3D-printed polymer composites in wearable sensors: A review of techniques and applications

Wearable sensors fabricated through 3D printing technologies have emerged as a promising solution for next-generation electronics, offering real-time, non-invasive, and continuous monitoring of physiological and environmental parameters. This review provides a comprehensive overview of recent advancements in 3D-printed polymer composites for wearable sensors, focusing on additive manufacturing techniques such as fused deposition modeling (FDM), direct ink writing (DIW), stereolithography (SLA), inkjet printing (IJ), binder jetting (BJ), and selective laser sintering (SLS). It highlights the unique capabilities and limitations of each method in constructing flexible, stretchable, and multifunctional devices. Key sensor types including strain, pressure, temperature, and humidity sensors are examined with an emphasis on materials, design architectures, sensitivity, and durability. Special attention is given to multifunctional, self-healing, and self-powered systems, as well as emerging trends such as hybrid fillers, hierarchical structures, and dual-scale porosity. This review discusses the critical role of material selection, structural design, and printing precision in addressing current challenges and enhancing wearable sensor performance. Finally, future perspectives are outlined, emphasizing the development of fully integrated systems, stimuli-responsive materials, and scalable fabrication strategies for practical applications in healthcare, robotics, and beyond.