of smooth surfaces. The resistance to off-axis loading makes the materials more resistant to peeling off of smooth surfaces as well when examined on the macroscale [48]. This, in turn, greatly improves the final pull-off force, because once the perimeter begins to peel the whole area loses contact quite quickly.…”

Section: Discussionmentioning

confidence: 98%

“…The PDMS adhesives are well characterized in other work [48], and are only used as comparison in this paper for their behavior for the smallest diameter indenters, but offer insight into the behavior of nearly optimal elastomeric dry adhesive designs with relatively easy to fabricate dimensions. The polyurethane fabrication method is much more easily scaled to several square feet or more in size, and is therefore the focus of this paper on manufacturability and adhesion quality.…”

Section: Fiber Geometriesmentioning

confidence: 99%

“…The silicone dry adhesives were cast from the same mold as described in other work [48], and had pillar heights of 20 μm, pillar diameters near the top of 10 μm, and cap tip diameters of either 13 or 16.4 μm. As a result, the fibers were of high quality, but the molds and fibers tend to be more fragile, especially for those with the largest overhangs as they can occasionally be vulnerable to tearing or collapse during demolding [34].…”

Section: Fiber Geometriesmentioning

confidence: 99%

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Robust large-area synthetic dry adhesives

Sameoto

Ferguson

2012

Journal of Adhesion Science and Technology

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Although bioinspired dry adhesives are nearly a decade old, there are to date no available commercial products based on these materials. Although commercialization is a while off, great strides have been made with respect to physical modeling of actual gecko adhesion, synthetic fabrication methods, and introduction of capabilities like self-cleaning, directional behavior, and superhydrophobic behavior into synthetic variations. Despite the large number of fabrication methods available, there are still specific difficulties in manufacturing these materials that limit their use in commercial applications. In this paper, we describe how a simple manufacturing technology can be adapted to create relatively high-strength adhesives at low costs on large areas. Our focus is on determining how larger diameter, easily manufactured fiber shapes can be best designed to adhere to smooth surfaces. This manufacturing method has been used to successfully produce adhesives from a variety of materials, and we demonstrate how it can be adapted to form the microscale mushroomshaped fibers necessary for strong adhesion without needing vacuum casting. Additionally, we present practical lessons learned in what makes an effective dry adhesive for industrial applications, where the expected surfaces to be encountered are mostly flat and rigid in comparison to the adhesive material. Finally, the importance of tip roughness due to manufacturing methods is demonstrated to be a significant source of adhesion reduction which must be accounted for when designing these materials.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 98%

Section: Fiber Geometriesmentioning

confidence: 99%

Section: Fiber Geometriesmentioning

confidence: 99%

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Robust large-area synthetic dry adhesives

Sameoto

Ferguson

2012

Journal of Adhesion Science and Technology

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“…In general, adhesive and frictional characteristics of fibrillar surfaces could be improved by changing the fiber shape [19], angle [20], [21], tip ending shape [21], [22], [23], and material [24]. Both angled fiber structures [21], [22], [25], [26], [27], [20], [28], [17] and non-angled asymmetrical fibers [19], [29], [28], [17] could result in friction anisotropy. Passive angled structures made of polyurethane could generate friction anisotropies of 5.6 [22] that is similar to gecko foot-hair friction anisotropy, the ratio of its backward to forward friction force [30].…”

Section: Introductionmentioning

confidence: 99%

Fiberbot: A miniature crawling robot using a directional fibrillar pad

Han

Marvi

Sitti

2015

2015 IEEE International Conference on Robotics and Automation (ICRA)

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Vibration-driven locomotion has been widely used for crawling robot studies. Such robots usually have a vibration motor as the actuator and a fibrillar structure for providing directional friction on the substrate. However, there has not been any studies about the effect of fiber structure on robot crawling performance. In this paper, we develop Fiberbot, a custom made mini vibration robot, for studying the effect of fiber angle on robot velocity, steering, and climbing performance. It is known that the friction force with and against fibers depends on the fiber angle. Thus, we first present a new fabrication method for making millimeter scale fibers at a wide range of angles. We then show that using 30 • angle fibers that have the highest friction anisotropy (ratio of backward to forward friction force) among the other fibers we fabricated in this study, Fiberbot speed on glass increases to 13.8 ± 0.4 cm/s (compared to v = 0.6 ± 0.1 cm/s using vertical fibers). We also demonstrate that the locomotion direction of Fiberbot depends on the tilting direction of fibers and we can steer the robot by rotating the fiber pad. Fiberbot could also climb on glass at inclinations of up to 10 • when equipped with fibers of high friction anisotropy. We show that adding a rigid tail to the robot it can climb on glass at 25 • inclines. Moreover, the robot is able to crawl on rough surfaces such as wood (v = 10.0 ± 0.2 cm/s using 30 • fiber pad). Fiberbot, a low-cost vibration robot equipped with a custom-designed fiber pad with steering and climbing capabilities could be used for studies on collective behavior on a wide range of topographies as well as search and exploratory missions.

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Switchable Adhesives for Multifunctional Interfaces

Croll

Hosseini

Bartlett

2019

Adv Materials Technologies

125

107

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The reliable bonding or attachment of materials is critical in many industries, is a common necessity of daily life, and is key to functionality in numerous biological settings. [1][2][3][4][5][6][7][8][9][10][11] Adhesives Joining two materials with an adhesive is an extremely common activity, but is most often irreversible. However, emerging and current applications ranging from consumer and medical products to soft robotics and wearable bio-monitoring devices demand strong adhesives which can be easily removed on-demand and subsequently reused. This requires new paradigms in adhesive science and engineering, resulting in the emergence of new classes of multifunctional switchable adhesives. Here summarized is the current state of the art in switchable adhesive systems, focusing on how devices fit into the basic science of adhesion while providing performance metrics for comparison across current approaches. Using fracture mechanics as a guide, systems are classified as functioning under one of three basic mechanisms: near-interface, contact area, or mechanical. These mechanisms must be initiated or "triggered" by a specific input, which can include mechanical, electromagnetic, fluidic, or thermal stimuli. Triggers and adhesion switching performance are compared through the use of a "switching ratio," the interfacial energy release rate, and an estimate of mechanism timing. Finally, it is discussed that how the fundamental mechanisms relate to challenges and opportunities for switchable interfaces in future applications and adhesive systems.

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Nonangled anisotropic elastomeric dry adhesives with tailorable normal adhesion strength and high directionality

Cited by 22 publications

References 29 publications

Robust large-area synthetic dry adhesives

Robust large-area synthetic dry adhesives

Fiberbot: A miniature crawling robot using a directional fibrillar pad

Switchable Adhesives for Multifunctional Interfaces

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