Microfabricated systems for next generation microrobotics and swarm microrobotics: scaling and technological challenges toward mass fabrication

Microrobotics is a field of the scientific and technological research that exploits Microtechnologies for the design and fabrication of miniaturized autonomous or semi-autonomous systems, i.e., in its strict sense, with millimetre or sub-millimetre size. Microrobotics has a particular relevance in the development of a relatively new scientific discipline named “Swarm Robotics”. This aims to apply Swarm Intelligence strategies to a large number of robotic agents, allowing collective, decentralized and self-organizing behaviours of the robots, which lead to an intelligent, often bio-inspired, emergent behaviours of the whole system, while considering issues of robustness and scalability. It is indeed in the perspective of miniaturization that Swarm Robotics becomes meaningful, leading to the concept of “Swarm Microrobotics”. This thesis describes new concepts, technical solutions and microfabrication methodologies of miniaturized systems and microsystems to be applied in Microrobotics, while considering mass-production issues in order to converge on Swarm Microrobotics. Biomimetics and bio-inspired swarm strategies for Swarm Microrobotics are also topics of discussion. The work presented in this thesis focuses in particular on some microrobotic subsystems: communication, sensors and tools. The ability to communicate is of paramount importance in natural (e.g., insect) and robotic swarms, where (direct or indirect) communication between units is the base of emergent behaviours. Communication capabilities between microrobots are strongly related to the microrobot size and power available onboard. The first implies that only highly miniaturized communication systems can be integrated, while the latter imposes strict limits on communication distance. An integrated and scalable optical microsystem for communication and sensing in microrobots operating in multi-agent systems or swarms, and methods of mass fabricating the same, are presented. Furthermore, in order to actively interact with the environment, microrobots need to be equipped with sensing micro-tools to detect objects and eventually transport micro-parts. Due to the size and power constraints, the optimal systems should be multifunctional and simple in order to facilitate integration onboard the microrobot and, eventually, mass fabrication. A large amount of microrobots is, in fact, necessary in order to sensibly affect the environment and accomplish significant tasks in the macro-world. The concept, design and simulations of a vibrating micro-cantilever, capable of working as microrobotic touch sensor, or “antenna”, and eventually as grasping tool with feedback sensing, are also presented. This thesis was written also trying to give the reader the feeling of the big efforts necessary to accomplish the challenging task to down scale a complete robotic system to these uncomfortable “mesoscale” dimensions, stressing the limits of “top-down” micro-fabrication and assembly. Beyond these limits, the fabrication method must be revolutionized, converging efforts towards the “bottom-up” approaches of bio-nanotechnologies and molecular engineering, and trying to boost research in micro and nano-robotics by means of hybridization of the simplest microorganisms (which can exhibit swarm behaviour too), e.g. bacteria, with technology, aiming to increasingly merge micro- and nano-technology with biology, towards a novel field that could be referred to as “micro- and nanobionics” or “micro- and nanocybernetics”.