Non-hazardous and fully recyclable ionic thermoelectrics for sustainable human-machine interfaces.

Yang, Jingyi; Wang, Zifeng; Yang, Zijie; Liu, Mengmeng; Lee, David Kwok Hung; Bian, Ka; Ouyang, Jianyong; Tee, Benjamin C K · Nat Commun · 2025

basic_science · Level V

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Abstract

Thermoelectric (TE) materials directly convert temperature gradients into electrical potential. However, conventional rigid TE materials are limited by poor mechanical compliance, potential toxicity, and non-recyclability. Here, we present an ionic TE hydrogel that addresses these challenges through high stretchability, full recyclability, and non-toxic composition. The hydrogel can be recycled through an environmentally friendly process that generates no hazardous byproducts. Our material exhibits exceptional mechanical stretchability with 1400% strain capacity, 98% optical transparency, high electrical conductivity (1.9 mS cm<sup>-1</sup>), and a Seebeck coefficient (-1.05 mV/K). When encapsulated in recyclable polyurethane, the resulting devices enable stable dual-mode sensing through both TE and triboelectric mechanisms, allowing simultaneous temperature and pressure detection without complex signal processing. The devices maintain 96% of their electrical performance even after recycling and self-healing cycles. This innovative hydrogel design strategy aligns with circular economy principles for environment-friendly human-machine interface applications.