Magnetic hysteresis for multi-state addressable magnetic microrobotic control

We present a new scheme of remote addressable magnetic actuation for sub-mm microrobotics which uses the hysteresis characteristics of multiple magnetic materials to achieve advanced state control of many magnetic actuators sharing the same magnetic control inputs. Using this standard approach, remote magnetic actuation of a single magnet has been achieved for untethered motion control with a single magnetic control input. We propose the simultaneous use of multiple magnetic materials with varying hysteresis characteristics to effectively gain multiple control inputs as different applied magnetic field strengths. As a first experimental implementation of this idea, we present a set of three heterogeneous magnetic modules floating on a liquid surface which can be remotely reconfigured by application of a field of varying magnitude. As a second implementation, we present a team of up to six independently actuated walking microrobots made from a composite material whose net magnetic moment can be selectively turned on or off by application of a large magnetic field pulse. We also demonstrate a team of two addressable microrobots performing a task requiring cooperative teamwork. The presented concept providing multiple magnetic control inputs could be applicable in various areas of milli- or microrobotics to address multiple magnetic elements for motion or actuation control.