Climbing robots are special mobile robots proposed for engineering tasks such as surveillance and maintenance activities in human inaccessible areas. These robots comprise of responsive gaits, efficient adhesion mechanisms, actuators, and intelligent sensors. Conventional climbing robots have limitations of overweight, specific deployment issues, and flexibility. Bio-inspired climbing robots have the versatility because robots can take up specific feature of natural creatures. Adhesion methods of bio-inspired robots have been represented in this paper. Classifications of such robots are prepared from their adapted adherence. Adhesion techniques of animals and small insects are also overviewed. Resemblance of grasping technique between natural species and climbing robots is discussed. Finally, robots are compared from their design aspects and presented for searching better adhesion system of robots
