Rugged thermoelectric generator by squeezing carbon nanotube-coated sponge for scalable manufacturing

Flexible and wearable electronics demand mechanically durable thermoelectric generators (TEGs) with reliable power generation. This study introduces a scalable two-step fabrication method for rugged thermoelectric elements. The approach involves forming a carbon nanotube (CNT) network by dip-coating porous substrates, followed by mechanical squeezing to densify the CNT network. This process enables the separate tuning of the CNT concentration (0.5 to 59 mg·cm^{− 3}) and the structural porosity (85% to 45%). The squeezed CNT sponge exhibited different electrical and thermal conductivities in response to the concentration and porosity values and ultimately achieved a thermoelectric figure of merit (zT) of 1.11 × 10^{− 3} under optimal conditions. The fabricated eight-pair rugged TEG delivered a maximum output power of 12.25 µW at a 30.44 K temperature difference. The impact tests revealed that the rugged TEG maintains the power output, even after impacts of 1.00 J, and structurally withstands forces up to 2.49 J, unlike the conventional inorganic TEG, which fails completely at 0.053 J. Additionally, bending tests confirmed the TEG maintained a stable performance after 10,000 cycles, and water immersion tests demonstrated environmental stability, with the TEG retaining 73.7% of its initial performance after 1 day of immersion and recovering to 95.7% upon drying. This rugged TEG provides a practical approach to implementing thermoelectric energy harvesting in various wearable electronics and Internet of Things applications.