Dissertation Title: Biologically-inspired Structural Color: Material Design and Fabrication Strategies Drawn from Nature’s Color Palette

Abstract: 

To harness the spectacular functionality found in nature, researchers have developed a multitude of biomimetic and bio-inspired techniques, each with strengths and constraints. A classic example is structural color, which abounds in nature, creating captivating visual displays from the brilliant plumage of the bird of paradise to the camouflage of the chameleon, with functional uses in mating, warning, communication, defense and more. Structural color provides a fascinating case study for exploring the role of material design on macroscale properties and can provide insights on animal evolution, photonic devices, human and animal communication, signaling, and art. These impressive effects result from interference and diffraction of light incident upon multilayer nanostructures, in which color is broadly tuned based on surface structure and geometry. Throughout the natural world, we see examples of clever, multifunctional features and solutions adapted to serve organisms in their local environments, interact with other living creatures, and maintain robustness and structural integrity over a lifetime. The processes and resulting hierarchical systems use few materials and demonstrate complex functional properties that inspire human-made engineered systems.

This thesis provides tools and design methodologies for directing design and fabrication of structurally-colored surfaces. First, we depict methodologies based around computational inverse design for the formulation of nanostructures exhibiting structural coloration, and demonstrate prototype surfaces fabricated from these designs. Next, we employ self-assembly of colloidal particles as a versatile, low cost approach for mimicking aspects of natural coloration. We explore the role of substrates on evaporative dynamics and interplay between pigment and structure in pattern formation. We further examine the social implications of such work; as commercialization of structural color becomes more feasible, we have an opportunity to critically examine the social and environmental impacts and contributions of this field. Through this work, we aim to provide methods and tools for researchers to control color production and devise new structurally-colored surfaces with directed properties by presenting material building blocks and demonstrating their role in color production.

This thesis provides a path towards expanding the palette of achievable colors and patterns through bio-inspired design techniques, and lends an understanding of the multitude of ways in which we can pattern, tune, and control factors that induce coloration. The benefits of such biomimetic nanostructures are plentiful: they provide brilliant, iridescent color with mechanical stability and light steering capabilities. Structural color can be harnessed for long lasting paints, fabrics, signaling and communication systems, and displays. The color changes achievable with these structures are intuitively interpretable by humans. We discuss the methods for control over material design to tune nano- and microscale structure and properties in order to achieve macro scale responses that humans can interact with in meaningful and interesting ways. Through this work, we aim to provide tools with which researchers can explore color through a material design lens.

Committee members:

Christine Ortiz, Professor of Materials Science & Engineering, MIT (advisor)
Pattie Maes, Professor of Media Arts and Sciences, MIT
Mathias Kolle, Associate Professor of Mechanical Engineering, MIT