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PRINTED ECO-MATERIALS FOR FLEXIBLE THERMOELECTRIC DEVICES
Publication . Figueira, Joana Roumeliotis Sampaio; Loureiro, Joana; Pereira, Luís
The Internet of Things is already a reality, driving the need for scientists to develop and integrate cost-effective, biocompatible, flexible, and lightweight solutions for universal connectivity, including sensing features. Additionally, sustainability emphasizes the importance of using eco-friendly materi-als and choosing energy-efficient production techniques.
While often promoted as a green energy source, thermoelectric materials excel in temperature-sensitive applications, being capable of detecting thermal stimuli such as human touch. The combina-tion of sustainable Seebeck coefficient holding materials with printing methods enables scalable and affordable thermal sensors that may be flexible, lightweight and biocompatible, opening the door for wearable applications.
This doctoral research focused on the development of printed thermoelectric sensors using graphite-based materials. Sustainability considerations guided the choice of substrates, solvents, and encapsulating materials. The results show that graphite flakes can be used as purchased, yielding pla-nar, vertical, and planar/vertical thermoelectric architectures, capable of containing multiple elements in series, which increases the signal output. The formulated cellulose-based inks can be printed directly onto untreated flexible substrates (paper and fabric). Sensors were also obtained using silicone elas-tomer-based composites, allowing for significant design flexibility and substrate absence. It was possi-ble to achieve touch sensors with fast response times (bellow 1 s) and to have a VON optimization surpassing 4.5 mV (when connecting multiple elements in series, in ~1.5 cm2) and high SNR values (above 300 for EC/GFlakes and up to 170 for PDMS/GFlakes). Regarding the planar sensors made with EC/GFlakes, the printed elements were evaluated and approved for flexible applications, with curvature radii down to 3.5 mm.
At its core, this research addresses the urgent need for versatile and sustainable sensing solu-tions in the era of the 'Internet of Things', showcasing advancements in the field through innovative material applications and low-energy consumption production techniques.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
PTDC/CTM-NAN/5172/2014