Check out this awesome bionic wall-climbing robot. The technology is based on biomimetics, where the robot mimics a gecko's innovative foot design as a template to climb walls without any artificial adhesion. Even though we do not see it, but a gecko's foot is hairy, fine enough to only be seen on the micro level. This molecular adhesion, combined with C-Bot's array of ultrasonic sensors presents exciting and innovative applications. Theoretically you can build such a robot big and strong enough to carry a human up and down a wall.