An insect-scale soft robot has fast relative speed of motion, high load-carrying capability, and exceptional robustness.

Running speed degradation of insect-scale (less than 5 cm) legged microrobots after carrying payloads has become a bottleneck for microrobots to achieve high untethered locomotion performance. In this work, we present a 2-cm legged microrobot (BHMbot, BeiHang Microrobot) with ultrafast untethered running speeds, which is facilitated by the complementary combination of bouncing length and bouncing frequency in the microrobot’s running gait. The untethered BHMbot (2-cm-long, 1760 mg) can achieve a running speed of 17.5 BL s⁻¹and a turning centripetal acceleration of 65.4 BL s⁻²at a Cost of Transport of 303.7 and a power consumption of 1.77 W. By controlling its two front legs independently, the BHMbot demonstrates various locomotion trajectories including circles, rectangles, letters and irregular paths across obstacles through a wireless control module. Such advancements enable the BHMbot to carry out application attempts including sound signal detection, locomotion inside a turbofan engine and transportation via a quadrotor.

Fleas in nature generally have potent muscles for jumping and crawling abilities to overcome obstacles in complex environments, while it is challenging for flea-sized robots to have powerful actuators due to the size effect. This work presents a novel high-voltage pulsed actuator for a flea-sized robot (3.4mm-in-length) to achieve powerful jumping and fast crawling locomotion. The working principle of the actuator is based on the electric arcing phenomenon between two electrodes under high-voltage pulses. The jumping height and length of the 3.4mm flea-sized robot can be up to 46 and 87 times of body lengths, respectively, and the crawling speed can be over 46 body lengths per second on a flat surface. With its tiny size and high jumping performance, the flea-sized robot can jump over obstacles and then crawl through narrow gaps. This work presents the world's first robot with the same body size and locomotor performance as fleas in nature, significantly expanding the use scenario of microrobots.

In nature, insects can swiftly move and actively morph to adapt to complex and varied conditions. However, replicating this capability in insect-scale robots requires sophisticated structural designs, which are difficult to achieve at such a small scale without fundamental hardware innovations. This work proposes a coupling mechanism between actuation and morphing by combining an arc-heating actuator and shape memory alloy wires, presenting a fast insect-scale robot (83.4 body lengths per second) capable of active morphing and self-recovery. The arc-heating actuator is designed to provide the kinetic energy and the thermal energy essential for deforming the wires. The robot can compress its body thickness to traverse through a gap of 70% its height smoothly within 2.2 seconds and is amphibious. Furthermore, after enduring pressure 5 million times its weight, the robot is flattened, but fully recovers its original size and performance in just a few seconds.

The ability to move backward is crucial for millimeter-scale microrobots to navigate dead-end tunnels that are too narrow to allow for turning maneuvers. In this study, we introduce a 15-mm-long legged microrobot, BHMbot-B, which is capable of rapid forward and backward locomotion through vibration mode transition control. By properly arranging the vibratory motions of the magnet, cantilever, and linkages, the pitching movement of the body and the vibration of the forelegs are in phase during the first-order vibration mode of the cantilever and in antiphase during the second-order mode, which induces the forward and backward movement of the microrobot. Owing to its outstanding load-bearing capacity, the BHMbot-B equipped with dual electromagnetic actuators, an onboard battery, and a control circuit, can execute complex running trajectories under wireless command. Its maximum untethered running speeds are evaluated as 18.0 BL/s (360 mm/s) in the forward direction and 16.9 BL/s (338 mm/s) in the backward direction.