Foldable flex-PCB electromagnetic actuation for insect-scale locomotion: design and experimental evaluation

A flexible printed circuit board (flex-PCB) can combine conductors, compliant mechanisms and load-bearing members in a manufacturable laminate, making it attractive for compact mobile robots. In this study, we develop a foldable flex-PCB electromagnetic actuator and use two such hindlimbs to produce insect-scale forward and turning locomotion. Each hindlimb integrates a four-layer, 40-turn planar coil, permanent magnets, a folded parallel-four-bar linkage and a pointed flex-PCB foot. Structural screening showed that a copper-reinforced moving link with localized polyimide-tape hinges operated fastest at 56 Hz. Shortening the foot tip from 8 to 2 mm increased mean speed from 57.1 ± 5.3 to 280.5 ± 11.1 mm/s. On wood, the final tethered robot achieved a mean speed of 400.9 ± 35.5 mm/s, equivalent to 17.4 body lengths per second (BL/s), while the fastest of the ten trials traversed 194 mm in 0.4 s, corresponding to 485 mm/s (21.1 BL/s). Differential excitation produced a turning radius of 38.5 mm. Under onboard battery power with a separate rigid controller, the robot achieved an average x-directed locomotion velocity of 63.4 mm/s (2.55 BL/s) and a turning radius of 58 mm. These results demonstrate a practical route for co-designing commercial flex-PCB conductors and folded mechanisms for rapid, low-voltage miniature locomotion.