Book excerpt: This book covers biodevices, mainly implantable or quirurgical, for the diagnosis or treatment of different pathologies, which benefit from the use of active materials as sensors or actuators. Such active or "intelligent" materials are capable of responding in a controlled way to different external physical or chemical stimuli by changing some of their properties. These materials can be used to design and develop sensors, actuators, and multifunctional systems with a large number of applications for developing biodevices and medical appliances. Current work on these fields entails problems related to synthesis, characterization, modeling, simulation, processing, and prototyping technologies, as well as device testing and validation, all of which are treated in depth in this book, for the several types of active or intelligent materials covered. The research presented in this book helps further development of medical devices, based on the additional functionalities that the use of active or "intelligent" materials, both as sensors and actuators, supplies. The main results exposed may help with the industrial expansion of this kind of materials as part of more complex systems.