An Insect-Scale Untethered Piezoelectric Robot with Multiple Biomimetic Features.

Load capacity and speed are 2 essential dimensions in the practical application of miniature robots. In recent years, numerous miniature robots with large load capacity or high speed have been developed. However, it is still a challenge to achieve high speed under large load. Inspired by mythological creatures such as dragon, qilin, and chimera that integrate the characteristics of different animals, an insect-scale tripedal piezoelectric robot incorporating multiple biomimetic features is proposed. By emulating the terrestrial flapping of fish tail, a single driving leg with 2 orthogonal bending vibrations is designed to achieve rapid and flexible motion. The tethered robot is 38 mm in length and weighs 8.6 g, exhibiting a maximum forward speed of 313.49 mm/s (8.25 body length per second), a maximum angular speed of 11.54 rad/s, and a minimum curvature radius of 12.64 mm. By emulating the functional roles of the forelimbs and hindlimbs in otariids galloping, a support scheme combining 2 passive wheels with a driving leg is proposed to realize high speed under large load. The forward speed achieves more than 300 mm/s under 200 g (23.26 times self-weight). Moreover, an untethered robot is fabricated. It exhibits a cost of transport of only 1.91 and can operate continuously for 70 min. The untethered robot demonstrates marked potential for operation in narrow spaces, owing to its small size, superior load characteristics, and high flexibility. We believe that this design method of integrating multiple bionic features can offer a new perspective for enhancing the performance of miniature robots.