Feng Huashan, Chai Ningli, Dong Wenhao
School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an, China.
Department of Gastroenterology, Chinese Peoples Liberation Army General Hospital, Beijing, China.
PLoS One. 2015 Nov 4;10(11):e0140776. doi: 10.1371/journal.pone.0140776. eCollection 2015.
The posterior sucker of a leech represents a fascinating natural system that allows the leech to adhere to different terrains and substrates. However, the mechanism of adhesion and desorption has not yet to be elucidated. In order to better understand how the adhesion is performed, we analyzed the surface structure, adsorption movements, the muscles' distribution, physical characteristics, and the adsorption force of the leech posterior suckers by experimental investigation. Three conclusions can be drawn based on the obtained experimental results. First, the adhesion by the posterior sucker is wet adhesion, because the surface of the posterior sucker is smooth and the sealing can only be achieved on wet surfaces. Second, the deformation texture, consisting of soft collagen tissues and highly ductile epidermal tissues, plays a key role in adhering to rough surfaces. Finally, the adhesion and desorption is achieved by the synergetic operation of six muscle fibers working in different directions. Concrete saying, directional deformation of the collagen/epithermal interface driven by spatially-distributed muscle fibers facilitates the excretion of fluids in the sucker venter, thus allowing liquid sealing. Furthermore, we found that the adhesion strength is directly related to the size of the contact surface which is generated and affected by the sucker deformation. Such an underlying physical mechanism offers potential cues for developing innovative bio-inspired artificial adhesion systems.
水蛭的后吸盘是一个迷人的自然系统，它使水蛭能够附着在不同的地形和基质上。然而，其吸附和解吸的机制尚未阐明。为了更好地理解吸附是如何进行的，我们通过实验研究分析了水蛭后吸盘的表面结构、吸附运动、肌肉分布、物理特性和吸附力。基于获得的实验结果可以得出三个结论。第一，后吸盘的吸附是湿吸附，因为后吸盘表面光滑，只有在潮湿表面才能实现密封。第二，由柔软的胶原组织和高延展性的表皮组织组成的变形纹理在附着于粗糙表面时起关键作用。最后，吸附和解吸是通过六条不同方向工作的肌肉纤维协同运作实现的。具体来说，由空间分布的肌肉纤维驱动的胶原/表皮界面的定向变形有助于吸盘腹部液体的排出，从而实现液体密封。此外，我们发现附着强度与吸盘变形产生并受其影响的接触面积大小直接相关。这种潜在的物理机制为开发创新的仿生人工附着系统提供了潜在线索。
