Fig. 5. Helical surface crawling locomotion mode in experiments and simulation.

(A) As a new locomotion mode of the sheet-shaped robot, the robot can move against or with the fluid flow by helical surface crawling inside a cylindrical tube. It can also withstand flow when $\stackrel{⃑}{\mathit{B}}$ is off. The blue arrows indicate the direction of the fluid flow. The fluid filled in the tube is water here. (B) The robot can crawl in a bending tube by controlling the direction of the rotating axis of $\stackrel{⃑}{\mathit{B}}$. (C) Simulation analysis on (i) distribution of the contact pressure and (ii) the anisotropic distribution of friction. In (ii), the rectangles represent the unwrapped sheet-shaped robot. The black dots indicate the positions of the contact area under the simulation settings. In (A) and (B), the yellow lines indicate the positions of the boundaries. The directions of the rotating magnetic field control inputs are indicated by red arrows. Scale bars, 1 mm (A) and 2 mm (B). Photo Credits: Ziyu Ren, Max Planck Institute for Intelligent Systems.