Peeling from a biomimetically patterned thin elastic film

Abstract

Inspired by the observation that many naturally occurring adhesives arise as textured thin films, we consider the displacement controlled peeling of a flexible plate from an incision-patterned thin adhesive elastic layer. We find that crack initiation from an incision on the film occurs at a load much higher than that required to propagate it on a smooth adhesive surface; multiple incisions thus cause the crack to propagate intermittently. Microscopically, this mode of crack initiation and propagation in geometrically confined thin adhesive films is related to the nucleation of cavitation bubbles behind the incision which must grow and coalesce before a viable crack propagates. Our theoretical analysis allows us to rationalize these experimental observations qualitatively and quantitatively and suggests a simple design criterion for increasing the interfacial fracture toughness of adhesive films.

Biologically inspired crack trapping for enhanced adhesion

“…Note in Fig. 5B that voids do in fact nucleate ahead of the opening crack tip in several instances, as is the case with thin soft films in confined geometry (40,41). 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).…”

“…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).…”

“…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.…”

Robotic Tentacles with Three‐Dimensional Mobility Based on Flexible Elastomers

“…Figure 6 shows a tentacle with a textured surface that is both more compliant than a flat surface of the same material, and also provides more traction. [27] To demonstrate the improvement in the ability of the tentacle to grip objects with slippery surfaces, we picked up a flat wrench (30 g) coated with gelatin (to make it more slippery) using a tentacle with a textured surface ( Figure 6C-D); this task is one in which similar tentacles with non-textured surfaces failed (an untextured tentacle would pick up the wrench without the gelating coating). Other physical or chemical modifications to the surface of the tentacle could also be applied.…”

Design of gecko-inspired fibrillar surfaces with strong attachment and easy-removal properties: a numerical analysis of peel-zone

“…It is practicable to fabricate adhesive surfaces with specially designed micro-fibrillar structures to modulate their reversible peeling and mechanical properties. Peeling tests have been widely applied to investigate bio-inspired conformal adhesion of fibrillar surfaces [27,[33][34][35]. Therefore, it is very important to understand the fundamental principles of various peeling behaviours to develop innovative gecko-inspired surfaces/adhesives [30].…”