Hassan Askari Self_Powered_Sensor

Hassan Askari, a doctoral candidate at Waterloo Engineering, has developed a small, self-powered sensor with potential applications in fields including surgical rehabilitation and self-driving cars.

Doctors may one day be able to monitor the recovery of surgical patients from a distance using a self-powered sensor developed at Waterloo Engineering.

The small, tube-like device is designed to be fitted to braces after joint surgery to wirelessly send information to computers, smartphones or smartwatches to track range of motion and other indicators of progress.

“That data would be continuously collected, so it would be as though the physician or physiotherapist was always there, always observing the patient,” says Hassan Askari, a mechanical and mechatronics engineering PhD candidate at Waterloo.

The same sensor could also be used in a variety of other ways, including in the tires of autonomous vehicles to detect and respond to icy roads.

A prototype built and tested by the researchers combines electromagnetism and triboelectricity, a relatively new energy harvesting technique that involves bringing different materials together to produce current.

When bent or twisted, the device generates enough electricity for sensing and powering electronic circuits for processing and wireless signal transmission.

“The aim was to develop a sensor that works without having a battery attached to it,” says Askari. “It is its own power source.”

That makes the device especially well-suited for applications that put a premium on reliability and where it would be difficult or expensive to replace worn-out batteries.

Self powered sensor

A graphic shows the two technologies – electromagnetism and triboelectricity – that work together to generate power when a flexible sensor developed at Waterloo Engineering is bent or twisted.

Askari estimates the sensors – about six centimetres long and one centimetre wide – could be commercially manufactured for $5 to $10 each.

Ongoing research is now focused on making them smaller and more sensitive using triboelectricity alone. Software is also being developed to process signals for the tire application.

When attached to the inside of tires, the devices could sense changing road conditions and instantly send information to control systems to enable self-driving vehicles to make adjustments.

“Based on the forces, the interaction between the road and the tires, we could actually detect ice or rain,” says Askari. “That is extremely important information for autonomous driving.”

Askari collaborated at the University of Waterloo with fellow PhD student Ehsan Asadi, and engineering professors Amir Khajepour and Mir Behrad Khamesee, as well as doctoral student Zia Saadatnia and professor Jean Zu at the University of Toronto.

A paper on their research, A flexible tube-based triboelectric-electromagnetic sensor for knee rehabilitation assessment, was published in the journal Sensors and Actuators A: Physical.