3D-Printed Single-Material Carbon Nanotube Thermocouple Microdevices

Miniaturized thermocouples have emerged as an essential component for the power generation or thermal management of microelectronic devices due to their capability to convert heat to electricity. Recently, extensive research focused on the structural design of micro-thermocouples to improve the thermoelectric performance, and one resulting insight is that a three-dimensional (3D) geometry can be beneficial in terms of integration density and thermal contact efficiency [1]. However, the construction of a 3D micro-thermocouple typically comprising two dissimilar materials suffers not only from the process complexity with high cost but also from the low mechanical strength of the junction.<br/><br/>Here, we have developed a micro 3D printing method for fabricating a single-material carbon nanotube (CNT) thermocouple device. The device is configured with an electrical junction of two freestanding CNT microwires with different widths, by exploiting the size-dependent Seebeck coefficient at the electron mean free path scale [2, 3] instead of using two different materials. The developed micro 3D printing method that uses a femtoliter ink meniscus enables a single-step, continuous, high-resolution (&lt; 1 µm) manufacturing of CNT micro-thermocouples in three dimensions. This greatly ensures structural robustness, cost-effectiveness, and design flexibility, which have not been attained by other traditional manufacturing approaches, reinforcing practicality. In this talk, we will present the experimental results including the fabrication and characterization of 3D CNT micro-thermocouples, and discuss the prospects of our work for potential applications.<br/><br/>References<br/><br/>[1] Q. Zhang, K. Deng, L. Wilkens, H. Reith, and K. Nielsch, "Micro-thermoelectric devices," <i>Nature Electronics, </i>vol. 5, no. 6, pp. 333-347, 2022, doi: 10.1038/s41928-022-00776-0.<br/>[2] A. Harzheim, F. Könemann, B. Gotsmann, H. van der Zant, and P. Gehring, "Single-Material Graphene Thermocouples," <i>Advanced Functional Materials, </i>vol. 30, no. 22, 2020, doi: 10.1002/adfm.202000574.<br/>[3] W. Sun, H. Liu, W. Gong, L.-M. Peng, and S.-Y. Xu, "Unexpected size effect in the thermopower of thin-film stripes," <i>Journal of Applied Physics, </i>vol. 110, no. 8, 2011, doi: 10.1063/1.3653824.