The sensor device study in China was tested on a robotic prosthetic hand and with three people with transtibial amputations. Aside from warning users how to react to the type and location of pressure, the researchers think the sensor, which acts like an artificial skin, will help clinicians personalize socket fitting and gait training.
As the participants sat, walked, climbed stairs, jumped, and ran, the sensors monitored where the socket pressed into the residual limb, how hard the pressure was, and how long it lasted. The sensor uses a haptic pathway to quickly report the location and intensity of pressure and a pain-inspired pathway that combines signals over time and across sensing points.
Huaping Wu, PhD, a mechanical engineer at Zhejiang University of Technology and senior author of the related study, spoke with Science Alert about the development. Wu said that the pressure-sensitive material and electronic components can change its response based on previous signals it has received, which Science Alert called “a simple form of memory. Following an injury-like input, its warning response becomes more sensitive, so weaker pressure can provoke a stronger response later.”
For example, the researchers first tested a level of pressure (10 kilopascals) for 0.21 seconds on the robotic hand, which the system identified as harmless. When that same pressure lasted 0.49 seconds, however, the system registered it as potentially harmful. Later, that same level of pressure caused a quicker reaction and made the hand withdraw based on the sensor’s previous feedback.
“This imitated the body’s heightened sensitivity after injury but did not mean the robot remembered consciously or felt pain,” Science Alert said. “Its faster response came from an engineered change in the warning threshold.”
“The device neither feels pain nor creates pain in the user,” Wu said. “Instead, it reproduces selected information-processing features associated with nociception, including stimulus thresholds, temporal and spatial summation, memory, and sensitization.”
When the sensor system was tested while the participants were running, it was able to detect that they were using an excessive hip hike to help the prosthesis clear the ground, which was producing uneven loading and increased pressure at the front of the residual limb. The feedback was then able to help them adjust their gait. Warnings could also prompt users to change position, rest, or have the socket checked.
The open-access study, “A bioinspired perceptual sensor for spatiotemporal decoding of haptic and pain stimuli in prostheses,” was published in Cyborg and Bionic Systems.
To read “Scientists built prosthetic ‘skin’ that mimics one crucial feature of pain,” visit Science Alert.
To read more about artificial skin research, visit “Prosthetic E-skin Senses Temperature, Pressure” and “Prosthetic Fingers May Benefit from Robotic Skin Research” on The O&P EDGE website.
