These SMA-based locomotion concepts have been extensively exploited in biomedical applications, to develop endoscopic devices capable of exploring complex environments such as the human colon. By properly controlling the SMAs, a sinusoidal undulatory motion at 0.17 Hz is produced, obtaining a locomotion comparable to that of a real worm. It is made of 12 separate driving units, whose activation is based on an SMA coil element working against an elastic bias. The inchworm robot is 300mm long and 2mm wide. to realize a microrobot capable of mimicking the crawling motion of the Caenorhabditis elegans. A similar concept was also exploited by Yuk et al. The fabricated microrobot can reach a stroke of 2 mm per activation cycle, with an average speed of 10 mm/min. A conceptual sketch of such a locomotion principle is reported in Fig. By activating the SMA coil in a periodic way, a locomotion pattern is achieved.
When the SMA is cooled down, the front part of the robot elongates while the rear stays still, clamped to the surface. When the SMA is activated, needles placed on the front part of the robot clamp to the walking surface, while the rear part of the robot slides forward.
The overall length and diameter of the robot are 50mm and 9.5 mm, respectively. The body of the robot consists of an SMA coil actuator embedded in a silicone bellow, which acts as an elastic biasing element. An example of an earthworm-like SMA microrobot capable of locomotion functionalities was presented by Kim et al.
The insertion of SMA actuators inside human bodies can be alternatively realized by means of a locomoting principle. Gianluca Rizzello, Paul Motzki, in Endorobotics, 2022 6.2.3.5 Locomoting robots for endoscopy
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