3D Printing of Branched Polyurethane with Tough Mechanical Properties for Stretchable Sensors

The poor mechanical properties and difficulties in manufacturing complex structures seriously limit the applications of elastomers especially in flexible electronic sensor. Herein, a series of polyether amine (PEA) grafted polyurethane acrylate oligomers (PUA‐g‐PEAs) and the corresponding low‐viscosity UV‐curable flexible 3D printing elastomers (PEA‐1/IDAs) are synthesized. The results show that a certain amount of PEA branch exactly has strengthening and toughening effect on polyurethane, resulting in 12% increase in tensile strength and 44% increase in elongation at break of PUA‐g‐PEA‐1. When mixed PUA‐g‐PEA‐1with acrylimorpholine and IDA in the ratio of 3:5:2, PEA‐1/IDA‐20 with best overall mechanical properties is obtained. Its tensile strength and elongation at break are 18.5 MPa and 297.4%, respectively. The unprecedented fatigue resistance of PEA‐1/IDA‐20 ensures that it can withstand 100 compression cycles at 80% strain without damage. Besides, piezoresistive sensors and wearable finger guard sensors are fabricated by laminating a layer of conductive hydrogel on the surface of the 3D‐printed devices. The impressive mechanical properties and 3D printing producing process of this branched PUA endow it with great potentials in advanced electronic sensors.