Highly Stretchable and UV Curable Elastomers for Digital Light Processing Based 3D Printing

A family of highly stretchable and UV curable (SUV) elastomer systems that are suitable for UV radiation based 3D printing were reported. By mixing epoxy aliphatic acrylate (EAA) and aliphatic urethane diacrylate (AUD) at various ratios, we developed digital light processing (DLP) printable elastomers that can be stretched by up to 1100% which is more than five times the elongation at break of the commercial UV curable elastomers. Using DLP printing with the SUV elastomer compositions enables the direct creation of complex 3D lattices or hollow structures that exhibit extremely large deformation. The SUV elastomer system will significantly enhance the capability of the DLP-based 3D printing of fabricating soft and deformable 3D structures and devices including soft actuators and robots, flexible electronics, acoustic metamaterials, and many other applications. The hyperelastic behavior of the SUV system with EAA-AUD mixing ratio was ranging from 5:5 to 0:10. It was observed that the increase in the AUD cross-linker concentration not only leads to the increase in Young's modulus from 0.58 to 4.21 MPa, but also significantly increases the elongation at break from =240 to =1100% which is about five times that of the best existing commercial UV curable elastomers. Upon mechanical loading, the breakage of hydrogen bonds dissipates energy and therefore results in the high stretchability of the elastomer system. Adding more EAA into the elastomer system does not only reduce the cross-linking density, but also nar the distribution of the hard segments of the cross-linked network, which significantly reduces the presence of the hydrogen bonds, therefore decreases the system's stretchability as well as stiffness. The SUV elastomer system will significantly enhance the capability of the DLP-based 3D printing of fabricating soft and deformable 3D structures and devices including soft actuators and robots, flexible electronics, acoustic metamaterials, and many other applications.