Researchers Create PEDOT Composite, Design Stretchable Thermoelectric Generators for Wearables

Based on a common but inflexible material, the new thermoelectric composite could power future projects through energy harvesting.

Future wearables could be powered by this stretchable, soft thermoelectric generator. (📷: Thor Balkhed)

Materials researchers at Linköping University, the University of Auckland, and the University of Mons have published a paper detailing an organic composite material they claim could have a massive impact in the fields of smart clothing, wearable electronics, and electronic skin — and could begin by offering a soft, stretchable thermoelectric generator for energy harvesting.

"Xavier Crispin is a pioneer in organic thermoelectric materials; Klas Tybrandt is an expert in soft electronic materials; and I contribute my knowledge of organic composites," says researcher Nara Kim of the team at Linköping responsible for the research project. "We came up with the idea for the new material together."

That material: A combination of common conducting polymer PEDOT:PSS, a water-soluble polyurethane, and an ionic liquid. Where PEDOT:PSS is thermoelectric, it's too hard and brittle for wearable projects; the rubber offers elasticity, while the liquid softens it without harming performance.

"Our material is 100 times softer and 100 times more stretchable than PEDOT:PSS," claims Klas Tybrandt of the resulting composite. "The ability to control the structure of the material both at the nanoscale and the microscale allows us to combine the excellent properties of the different materials in a composite."

"The composite was formulated by water-based solution blending and it can be printed onto various surfaces," adds Kim, in another boon for bringing the technology out of the lab and into manufacturing. "When the surface flexes or folds, the composite follows the motion. And the process to manufacture the composite is cheap and environmentally friendly."

"The presented strategy opens up a general route for creating elastic organic conductors through the exploration of many combinations of different conducting polymers/ionic liquids/elastomers," the researchers conclude in their paper.

"Moreover, as exemplified in the successful demonstration of the first intrinsically stretchable organic thermoelectric module, the combination of the mechanical properties of the developed PEDOT composites and the potential of PEDOT for various applications (electronic, electrochemical, ionic, optical, and TE devices) are expected to dramatically expand PEDOT's applicability to mechanically demanding applications, including on or inside human body, textiles, and any kind of irregular or moving surfaces."

The paper has been published in the journal Nature Communications under open-access terms.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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