Controllable adhesive mechanisms via the internal fibers in soft footpads of honeybees

• Published in: Materials today bio Vol. 21; p. 100704
• Main Authors: Liang, Lulu, Zhao, Jieliang, Niu, Qun, Yu, Li, Ma, Zhiyun, Wu, Xiangbing, Wang, Wenzhong, Yan, Shaoze
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.08.2023; Elsevier
• Subjects: Fiber; Full Length; Honeybees; Pressure; Shear force; Unfolding adhesive footpads; Honeybees; Shear force; Unfolding adhesive footpads; Pressure; Fiber
• ISSN: 2590-0064; 2590-0064
• DOI: 10.1016/j.mtbio.2023.100704

The dynamic adhesive systems in nature have served as inspirations for the development of intelligent adhesive surfaces. However, the mechanisms underlying the rapid controllable contact adhesion observed in biological systems have never been adequately explained. Here, the control principle for the unfolding adhesive footpads (alterable contact area) of honeybees is investigated. The footpads can passively unfold, even without neuro-muscular reflexes, in response to specific dragging activity (generating shear force) toward their bodies. This passive unfolding is attributed to the structural features of the soft footpads, which cooperate closely with shear force. Then, the hierarchical structures supported by numerous branching fibers were observed and analyzed. Experimental and theoretical findings demonstrated that shear force can decrease fibril angles with respect to the shear direction, which consequently induces the rotation of the interim contact area of the footpads and achieves their passive unfolding. Furthermore, the decrease in fibril angles can lead to an increase in the liquid pressure within the footpads, and subsequently enhance their unfolding. This study presents a novel approach for passively controlling the contact areas in adhesive systems, which can be applied to develop various bioinspired switchable adhesive surfaces. [Display omitted] •Foldable adhesive footpads of honeybees controlled by shear force were found.•Hierarchical footpads supported by branching fibers were observed and analyzed.•Shear force can decrease fibril angles and then lead to the unfolding of footpads.•As the angle decreases, the increasing inner pressure can enhance the unfolding.