The combination of rising populations, climate change, and depleted natural resources has emphasized the need for sustainable technology. This technology isn't limited to big devices like photovoltaic panels and wind turbines; recently, a team of researchers has developed a textile capable of harnessing energy from both sunlight and wind.

The team developed a fabrication strategy that merged two different lightweight, low-cost polymer fibers to create energy-producing textiles. The first component of the textile is a microcable solar cell, able to gather power from ambient sunlight. The second is a nanogenerator capable of converting mechanical energy into electricity.

The photovoltaic portion of the textile was composed of a copper-coated polymer fiber that was then further coated with concentric layers of manganese, zinc-oxide/dye, and copper iodide—the zinc oxide is a photovoltaic material, while the copper helps harvest the charges. These solar-cell microcables were then woven together with a copper wire.

The second energy-generating material was based on triboelectric generation, where certain materials generate electricity when they experience friction. For their textile, the researchers used copper-coated polytetrafluoroethylene strips woven together with a copper wire.

The solar-cell microcables and triboelectric nanogenerator stripes were woven together with yet more copper wire. This was done using an industrial weaving machine, so no specialized equipment is needed. The end result was a wearable textile that exhibited an interlaced, single-layer structure with a thickness of 320µm.

The researchers demonstrated the ease of the weaving process by fabricating colorful textiles with arbitrary size and weaving patterns. They also integrated the textile into many common fabric items, such as cloth, curtains, and tents.

The team then optimized the properties of individual components, starting with the photovoltaic textile. Here, the electrical connection among the solar cell microcables strongly impacts the power output. By altering the number of strings and the connections they form, the researchers demonstrated the ability to tune the electrical output of the photovoltaic textile to fulfill various power delivery requirements. They also found that the weaving patterns impacted the ambient solar energy conversion and determined that the plain-weave structure generated the highest current density.

The researchers went on to focus on the triboelectric component. They evaluated how the weave pattern influenced mechanical energy conversion of the textile, but found that it worked well with most patterns (although a plain-weave provided the highest electrical output). Evaluation of various ways of providing stress to the fabric revealed that the highest energy output was produced when the fabric was slapped against a surface.

After optimizing the individual components, the researchers worked on optimizing the overall textile. To maximize its energy output, they had to perform a systematic optimization of the individual electrical connections and overall patterns between the photovoltaic and triboelectric components. After the system was optimized, the team put together a plain-weave fabric that included a four-centimeter-square triboelectric textile and a 1 x 4 centimeter photovoltaic textile, mixed with wool fibers.

Under ambient sunlight, and in the presence of wind blowing or human motion, the textile swatch was able to charge a small commercial capacitor up to 2V in one minute. The textile could continuously power an electric watch, charge a cell phone, and even drive water-splitting reactions, releasing hydrogen.

Due to the breathability, flexibility, and robustness of the textile, it is a prime candidate for wearable electronics. Using a textile swatch of 4×5cm, the team evaluated the textile’s properties on a person who was walking under sunlight (80 mW/cm2 intensity). The textile was highly deformable and responded well to human motion. They found that the fabric was able to deliver an output power of 0.5 mW even when elements in the circuit itself drew significant amounts of power (with loading resistances ranging from 10 KΩ to 10 MΩ).

Overall, the fabric doesn't generate a lot of electricity. But it has the advantage of being able to generate electricity where it may be needed—there's something to be said for charging your phone while you walk or powering up your GPS by plugging it into your tent.

Nature Energy, 2016. DOI: DOI: 10.1038/NENERGY.2016.138 (About DOIs).