Miniaturized machine moving in a pipe using photothermal effect

Optically driven small machines have such features as easily miniaturized in fabricaiont and as controlled by optical energy which is supplied in wireless. We reported an optically controled machine which moves like a caterpillar on the basis of photo-thermal effect. It constis of two parts; a body and feet. The feet can stick to the floor due to magnetic force and therefore it has such ability as ascending a slope, and ultimately it succeeded in climbing the vertical wall and moved underneath the ceiliing. A lot of applications are expected to this kind of machine. However, if the prupose is restircted to the movement inside the pipe, the structure can be more simplified. This time we propose a miniaturized machine which moves like a mole or an earthworm. It mainly consists of a shape-memory alloy and a spring, and nylon wires are attacehd at the head and tail. When the machine moves in the pipe, these wires cause difference in friction force bewteen the forward movement and the backward movement. Stretching and contracting are brought by photon-thermal effect of the body part constising of the alloy and spring. This machine is placed in a vinyl tube and controled by a light beam outside from a halogen lamp. In room tempertuare the alloy is kept stretched by the spring, but when the beam is projected ontothe body from outside, it contracts to the original size becasue photo-thermal effect brings much larger force than the stretching force due to the spring. Then the wires at the head prevent moving back and the wires at the tail easily slip. This fact brings forward movement of the machine. At this moment 25 seconds are necessary for one cycle of movement and the moving speed is 2.6 mm/cycle.