Fig. 6.

The robot inspired by the dual helical sections of Ray sperms. (A) Structure of the bio-inspired robot. The robot is powered by motors with the rigid helical head and soft tail made of iron wire and cotton wire, respectively. (B) Fitting surface of the rotational speed of head and tail and the forward velocity through the interpolation method. The forward velocity is positively correlated with these two rotational speeds, consistent with the theoretical analysis of sperms’ motions. Forward velocities (mean ± SD) (C) and images (D) of the robot with dual or single helical sections under the same power input (n = 3). The robot with the dual helical sections moves fastest in all solutions, demonstrating its ultra-adaptability in all solutions. The robot with a helical tail relatively adapts to the dilute solution while the robot with a helical head performs better in highly viscous solutions.