Bioinspired Colorimetric Metasurfaces for Next Generation, On-Chip Imaging of Tissue Microstructure

The origin and progression of a variety of leading health challenges, encompassing Alzheimer’s disease, heart disease, fibrosis and cancer, are directly linked to changes in the presence and orientation of fibrous matter in biological tissue. Fibrous biological tissue exhibits distinct anisotropic optical properties, which can be leveraged for selective imaging. However, these naturally occurring light-matter interactions are inherently weak, posing barriers to their visualization in a clinically translatable manner. Existing imaging techniques which visualize the fibrous properties of biological matter face challenges in complexity, cost, destructiveness, or precision. Thus, innovation in imaging technology of fibrous tissue with facile clinical implementation is urgently needed.<br/><br/>To address this challenge, we develop a new class of anisotropic, colorimetric metasurfaces to selectively visualize disease-relevant fiber density and orientation in biological tissue. We draw inspiration from iridescent structural color which is abundant in nature, arising in the saturated blues of the Morpho butterfly wing or the greens of jeweled beetle shells. At the micrometer scale and smaller, these naturally occurring, three-dimensionally (3D)-architected photonic crystals are composed of ordered, geometrically anisotropic features which exhibit distinct interactions with light at varying angles of incidence or polarization state. Due to their 3D hierarchical architecture, these nature-derived systems are unique sources of polarization-sensitive structural color with high color purity and brightness. Based on these principles, our colorimetric metasurfaces are designed to exhibit a high sensitivity to varying polarization states of light. We implement our colorimetric metasurfaces as a next-generation tissue microstructure imaging technology. Starting with the example of breast cancer diagnostics, we then expand our view to the rich palette of fiber-affecting diseases where metasurfaces hold great potential to achieve rapid, precise and low-cost tissue diagnostics with facile clinical implementation.