THE DEVELOPMENT OF TEXTILE-BASED CONDUCTIVE WEARABLES VIA DIRECT INK WRITING (DIW) 3D PRINTING TECHNOLOGY

The integration of smart sensing materials into textile products presents transformative opportunities in healthcare, sports, robotics, and human–computer interaction. Although textile-based smart wearables offer inherent advantages such as comfort, flexibility, and seamless integration into everyday life, making them ideal for continuous monitoring, their development is often limited by the complexity of current manufacturing methods and the intricate interplay between functional materials and the anisotropic, hierarchical structures of textile substrates. Existing fabrication approaches primarily rely on weaving conductive fibers into fabrics or attaching rigid sensors onto their surfaces. These methods pose significant challenges in achieving a balance between comfort, durability, and high sensitivity. Moreover, they often overlook the influence of textile substrates and fail to fully utilize the structural properties of textiles to enhance sensor performance. Therefore, there is a critical need for advanced fabrication strategies and a comprehensive understanding of fabric–material interactions to enable the direct integration of functional materials into textile structures while maintaining the essential performance characteristics required for ideal wearable devices. This dissertation proposes a Direct Ink Writing (DIW) 3D printing approach for fabricating high-performance textile-based sensors by understanding the interrelationship among conductive ink formulations, printing parameters, printing patterns, and textile substrate characteristics. The key to the success of this approach was the precise design and control of multiple processing factors, including ink formular, ink rheology, printing parameters, printing geometries, fabric porosity, and fabric structures to achieve strong interfacial bonding and maintain stable electrical performance under mechanical deformation. Through comprehensive characterizations and analysis, the results showed that the performance of textile-based smart wearables fabricated via Direct Ink Writing (DIW) can be effectively tuned by engineering ink–fabric interactions, fabric structural properties, and processing geometries. A biodegradable conductive ink composed of polybutylene succinate (PBS), carbon nanotubes (CNTs), and Cyrene was formulated to ensure strong adhesion, flexibility, and conductivity when printed onto various textile substrates. The ink’s penetration into fiber and yarn structures enhanced durability, abrasion resistance, and washability. Meanwhile, fabric parameters such as yarn twist, weave type, and density were found to significantly influence ink spreading, conductive network formation, and strain sensitivity, with high-twist yarns and plain weaves yielding superior performance. Beyond material formulation and fabric architecture, the design of printing patterns also played a crucial role in determining sensor response under mechanical deformation. Reentrant repeat geometries enabled reliable sensing across a wide strain range, with the linear reentrant pattern excelling in small-strain detection and the offset pattern in large-shape deformation scenarios. This work offers a comprehensive framework for integrating functional materials into textiles, advancing the development of comfortable, stretchable, and customizable smart fabrics for real-world applications in motion monitoring, soft robotics, and remote healthcare.