ABSTRACT
This chapter is focused on the study of different chromoactive (or optoactive) materials that can change their colour or optical properties in response to different stimuli, and different photoactive materials that can emit light as a response to a range of stimuli or react to light stimuli. This opens up many possibilities for their being used to develop sensors, actuators and multifunctional devices. Therefore, this chapter deals with a range of materials with different working principles but with some things in common that link optical properties and light effects to different thermal, electrical and mechanical stimuli, among other things. For these reasons we have grouped them together in one chapter (as we also did with Chapter 10). Due to their current low impact on the medical sector only one chapter has been devoted to it, although an entire handbook could be devoted to the optically active materials we have dealt with as they have enormous future potential. These materials are usually formed from combinations of ceramic and polymer materials that have generally been processed to obtain
multilayer structures possessing different functionalities, adapting the properties of the whole to specific requirements, which makes them attractive to different sectors of industry. Regarding the family of chromoactive or optoactive materials that can change their colour or optical properties in response to different stimuli, the major medical applications of some of the main materials are detailed. Such materials are electrochromic or electrochromatic, thermochromic or thermochromatic, photochromic or photochromatic and piezochromatic and hydrochromatic. Regarding the family of photoactive materials that can emit light as a response to a range of stimuli or react to light stimuli, the major medical applications of some of the main materials are detailed. Such materials are electroluminescent, fluorescent, photosensitive, photoelectric or phototropic. The materials in this family have numerous applications for the development of sensors and actuators. We will also take a brief look at optical fibres as passive materials for transporting information but that can also be integrated into complex systems in order to produce active devices. The importance of these fibres in other sectors of industry, such as telecommunications or computing, has been fully demonstrated and also has an important place in the Medical Industry. After describing the different aspects of the main families of materials that respond to light and colour, we will examine the different methods that can be used to synthesise, process and characterise the numerous materials belonging to these families. Additionally we will describe the main challenges and research trends concerning these chromoactive and photoactive materials and briefly analyse how Nature is a continuous source of inspiration, as we have seen when dealing with other kinds of intelligent materials.
