Buckminster Fuller: Tensegrity

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"Tensegrity" is a term with a rich and sprawling history. It was coined by Buckminster Fuller, the iconoclastic architect, engineer, and poet, to describe his vision of a new kind of architecture, one that looked like it was built by nature instead of by humans. 

In contrast to the pyramids, columns, and brick-on-brick buildings of the past, which pile solid elements compressively, one on top of the other, Fuller imagined a world full of unconventional structures that maintain their stability, or integrity, through a pervasive tensional force, hence the term tensegrity.

Fuller began developing his vision in the 1920s, at a time when many were exploring new directions in design and architecture. But it was his student, the sculptor Kenneth Snelson, who, in 1949, created the first structure to be defined as a tensegrity. Using two X-shaped wooden struts suspended in air by a taut nylon cable, Snelson captured the defining features of tensegrity:

Pervasive tension and a separation of rigid elements. In Snelson's now iconic structure, the compression-resistant struts do not touch but instead are individually lifted, each embraced and interconnected by a system of continuously tensed cables, a condition that Snelson and Fuller called "continuous tension, discontinuous compression."

Stable. Though ethereal in appearance—its wooden Xs appear almost to float—Snelson's sculpture is remarkably stable, despite its minimal use of rigid elements. This stability is due to the fact that tensile and compressive components are, at all times, in mechanical equilibrium.

Prestressed. This mechanical equilibrium results from the way the compression and tensile components interact to bring out each other's essential nature: the cables pull in on both ends of the struts, while the struts push out and stretch the cables. The result is that each element in a tensegrity structure is already stressed—the compression elements are already compressed, the tensile elements already tensed—and they are stressed by each other, a condition known as "self-stress" or "prestress."

Resilient. While they are stabilized by prestress, tensegrity structures are also exquisitely responsive to outside perturbation. Their components immediately reorient when the structure is deformed, and they do so reversibly and without breaking.

Globally Integrated. Because the components are so intimately interconnected, what is felt by one is felt by all, producing a truly holistic structure.

Modular. Though complete on its own, a tensegrity structure can combine with other such structures to form a larger tensegrity system. In these systems, individual tensegrity units can be disrupted without compromising overall system integrity.

Hierarchical. In fact, smaller tensegrity structures may function as compressive or tensile components in a larger tensegrity system, which in turn may perform a similar function in still larger systems.

For much of history, architecture had been preoccupied with making things stable but Snelson's X-structure unlocked a world in which structures could be flexible and firm, holistic and hierarchical. Over the past 60 years, artists, engineers, and architects have used the lessons of tensegrity to build previously "impossible" structures --.space frames, deployable moon-base shelters, as well as sky-piercing sculptures -- helping to realize Fuller's vision of a universe filled with man-made tensegrity structures.

Snelson would later argue that tensegrity is a principle that is realized only through man-made objects. But Fuller's vision rested on the conviction that nature builds using tensegrity. Indeed, the human frame with its many tensile muscles, ligaments, and tendons pulling up on the rigid bones of the body, thereby stabilizing and supporting them against the force of gravity, is a prime example of tensegrity at work. In the last few decades, scientists have shown that tensegrity is a fundamental design principle of nature, operating at the level of organs, tissues, cells, and even molecules (Ingber, 1998). Their discoveries are leading to a whole new array of man-made tensegrity structures, this time at the micro- and even the nano-scales.

Tensegrity is not an easy concept to grasp. It is best seen and felt, and authors often suggest that readers build their own tensegrity structures. Another way in is through history. What follows is essentially a story: the rise of tensegrity from a concept known to an esoteric few to become a well-recognized design principle of nature, one that is leading to radically new solutions to age-old problems in medicine, engineering and beyond.