Multimodal Motion Control of Soft Ferrofluid Robot With Environment and Task Adaptability

Abstract

Soft microrobotics has recently been an active field that advances new microrobot design, adaptive motion, and biomedical applications. In this work, we study the ferrofluid robot (FR), which has soft nature and exhibits paramagnetism. Currently, motion of the FR is usually realized by magnetic force, and the task execution requires relatively complex systems for simultaneous field and gradient control. To enable the FR with more motion modes for environment and task adaptability, we program three dynamic field forms and realize three corresponding torque-actuated motion modes: <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Rolling</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Wobbling</i> , and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Oscillating</i> . Together with the force-based <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Dragging</i> mode, we provide a complete motion control scheme for the FR. As this scheme only requires 3-D dynamic fields or gradients for actuation, the complexity of the magnetic actuation system is reduced. We formulate the motion and deformation actuation principles of the FR, and the four motion modes are demonstrated and characterized. With the implementation of automated tracking and control algorithms, controllability of the new torque-based modes is testified. We then fabricate different kinds of environments and cargoes to validate the environment and task adaptability of the FR by using the proposed scheme. Especially, we implement the scheme on a self-constructed system consisting of three mobile coils, and experiments realize the long-distance navigation of the FR via <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Rolling</i> or <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Dragging</i> modes. The ultrasound-guided navigation in a 3-D tissue-mimicking endovascular environment shows the potential for delivery applications.