**3.1. Proposal and features of movement principle**

This section describes the proposed movement principle of the robot, which has a soft and deformable body that can move through a confined space. The mechanism of a toy water

**Figure 18.** A toy WATER SNAKE, a cylindrical water balloon which will jump out if it grasps tightly

snake is applied to this principle (Fig.18). The water snake is similar to a cylindrical water balloon. The internal pressure of water inside the balloon is increased by externally grasping and pressing the balloon. Not grasped part is swelled by water pressure and pushed by movement. In the water snake, the external skin rotates and moves inward simultaneously with the outward pushing of the internal skin. Due to this buildup in pressure, no slippage in rotation occurs and the water snake slips from the examiner's grasping hand.

Fig.19 shows the proposed movement principle of the cylindrical soft robot. Magnetic particles inside the water balloon are affected by the external magnetic field and push the inner side of a balloon to the direction of a magnetic field in a manner similar to the examiner's grasping hand, as explained for the case of the toy water snake (Fig.19(2)). This causes the water balloon to rotate (Fig.19(3)(4)).

The key features of the proposed movement principle are


12 Will-be-set-by-IN-TECH

intestines by clockwise rotation of the front body and anticlockwise rotation of the rear body. These capsule-type robots require power supply wires and a permanent magnet. A potential problem with this design is that the rotational drive could cause engulfment. P. Glass et al. developed new controllable capsule endoscopes, the prototypes have used shape memory alloy or micro motors to press elastomer micropillar legs into the gastrointestinal lining to anchor the capsule in place.[14][15] Bio-inspired adhesives by the elastomer micropillar legs to stick the capsule to the intestinal lining allow the clinician to control the progress of the capsule along the patient's gastrointestinal tract. Another type of capsule robot mounts a ferromagnetic material inside the body and is moved by applying a gradient magnetic field. [16] The limitation of this design is that slipping locomotion is affected by the surface friction of organs. A magnetic particle has been reportedly developed that is lighter than liquid, and

This section presents an advanced locomotion method that produces non-slipping motion in digestive organs and the abdominal cavity by developing an endoscopic robot. The developed endoscopic robot is soft, deformable, and can move through a confined environment of

This section describes the proposed movement principle of the robot, which has a soft and deformable body that can move through a confined space. The mechanism of a toy water

**Figure 18.** A toy WATER SNAKE, a cylindrical water balloon which will jump out if it grasps tightly

on mixing with liquid creates a new impetus. [17]

**3.1. Proposal and features of movement principle**

internal organs.


This section also explains the condition that realizes the movement principle. Each parameter is shown in Fig.20. The parameters of the condition are


The condition required for movement without slippage is given by Eq. 2. This equation determines the value of the external magnetic field to be input.

$$a < F < a + b \tag{2}$$
