Source: Rice University News & Media

Tactile feedback adds ‘muscle sense’ to prosthetic hand

US, Italian researchers test ‘proprioceptive’ feedback with skin-stretch device

Engineers working to add “muscle sense” to prosthetic limbs found that tactile feedback on the skin allowed blindfolded test subjects to more than double their ability to discern the size of objects grasped with a prosthetic hand. The results will be presented next month in Germany by researchers from Rice University and the Research Center “E.Piaggio” of the University of Pisa and the Italian Institute of Technology (IIT).

“Humans have an innate sense of how the parts of their bodies are positioned, even if they can’t see them,” said Marcia O’Malley, professor of mechanical engineering at Rice. “This ‘muscle sense’ is what allows people to type on a keyboard, hold a cup, throw a ball, use a brake pedal and do countless other daily tasks.”

The scientific term for this muscle sense is proprioception, and O’Malley’s Mechatronics and Haptic Interfaces Lab (MAHI) has worked for years to develop technology that would allow amputees to receive proprioceptive feedback from artificial limbs.

Subject testing proprioceptive feedback in Rice's MAHI lab
Test subjects were more than twice as likely to correctly discern the size of grasped objects grasped with a prosthetic hand when they received haptic feedback from a simple skin-stretch device on the upper arm.
(Photo by Jeff Fitlow/Rice University)

In a new paper to be presented June 7 at the World Haptics 2017 conference in Fürstenfeldbruck, Germany, O’Malley and colleagues demonstrate that 18 able-bodied test subjects performed significantly better on size-discrimination tests with a prosthetic hand when they received haptic feedback from a simple skin-stretch device on the upper arm. The study is the first to test a prosthesis in combination with a skin-stretch rocking device for proprioception, and the work has been recognized as a finalist for best paper award at the conference.

An estimated 1.7 million people in the U.S. live with the loss of a limb. Traditional prostheses restore some day-to-day function, but very few provide sensory feedback. For the most part, an amputee today must see their prosthesis to properly operate it.

Improved computer processors, inexpensive sensors, vibrating motors from cellphones and other electronics have created new possibilities for adding tactile feedback, also known as haptics, to prosthetics, and O’Malley’s lab has done research in this area for more than a decade. -