Elastomers for Photonic Applications

This PhD Thesis investigates the design, fabrication, and characterization of mechanically tunable photonic structures, with particular emphasis on stretchable Distributed Bragg Reflectors (DBRs) and planar microcavities. The research explores how elastic photonic architectures can be integrated with responsive molecular systems to create multifunctional optical devices for sensing applications, particularly within the field of Structural Health Monitoring. The work begins with an introduction to the fundamental principles of photonic crystals, focusing on DBRs as one-dimensional periodic structures capable of generating photonic bandgaps that can be exploited for optical sensing. Building on this theoretical framework, the Thesis presents the development of stretchable DBRs based on elastomeric materials. Fabrication strategies, multilayer deposition methods, and optical characterization techniques are discussed, with particular attention to the opto-mechanical behavior of these structures under mechanical strain. The results demonstrate that mechanical deformation can reversibly modulate the periodicity of the multilayer, enabling controlled tuning of the photonic bandgap and the corresponding optical response. A central contribution of this work is the realization of a hybrid dual-response platform combining stretchable DBRs with polymer mechanophores. This system integrates photonic and molecular responses to mechanical stimuli, enabling simultaneous modulation of structural color and activation of mechanophore fluorescence. The experimental results reveal the potential of such architectures for the development of smart materials and mechanochromic sensing devices. The Thesis further investigates stretchable planar microcavities incorporating fluorophores, providing preliminary insights into the modulation of emission properties through mechanical deformation. In addition, an independent project explores a low-cost fabrication strategy for photonic multilayers using a modified fused deposition modeling (FDM) 3D printer repurposed as a dip-coating system, demonstrating an accessible approach to photonic structure fabrication. Overall, this research contributes to the advancement of stretchable photonics by demonstrating how mechanically tunable photonic structures can be combined with functional molecular systems to create responsive optical devices with potential applications in sensing, smart materials, and structural monitoring technologies.