Dr. Kiisa Nishikawa, Northern Arizona University – Stability and Prosthetic Limbs

Nov 13, 2012

In today’s Academic Minute, Dr. Kiisa Nishikawa of Northern Arizona University explains how advanced materials are leading to an increase in the mobility and stability of prosthetic limbs.

Kiisa Nishikawa is a Regents’ Professor of biology at Northern Arizona University in Flagstaff, Arizona.  Through her lab, she has overseen projects investigating the elastic properties of muscles and the neuromechanics of how frogs capture prey. Her work has been widely published and she holds a Ph.D. from the University of North Carolina at Chapel Hill.

About Dr. Nishikawa

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Dr. Kiisa Nishikawa – Stability and Prosthetic Limbs

Imagine a young veteran with a prosthetic leg walking down the street, chatting with his wife. He doesn’t notice he’s approaching a pothole, and the sudden shift in terrain causes him to stumble. The artificial leg that has served him well cannot possibly anticipate and adjust to a pothole.

Despite the many advances in prosthetic technology, science has not yet been able to mimic the intrinsic adaptive properties of your muscles, which allow them to instantaneously accommodate changes in the environment—even before your brain can react. But this may change soon.

Our research at Northern Arizona University is proving it is possible to reproduce the responsiveness of human muscles using a muscle-like actuator. Researchers are working on a prototype based on decades-long examination into the rapid movement of animals, such as chameleons, frogs, and toads. Study of animals that project their tongues to catch prey led to a breakthrough discovery of the spring-like protein called titin that plays an important role in muscle contraction.

The discovery has led a to fundamental shift in how to build actuators as well as sensors for prosthetics. Currently, control of prostheses requires sensors to predict what the wearer is trying to do so that the motor power can be adjusted accordingly. While muscles adjust automatically to unanticipated changes, prostheses need a mechanism to tell then when to make changes to accommodate new, sudden input.

In contrast, a muscle-like actuator can adapt instantly, which will allow a simple control system to react more like what the human brain expects.

In addition to its prosthetic applications, this new actuator can enhance the fields of robotics by smoothing out jerky movements. It also will benefit bionics, and perhaps even lead to exoskeletal robotic suits that can boost physical performance—reminiscent “The Six Million Dollar Man.”