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

Brain–computer interfaces depend critically on microelectrodes implanted within neural tissue to detect or stimulate electrical activity with high fidelity. Conventionally, metal and silicon-based microelectrodes have been widely used due to their robust electrical properties. However, their intrinsic rigidity leads to persistent mechanical mismatch with the brain’s delicate soft tissue, provoking chronic inflammation, gliosis, and neuronal loss, all of which undermine device longevity and signal quality. On the other hand, polymer-based electrodes offer improved biocompatibility and mechanical compliance but fall short in conductivity and signal stability, limiting their practical utility in long-term implants.

The research team, led by Associate Professor Jong G. Ok and Dr. Maesoon Im, tackled this dichotomy by engineering three-dimensional CNT “forests” precisely grown and vertically aligned, then embedded seamlessly within an elastic polymer substrate. This CNT-polymer hybrid achieves a remarkable synergy: the CNT structures confer highly efficient electrical conduction that rivals metals, while the polymer matrix imparts extreme mechanical flexibility, with a softness approximately 4,000 times greater than silicon and 100 times that of polyimide. This combination drastically reduces mechanical mismatch with brain tissue, fostering a more harmonious and less inflammatory interface.

Fabrication of the microelectrode arrays employed a meticulously refined multi-step process. Firstly, CNTs are vertically grown through chemical vapor deposition techniques to form dense, forest-like architectures with nanoscale precision. Subsequently, a proprietary polymerization and hybridization technique embeds these CNT forests within a flexible polymer, ensuring robust adhesion and structural integrity without compromising electrical pathways. This multi-material strategy preserves the electrical advantage of CNTs while addressing mechanical compliance, a feat rarely achieved in neural interface engineering.

The arrays demonstrated remarkable stability and functionality upon implantation in mouse models. They enabled precise recording of visual-evoked neural signals from the visual cortex, confirming their efficacy in capturing dynamic brain activity. Notably, the arrays exhibited significantly reduced inflammatory responses compared to traditional tungsten microwires, as evidenced by diminished activation of astrocytes and microglial cells responsible for immune reactions. This reduction points to a more biocompatible long-term implant capable of enduring weeks or potentially months without eliciting adverse tissue remodeling.

The implications of this technology extend far beyond fundamental neuroscience research. Visual prosthetic applications stand to benefit enormously, particularly for patients suffering from retinal degeneration or optic nerve damage who currently have limited therapeutic options. The capability to record stable neural signals from brain regions processing vision underpins potential brain-machine interfaces that could restore or augment visual perception by bypassing damaged ocular pathways.

Moreover, the intrinsic flexibility and biointegration of these arrays make them promising candidates for incorporation into increasingly sophisticated neuroprosthetic devices. By scaling down the arrays to subcellular dimensions, the researchers envision achieving neural signal recording at unprecedented spatial resolution, enabling richer decoding of brain states. This could catalyze new frontiers in brain-assisted communication technologies, such as systems that read and interpret visual attention in real time, creating immersive augmented or virtual reality experiences controlled directly by brain activity.

Dr. Jong G. Ok emphasizes the dual functionality of the CNT-polymer hybrid: “By combining vertically aligned carbon nanotubes with a flexible polymer, we have realized a neural interface device that maintains both high electrical performance and mechanical compliance. This dual capability enables long-term, stable neural recordings without damaging surrounding brain tissues.” This balance addresses the two most critical and often conflicting design requirements for implanted neural electrodes.

In the in-vivo experiments, light stimuli triggered measurable responses in visual cortex neurons recorded through the CNT-based arrays, confirming that the device can faithfully capture physiologically relevant sensory information. Furthermore, the one-month implantation study highlighted the device’s minimal immune activation compared to more conventional electrodes, suggesting a reduced risk of gliotic encapsulation and signal degradation over time.

These findings open new avenues not only for therapeutic interventions but also for basic neuroscience, providing researchers novel tools to study neural processing with greater resolution and less interference. The envisioned subcellular-scale electrodes could help unravel complexities of neural circuits by reading out signals from individual neurons or even synaptic connections, advancing understanding of brain function and dysfunction.

Looking forward, the research team seeks to refine fabrication methods to produce even smaller and denser electrode arrays capable of chronic implantation. Such progress may fulfill long-held aspirations for seamless brain-computer interfaces with high data throughput, opening possibilities for restoring sensory modalities, enhancing cognitive functions, and developing neuroprostheses that respond naturally to brain intentions.

In summary, this CNT-polymer hybrid microelectrode technology marks a significant milestone in neural engineering. By resolving the long-standing trade-off between electrical performance and mechanical compatibility, it lays a foundation for safer, more effective, and longer-lasting brain implants. Its potential to transform visual prosthetics and other neurotechnologies heralds a promising chapter in the quest to harness brain signals for therapeutic and augmentative applications, blending nanomaterials science, biomedical engineering, and neuroscience into a single visionary platform.

Subject of Research: Animals

Article Title: Polymer-Incorporated Mechanically Compliant Carbon Nanotube Microelectrode Arrays for Multichannel Neural Signal Recording

News Publication Date: 27-Jun-2025

Web References:
https://doi.org/10.1002/adfm.202509630
https://en.seoultech.ac.kr/

References:
DOI: 10.1002/adfm.202509630

Image Credits:
Seoul National University of Science and Technology

Keywords:
Health and medicine, Neuroscience, Nanotechnology, Biomedical engineering, Carbon nanotubes, Medical technology, Prosthetics, Vision disorders, Bionics, Nanomaterials