In response to the rising need for flexible and lightweight materials capable of efficient heat transport, many studies have been conducted to improve the thermal properties of polymers via nanofillers. Among the various nanofillers, carbon nanotubes (CNTs) are considered as the most promising, owing to their excellent thermal and electrical properties. Accordingly, CNT/polymer composites can be used as flexible and lightweight heat transfer materials, owing to their low density. In this study, we fabricated multi-walled CNT (MWCNT)/polymer composites with different aspect ratios to investigate their effects on electrical and thermal properties. Through a three-roll milling process, CNTs were uniformly dispersed in the polymer matrix to form a conductive network. Enhanced electrical and thermal properties were observed in MWCNT composite with a high aspect ratio as compared to those with a low aspect ratio. The thermal conductivity of composites obtained as a function of the filler content was also compared with the results of a theoretical prediction model.

Carbon-based polymer composites are widely used in wearable devices due to their exceptional electrical conductivity and flexibility. However, their temperature-dependent resistance variations pose significant challenges to device safety and performance. A negative temperature coefficient (NTC) can lead to overcurrent risks, while a positive temperature coefficient (PTC) compromises accuracy. In this study, we present a novel hybrid composite combining carbon nanotubes (CNTs) with NTC properties and carbon black (CB) with PTC properties to achieve a near-zero temperature coefficient of resistance (TCR) at an optimal ratio. This innovation enhances the safety and reliability of carbon-based polymer composites for wearable heating applications. Furthermore, a thermochromic pigment layer is integrated into the hybrid composite, enabling visual temperature indication across three distinct zones. This bilayer structure not only addresses the TCR challenge but also provides real-time, user-friendly temperature monitoring. The resulting composite demonstrates consistent performance and high precision under diverse heating conditions, making it ideal for wearable thermotherapy pads. This study highlights a significant advancement in developing multifunctional, temperature-responsive materials, offering a promising solution for safer and more controllable wearable devices.

The transition metal dichalcogenide (TMDC) NbSe₂ is a highly conductive and superconducting material with great potential for next-generation electronic and optoelectronic devices. However, its bulk form suffers from reduced charge density and conductivity due to interlayer van der Waals interactions. To address this, we exfoliated NbSe₂ into nanosheets using lithium-ion intercalation and utilized them as diaphragms in acoustic transducers. Conventional electromagnetic and electrostatic mechanisms have limitations in sound pressure level (SPL) performance at high and low frequencies, respectively. To overcome this, we developed a hybrid force mechanism combining the strengths of both approaches. The NbSe₂ nanosheets were successfully prepared and analyzed, and the NbSe₂-based hybrid acoustic transducer (N-HAT) demonstrated significantly improved SPL performance across a wide frequency range. This study offers a novel approach for designing high-performance acoustic devices by harnessing the unique properties of NbSe₂.