You’re looking at a smartphone case’s material of the future, which will allow for self-charging cell phones with the literal touch of a finger.
A “smart” felt, created by researchers from the Center for Nanotechnology and Molecular Materials at Wake Forest University, converts the difference between two differing temperatures into an electrical current.
The research was published in the latest issue of nanotechnology journal, Nano Letters.
Named the “Power Felt,” the fabric-like material generates heat when immersed in an environment where differences in temperature exist between one side of the felt and the other. If one side of the surface is exposed to heat, while the other is exposed to a cooler room temperature air, an electrical current is generated within the fabric.
The fabric-like feel is attributed to layers of carbon nanotubes intertwined with plastic fibers that work together to facilitate the creation of energy with what’s known as the thermoelectric effect. Digital Trends talked to the head researcher leading the study, Professor David Carroll, who explained the process.
It works like this: “If you grab a piece of metal at one end with your hand, you warm it up. The electrons there become warm and move rapidly. Many of those hot electrons move away from the heat to settle in the cooler regions of the material. The difference in the number of electrons in the warm region and the cool region is what give the voltage that is used to create power,” Carroll said. “As long as there is a temperature difference, there will be a voltage.”
As our own bodies are living, breathing, furnaces, heat is wasted readily, but not often harnessed on a consumer scale due to inefficiencies and more importantly, cost. Current thermoelectric devices are most often seen in refrigerators, air conditioners, DC power cords and CPU coolers, which incorporate the semiconducting material, bismuth telluride. But the thermoelectric devices made of bismuth telluride are thicker, more expensive, and its malleability pales in comparison to the Power Felt. The commercial compound can cost nearly $1,000 per kilogram.
In retrospect, Power Felt is cheap and the research team is working to bring down the cost to nearly one dollar to add to a cell phone case. To do so, the team will add more nanotube layers and further decrease its thickness. “Also because it is so cheap, if you need more power, simply make it larger,” Carroll added. “In a year we hope to have increased its power output so that smaller strips of the fabric can power larger things so that you might increase the cell phone battery by 20 percent with a simple strip of the paper in the back of you iPhone cover.”
The competitive advantage of Power Felt is its ubiquity due to its potentially inexpensive manufacturing costs and thereby the likely replacement for current thermoelectric devices. Cell phone cases, heat-capturing jackets, coverings for cars, housing insulation, pool covers and a myriad of other practical applications are among what professor Carroll and his team has in mind. “Ideally we would like to make power generation and advanced wearable item, with usable power for pacemakers, sensors for neuromuscular disease, and the elderly,” Carroll revealed.
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