Animals have greatly inspired the development of robotics with their sophisticated bodies after the evolution of millions of years. By directly harnessing the intelligence of animals, the technical bottlenecks such as integration of actuation mechanism and energy source for untethered microrobot could be overcome. Our research group proposed an approach to develop a living soft microrobot by optogenetic locomotion control of Caenorhabditis elegans, called RoboWorm. This thesis work further improves the RoboWorm technology. Firstly, the applications of RoboWorm to support biophysical research of C. elegans are illustrated through a literature review. Secondly, the performance of RoboWorm has been significantly improved by generating a new transgenic strain of C. elegans, with a different approach to hijack the worm motor neurons. The third aspect is to improve the operation and enhance the user-friendliness of the RoboWorm system. Overall, this thesis improves the performance and demonstrates applications of the RoboWorm technology.