In this study, the authors developed a novel active guidewire including a spiral-type magnetic microrobot and ball joint to realize active locomotion and improve the steering capability within external magnetic fields. Most active guidewires provide only steering ability without active locomotion, and their steering angles depend on the physical properties of the wire. The developed mechanism provides a wider range of steering angles because the total steering angle is the sum of the joint angle and wire angle. To evaluate the performance of the proposed mechanism, we compared and analyzed the steering and active locomotion in a dc field and rotating magnetic field in conditions involving and not involving the ball joint mechanisms. At a low magnetic field strength (up to 4 kA/m), considerable improvement in the steering angle owing to the use of the ball joint was noted. The dc and rotating fields with an intensity of 8 kA/m generated peak steering angles of 189 • and 135 • , respectively. Various experiments were conducted, and the results confirmed that the proposed mechanism could improve the steering ability while realizing active locomotion. In particular, the steering stability and movement ability corresponding to different types of magnetic fields could be analyzed. INDEX TERMS Active guidewire, ball joint, spiral-type magnetic microrobot, steering ability, electromagnetic field control.

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