Carbon nanotubes (CNTs) are popular in strain sensors due to their exceptional electrical conductivity, flexibility, and sensitivity to deformation. In this study, a high-sensitivity strain sensor was fabricated by spray-coating CNT ink onto various paper substrates, with “lint-free paper” identified as the optimal choice. A total of 10 spray cycles ensured a reliable conductive coating. To enhance durability and broaden application potential, a PET protective layer was incorporated. The sensor's performance was assessed through bending tests using a push-pull gauge across a strain range of 0-2%. The lintfree paper-based sensor exhibited a consistent response up to 1.4% strain. The measured gauge factors (GF) were 121.370 in the 0-0.3% range, 70.999 in the 0.3-0.8% range, and 20.935 in the 0.8-1.4% range. A precise response was also noted when adjusting the bending angle in 1° increments, particularly within the 0-20° range. Additionally, the sensor was tested on the human wrist, confirming its viability for wearable applications. These findings indicate that the lint-free paper-based CNT strain sensor offers high sensitivity and measurement precision within narrow strain ranges. Its lightweight structure and flexible design suggest strong potential for practical use in areas such as sports monitoring and human motion detection.

In this study, thin-shell surface observation, storage capability test, and micro-compressive test were performed for self-healing microcapsules using a field emission scanning electron microscope (FE-SEM) and a micro-compressive testing machine. A microcapsule having a melamine-urea-formaldehyde thin-shell and a microcapsule having a melamine-urea-formaldehyde thin-shell reinforced with carbon nanotubes were used. Two carbon nanotube contents were considered: 0.17 wt% and 0.50 wt%. Thin-wall shell state was relatively smooth when microcapsules were not reinforced with carbon nanotubes. It was uneven when microcapsules were reinforced with carbon nanotubes. Prepared microcapsules showed little decreases of weights even when the exposure time was increased regardless of whether they were reinforced with carbon nanotubes. Thus, their storage capability was good. When carbon nanotube content was the same, the fracture load was almost constant without being affected by the diameter of the microcapsule. However, fracture displacement increased with increasing diameter of the microcapsule. When diameters of microcapsules were similar, fracture load and fracture displacement increased when carbon nanotube content increased. It was found that self-healing microcapsules had good storage capability and mechanical properties. Thus, they could be applied to repair damage to composite materials if thin-shell formation mechanism for adding carbon nanotubes is supplemented.

As a heating method for RHCM (Rapid Heating Cycle Molding) various heating technologies such as high frequency induction heating, IR heating, gas heating, and high temperature steamare applied, but these methods are not satisfying high productivity due to low energy efficiency. Research has been actively conducted on RHCM based on planar heating elements with high heating efficiency, such as carbon nanotubes, which are applied. To apply the CNT web film to the RHCM, a heating element must be applied inside the injection mold and power must be applied. As electricity is directly applied to the CNT web film to generate heat, all mold parts in contact with the CNT web film must be insulated, and high heat transfer is required for rapid heating performance. Thus, in this study, a multi-layer structure mold module for insulation and high heat transfer was designed to enable rapid heating by applying a CNT web film as a heat source. To this end, we intend to present a research direction for the commercialization of rapid heating molds, by identifying the main variables of rapid heating through heating experiments by the mold metal and insulator materials, and reflecting them in the mold design.