3D Printed Embedded Strain Sensor with Enhanced Performance

This paper presents the use of an optimized conductive thermoplastic filament as a strain sensing material in embedded structures with enhanced sensing performance. The custom filament was produced from low aspect ratio multi-walled carbon nanotubes (MWCNT) dispersed in a thermoplastic polyurethane (TPU) polymer matrix. Multi-material fused deposition modelling (FDM) was used to 3D print the TPU/MWCNT filament and the embedding TPU materials. The design and fabrication of the sensor and its characterization at different bending angles are presented in this paper. The sensor exhibited a change of resistance of ~30% at 90º bending which is far superior to all other similarly fabricated non-functionalized MWCNT-based strain sensors. Gaps were introduced in the printed sensor design by altering the infill percentage to further enhance its performance. The use of 50% infill showed the highest change in resistance values at the same bending angle. By optimizing the filler particle morphology, filler concentration, and sensor design, a high performance and durable strain sensor was developed in this work. 3D printed embedded strain sensors find application in various fields such as prosthetics, robotics, wearables, and medical electronics.