An earthworm-like locomotive mechanism for capsule endoscopes

A wireless capsule endoscope, M2A, has been developed to replace the conventional endoscope. However, the commercialized capsule endoscope moves passively by peristaltic waves and gravity, which has some limitations for doctors to diagnose more thoroughly and actively. In order to solve this problem, a locomotive mechanism is proposed for a wireless capsule endoscope. Based on the tests of various actuators, a piezoactuator is selected as a microactuator for the capsule endoscope. Piezoactuators are known to have limited displacement with high voltage supply. In order to overcome the limitation of common piezoactuator, the impact based piezoactuator is developed to realize long stroke up to 11 mm. Moreover, clampers mimicked the claw of insects are employed. A prototype of the earthworm-like locomotive mechanism integrated with an impact based piezoactuator and engraved clampers is developed. It has 15 mm in diameter and 30 mm under retraction stage and 41 mm under elongation stage in total length. Hollow space is allocated to comprise essential endoscope components such as a camera, communication module, battery, and biosensors. For the feasibility test of proposed locomotive mechanism, a series of experiments was carried out including in-vitro tests. Based on results of the experiments, we conclude that the proposed locomotive mechanism is effective to be used for microcapsule endoscopes.