Hybrid Material Extrusion Process Optimization for Printability and Adhesion in 3D-Printed Electronics

3D printing exhibits strong potential in electronics manufacturing for its capability of manufacturing complex structures with a wide range of materials. However, thermoplastic polyurethane (TPU) has rarely been fabricated by 3D printing for electronics due to the limited understanding of its printability and the adhesion of the conductors on it. Herein, we invetigate the printability of TPU using varying layer height and printing temperature in the Materials Extrusion (MEX) process, their impacts on the printability, and the adhesion of conductive trace on TPU. The printability is characterized by the surface roughness, stability of dimension and mass, and the adhesion is evaluated by a standard cross-cutting method. In this research, 0.20 mm layer height and 220 degrees C printing temperature have consistently proven to be optimal configuration parameters for MEX printing of TPU. Larger layer height in TPU printing causes poorer printing quality (lower dimensional accuracy, more porous structure, rougher surface), lower ink-TPU adhesion, and transforms the adhesive failure of ink against peeling to cohesive failure. Higher printing temperature causes less homogeneous structure and rougher surface with minor influence on the width and conductivity of ink on TPU, and no influence on the mechanism of ink failure against peeling. To achieve fully 3D-printed stretchable electronics, understanding the printability of elastic polymer and the adhesion of the conductors printed onto it is essential. This study found that lower layer height and lower printing temperature in thermoplastic polyurethane (TPU) fabrication via Materials Extrusion achieve better printability, lower surface roughness of fabricated TPU, and higher adhesion of conductive ink printed onto it.image (c) 2024 WILEY-VCH GmbH