Fig. 2. Undulatory crawling and swimming locomotion modes inside fluid-filled channels.
(A) Experimental transition of the propulsion direction of the robot’s undulating body by changing the magnetic actuation frequency. (i) The sheet-shaped robot performs undulatory crawling when the actuation frequency is 1 Hz. (ii) The sheet-shaped robot performs undulatory swimming when the actuation frequency is 10 Hz. The yellow lines indicate the position of the boundaries. Scale bars, 1 mm. (B) The simulation of the undulatory locomotion modes. The simulated robots were actuated at ∣∣ = 40 mT, f = 5 Hz. (i) The simulated robot performed undulatory crawling when the friction was considered. (ii) The simulated robot performed undulatory swimming when the friction was removed. The black dashed lines indicate the displacement along the x direction. (C) Frequency sweeping experiments for three different fluid viscosities. (D) The variation of the undulatory amplitude for three different fluid viscosities. The trendline is fitted by the least-square method. In (C) and (D), N is the number of trials in each case. The error bars stand for the error of the mean. Photo Credits: Ziyu Ren, Max Planck Institute for Intelligent Systems.