Liang Lulu, Zhao Jieliang, Niu Qun, Yu Li, Ma Zhiyun, Wu Xiangbing, Wang Wenzhong, Yan Shaoze
School of Mechanical Engineering, Beijing Institute of Technology, Beijing, 100081, PR China.
Division of Intelligent and Biomechanical Systems, State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing, 100084, PR China.
Mater Today Bio. 2023 Jun 16;21:100704. doi: 10.1016/j.mtbio.2023.100704. eCollection 2023 Aug.
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.
自然界中的动态粘附系统一直是智能粘附表面发展的灵感来源。然而，生物系统中观察到的快速可控接触粘附背后的机制从未得到充分解释。在此，对蜜蜂可展开的粘性脚垫（可变接触面积）的控制原理进行了研究。即使没有神经肌肉反射，脚垫也能响应朝向其身体的特定拖动活动（产生剪切力）而被动展开。这种被动展开归因于柔软脚垫的结构特征，其与剪切力密切配合。然后，观察并分析了由大量分支纤维支撑的分层结构。实验和理论结果表明，剪切力可使原纤维相对于剪切方向的角度减小，从而导致脚垫临时接触面积的旋转并实现其被动展开。此外，原纤维角度的减小会导致脚垫内液体压力增加，进而增强其展开。本研究提出了一种被动控制粘附系统中接触面积的新方法，可应用于开发各种受生物启发的可切换粘附表面。
