Joseph’s technocapable coat: energy harvesting for smart clothes

Smart clothes are the territory where style and science are destined to meet. Their rendezvous is already taking place, giving garments a whole host of innovative applications, such as charging depots for personal electronic gadgets, fitness trackers for capturing biometric data and colour-changing fashionable assets that go with everything. After a slow start technology-laden clothing is now available. Practical energy harvesting would drive development faster: there are clear practical problems with plugging clothes in to charge – not least because washing and electricity generally don’t go well together.

A growing number of universities and innovation-focused companies are working on adding “smartness” to the conventional features of clothes without having to reply on external power. How is it done? One way is by impregnating textiles and fabrics with nanomaterials capable of conveying electricity harvested from motion of the body to small wearable electronics. Nanomaterials are too tiny (atomic thin) to alter fabrics in terms of appearance and softness; they are also good at drawing out energy from movements that are under 10 Hz (that kind of frequencies correspond to human motion). 

Ideas for energy harvesting

At present, scientists are experimenting with many ideas for energy harvesting from smart clothes. Some ideas rely on atom-sized generators with piezoelectric characteristics (electric charge accumulated in response to applied mechanical stress) to convert body movements into electricity, while others are concentrating their effort on triboelectricity (electricity generated by friction) for achieving the same aim.  Regardless of the approach, they all share a common goal – letting people become their own electricity source. If successful, such energy harvesting would eliminate the need to carry chargers for digital devices, or to attach fitness trackers to the body. Each of us will be in possession of wardrobe-kept smart powerplants.  

One example is the work of Vanderbilt University scientists, who are using black phosphorous layers to harvest energy from fabrics – they say it has better low-frequency energy conversion efficiency than other piezoelectric materials.

Another is Massachusetts Institute of Technology, which has developed a fabric that can absorb solar power and keep it the form of a chemical charge to produce heat when needed. Scientists believe that it can be applied to clothes worn by skiers and other winter athletes, cold-weather workers, as well as everyone exposed to chilly environments.

Just how smart can clothes get?

A team at Université Laval's Faculty of Science and Engineering and its Centre for Optics, Photonics, and Lasers in Canada have developed a T-shirt whose embedded sensors can detect respiratory abnormalities. It uses an antenna made of multi-material fibres. Deep and shallow breathing cause the operational frequency of the antenna to shift in response to each change in the respiratory pattern. However, the team did not address the issue of powering the garment.

The concept of smart clothes is not strictly confined to medical or fitness measurement. A team at The University of Central Florida’s College of Optics and Photonics has developed “ChroMorphous” technology that can let people change the colour of their garments by sending Wi-Fi signals from a smartphone to a tiny battery attached to the garment. The battery transfers electric current into the yarn’s copper wire, heating the pigment to facilitate a colour change.

According to scientists at the University of Washington, smart clothes of the future will also be capable of storing passcodes by using magnetic orientation of nanometallic filings to encode data – a process that doesn't require any electronics, or power, on the garment itself

While the above examples don’t involve energy harvesting, some smart clothes being developed by big companies certainly do: Samsung’s vision of energy harvesting will take the form of clothing that could charge a smartphone, though it’s at patent application stage only at the moment. And Adidas has patented self-charging smart shoes capable of storing energy from piezoelectric modules for future use, for instance taking foot movement measurements and transmitting the data to nearby devices.

Commercial smart clothes are appearing, but EH remains elusive

Applying the principles of energy harvesting in smart clothing relies on technologies to enable the transfer of electricity around the garment, and the printing of circuitry in specific locations. Some of the currently available smart clothes rely on DuPont’s Intexar stretchable electronic inks and films. These are incorporated into Body Plus fitness shirt for monitoring of biometrics, available in China, and OMsignal sports bra whose sensors measure heart electrical activity, breathing rates and physical activity.

Google and Levi Strauss worked side by side on Project Jacquard to create conductive yarn that can be woven into fabrics for garments; the project resulted in a smart denim jacket that can connect its owner to the internet by simply tapping the sleeve. There is a small Bluetooth dongle attached to a button to communicate to the wearer’s phone … but this has a battery that must be recharged every two weeks – and it’s recommended it is removed when you wash the jacket.

While smart clothing is available, energy harvesting has been developing only slowly. Research by universities and tech companies, suggests that there is a lot more to come.

 

[Images licensed to Ingram Image]

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