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Curling Iron: How Thermobimetal Could Change Architecture

Line/Shape/Space Ι Oct. 13, 2015

Ever since the Industrial Revolution gave architects a smorgasbord of new factory-made materials to create buildings with, certain designers have based their identity and designs around signature elements. For Ludwig Mies van der Rohe, it was brawny steel beams and glass. Frank Gehry chose billowing waves of titanium. Mario Botta indulges his postmodern influences with brick. And dramatically sculpted concrete gives Zaha Hadid’s buildings their instantly recognizable look.

For Doris Sung, it’s thermobimetal.

Sung’s research-based practice, located in Rolling Hills, California, near Los Angeles, is dedicated to turning this odd, little-known material into a dynamic and transformative building element. Operating primarily from grant money (“We don’t have clients,” Sung says), her firm DO|SU Studio Architecture pursues open-ended experiments, focusing on new properties and behaviors of the material first and worrying about practical applications later. “We don’t know exactly what it is until we get there,” she says.

Thermobimetals are composite alloys that exploit a common trait most materials have. Two types of metal are slammed together with an industrial press, permanently fusing them. One material expands at a rapid clip when heated, as all materials do. The other expands at a slower rate. As the first material expands, it’s held in place by the slower expanding material, and it begins to curl.

Sung’s studio is using thermobimetals to build art installations, pavilions, and building components. Her job is to figure out how to take advantage of this seemingly simple curling action and transform it into functional architecture. So far, she’s used thermobimetals as self-regulating ways to open or close apertures for ventilation and sun shading, to increase strength of lightweight structural surfaces, and to self-assemble without the use of tools or hands.

Her Bloom pavilion, for example, is a space installed at the Los Angeles Materials and Applications Gallery. Recently honored with a 2015 AIA Small Project Award, it’s made up of 14,000 unique leaf-like thermobimetal sheets. Shaped like a series of conjoined vaults topped by a funnel, it resembles a mechanical orchid that shifts, stretches, and undulates in response to the sun’s heat. As the day progresses, the pavilion’s tiles curl and bend to let in sunlight and fresh air, or exclude them.

It might seem like an overly simple and determined process, designing within this basic, binary reaction, but Sung says there are more variables at play. There’s the amount, and at what temperature, the metal curls. And there’s the geometry of how the metal is cut and placed in a given design, which can turn a curl into a twist. “It’s actually super complicated,” she says. “Our difficulty is that we have to design something [that goes] from the closed position to the extreme open position and for the thousands of positions in between because we can’t always say it’s going to be 95 degrees that day.”

There is a strong biomorphic, organic quality to Sung’s thermobimetal projects, though the chrome-like metallic sheen gives each object a sci-fi edge. (Sung studied biology before she became an architect.) There are flower petal-like hyperboloids, abstracted mollusk-shell spirals, and intricate symmetry resembling snowflakes. These objects’ heat-responsive movement is akin to watching a Venus flytrap snap up prey: Thin sheets of material spring into action unexpectedly and waveringly, but constrict steadily.

However, Sung says that no matter how consistent they appear, there is no formal preconception or goal for her work. “We don’t worry about aesthetics very much,” she says. The form of DO|SU’s objects are determined by math and geometry, with limited room for artistic preference.

And beyond the Bloom pavilion, there’s the Armoured Corset installation, which resembles a giant metallic beetle carapace. The Exo Structural Tower stands tall like a reed in a marsh. Her Tracheolis prototype is inspired by the perforations (called spiracles) in a grasshopper’s abdomen that allow it to take in oxygen. Here, 3D-printed concrete blocks are made with a series of tubular cavities, alternately plugged up or uninhibited by sheets of thermobimetal, allowing air to enter or exit an otherwise solid block of material. These breathing building components could be put together to form a dynamically self-ventilating wall system, lessening the need for traditional HVAC systems.

Where DO|SU projects bring to mind plants, there’s a set of parallel functions driving their resemblance. The Bloom pavilion, like a flower, is meant to collect sunlight. But, Sung says, “The biggest connection to biology is the fact that this material has its own behavior system.”

The most commercially promising research at DO|SU is focused on a thermobimetal window system that puts sheets of the metal between dual-paneled glass. At cool temperatures, the metal sheets are parallel to the sun’s angle, allowing in ample sunlight and heat. As the temperature rises, the metal sheets begin to curl, eventually blocking out the sun.

Systems like that, which require no external energy to operate yet dynamically react with their environment, stand beyond the typically binary division of passive versus active sustainable building systems. As the green-building movement has matured, a consensus has settled around the notion that the most sustainable buildings first begin with static, passive elements (like quality insulation) before proceeding to more expensive, active energy generation and climate control systems, such as solar panels. Like passive systems, thermobimetals require no energy or attention to use once installed. But like active systems, they respond to their climate and environment. It’s a reminder that “smart” materials and systems don’t always require a computer. Sung calls it a “passive-active system. It falls into its own category.”

Sung has mostly developed her work with thermobimetals in sunny Southern California, but she says that nearly any temperature can trigger the curling threshold, even if she hasn’t tested its capacities in colder climates herself. “I didn’t want to stand out in the cold and build it,” she says. “It’s kind of selfish.”

But Sung’s aversion to shivering helped spawn a new direction for DO|SU’s research: self-assembly. If she didn’t want to shuffle through snowdrifts with mittened hands gripping a blowtorch, how about working on a thermobimetal system that would snap itself into place once the mercury hits a balmy 20 degrees?

Sung envisions (and is researching) an IKEA-like flat-packed sheet of thermobimetal that folds up into a chair at a given temperature threshold. “Instead of ‘do-it-yourself,’ in this case it’s ‘do-it-with-no-one,’” she says.

Like much of DO|SU Studio Architecture’s output, a self-assembling chair seems far off from traditional notions of architecture. But as her research has asserted again and again, practical applications are what happens after you’ve followed the chain of logic each experiment demands without asking too many questions about where it’s all leading. “If we can do a chair,” Sung says, “we can also [do] an emergency shelter.”

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