Journal of Bionic Engineering (2024) 21:754–763 https://doi.org/10.1007/s42235-023-00450-x RESEARCH ARTICLE Deformation and Locomotion of Untethered Small?Scale Magnetic Soft Robotic Turtle with Programmable Magnetization 

Lin Xu1,2  · Liu Yang1  · Tao Li1  · Xingbang Zhang3  · Jianning Ding4 

1 School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China 2 The Key Laboratory of Bionic Engineering (Ministry of Education), Jilin University, Changchun 130012, China 3 Shanghai Tianchun Technology Co.,Ltd, Shanghai 201802, China 4 School of Mechanical Engineering, Yangzhou University, Yangzhou 225009, China

AbstractInspired by the way sea turtles rely on the Earth’s magnetic feld for navigation and locomotion, a novel magnetic soft robotic turtle with programmable magnetization has been developed and investigated to achieve biomimetic locomotion patterns such as straight-line swimming and turning swimming. The soft robotic turtle (12.50 mm in length and 0.24 g in weight) is integrated with an Ecofex-based torso and four magnetically programmed acrylic elastomer VHB-based limbs containing samarium-iron–nitrogen particles, and was able to carry a load more than twice its own weight. Similar to the limb locomotion characteristics of sea turtles, the magnetic torque causes the four limbs to mimic sinusoidal bending deformation under the infuence of an external magnetic feld, so that the turtle swims continuously forward. Signifcantly, when the bending deformation magnitudes of its left and right limbs difer, the soft robotic turtle switches from straight-line to turning swimming at 6.334 rad/s. Furthermore, the tracking swimming activities of the soft robotic turtle along specifc planned paths, such as square-shaped, S-shaped, and double U-shaped maze, is anticipated to be utilized for special detection and targeted drug delivery, among other applications owing to its superior remote directional control ability. 

Keywords Magnetic soft robotic turtle · Programmable magnetization · Untethered soft robotics · Bending deformation