Sometimes the same technology designed to help people extracts a high cost. It has long been established that when stroke or Parkinson’s Disease patients walk, they use more energy than healthy individuals: as much as 70 percent more. In the last 10 years, several rigid wearable robotic devices to assist human walking and reduce energy expenditure have been developed, but they often have drawbacks including increased energy because of gait dynamics and because proper alignment is crucial, and often tricky to set and maintain. The rigid structures can apply unintended pressure on joints, resulting in gait disruption.
Scientists led by B. T. Quinlivan and S. Lee, both at the Harvard University’s School of Engineering and Applied Sciences and Wyss Institute for Biologically Inspired Engineering, worked in conjunction with researchers at the University of São Paulo Ribeirão Preto Medical School, Technische Universität Darmstadt, and the Virginia Tech Department of Mechanical Engineering to design and successfully tested a soft exosuit designed to assist the wearer and to measure gait mechanics.
The exosuit was designed to provide extra power for walking, in the amount and manner that would happen with normal biological processes. The suit is constructed of lightweight Spandex for less stress on joints compared to rigid robotic legs. The brace “zaps” energy into ankle joint by mimicking the force and leverage of natural stride without affecting gait alignment. In tests, the soft robot “suit” cut the patient energy use when walking by 23 percent. The whole point of the robotic assistance is to make walking easier without adding other burdens.
Further studies on the soft robotic suit will address the precise reasons for the energy expenditure reduction, which the study’s authors reported as the highest ever measured with an exosuit of any type. Other tests providing hip and ankle assistance separately may yield further understanding. As work on exosuits and exoskeletons continues, applications to help patients in recovery and with permanent muscle loss, weakness, or control issues are getting closer.