One of the most graceful phenomena widely observed in nature is self-assembly; living systems spontaneously form their body structure through the developmental process. While this remarkable phenomenon still leaves much to be understood in biology, the concept of self-assembly becomes undeniably indispensable also in artificial systems as they increase in size and complexity. Based on this consideration, this paper discusses the realization of self-assembly with the use of a modular robot. The main contributions of this paper are twofold: the first concerns the exploitation of emergent phenomena stemming from the interplay between the control and mechanical systems; the second is related to the implementation of the different adhesiveness among the modules. Here, form generation by self-assembly is considered as the result of time evolution toward the most dynamically stable state. Owing to this, the proposed method also satisfies significant ability of self-repair without making any modification to the proposed algorithm. Simulation results show that stable and spontaneous self-assembly is achieved irrespective of the initial positional relationship among the modules.