Photonic Materials Inspired by Biological Cells
Photonic band gap (PBG) materials have remained an intense focus of research since their introduction and have given rise to a wide range of applications such as radiation sources, sensors, wave guides, solar arrays and optical computer chips. Most studies have been devoted to the design and optimization of photonic crystals — a periodic arrangement of dielectric scattering materials that have photonic bands due to multiple Bragg scatterings. However, periodicity is not necessary to form PBGs and amorphous structures with PBGs can offer many advantages over their crystalline counterparts. For example amorphous photonic materials can exhibit band gaps that are directionally isotropic and are more robust to defects and errors in fabrication.
Our group works on a new design for amorphous 2D and 3D PBG materials that is inspired by how cells pack in dense tissues in biology. We can generate structures that exhibit broad PBGs based on a simple model that has been shown to describe cell shapes and tissue mechanical behavior. An advantage of this design is that the photonic and mechanical properties of the material are closely coupled. The material can also be tuned to undergo a density-independent solid-fluid transition and the PBG persists well into the fluid phase. With recent advances in tunable self-assembly of nanoparticles or biomimetic emulsion droplets, this design can be used to create a `photonic fluid’.