Senior project spotlight: Kit McArthur

Engineering Design Projects (ES 100), the capstone course at the Harvard John A. Paulson School of Engineering and Applied Sciences, challenges seniors to engineer a creative solution to a real-world problem.

Developing a Variable Stiffness Ankle Prosthesis

Kit McArthur, S.B. ’20, mechanical engineering

A human ankle varies in stiffness depending on how fast an individual is walking, but commercially available prosthetic feet are unable to emulate this process, which can lead to joint disorders in patients with these prosthetics. So McArthur set out to develop an inexpensive, low-power prosthetic ankle that could better mimic the mechanics of a normal human ankle, using a cantilever beam-based design. A slider on the device varies the ankle stiffness by moving along a cantilever beam (pushing a cantilever beam at a point further from its base has a smaller stiffness than pushing it close to the base). For McArthur, the biggest challenges of the project came from all the requirements of the foot—such as the need for low power, the ability to withstand the torques exerted as a user walks, and a design that is similar in size and operation to a normal human ankle.

“I feel that working on this project gave me a much more deep and thorough understanding of all the steps needed to design a new product,” he said. “It especially helped me develop the ability to hypothesize possible problems and come up with solutions for those problems.”