A locomotive system mimicking pedal locomotion of snails for the capsule endoscope

Recently, a capsule endoscope has been used for medical diagnosis for the small intestine. It doesn't cause much pain to patients during the operation unlike a conventional endoscope. However, the capsule endoscope has some limitation in obtaining an image of the digestive organ because its movement depends only on the peristaltic motion. To overcome this problem, the locomotive system is necessary for the capsule endoscope. In this paper, we proposed two locomotive systems, mimicking the locomotive mechanism of snails and earthworms. First, we developed a scale up prototype of the crawler mimicking the locomotive mechanism of snails. It has five segments and four joints, where two of four joints are actuated by DC motors. In the front and rear segments, a suction cup is installed, which consists of an electromagnetic solenoid and a rubber sheet. In locomotion experiments on a horizontal plane and on an inclined plane of 10 degrees, we confirmed that the developed crawler could locomote at the speed of 17 mm/cycle. Secondly, we developed a prototype crawler mimicking the locomotive mechanism of snails and earthworms. It can elongate and contract itself longitudinally by using shape memory alloys (SMA) and compression springs. By using this mechanism, we could successfully shrink its size. This prototype crawler could stick and locomote on a horizontal plane. In locomotion experiments on a horizontal plane, we confirmed that the developed crawler could locomote at the speed of 3 mm/cycle. We think that this locomotive system is useful for the capsule endoscope for digestive organs.