A High-Performance Prosthetic

In celebration of the museum’s inaugural Cooper Hewitt Lab: Design Access taking place in the Barbara and Morton Mandel Design Gallery through February 16, we are highlighting innovative accessible design from the permanent collection.

The Flex-Foot Cheetah incorporates untraditional materials to solve a design problem that had vexed the medical field for years: finding a prosthetic solution that allows the user to live a normal, active lifestyle. Van Phillips lost his leg below the knee at the age of 21. Unsatisfied with the prosthetics then available to him, he set about researching a material that had to satisfy three key requirements: it needed to be strong, lightweight, and flexible. He settled on a carbon-fiber composite, traditionally used in the aerospace industry. The result of Phillips’ research is a J-shaped high-performance prosthetic tool used primarily for sports activities that mimics a person’s foot/ankle joint anatomy.

Inspired by the rear leg of the cheetah, the fastest animal on earth, the woven carbon fibers are molded into an elegant shape that acts as a springboard. The carbon fiber material is not uniformly distributed throughout the prosthetic, however. Instead, areas of high stress, like the J-curve and apex, feature more layers of the material; areas requiring increased flexibility feature less. This creates a more anatomically accurate prosthetic experience: the inclined midsection directs the ground contact toward the front two inches of the “toe” in much the same way the cheetah’s paw presses into the ground. The C-shaped segment stores energy like the animal’s hind leg by compressing and springing back, which propels the runner forward.