Harvard prototype inflatables lock into multiple stable shapes

On the lawn of Harvard's Science and Engineering Complex, a deflated polyurethane shell can be carried by a few people. Fill it with air, and the roughly person-height structure becomes a pavilion-scale form; shift its programmed hinges, and it reconfigures between a cone-like enclosure, a tunnel and a canopy. The demonstration is the centerpiece of a Harvard project that gives inflatable membranes more than their usual two stable states.

The trick begins with a flat rectangular pouch. Most inflatable membranes bend rather than stretch under pressure, producing wrinkles or crumples that designers typically try to eliminate. Harvard researchers instead placed notches along the pouch's edges, directing those crumples across the surface so they act as mechanical hinges. Tuning the notches' geometry and spacing let the team switch each hinge between two mirror-image positions while keeping the internal pressure constant.

The work grew from modular shapes designed by Hye Jun Youn, then a master's student at Harvard's Graduate School of Design. She worked with structural designer Martin Bechthold and Katia Bertoldi's applied mechanics group, including Leon Kamp and Yi Yang, to understand why the small polyurethane forms curled and held their shapes. Once the mechanism was established, the team arranged the units into one-dimensional chains and two-dimensional sheets that could fold or snap into different three-dimensional forms. A small demonstration even toggled a lamp when a crumpled hinge flipped.

Scaling the pattern demanded new fabrication work. Staff at the Graduate School of Design's fabrication lab adapted a large CNC cutting machine to weld intricate designs into wide polyurethane rolls. A commercial inflatable manufacturer in Providence, Rhode Island, completed the edge sealing for the largest prototype, which the researchers then demonstrated outdoors.

So what changes, concretely? Inflatable structures could become reconfigurable objects rather than single-purpose shells: a panel could change curvature, while a larger structure could take different spatial forms after inflation. The immediate result is a mechanics-based framework and a meter-scale demonstration. The research, published in Advanced Science, lays groundwork for further inflatable devices, while the Harvard team has shown that controlled crumples can survive the jump from small laboratory units to pavilion scale.