One of the most celebrated models of biomimetic design is the butterfly wing. More specifically, the wing of the Morpho menalaus, or blue morpho butterfly, exhibits a model biological phenomenon called structural color.
Unlike pigments or dyes, structural color scatters light of particular wavelengths based on particular micron- and submicron-scale surface structures. A significant benefit of structural color is that it does not fade like pigments and dyes. Manufacturers have attempted to replicate these characteristics in industrially produced products, although achieving optimal results is difficult.
In a recently published article in Advanced Materials entitled “Molecules to Masterpieces: Bridging Materials Science and the Arts,” a multidisciplinary team describes its process for developing a structural color coating for a 46-foot-tall art installation. Materials scientists from Cornell University’s Wiesner Lab partnered with the artist Kimsooja to create a new iridescent surface treatment for her work, A Needle Woman: Galaxy was a Memory, Earth is a Souvenir, now part of the Wakefield, UK, Yorkshire Sculpture Park’s permanent collection. The team focused on the self-assembly properties of block copolymers (BCPs), a scalable nanotechnology enabling the creation of complex nanostructures of varying lengths required for structural color behavior. The scientists devised a custom casting-lamination process to coat PET sheets, which were adhered to flat steel plates, with BCPs—reportedly the first known application of BCPs at an architectural scale.
The Wiesner-Kimsooja collaboration is indicative of other innovative endeavors to bring novel visual properties to architecture and design materials. For example, researchers at ETH Zurich are developing new light-emitting properties in wood. Recognizing wood’s capacity as a substrate for new kinds of functional materials, including unexpected optical characteristics like transparency, the scientists sought to experiment with luminescence.
Adopting a process similar to glow sticks, which combine two chemicals to generate light, the team soaked wood veneers with one chemical and allowed them to dry. Once primed, the scientists could coax the veneers to illuminate by adding the counterpart ingredient. The new chemiluminescent wood suggests intriguing design possibilities, such as environmental graphics or emergency wayfinding applications.
Transforming patterns and images is another current pursuit. Researchers at MIT’s Computer Science & Artificial Intelligence Laboratory developed a color-changing printmaking process that enables the creation of imagery that can transition between two visual states. Thermochromic materials that transform with temperature changes are a familiar technology, but thus far, have typically been limited to a single color of ink.
The MIT researchers developed a full-color (CMYK) approach using multiple inks that transition from colored to transparent and vice versa. The effect can be useful whenever heat-initiated visual changes are desired, such as vessels or appliances that warn of unsafe surface temperatures, medical packaging that alerts users of expired contents, or exterior graphics that transform in the warmth of direct sunlight.
Another potential benefit of thermochromism is energy savings. Inventor Joe Doucet developed a specially formulated exterior paint with seasonal color-changing capability. “In summer, a white house can be ~12ºF cooler internally than a black house, while in winter, a black house can be ~7ºF warmer internally, with the opposite closely mirroring this result,” he explains. The dark gray-colored paint, which is good at heat absorption and retention, changes quickly to white above a set temperature of 77ºF, becoming heat-reflective.
Based on rough estimates that a 1ºF interior temperature change equates to approximately 3% of a building’s operating energy, Doucet claims that the paint could save up to 25% of energy costs during peak seasons. He adds that various tints can be added to the paint to add different hues while retaining the paint’s thermal functionality.
As these examples reveal, novel smart technologies are expanding the capabilities of design materials as well as shifting cultural perceptions about material characteristics in general. For example, the aesthetic qualities of materials are typically isolated from their functionality, yet these developments demonstrate that aesthetic performance can also be functional.
Such new material approaches will allow the built environment, which has long been perceived as a static entity, to transform and adapt to changing conditions in dynamic and advantageous ways.
