FDM printed MXene/MnFe2O4/MWCNTs reinforced TPU composites with 3D Voronoi structure for sensor and electromagnetic shielding applications

Wearable sensors with a three-dimensional (3D) structural design and electromagnetic shielding performance are significant for the future development of wearable electronic devices. However, it remains a challenge to achieve the target goals. Herein, the thermoplastic polyurethane (TPU)/Ti(3)C(2)Tx (MXene)/MnFe2O4/Multi-walled carbon nanotubes (MWCNTs) (i.e., TMMM) composites were innovatively designed using parametric Voronoi structure with different pore sizes and porosity upon fused deposition molding (FDM) printing. The two-dimensional (2D) MXene/zero-dimensional (0D) MnFe2O4 hybrid fillers were built initially by electrostatic bonding strategy, followed by adding the one-dimensional (1D) MWCNTs as a conductive bridging agent, this way endowed the nanofillers with different dimensions uniformly dispersed to form a superb conductive network structure in the TPU matrix. When applied as pressure sensors, the TMMM composites exhibited adjustable gauge factor (GF = 1.33-3.73), extensive sensing compression range (similar to 89% strain with 12.03 MPa stress), good durability (6000s cyclic compression), which was very conducive to monitoring human motion, such as finger bending, wrist bending, speech recognition, etc. The sensing mechanisms were also studied using the Finite element simulations, and the variation trend of resistance change was in good agreement with the simulation results. The average electromagnetic interference shielding efficiency (EMI SE) value of the 2.1 mm-thick printed composite reached 31.2 dB, suggesting that 99.9242% of electromagnetic waves can be shielded. The proposed strategy not only provided a solution to reduce the weight of electromagnetic shielding materials, but also provided an efficient method for developing porous 3D printed parts with adjustable sensing properties at the macroscopic scale towards wearable electronic devices.