Happenings RESEARCH ROUNDUP
Army Scientists Develop Rate-Activated Tethers for Orthoses
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MAY 2021 | O&P ALMANAC
Focusing on the mental effort of users operating prostheses, a research team from Johns Hopkins University and Drexel University is studying whether adding haptics, or an artificial sense of touch, to upper-limb prostheses reduces the mental effort required to operate the device. “Normally, vision is heavily used to successfully operate a myoelectric prosthesis, and this can cause high mental fatigue,” explained researcher Jeremy D. Brown, PhD, A study participant tests a prosthesis an assistant professor of featuring haptic feedback. mechanical engineering at Johns Hopkins. “Haptic feedback that whose stiffness were difficult to differsubstitutes for vision can reduce this entiate,” according to the researchers. cognitive load, which helps bridge the “This research suggests that future gap between the function of the healthy upper-limb prosthetic technologies limb and that of a prosthetic limb.” need to incorporate haptic feedback in Brown and his team proposed weartheir design,” said Brown. “In addition, able, wireless functional near-infrared this research provides a framework spectroscopy (fNIRS) neuroimaging for using brain imaging techniques to provide a continuous direct assesslike fNIRS to evaluate the cognitive ment of operator mental effort during load of new prosthetic technologies use of prostheses. Study participants in a variety of natural scenarios and were asked to differentiate objects in environments.” The findings were three distinct ways: using their natural published in April in IEEE Transactions hand; using a traditional myoelectric on Human Machine Systems. prosthesis without sensory feedback; Future projects for Brown’s team and using a myoelectric prosthesis with include investigating how haptic haptic (vibrotactile) feedback of grip feedback and automated grip control force. Results indicated that “discrimcan enable a prosthesis wearer to ination accuracy and mental effort are operate their prosthesis without visual optimal with the natural hand, followed observation. “An example scenario by the prosthesis featuring haptic would be the ability to watch TV while feedback, and then the traditional simultaneously picking up the TV prosthesis, particularly for objects remote out of view,” said Brown.
PHOTO: Courtesy of Jeremy Brown, Haptics and Medical Robotics Lab, Johns Hopkins University. All rights reserved.
U.S. Army researchers have debuted an orthotic device design that features adaptable coupling elements and rate-activated tethers incorporated into elastic materials, comprising the body of orthoses. The tethers are “cable-like devices that are filled with fluid and filaments,” according to an announcement from the DEVCOM Army Research Laboratory, and are made from materials that are both elastic and able to seal fluid inside, such as rubber, silicone, polymer, or latex. The filaments inside the tethers are made of steel, polymer, glass, or carbon; these filaments may be either free-floating or attached to one or both sides of the tethers. Orthoses made using the new design provide variable support, depending on the wearer’s speed and movement intensity. Because they can stretch and recover quickly during movement, they provide a unique balance of comfort, performance, and support, according to the research team. Used in an ankle brace, for example, the tethers will support regular daily activities without causing the joint’s weakening, but will limit motion during fast movement to prevent supination of the ankle, according to the researchers.
Researchers Study Benefits of Prostheses Integrated With Haptic Sensory Feedback
