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

Abstract

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.

Fly on the wall

“…A more finely tuned or altogether different attachment mechanism is needed. It is nontrivial to construct a detachable attachment mechanism similar to those seen in [20], [21], let alone at this much smaller scale. However, we predict that once a more elaborate attachment mechanism is developed, the control strategy illustrated in this paper is suitable for direct application.…”

A Study on the Effect of Electrolyte Concentration on Surface Integrity in Micro Electrochemical Discharge Machining

“…However, change in surface integrity characteristics with varied electrolyte concentration in ECDM need to be studied to understand the influence of electrolyte concentration on the material removal mechanism and resulting machining quality of ECDM. Furthermore, control over the profile of surface wrinkles may lead to novel applications such as self-cleaning surfaces [10].…”

Biomimetic self-cleaning surfaces: synthesis, mechanism and applications

“…To account for this contradiction, Lee & Fearing [87] proposed that the shaking of the particles during the shearing process was the main reason that seta arrays shed most of the particles (figure 6c). Mengü ç et al [9] believed that the particles rolling under the fibre could enhance the self-cleaning property of a fibrillar adhesion system. Moreover, they suggested that the dragging rate and average load are two critical parameters that affect the performance of the self-cleaning process.…”

“…However, soft fibres showed only 55% recovery upon fouling with large particles, as particles prefer to embed readily within the soft polymers (figure 5c-d) and prevent the further self-cleaning of soft polymers. Further, Mengü ç et al [9] designed vertically aligned elastomer microfibres and tested the self-cleaning properties of the biomimetic material after rsif.royalsocietypublishing.org J. R. Soc. Interface 13: 20160300…”

“…By contrast, various surfaces in Nature exhibit a high intrinsic ability to clean themselves without any external aid. This phenomenon, due to its unique mechanism and high adaptability, has attracted tremendous research curiosity in past decades [1][2][3][4][5][6][7][8][9][10]. The concept of self-cleaning was initially unveiled based on the superhydrophobic nature of certain plant leaves.…”