Fabrication of CNT/polymer composite ribbons as flexible and lightweight heat conductors Naw Blessing Oo, Nikita Kumari, Ryo Abe, Naofumi Okamoto, Manish Pandey, Hiroaki Benten, Masakazu Nakamura Nara Institute of Science and Technology, Japan With the increased utilization of electronic devices, their accelerating power densities lead to failure in electronic functions. Therefore, thermal reliability becomes more critical across such applications. Amongst the thermal management materials, carbon nanotubes (CNTs) are widely considered as they possess superior thermal conductivity ( κ ), chemical stability, and desirable elastic modulus [1]. However, typical κ values of CNT bulk materials are much lower than expected, probably due to the internal contact resistance between and randomly orientated CNT bundles. Recent studies have shown that shear-induced methods can prominently improve the alignment of CNTs [2], leading to an increase in κ of CNTs. We have also proposed a fabrication method of oriented CNT/polymer composite ribbons using the direct ink writing method via a robotic dispenser. In this work, factors influencing the κ of the CNT/polymer composite ribbon have been studied. The CNT dispersion was drawn on two types of substrates: hydrophilic bare glass and relatively hydrophobic poly(3-hexylthiophene-2,5-diyl) (P3HT)-coated glass with the optimized drawing parameters for CNT alignment such as the needle’s inner diameter ( φ ), the relative drawing speed ( RS ), the dispensing speed ( DS ) and the gap between the tip and the substrate ( d )as shown in Fig. 1. Free-standing CNT ribbons were then peeled off by immersing them in a methanol bath. The κ of the ribbon was evaluated using the cross-junction method, which is improved from the DC-heating T-junction method, proposed for the film-type materials [4]. It was found that as the CNT concentration decreases, the κ increases for both substrates. Besides, higher κ of CNT ribbon (~200 W/ mK) was observed on the bare glass substrate, while that on P3HT-coated glass was ~160 W/mK for the same optimum CNT concentration of 0.075% w/v. This can be attributed to the smaller ribbon thickness on the bare glass substrate than on the P3HT-coated glass (Fig. 2). The results will be discussed in detail on the poster.
References 1. B. Kumanek et al. J. Mater. Sci. 54, 7397-7427 (2019). 2. G. L. Goh et al. Adv. Mater. Interfaces 6, 1801318 (2019). 3. M. Pandey et al. Appl. Phys. Express 13, 065503 (2020). 4. R. Abe et al. J. Therm. Sci. 31, 1037 (2022).
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