Chinese team develops “thermoelectric rubber” for wearable devices

Beijing, China – Researchers at Peking University have developed "the world’s first thermoelectric rubber,” designed to generate electricity from body-heat while maintaining elastomeric properties.

Thermoelectric devices convert temperature differences into electrical energy, however inorganic substances such as Bi?Te? and PbTe make the materials “efficient but brittle”.

The organic versions of such elastomers remain flexible but prone to performance loss when stretched.

To address this, the team led by professor Lei Ting at the School of Materials Science and Engineering used three key strategies:

In a ‘uniform nanophase separation’ phase, the team used ‘Hansen solubility parameters to screen rubber materials that match ‘a conjugated polymer to form a uniform semiconductor nanofibre network.’

This, explained the team, can significantly improve the carrier mobility of the semiconductor polymer.

In the ‘thermally activated crosslinking stage’, the team introduce ‘azo crosslinkers’ to lower modulus and allow >850% ductility, with more than 90% elastic recovery under 150% strain.

In the final phase, ‘directional doping’, the researchers used selected dopants to improve both conductivity and the ‘Seebeck coefficient’, while creating a “strain conductivity enhancement” effect.

The three-step strategy “not only improved the mechanical properties of the material but also significantly enhanced its thermoelectric performance,” said a Peking University report.

The report linked the improvement in thermoelectric performance was linked to two factors: first the nanophase-separated structure, which it said “enhances carrier mobility, thereby increasing electrical conductivity and the Seebeck coefficient.”

Secondly, the report said, “the traditional rubber wrapping of the conjugated polymer enhances interfacial propagator scattering, reducing the overall thermal conductivity of the material.”

The resulting material achieved a thermoelectric figure of merit (ZT) of 0.49 at room temperature,
“approaching or surpassing the performance of flexible inorganic thermoelectric materials.”

The material also retained rubber-like resilience and stretch recovery.

Based on this work, the team constructed a stretchable thermoelectric module using a pie-shaped design with integrated electrodes.

The module harvested body heat to generate stable power while conforming to the skin, demonstrating low interfacial thermal resistance and improved comfort.

“This marks important progress in wearable energy harvesting,” said the Peking University report.