Living Optical Networks for Light Redistribution Inspired by Orchid Leaves

Plants and animals have developed sophisticated hierarchical systems that integrate physicochemical material properties with functional micro- and nanostructures to effectively manage energy, motion, and species survival. These biological systems, besides providing cues on bottom-up manufacturing of technological structures, can offer insight on strategies for efficient energy management. In this study, we investigate the light harvesting and redistribution capabilities of tropical orchid leaves, which employ a cell-based optical network. Unlike regular orchid leaves, the outer epidermal cells of these leaves exhibit a distinctive hexagonally packed short-range order lattice and rounded shape, facilitating optical cross-communication. By replicating this optical network within a tunable biopolymer matrix, we can fabricate versatile devices such as omnidirectional light couplers, wavelength selective optical networks, and cryptographic systems including all-optical unclonable security tags. To reproduce this propagation mechanism, we mimic the leaf structure using free-standing silk fibroin films. The response of the bioinspired cell-based optical networks can be controlled through functionalization achieved by selective doping with pigments and absorbers, as well as by modulating the silk protein conformation. We explore the structure-function relationship of the bioinspired optical networks using finite-difference time-domain optical modelling, revealing that the lateral redistribution of light through cross-communication is not only geometrically but also wavelength dependent.