Nature’s Intricate Engineering Inspires Advanced Material Development
The delicate and complex structures of butterfly wings have long fascinated scientists, and now, researchers at MIT have made a groundbreaking discovery that could pave the way for the development of revolutionary new materials. By capturing the initial moments of butterfly wing scale formation, the team has uncovered the mechanics behind the formation of the intricate ridges that give butterfly wings their unique properties. This insight into nature’s engineering could lead to sustainable and advanced functional materials with tailor-made optical, thermal, chemical, and mechanical characteristics.
The Complexity of Butterfly Wings
Butterfly wings are covered with tens of thousands of minute scales, akin to tiny tiles on a paper-thin roof. Each scale, no larger than a grain of dust, is astonishingly complex, with a corrugated surface that aids in water absorption, heat dissipation, and light reflection, giving the wings their iridescent glow.
The MIT research team has managed to capture the very first moments of this transformation, when a single scale begins to form its ridged pattern. Using advanced imaging techniques, they observed the micro-scale features on the wings of butterflies as they metamorphosed from pupae.
The Formation of Ridges
The team sequentially imaged a single scale as it grew from the wing membrane, revealing for the first time how the initially smooth surface began to wrinkle, forming tiny parallel ridges. These corrugated structures eventually developed into the fine ridges that define the function of the adult scale.
The researchers found that the transformation from a smooth to a ridged surface was likely the result of a process called buckling – a general mechanism describing how a smooth surface wrinkles when growing in a confined space.
Normally, as engineers, we don’t want buckling to happen because it’s an instability. But in this case, the organism is using buckling to initiate the growth of these intricate functional structures, explained Mathias Kolle, Associate Professor of Mechanical Engineering at MIT.
Nature’s Engineering Insights
The research team is now working to visualize more stages of butterfly wing growth, hoping to gain insights into how they might design advanced functional materials in the future.
We hope to understand and emulate these processes to design and fabricate new functional materials sustainably. These materials will exhibit custom-tailored optical, thermal, chemical, and mechanical properties, suitable for textiles, building surfaces, vehicles – essentially, any surface that needs to exhibit properties dependent on its micro- and nanoscale structures, Kolle added.
The team’s findings were recently published in the journal Cell Reports Physical Science. The study’s co-authors include the lead author, former MIT postdoc Jan Totz, co-lead author and postdoc Anthony McDougal, graduate student Leonie Wagner, former postdoc Sungsam Kang, Professor of Mechanical and Biomedical Engineering Peter So, Professor of Mathematics Jörn Dunkel, and Professor of Materials Physics and Chemistry at the University of Salzburg Bodo Wilts.
The Development Mechanism of Ridges
The researchers observed that the ridges form as the butterfly’s wing scales grow, with the cells of the scale’s membrane being effectively anchored by actin filaments – long threads that run beneath the growing cell membrane, acting as a supportive scaffold.
The team suspects that as the wing scale grows, it buckles between these actin filaments, forming the initial parallel ridges. To test this hypothesis, they developed a theoretical model that describes the general mechanics of buckling, incorporating image data such as the height of the scale membrane at different stages of development and the spacing between actin filaments across the growing membrane.
By reversing the model, the researchers found that the principles of mechanical buckling could produce the same ridged patterns observed in actual butterflies.
Conclusion and Implications for Materials Science
McDougal noted, We want to learn from nature, not only about the function of these materials but also about how they are formed. For instance, if you want to make a wrinkled surface, which is useful for a variety of applications, this provides two very easy-to-adjust ‘knobs’ to customize the way these surfaces wrinkle. You can change the spacing of the materials that are fixed, or you can change the amount of material that grows between the fixed parts, and we found that the butterfly uses both strategies.
This research not only deepens our understanding of the natural world but also offers a promising path forward for the development of new materials that could transform various industries.
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