Magnetic-driven 3D-printed biodegradable swimming microrobots

A magnetic object subject to an external rotating magnetic field would be rotated due to the alignment tendency between its internal magnetization and the field. Based on this principle, 12 shapes of swimming microrobots around 1 mm long were designed and 3D-printed using biodegradable materials Poly (ethylene glycol) diacrylate (PEDGA). Their surface was decorated with superparamagnetic iron oxide nanoparticles to provide magnetic responsivity. An array of 12 permanent magnets generated a rotating uniform magnetic field (∼100 mT) to impose magnetic torque, which induces a tumbling motion in the microrobot. We developed a dynamic model that captured the behavior of swimming microrobots of different shapes and showed good agreement with experimental results. Among these 12 shapes, we found that microrobots with equal length, width, and depth performed better. The observed translational speed of the hollow cube microrobot can exceed 17.84 mm s⁻¹ (17.84 body lengths/s) under a rotating magnetic field of 5.26 Hz. These microrobots could swim to the targeted sites in a simplified vessel branch. And a finite element model was created to simulate the motion of the swimming microrobot under a flow rate of 0.062 m s⁻¹.