Size, shape, and orientation of macro-sized substrate protrusions affect the toe and foot adhesion of geckos [RESEARCH ARTICLE]

Yi Song, Jiwei Yuan, Linghao Zhang, Zhendong Dai, and Robert J. Full Geckos are excellent climbers using compliant, hierarchically-arranged adhesive toes to negotiate diverse terrains varying in roughness at multiple size scales. Here, we complement advancements at smaller size scales with measurements at the macro-scale. We studied the attachment of a single toe and whole foot of geckos on macro-scale rough substrates by pulling them along, across, and off smooth rods and spheres mimicking different geometric protrusions of substrates. When we pulled a single toe along rods, the force increased with the rod diameter. Whereas, the attachment force of dragging toes across rods increased from about 60% on small diameter rods relative to a flat surface to approximately 100% on larger diameter rods, but showed no further increase as rod diameter doubled. Toe force also increased as the pulling changed from along-rod loading to across-rod loading. When pulled off from spheres, toe force increased continuously with sphere diameter as observed in along-rod pulling. For feet with separated toes, attachment on spheres was stronger than that on rods with the same diameter. Attachment force of a foot decreased as rod and sphere size increased, but remained sufficient to support the body weight of geckos. These results provide a bridge to the macro-scale roughness seen in nature by revealing the importance of the dimension, shape, and orientation of macro-sized substrate features for com...
Source: Journal of Experimental Biology - Category: Biology Authors: Tags: RESEARCH ARTICLE Source Type: research