To build a wearable device you typically need a sensor, a “brain” to analyze any raw data, and an enclosure.
Researchers from the University of British Columbia have developed all three components; their stretchable sensor can be weaved into a fabric to detect and interpret a range of complex human movements, including finger gestures and heartbeats.
The First Step
The sensor creators, led by UBC School of Engineering professors Homayoun Najjaran and Mina Hoorfar, made the device by infusing graphene nano-flakes (GNF) into a rubber-like, stretch-able polymeric substrate.
But no technology development is without its stress – in this case, on both the inventors and the invention.
The "GNF-Pad" device endured more than 10,000 cycles of stretching and relaxing – and maintained its electrical stability and accuracy under strains of up to 350 percent of its original state, according to the professor.
“We tested this sensor vigorously,” said Najjaran in a press release last week. “Not only did it maintain its form, but more importantly it retained its sensory functionality.”
Unlike an inertial measurement unit that allows step-based wearables to measure force and movement, Najjaran wanted a sensor to be sensitive enough to respond to infinitesimal motions: a heartbeat, a twitch of a finger, a walking stride.
The Second Step
After first building and calibrating the stretch sensors, the work shifted into an interdisciplinary effort to create a wearable device capable of Step #2: interpreting the signals to render the sophisticated human motion.
“Much of the work is around the interpretation of the signals, and the way we understand complex motion from the raw measurements.” Najjaran told Tech Briefs.
To demonstrate the system’s practicality, Najjaran's team built three wearable devices, including a knee band, a wristband, and a glove.
Both artificial intelligence (AI) and machine learning, pulled from “big data” sources, were used to interpret the sensor readings and understand the motion in real time (For more in-depth detail regarding the algorithm, read the report published in the Journal of Sensors and Actuators A: Physical.)
The wristband monitored heartbeats by sensing the pulse of the artery. In an entirely different range of motion, the finger and knee bands detected finger gestures and larger-scale muscle movements involving walking, running, sitting down, and standing up.
The Next Step
The results demonstrate high sensitivity, selectivity, and durability characteristics – an advancement of the technology, according to the researchers.
“We believe [the sensor] is ‘next level’ because the work has offered a turnkey package, an end-to-end solution,” said Najjaran. “Our work has introduced not only the sensor but also the sophisticated data analysis needed to reconstruct the body motion and biological signals.”
The team hopes to commercialize the device, and says their results could someday help manufacturers create tomorrow’s health monitoring and biomedical devices.
Najjaran believes the essential, exciting aspect of the technology is its versatility and applicability to a variety of industries. The device, for example, could be placed on a child’s clothing, an athlete’s jersey, or a machine operator’s uniform to monitor movements – the choice is yours, says the UBC professor.
“The examples of the knee band to monitor body motion, a glove to control a robot, and a wristband to read pulses are meant to show the versatility of the sensor for a wide range of applications, and have less to do with a certain application or use for the sensor,” Najjaran told Tech Briefs.
Hoorfar and Najjaran are both members of the Okanagan node of UBC’s STITCH (SmarT Innovations for Technology Connected Health) Institute that creates and investigates advanced wearable devices.
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