Untethered Soft Millirobot with Magnetic Actuation

This paper presents scalable designs and fabrication, actuation, and manipulation techniques for soft millirobots under uniform magnetic field control. The millirobots were fabricated through an economic and robust moulding technique using polydimethylsiloxane (PDMS), acrylonitrile butadiene styrene (ABS) filaments, and 3D printed polylactic acid (PLA) rings. The soft millirobots were simple hollow rod-like structures with different configurations of embedded permanent magnets inside of their soft-body or at their ends. The soft-robots were actuated using six different motion modes including: pivot walking, rolling, tumbling, side-tapping, wiggling, and wavy-motion under an external uniform magnetic field control system. The velocities of the millirobots under different motion modes were analyzed under varying magnetic flux densities (B). Moreover, deformation of the soft-robotic body in response to the magnetic field strength was measured and a deflection curve showing bending angle (ϕ) was produced. Soft millirobots were navigated through a maze using a combination of the available motion modes. Different arrangements of the embedded permanent magnets enabled individual soft millirobots to respond heterogeneously under the same magnetic field inputs towards performing assembly and disassembly operation as modular subunits. Overall, this soft millirobot platform shows enormous potential for minimally invasive in vivo applications.