Contribution of friction and adhesion to the reliable attachment of a gecko to smooth inclines  

作　　者：Zhouyi WANG Qiang XING Wenbo WANG Aihong JI Zhendong DAI 

机构地区：[1]Institute of Bio-inspired Structure and Surface Engineering,Nanjing University of Aeronautics and Astronautics [2]School of Mechanical Engineering,Nantong University

出　　处：《Friction》2018年第4期407-419,共13页摩擦（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 51435008 to Z.D. and 31601870 to Z.W.);Natural Science Foundation of Jiangsu Province, China (Grant No.SBK2016040649 to Z.W.).

摘　　要：Geckos' ability to move on steep surfaces depends on their excellent adhesive structure, timely adjustments on locomotor behaviors, and elaborates control on reaction forces. However, it is still unclear how they can generate a sufficient driving force that is necessary for locomotion, while ensuring reliable adhesion on steep inclines. We measured the forces acting on each foot and recorded the contact states between feet and substrates when geckos encountered smooth inclination challenges ranging from 0° to 180°. The critical angles of the resultant force vectors of the front and hind-feet increased with respect to the incline angles. When the incline angle became greater than 120°, the critical angles of the front- and hind-feet were similar, and the averages of the critical angles of the front - and hind-feet were both smaller than 120°, indicating that the complicated and accurate synergy among toes endows gecko's foot an obvious characteristic of "frictional adhesion" during locomotion. Additionally, we established a contact mechanical model for gecko's foot in order to quantify the contribution of the frictional forces generated by the heel, and the adhesion forces generated by the toes on various inclines. The synergy between multiple contact mechanisms(friction or adhesion) is critical for the reliable attachment on an inclined surface, which is impossible to achieve by using a single-contact mechanism, thereby increasing the animal's ability to adapt to its environment.Geckos＇ ability to move on steep surfaces depends on their excellent adhesive structure, timely adjustments on locomotor behaviors, and elaborates control on reaction forces. However, it is still unclear how they can generate a sufficient driving force that is necessary for locomotion, while ensuring reliable adhesion on steep inclines. We measured the forces acting on each foot and recorded the contact states between feet and substrates when geckos encountered smooth inclination challenges ranging from 0° to 180°. The critical angles of the resultant force vectors of the front and hind-feet increased with respect to the incline angles. When the incline angle became greater than 120°, the critical angles of the front- and hind-feet were similar, and the averages of the critical angles of the front- and hind-feet were both smaller than 120°, indicating that the complicated and accurate synergy among toes endows gecko＇s foot an obvious characteristic of ＂frictional adhesion＂ during locomotion. Additionally, we established a contact mechanical model for gecko＇s foot in order to quantify the contribution of the frictional forces generated by the heel, and the adhesion forces generated by the toes on various inclines. The synergy between multiple contact mechanisms （friction or adhesion） is critical for the reliable attachment on an inclined surface, which is impossible to achieve by using a single-contact mechanism, thereby increasing the animal＇s ability to adapt to its environment.

关 键 词：FRICTION ADHESION INCLINE frictional adhesion GECKO 

分 类 号：Q959.62[生物学—动物学] Q-4