In recent years, the convergence of nanotechnology and additive manufacturing has opened unprecedented avenues for creating advanced materials with multifunctional capabilities. Among the forefront innovations is the development of conductive polymer-based nanocomposites infused with carbon nanotubes (CNTs), which promise to revolutionize flexible electronics, wearable health monitoring systems, and soft robotics. Despite their potential, fabricating CNT nanocomposites with consistent dispersion and optimal electrical and mechanical properties remains a formidable challenge due to the intrinsic tendency of CNTs to agglomerate. Uniform dispersion is critical not only for maintaining conductivity but also for ensuring mechanical integrity and printability when employing advanced fabrication methods like 3D printing.
Addressing these challenges, an innovative research team led by Professor Keun Park and Associate Professor Soonjae Pyo at Seoul National University of Science and Technology has pioneered the fabrication of highly stretchable and electrically conductive CNT nanocomposites using vat photopolymerization (VPP)-based additive manufacturing. VPP is a sophisticated 3D printing technique that leverages selective light curing within a resin vat to create finely detailed, complex structures. The researchers expertly overcame traditional issues related to CNT agglomeration and ink curing, achieving a formidable balance between stretchability, conductivity, and print resolution—factors that usually exhibit trade-offs in composite materials.
The core strategy employed involved dispersing multi-walled carbon nanotubes (MWCNTs) within an aliphatic urethane diacrylate (AUD) photopolymer matrix. This required meticulous ultrasonic agitation to achieve a homogeneous mixture, which is essential for ensuring consistent electrical pathways and mechanical reinforcement throughout the printed material. Ranging from 0.1 to 0.9 weight percent MWCNTs, the polymer nanocomposite inks were rigorously evaluated to determine optimal properties for 3D printing, including viscosity, curing kinetics, and compatibility with VPP’s photopolymerization process.
Key to their breakthrough was the identification of the 0.9 weight percent MWCNT concentration as the sweet spot that balanced conductivity and mechanical resiliency. Test specimens exhibited remarkable stretchability, enduring elongations up to 223% of their original length without failure, an exceptional value that far exceeds typical CNT nanocomposite performance benchmarks. Concurrently, the electrical conductivity reached an impressive 1.64 × 10^−3 S/m, surpassing earlier reports of similar 3D printable composite materials. This dual achievement of high stretchability and conductivity while maintaining a print resolution of 0.6 mm signifies a new frontier in material science and engineering.
Leveraging the optimized nanocomposite formulations, the team fabricated triply periodic minimal surface (TPMS) structures—complex 3D lattice geometries known for their outstanding mechanical properties and lightweight architectures. These structures functioned as piezoresistive sensors characterized by high sensitivity to mechanical deformation, which is vital for accurate detection of pressure and strain in wearable devices. Incorporating these sensors into a flexible insole demonstrated practical application potential, whereby the pressure distribution exerted by a user’s foot could be monitored in real time. This capability paves the way for advanced health monitoring systems that can detect gait anomalies or postural changes with high spatial and temporal resolution.
The integration of the CNT-based piezoresistive sensors into wearable platforms, such as smart insoles, embodies the intersection of materials innovation and human-centric design. The use of additive manufacturing allows for the precise tailoring of sensor architectures, enabling bespoke designs optimized for sensitivity, durability, and wearer comfort. Moreover, the piezoresistive effect in CNT nanocomposites offers a promising alternative to conventional rigid sensors, which often suffer from limited flexibility and poor adaptability to dynamic human motion.
Beyond the sensor application, the researchers underscore the broader implications of their work for fields ranging from soft robotics to smart textiles. The tailored VPP-based synthesis of CNT nanocomposites can lead to next-generation electronic components that combine mechanical compliance with conductive functionality, a crucial requirement for devices embedded in flexible and deformable substrates. This advance fundamentally changes how we conceive the design and manufacture of wearable health monitors by integrating sensing capabilities directly into customized 3D-printed form factors.
While prior approaches struggled with CNT dispersion and UV-light induced curing limitations, this study’s methodical optimization allowed the preservation of photopolymerization efficiency despite the presence of electrically conductive fillers. The ultrasonication technique effectively broke down CNT bundles, facilitating homogenous dispersion and minimizing light scattering during the VPP curing process. This breakthrough enables a radical enhancement in print fidelity for complex geometries, pushing the envelope of what additive manufacturing can achieve with multifunctional nanocomposites.
This development arrives at a time when the demand for wearable health devices is surging, fueled by the growing population of health-conscious and aging individuals. The ability to manufacture stretchable, conductive, and highly sensitive sensors affordably and at scale could democratize advanced healthcare monitoring, providing continuous, real-time data to both patients and healthcare providers. This would allow early detection of abnormalities and personalized interventions outside clinical settings, significantly impacting patient outcomes and healthcare economics.
Professor Keun Park emphasizes that their optimized CNT nanocomposites are not only suited for piezoresistive sensor fabrication but also open avenues for creating architectured materials with tunable mechanical and electrical properties. Such materials can be tailored to specific application requirements, enhancing the functionality and integration capacity of flexible devices. The research demonstrates critical progress in the feasibility of 3D printing these complex materials in forms that were previously impossible due to material or process constraints.
Associate Professor Soonjae Pyo highlights the multidisciplinary synergy required to realize these advancements, combining expertise in nanoscale material science, additive manufacturing technology, and sensor engineering. Their collaborative efforts embody the future trajectory of materials innovation, where precise control at multiple length scales—from molecular dispersion of CNTs to large-scale device architecture—enables transformative device capabilities.
The significance of this study extends beyond academia, potentially impacting industries such as healthcare, consumer electronics, athletics, and even aerospace, where lightweight, multifunctional, and flexible materials are in high demand. The scalable VPP-based process for these CNT nanocomposites also implies cost-effective manufacturability, critical for commercial viability. As flexible and wearable electronics continue to push boundaries, the materials enabling these devices must evolve. This research provides a key technological leap, signaling a paradigm shift in how conductive, stretchable materials are created and utilized.
In summary, the team at Seoul National University of Science and Technology has successfully demonstrated a photopolymerization additive manufacturing method that fabricates highly stretchable, electrically conductive CNT nanocomposites with exceptional mechanical and electrical performance. Their ability to create complex, architectured sensors using 3D printing marks a significant advancement in wearable technology. By embedding these sensors into smart insoles capable of real-time pressure monitoring, they exemplify the practical impact and transformative potential of their materials innovation. As the field advances, such breakthroughs will undoubtedly accelerate the development of next-generation smart, flexible devices vital for personalized health monitoring and beyond.
Subject of Research: Not applicable
Article Title: Photopolymerization additive manufacturing of highly stretchable CNT nanocomposites for 3D-architectured sensor applications
News Publication Date: 15-Nov-2025
References: DOI: 10.1016/j.compstruct.2025.119614
Image Credits: Seoul National University of Science and Technology
Keywords: Nanotechnology, Additive manufacturing, Carbon nanotubes, Conductive polymers, Wearable devices, Health and medicine, Sensors, Materials science
