Dynamic self-cleaning in gecko setae via digital hyperextension

Hu, Shihao; Lopez, Stephanie; Niewiarowski, Peter H.; Xia, Zhenhai

doi:10.1098/rsif.2012.0108

Cited by 80 publications

(96 citation statements)

References 45 publications

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“…We hypothesized that the high contact angle hysteresis of the dry toe pad would expel droplets of water and allow a dry interface for adhesion, similar to results from experiments using a thin water layer (Hsu et al, 2012) and self-cleaning experiments (Hansen and Autumn, 2005;Hu et al, 2012). In support of this, force measurements from geckos with dry toe pads tested on misted glass (DM) were closer to the control treatment values than all other treatments.…”

Section: Initialmentioning

confidence: 62%

“…These results contradict the innate dry self-cleaning property of the toe pads (Hansen and Autumn, 2005;Hu et al, 2012). The adhesive toe pads can effectively displace dry particulate simply by maintaining a lower attractive force than the surface (Hansen and Autumn, 2005), and this self-cleaning property is magnified when the geckos are allowed to perform their natural stick-peel behavior (Hu et al, 2012). Unlike adhesion tests where a dry fouling agent was used, we found that toe pads do not regain full adhesive performance after repeated use when water was used as the fouling agent.…”

Section: Initialmentioning

confidence: 75%

“…In contrast we found that natural replacement did not significantly increase shear adhesive force in the treatment groups. These results contradict the innate dry self-cleaning property of the toe pads (Hansen and Autumn, 2005;Hu et al, 2012). The adhesive toe pads can effectively displace dry particulate simply by maintaining a lower attractive force than the surface (Hansen and Autumn, 2005), and this self-cleaning property is magnified when the geckos are allowed to perform their natural stick-peel behavior (Hu et al, 2012).…”

Section: Initialmentioning

confidence: 92%

“…One of the gecko's more touted achievements is its ability to self-clean dirt particles from its adhesive pads. This process occurs by repeatedly stepping on clean surfaces (Hansen and Autumn, 2005;Hu et al, 2012). We therefore controlled stepping for two reasons: first, to control for the level of wetting in each treatment such that all geckos were tested under the same conditions; and second, to test for a self-cleaning effect, which is supported by the low contact angle hysteresis of water droplets to the setal mat (Autumn and Hansen, 2006).…”

Section: Introductionmentioning

confidence: 99%

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The effect of surface water and wetting on gecko adhesion

Stark

Sullivan

Niewiarowski

2012

Journal of Experimental Biology

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SUMMARYDespite profound interest in the mechanics and performance of the gecko adhesive system, relatively few studies have focused on performance under conditions that are ecologically relevant to the natural habitats of geckos. Because geckos are likely to encounter surfaces that are wet, we used shear force adhesion measurements to examine the effect of surface water and toe pad wetting on the whole-animal performance of a tropical-dwelling gecko (Gekko gecko). To test the effect of surface wetting, we measured the shear adhesive force of geckos on three substrate conditions: dry glass, glass misted with water droplets and glass fully submerged in water. We also investigated the effect of wetting on the adhesive toe pad by soaking the toe pads prior to testing. Finally, we tested for repeatability of the adhesive system in each wetting condition by measuring shear adhesion after each step a gecko made under treatment conditions. Wetted toe pads had significantly lower shear adhesive force in all treatments (0.86±0.09N) than the control (17.96±3.42N), as did full immersion in water (0.44±0.03N). Treatments with droplets of water distributed across the surface were more variable and did not differ from treatments where the surface was dry (4.72±1.59N misted glass; 9.76±2.81N dry glass), except after the gecko took multiple steps. These findings suggest that surface water and the wetting of a geckoʼs adhesive toe pads may have significant consequences for the ecology and behavior of geckos living in tropical environments.

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Section: Initialmentioning

confidence: 62%

Section: Initialmentioning

confidence: 75%

Section: Initialmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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The effect of surface water and wetting on gecko adhesion

Stark

Sullivan

Niewiarowski

2012

Journal of Experimental Biology

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“…Interestingly, the large microfibres in the large contaminants regime were comparable in absolute adhesion and contact self-cleaning performance to the natural gecko (figure 5d). In making this comparison, it is important to note the differences and similarities in the test protocols between our study and natural gecko self-cleaning studies [7,8]. First, our observations were for a patch area smaller than a single gecko toe, and as the patch size increases, the observed adhesive performance may decrease [28].…”

Section: Comparison Of the Self-cleaning Performance Of The Syntheticmentioning

confidence: 87%

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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Bio‐inspired Dry Adhesives: Contact Electrification and Electrostatic Interactions

Izadi

Zandieh

Penlidis

2017

Kirk-Othmer Encyclopedia of Chemical Technology

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This article discusses contact electrification and related electrostatic forces as they pertain to the adhesive properties of gecko foot pads and gecko‐inspired adhesives. Following an introduction to gecko adhesion and gecko‐inspired adhesives, fundamentals of contact electrification‐driven electrostatic interactions are discussed, along with electrostatic phenomena that can affect these interfacial interactions. Particular attention has been given to three special phenomena: electrostatic discharge, surface charge leakage, and charge penetration into the matrix of fibrillar dry adhesives. Through the analysis of the effects of these three phenomena, it is demonstrated how the general characteristics of fibrillar dry adhesives, such as strong attachment, easy detachment, and self‐cleaning, can be considered and explained in terms of contact electrification‐driven electrostatic interactions of these materials. In this connection, the effects of many factors (electrical conductivity, dielectric properties, and geometrical properties) on contact electrification‐driven electrostatic interactions of fibrillar dry adhesives have also been discussed. The ensuing discussion on the magnitude of electrostatic adhesion forces that fibrillar dry adhesives can develop via contact electrification has been carried out with respect to three key parameters (surface roughness, humidity, and tip geometry) and the effects that these can have on the strength of the contact electrification‐driven electrostatic interactions of gecko and gecko‐inspired adhesives.

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Dynamic self-cleaning in gecko setae via digital hyperextension

Cited by 80 publications

References 45 publications

The effect of surface water and wetting on gecko adhesion

The effect of surface water and wetting on gecko adhesion

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

Bio‐inspired Dry Adhesives: Contact Electrification and Electrostatic Interactions

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