Locomotive Mechanism Design and Fabrication of Biomimetic Micro Robot Using Shape Memory Alloy Young Pyo Lee, Byungkyu Kim*, Moon Gu Lee and Jong-Oh Park Microsystem Research Center Korea Institute of Science and Technology, KIST P.O.Box 131, CheongRyang, Seoul 130-650, Korea {yplee93, bkim , crystalship}@kist.re.kr, jop@microsystemt.re.kr * The author to whom all correspondence should be addressed. Abstract— Recently, micro robots have been applied in various industrial areas. Some of them are requested to be able to move in small space or rough environment that people can not reach. It is necessary to have a capability to move at even overturned and adapt simple mechanism to fabricate it easily with small size. In this paper, a novel bio-mimetic micro robot with simple mechanism using shape memory alloy (SMA) is introduced to generate earthworm-like locomotive motion. There have been many kinds of mobile micro robot using the SMA. However, these actuators generally require electric cable for power supply, which might have an adverse effect on the mobility of the micro robot. The proposed micro robot system is composed of an actuator with SMA spring and silicone bellows, wireless control system, wireless power supply (battery) and body frames. The robot is also analyzed to customize required specifications. After the design and experiment, we find out that the micro robot can move a wireless free motion and be fabricated easily. Like an earthworm, the robot can travel on uneven, slippery and flexible environment. Keywords-locomotion; bio-mimetic; earthworm; shape memory alloy; micro robot I. INTRODUCTION Currently, millimeter or micrometer scale robots have been widely studied. From the literatures, robot’s mobility is essential functions. To propose and design effective moving robots, various locomotive mechanisms have been were investigated. Rotating wheel has been the most conventional method for the robot’s locomotion. In this case, the mobility is not sufficient when the robot moves on uneven, slippery or flexible environments [1]. Some of legged robot has been studied, but the mechanism is complex and hard to control [2][3]. In addition, the miniaturization of robots does not mean downsizing the existing macro technologies. It is often necessary to use new principle for actuation and fabrication. In the prior technologies, meso or micro scale robots have needed cable wire for power supply or control. The cable causes limitation of working area and mobility. Therefore, it is necessary to integrate robot with its own control system and power sources. It is also required that the robot moves on the rough environment. In this paper, a bio-mimetic micro robot is proposed in order to create an autonomous free mobility. A two-way linear actuator using shape memory alloy (SMA) spring and silicone bellows is applied to the micro robot. A simple passive clamping mechanism is mounted on the surface of the micro robot. All of locomotive and clamping mechanism is mimicked from earthworm. II. SHAPE MEMORY ALLOY ACTUATOR Generally, SMAs return to their original shape after they are heated even if they undergo shape. That is called shape memory effect. Shape memory effect occurs as the result of a change in the atomic crystal structure of the alloys by a temperature change: austenite phase at a high temperature and the martensite phase at a low temperature. This kind of simple actuation principle is easy to be realized. Also SMA has the advantage of low driving voltage. However, straight SMA wire has some problems with small displacement and difficulty to provide bias force, so called deformation force. Therefore, we make use of SMA spring to compensate the disadvantages. To achieve the two-way linear actuator which moves back and forth, the deformation force is needed because the SMA memorizes the only one shape at the high temperature. A bias spring (steel spring) can be used to provide the deformation force as depicted in Fig.1. The bias spring is stretched when the left SMA spring is heated. At the same time, deformation energy is stored in the steel spring. Then, the energy deforms the SMA spring to its initial length when it cools. Instead of the bias spring, one more SMA spring Figure 1. Two-way linear actuator using SMA spring This research was supported by the Intelligent Micro system Center, Seoul, Korea, which is carrying out one of the 21st century’s New Frontier R&D Projects sponsored by the Korea Ministry of Science & Technology.)