🧱 New origami turns sheets into building bricks

Researchers at McGill University have developed a new method for folding flat sheets into smooth, curved shells that can switch, as needed, from a flexible state to a rigid one capable of supporting loads.

Using an origami pattern that incorporates cable-like elements, the team can control both the final three-dimensional shape of the material and its degree of stiffness. According to the researchers, this innovation, a "double-curvature lens module," could advance technology applied to objects such as emergency tents, shape-shifting robots, and smart fabrics.


"Existing foldable structures force us to make a trade-off: if they are smooth and curved, they tend to be soft and floppy; if they are strong and rigid, they usually have angular, irregular shapes that are impractical and difficult to adjust after assembly," explains Damiano Pasini, co-author of the study and professor of mechanical engineering at McGill University.

"This represents a significant constraint for technologies such as wearable devices, medical implants, soft robots, and deployable space structures, which often need smooth shapes and reliable strength to properly support external forces."

To address this issue, the team designed an origami pattern with curved folds that forms smooth, doubly curved surfaces, such as spheres or tori (doughnut shapes). The resulting structure can be "locked" into a rigid state capable of supporting loads. By adding internal tendons whose tension can be adjusted, the same structure can then be reprogrammed to be ultra-flexible or very rigid, without changing its shape or materials.

Adjustable cables to modulate rigidity The new folding pattern combines curved and straight folds, allowing flat sheets to be transformed into continuous, smooth surfaces rather than the angular shapes characteristic of traditional origami.

Starting from a desired curved shape (sphere, torus, vase), the researchers used differential geometry—which encompasses mathematical theories related to tiling, origami, and developable surfaces—followed by numerical optimization to calculate the exact fold pattern needed so that, once folded and locked, the origami shell takes on the desired shape.

They then laser-cut and folded cardboard sheets according to this pattern, assembled them into shells, and inserted thin cables ("tendons") at precise locations.

"By tightening or loosening the tendons, we measured the change in stiffness and demonstrated that the shells could transition from a floppy, flexible state to a rigid state resistant to twisting and bending," says Professor Pasini.

Validated using mechanical theory, rigid origami, and geometric simulations, the results confirm that the folding kinematics—the object's movements—is feasible. Simulations also confirmed that the surfaces remained smooth and that the pattern could be scaled up and repeated as a mosaic.

A new design paradigm According to Damiano Pasini, this work paves the way for a new paradigm in designing origami-inspired metamaterials.

"Our approach opens new possibilities for designing load-bearing, deployable, and adaptive curved structures. Our results challenge the notion that complex materials or external systems are required to achieve tunable rigidity. Instead, they demonstrate that clever geometry can do much of the work."

The study The article titled "Smooth doubly curved origami shells with reprogrammable rigidity," by Morad Mirzajanzadeh and Damiano Pasini, was published in Nature Communications.