Charging through movement

A significant challenge for researchers has been trying to harvest enough energy to power these tiny wearable circuits.

 “The issue has been powering the wearable. Capturing just ambient light, for example, requires photo voltaic technology, but obviously you can’t have rigid solar panels on your clothes so we are trying to make the textile itself photo voltaic,” says Steve.

“We have managed to reach up to two per cent efficiency and, although that doesn’t sound much, scientifically it is quite a step forward.”

Cutting edge research into harvesting kinetic energy is also taking place in our industry-standard cleanroom laboratories.

Mobile phone companies have been investing in research to see whether a device could be charged from a person’s own movement and have tested the idea at festivals where movement is increased.

Steve says: “Harvesting energy from human movement relies on people dancing around and being active. In reality we aren’t all dancing all the time, we are mostly sat or still.  Mobile phones are very, very thirsty devices and are, at times, consuming watts of power. Realistically, that comes back to the amount of energy that can potentially be harvested.”

Harvesting mechanical energy from the movement of the textile is even more challenging because the fabric by its very nature is designed to be compliant. Its ability to bend and move with the person wearing it means it is not ideal for capturing the energy needed.

So while wearable device charging would rely on a huge change in direction by phone manufacturers for it to work – from functionality to efficiency –  smaller, less powerful devices are very much within sight for practical application.

Steve and his team have been working on using smart materials in shoes to power wearable technology.

He says: “We are looking at converting shoe insoles that act both as a sensor and an energy harvester. This has been developed to act as a self-powered pedometer, power transmissions for indoor localisation and potentially monitor foot pressure and distribution.

“The sensors can calculate how active you are, they can let people know where you are and it is all self-powered. It works by the force of your foot as you walk, squashing this material and generating electrical energy.”

Medical monitoring

Working in partnership with other universities, businesses and through spin-out companies of our own, the University is forging forward with the practical application of the technology, particularly in the healthcare sector.

In a project being led by Bristol University, Steve and his team are currently involved in developing wearable technology that can be used to monitor patients in their own home, providing data that can then be assessed by medics without the need for a face-to-face consultation – a field known as ambient assisted living.

The tech could also be used to assess disease progression by monitoring movement.

Steve explains: “The issue with monitoring patients in their own home using a watch-type device or wrist strap is one of compliance. If it doesn’t offer any functionality for the wearer they are less likely to put it on and we know that has an impact on compliance rates. If the tech was in their clothes that they are wearing anyway, it is monitoring them without them even knowing it.

“We are looking at having this technology in peoples’ homes so that we can detect activity and that can be incredibly useful information for doctors to have in terms of monitoring rehabilitation or to see, for example, the progression of diseases such as Parkinson’s.

“All that data can be collected in the home, analysed, then acted upon.”