Industrial design researchers at Brunel University in London have devised a method to economically produce supercapacitor thread of sufficient voltage to allow everyday items of clothing to power smartphones, tablets and other personal electronics. “[Supercapacitors] store energy without a chemical reaction, so [they] can be charged and discharged almost indefinitely. But in thread form, they have never before been able to break the 1V barrier," says David Harrison, professor of design research.

Advances made by Harrison and colleagues at Brunel’s Department of Design could mean that thread capable of storing and supplying enough power for common devices, and of being manufactured at industrial scale, may be a reality. The researchers fabricated thread supercapacitors with two capacitive layers using a semi-automatic dip coating method. The two capacitive layers were coated sequentially on a 50-micron stainless steel core wire with ink, aqueous-based gel electrolyte and silver conductive paint.

ISchematic of the new energy-storing thread. Image credit: Brunel University London.Schematic of the new energy-storing thread. Image credit: Brunel University London. The two capacitive layers of the thread supercapacitor can work independently or be combined in parallel and series. Cyclic voltammograms showed that all the flexible circuit combinations have high electrochemical stability, the researchers say. For the case of the series circuit configuration, with H3PO4/PVA (polyvinyl alcohol) gel electrolyte, a working potential window of 2V was achieved.

“Breaking the 1V threshold is important, as in the real world we work on the voltage of common batteries: 1.5V," says Harrison. “We also wanted to address mass production issues, so [we] developed a process to semi-automatically coat stainless steel wire the thickness of a human hair with eight separate layers.”

The work is part of the EU-sponsored Powerweave program, which brings together researchers from seven countries to produce textiles that can both generate and store power.

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