Enhancing sensing performance of 3D-printed TPU/CB piezoresistive strain sensors through integration of silver ink IDE

Abstract

In recent years, flexible strain sensors have gained prominence in applications such as wearable electronics, soft robotics, and health monitoring. This trend is attributed to advancements in composite materials and 3D printing techniques. In this study, we fabricated a piezoresistive strain sensor using a commercial conductive filament made from thermoplastic polyurethane (TPU) embedded with carbon black (CB) particles through the fused filament fabrication (FFF) method. We then enhanced this TPU/CB strain sensor by adding a silver ink interdigitated electrode (IDE) to its surface using a direct ink writing (DIW) technique and assessed the effects of this modification. The results showed that the TPU/CB and TPU/CB/Ag samples reached a strain greater than 200% and exhibited an abnormal negative piezoresistive response during stretching. The addition of IDE silver ink improved the sensitivity at 2% strain for a gauge factor (GF) of -23.78 and decreased the static electrical drift by 5.3%. It proves an accurate response to small external stimuli and improves electrical stability while preserving the sensor’s intrinsic piezoresistive behavior. The TPU/CB/Ag sensor detected deformations of different magnitudes and frequencies, maintaining stability and durability over 500 cycles. The practical utility of the TPU/CB/Ag sensor was validated through both human motion detection and integration into a soft robotic link. This research provides valuable information on the trade-off between mechanical and electrical performance of functionalized piezoresistive sensors, offering a viable option for optimization. • This work focuses on enhancing the sensing performance of a 3D-printed TPU/CB piezoresistive strain sensor via silver ink IDE integration. • Mechanical and electrical trade-offs are thoroughly analyzed, showing that the silver ink IDE ensures stable conductive pathways under strain and significantly enhances the sensor’s stability during static measurements by reducing electrical drift. • The proposed solution offers a scalable, cost-effective fabrication approach, making it ideal for wearable systems, robotics, and health monitoring applications.