  High-speed locomotion of animals gives them tremendous advantages in
exploring, hunting, and escaping from predators in varying environments.
Enlightened by the fast-running gait of mammals like cheetahs and wolves, we
designed and fabricated a single-servo-driving untethered soft robot that is
capable of galloping at a speed of 313 mm/s or 1.56 body length per second
(BL/s), 5.2 times and 2.6 times faster than the reported fastest predecessors
in mm/s and BL/s, respectively, in literature. An in-plane prestressed hair
clip mechanism (HCM) made up of semi-rigid materials like plastic is used as
the supporting chassis, the compliant spine, and the muscle force amplifier of
the robot at the same time, enabling the robot to be rapid and strong. The
influence of factors including actuation frequency, substrates,
tethering/untethering, and symmetric/asymmetric actuation is explored with
experiments. Based on previous work, this paper further demonstrated the
potential of HCM in addressing the speed problem of soft robots.
