We present a study of collective robotics by including a mechatronics point of view. In the field it is usually claimed that collective robots are simple and relatively cheap because they are produced in large quantities. Instead in our study we show that collective robots are not simple because they need sensors and actuators for additional work. Our experience in designing robots and producing them allows us to analyze the manufacturing costs of different collective robots . We present in this work four robots developed prior and during to this thesis. Chapter 2 concerns the e-puck robot. This is a robot designed for education, however, it is used in research to experiment collective behaviors. The s-bot robot is presented in Chapter 3. This is a robot that has the collective ability to self-assemble to form larger structures and increase its performance. In Chapter 4 we present the marXbot robot. It is a modular robot developed in the laboratory to meet the needs of different research hubs. One of its modules allows it to self-assemble with its teammates and with the robot handbot presented in Chapter 5. The handbot is a robot that can climb and handle objects. It can climb for example a shelf to grasp a book. On the ground it is transported by marXbot. In Chapter 6 the performance of robots are presented. We expose a study of their performance gain when the robots are self-assembled. Finally we compare in Chapter 7 the four robots from the mechatronics point of view and in respect to their cost.