Swallows have been building this way for millennia. Why don’t we?
That question grew out of an unscheduled meeting in 2014 between MIT Assistant Professor of Architecture Caitlin Mueller and Professor Pierre Latteur of the Université catholique de Louvain (UCL) at the annual symposium of the International Association for Shell and Spatial Structures in Brasilia. Mueller had just delivered a talk about one of her research specialties—the three-dimensional printing of structures—and Latteur suggested that Mueller’s approach could be pushed to new heights using drones.
“Up to that point, the application of additive manufacturing technologies to buildings was conceived primarily as a scaled-up version of tabletop 3D printing,” explains Mueller. “Pierre’s vision was to treat unmanned aerial vehicles as the extruders and prefabricated structural components as the extrusion.” With only a few weeks left before the MISTI submission deadline, Mueller and Latteur assembled a proposal for the MIT-Belgium – Université catholique de Louvain Seed Fund grant to investigate the feasibility of Latteur’s methodology.
“We were new professors at our respective institutions,” says Mueller, “but we immediately recognized the complementary nature of our schools’ strengths. UCL offered large-scale manufacturing and testing facilities, which were essential to us because FAA regulations prevent us from flying drones in Cambridge. At MIT, we contributed by expanding on our digital modeling of structural blocks. We created a physical prototype that could be maneuvered by drones and assembled into complex architectural forms.”
A key objective on both sides of the collaboration was to test the limits of the approach and define its advantages and disadvantages. “At UCL, they were looking to push the hardware’s capabilities—payload, energy capacity, and range—as far as possible,” Mueller says. “Here at MIT, we had to adapt our thinking to the reality that a drone is somewhat imprecise in knowing its location in space. To make our blocks viable, we had to abandon the centimeter-or-so tolerances that apply to the assembly of typical structural systems.”
What the MIT-UCL team invented was a portable concrete block they dubbed the “droxel”—a portmanteau of “drone” and “voxel” (a digital building block in computer-based modeling). Droxels expand the properties of traditional structural concrete blocks by incorporating sloped surfaces and interlocking elements. “The stacking of traffic cones is a useful analogy to the droxel’s functionality,” Mueller explains. “Much the way cones center themselves during stacking, the droxel’s facets enable it to slide into place even when its initial placement by the drone is less than precise. The droxel’s geometry also enables us to aggregate them into an interesting variety of complex, self-supporting structures.”
The UCL and MIT teams view the success of their initial collaboration as a proof of concept for further development. “We see great potential now to move beyond the notion of 3D-printed construction as a giant version of tabletop printing,” says Mueller. “When teams of drones are no longer tethered to human pilots, we believe large-scale, self-supporting structures could be assembled autonomously and efficiently in conditions and environments that would prove daunting with traditional construction methodologies.” Next up for Mueller and her collaborators? Guiding their drone automatically using BIM (building information modeling), customizing the drone for more precise movement, and developing a drone-compatible timber building system.
Watch the drone in action here.