In 1995, Museum of Modern Art architecture and design senior curator Paola Antonelli exhibited "Mutant Materials in Contemporary Design," a show that explored the changing character of materials in the last decade of the 20th century. Antonelli revealed two types of mutation in her selection of works for display: materials that resemble others in appearance, such as plastics modified to look like metals; and materials that assume new and unexpected physical properties, such as wood made as soft as fabric.
In the two-plus decades since that exhibition, scientists have made significant advances in material technology, even adding a new mutation to the mix: materials that actively tune their properties in response to external stimuli. Such discoveries fit the general category of smart materials, which include responsive materials like shape-memory alloys or piezoelectric films. However, compared to early smart materials, some recent versions involve more intricately designed nanostructures whose tunable properties are the result of precisely defined and changeable physical compositions. These versatile substances demonstrate the impressive possibilities enabled by designing the architecture of materials.
One example is a shape-shifting material developed by scientists from Georgia Tech, the California Institute of Technology, and ETH Zurich. The substance is composed of a silicon-lithium alloy arrayed in a 3D arrangement akin to trabeated (post-and-lintel) structures in buildings. When a current is applied, an electrochemical reaction causes the nanomaterial to deform via thickening and bending—a process that translates new geometry across the whole system. As a result, the tetragonal microlattices generate regular sinusoidal patterns or, in one sample, a dome-like structure that emerges out of a flat disc. Unlike prior shape-changing materials that required constant current, this novel substance is truly switchable—meaning it remains in its new state without the need for additional electricity. Notably, this substance is known as an architected material—one that incorporates physical principles of architecture and engineering in the efficient arrangement of cellular structures. Deformation provides a shape-shifting advantage here for applications such as implantable medical devices or battery electrodes.
A team of researchers from Zhejiang University, Hangzhou, and the Qingdao University of Science and Technology, Qingdao, China, has developed another electrochemically responsive material. In this case, a reversible switch enables a porous metallic material to change from a hydrophilic surface to a hydrophobic one. The so-called wettability switch includes many potential commercial and industrial applications ranging from data encryption to water collection via fog-harvesting. The scientists also created a smart anti-fouling fluid gate that allows the selective absorption and passage of oil or water—an approach that could be used for sophisticated oil and water separation applications.
Metamaterials have also attracted scientific attention due to their intrinsic ability to manipulate the physical characteristics of electromagnetic waves. Collaborators representing Peking University in Beijing, and Southeast University and Jiangsu Cyber-Space Science & Technology in Nanjing, China, have created a self-regulating metasurface, or a nanostructured interface that can control light without human intervention. The smart and reprogrammable material can adapt to changing environmental conditions, reconfiguring itself as needed to accomplish a given task. For example, the scientists consider a flying airplane that must maintain uninterrupted communications with a satellite. Current technologies used for this purpose are intricate and costly mechanisms that include beam-steering units and signal-processing equipment. However, the researchers demonstrate that a smart metasurface equipped with a microprocessor and gyroscope sensor can accomplish the same function at reduced cost and complexity—and without the need for manual control. This self-adapting surface shows that the dynamic capabilities of a sophisticated communications system can be incorporated into a material itself.
Perhaps the most significant expression of a mutant material is the creation of a wholly new state of matter, as Brown University scientists recently achieved. Physics professor Jim Valles and his colleagues, who research superconducting materials, ascertained the unusual behavior in a strip of superconductive thin-film made of yttrium barium copper oxide. The scientists perforated the film with a regular array of holes to monitor the characteristics of a magnetic field when charged with electricity. With current applied, particles in the material circle the holes and form relationships called Cooper pairs, twinned electrons that exhibit either superconductive or insulating characteristics. In this experiment, however, the material behaved like a metal, conducting electricity with a small amount of resistance. Although the scientists had hypothesized this possibility, they had not seen it demonstrated. “We showed that, indeed, Cooper pairs are responsible for transporting charge in this metallic state,” Valles explained in a Brown University press release. “What’s interesting is that no one is quite sure at a fundamental level how they do that, so this finding will require some more theoretical and experimental work to understand exactly what’s happening.” In the future, the discovery could lead to entirely new kinds of electronic devices.
In addition to making novel scientific findings, researchers focused on mutant materials anticipate a future of entirely new and unexpected technological capabilities. That these capacities are, in large part, the result of designing architectural structures at the nanoscale should intrigue architects for two primary reasons. First, some architectural principles and approaches are transscalar—such as the relationships between form and performance, structure and space, and design and construction. For example, in a Journal of Materials Research article, engineer Lorenzo Valdevit and collaborating authors address the need for the equivalent of better CAD/CAM tools at the nanoscale: “The ordered topologically complex nature of these materials and the degree of precision with which their features can now be defined suggest the development of new multiphysics and multiscale modeling tools that can enable optimal designs.”
Second, these materials demonstrate new possibilities for architecture at the building-scale. The substances described above may one day provide new functionality to architectural structures and surfaces—such as responsive, solar harvesting building skins that continuously calibrate with sun angles without mechanical parts. Alternatively, other discoveries made from dynamic, shape-changing, tunable material architecture may apply to buildings themselves—such as resilient structures that can reversibly deform to deflect hurricane winds. Considering these possibilities, is it, therefore, time for hybrid design and science firms to create architecture at extreme scales?
