Highly elastic and tear resistant elastomers for stretchable electronic sensors based on 3D printing

Abstract Additive manufacturing elastomers are highly favored for their significant potential applications in the field of wearable electronics. However, there are still limited photocured elastomers that can satisfy the requirements of printability and high performance for vat photopolymerization (VPP) 3D printing. In this study, a class of photosensitive polyurethane acrylate elastomers was designed and synthesized. Isophthalic dihydrazide with a hydrazide group was chosen as the chain extender. The reaction of the hydrazide group with the isocyanate group to generate acylsemicarbazide (ASCZ) could provide abundant strong hydrogen bonds for the crosslinked network of the elastomer, which significantly affects the state of the microphase separation of the polyurethane elastomer. It is discovered that the ASCZ may significantly improve the elastomer's mechanical characteristics. This allows the photosensitive polyurethane's tensile strength and strain at break to reach a maximum of 8.9 ± 0.3 MPa and 460% ± 17%, respectively, demonstrating exceptional resilience and fatigue resistance. Furthermore, the photocurable elastomer containing Lithium bis((trifluoromethyl)sulfonyl)azanide conductive material is compatible with the VPP‐based digital light processing technology, allowing the manufacturing resolution to be as high as 50 μm. It can not only customize the manufacture of strain sensing equipment but also accurately and sensitively monitor human movement signals. Highlights The photosensitive polyurethane has a transmittance of 92%. The ASCZ bond endows the elastomer with a good tear resistance (79.9 kJ/m ² ). The elongation at the break of the elastomer can reach 470%. The residual strain under 100% strain is only 15%, showing a good elasticity. The sensor prepared by this material has a wide working range.