3D printed optical devices with strain- and light-dependent properties

Stimuli-responsive materials have attracted an increasing attention because of their capability of sensing the environmental signals and of modifying their physical or chemical properties, accordingly. The recent development of 3-dimensional (3D) printing technologies has enabled the creation of objects with unprecedented complex geometries. By combining the appropriate 3D printing method with specific stimuli-responsive molecules in a 3D shape, novel architected materials have been proposed and realized. Most of these studies have been focused on shape transformation and volume shifting, with target applications such as drug delivery, tissue engineering and soft robotics, whereas little has been done in the field of photonics and optoelectronics. In particular, 3D printing of photonic components with optically active and light-responsive materials is poorly explored, since the 3D printing process, involving exposure to ultraviolet (UV) radiation or high temperatures, can modify the optical properties of the embedded compounds.This PhD thesis aims at the development of optical components with 3D shape and properties tailorable by external physical stimuli. To this aim, 3D printing technologies based on photopolymerization have been used and three sets of optical components realized.First, refractive freeform optics capable of generating complex light patterns have been designed and manufactured. The combination of 3D printing technologies and replica molding process enabled the fabrication of elastomeric refractive freeform optical components whose 3D shape and, consequently, the generated light pattern can be changed through controlled device strain. These properties have been used to realize cryptographic devices. Moreover, light-emitting and photochromic molecules have been successfully embedded in transparent photocurable materials. The composition of the photocurable materials and the printing parameters have been optimized to obtain single color light-emitting 3D structures, as well as a compact white light source. Novel 3D optical devices have been introduced by using two photochromic molecules incorporated into a transparent printable material. Such devices featured optical properties (e.g. absorption in the visible range and fluorescence), which can be controllable by external light stimuli, and provide a valuable platform for demonstrating the possibility of performing optical arithmetic processing.