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PhD Student’s Tiny Solar Cells Make Smart Textiles to Power Your Phone

Sunlight: readily available, free of cost and potentially the sustainable solution to how the future will be powered.

Solar panels are already a common sight atop buildings in places where the sun shines constantly, but recently there’s been a flurry of activity from brands and tech startups infusing solar cells into clothing as a way to ensure people always have a way to charge their numerous power-dependent devices.

However, there’s another reason why solar is the central focus for many innovators. The wearables market, once thought to be the next big thing, has stalled somewhat as the fervor over devices like smartwatches and similar wrist-worn accessories wanes; there’s only so much functionality they provide, after all.

Many see smart clothing as the true future of the wearable tech movement. From Tommy Hilfiger’s 2014 partnership with Pvilion that put solar panels on the back side of a “smart jacket,” to the ThermalTech outerwear line that got off the ground via Kickstarter, solar is, well, hot.

Now, a Nottingham Trent University Ph.D.’s doctoral research indicates how “flea-sized” solar cells incorporated into fibers create smart textiles capable of harnessing enough solar energy to charge a cell phone.

Achala Satharasinghe, already a master of science degree holder in nanoscience and nanotechnology, previously worked for Sri Lanka’s MAS Innovations—an investor in period- and pee-proof undies brand Thinx—before pursuing his doctoral degree with the British institution’s Advanced Textile Research Group (ATRG).

“The electrical power demand for smart e-textiles has always been its Achilles heel and this technology will allow people to use smart textiles while on the move,” project lead professor Tilak Dias, who serves as the professor of knitting and founded the ATRG, said in an NTU article announcing the research.

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The ATRG team came up with solar cells measuring 3 cm long by 1.5 cm wide, tiny enough to be barely visible to the naked eye. They’re ensheathed within resin so that when they’re knitted or woven into textiles, the resulting clothing can be worn, washed and treated like regular apparel. These solar cells can work in any fiber from cotton to silk, Satharasinghe told Sourcing Journal, but fabric thickness could influence how well the solar cells perform.

Like any solar initiative, how quickly these solar cells charge depends on how much sunlight they receive, calling into question their effectiveness during the dark, wintry months versus sunny summers when the days are long. “The power generated will be proportionate to the intensity of light available,” Satharasinghe explained. “Lower sunlight will make the charging time longer.”

The ATRG team’s proof-of-concept project simulated full sunlight conditions to power its 5 cm by 5 cm solar-cell textile swatch packed with 200 cells, capable of generating between 2.5 and 10 volts and as much as 80 miliwatts of power. The researchers successfully charged a Fitbit and a cell phone during their test and believe that a large piece of smart fabric containing more solar cells could charge larger, more power-intensive devices.

Satharasinghe and the ATRG team estimate that fabric containing 2,000 cells could charge a smartphone, though how quickly the device powers up depends on the size of the battery. “We have not conducted actual testing with a 2,000 cell solar charger, but we expect that it can take similar time as a normal phone charger if continuous sunlight is available,” he added.

Outerwear is the most logical category application for this technology, and Satharasinghe noted that he’s working on optimizing this proof-of-concept. The team hopes to produce a full garment built with the solar textile before Satharasinghe concludes his Ph.D.

Beyond charging phones and Fitbit, these small-scale solar cells could help to power the sensors and other innovations driving the global wearable medical device market, which ReportLinker projects will reach $19.5 billion by 2021, a sizable increase over its 2016 $5.5 billion value.

“Let’s imagine you have a garment which can monitor your health, especially the heart rate, skin temperate and blood sugar,” Dias said in a video detailing the solar textile research. Instead of clunky battery packs, one days these devices could be powered by solar energy cells virtually invisible to the naked eye.