CF/Sb2Te3 Films for Comfortable and Efficient Wearable Electronics

According to a study published in the Journal of Advanced Ceramics on June 5^th, 2024, a team led by Peng-an Zong from Nanjing Tech University’s School of Materials Science and Engineering in China has created CF/Sb2Te₃ (CF/Bi₂Te₃) films with superior thermoelectric and moisture permeability.

Thermoelectric technology converts heat directly to electricity and has emerged as a possible alternative energy source. Notably, this technology can efficiently convert body heat into electrical energy, gaining traction in wearable electronics.

However, the dense structure of most thermoelectric materials results in extremely low moisture permeability. In practical applications, low moisture permeability can trap heat and humidity, promoting bacterial development and possibly causing skin lesions. Hence, creating thermoelectric materials with high moisture permeability is critical.

The cross-linked core-shell structure of carbon fiber internals, obtained by electrodeposition, improves electrical conductivity. In addition, the composite film’s electromagnetic interference shielding efficiency (EMI SE) was substantially improved. The films were then used as sensors, displaying good touch and breath-detecting capabilities.

The researchers used carbon fiber (CF) as the substrate material and electrodeposition to grow Sb₂Te₃ and Bi₂Te₃ on the CF. They investigated the films’ performance by changing the deposition coulombs, deposition potential, and other factors.

The larger internal fiber width enabled carrier movement, resulting in improved electrical conductivity and thermoelectric properties. As a result, the composite film's power factor was 300 times greater than that of the CF substrate.

The electrodeposition of thermoelectric materials lowers the surrounding pore size, resulting in a moisture permeability 5 % lower than that of CF. However, it still exceeds 3000 g m⁻² day⁻¹. Due to numerous reasons, the composite film’s EMI shielding efficiency (EMI SE) can reach 93 dB.

Electrodeposition of thermoelectric materials reduces surrounding pores and increases fiber column diameter, resulting in a moisture permeability of just 5 % lower than CF (around 3000 g m⁻² day⁻¹). Thanks to its intrinsic fiber structure, the composite film's EMI SE can reach 93 dB.

The researchers chose the composite films with the optimum performance to integrate the sensor, which was used in touch sensing and respiratory sensing applications. The sensor’s practical application situations were displayed, and its cycle performance was verified to prove its stability.

NSAF (no. U2230131), Natural Science Foundation of Jiangsu Province (no. BK20211264), State Key Laboratory of New Ceramic and Fine Processing Tsinghua University (no. KF202207), the Postgraduate Research & Practice Innovation Program of Jiangsu Province (SJCX24_0548 and KYCX23_1396), and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) supported the study.

Journal Reference:

Zhu, J., et al. (2024) Permeable carbon fiber based thermoelectric film with exceptional EMI shielding performance and sensor capabilities. Journal of Advanced Ceramics. doi:10.26599/JAC.2024.9220922