Due to its excellent material properties of elasticity, resilience, and electrical and thermal insulation, elastomers have been used in a myriad of applications. They are especially ideal for fabricating soft robots, flexible electronics, and smart biomedical devices that require soft, deformable material properties to establish safe, smooth interactions with humans externally and internally.
However, the most widely used silicon-rubber-based elastomers require a thermal curing process, which significantly limits their fabrication in traditional ways, such as by cutting, molding, and casting, and constrains design freedom and geometric complexity. To improve design and fabrication flexibility, researchers have been attempting to use 3D printing techniques to fabricate elastomeric 3D objects. These include UV-curing-based 3D printing techniques, which solidify liquid polymer resins to 3D objects through patterned UV light. Nevertheless, most commercially available UV-curable, thus 3D printable, elastomers break at less than 200 percent (two times the original length), which makes them unsuitable for many applications.
Recently, researchers have developed a family of highly stretchable UV-curable (SUV) elastomers that can be stretched by up to 1100 percent and are suitable for UV-curing-based 3D printing techniques. This work is a collaborative effort between researchers from the Singapore University of Technology and Design's Digital Manufacturing and Design (DManD) Center, which is funded by the Singapore National Research Foundation, the Hebrew University of Jerusalem, and the Campus for Research Excellence and Technological Enterprise.
"We have developed the most stretchable 3D printable elastomer in the world," said Assistant Professor Qi (Kevin) Ge from the DManD Center, who is one of the co-leaders in developing SUV elastomers. He added: "Our new elastomers can be stretched by up to 1100 percent, which is more than five times the elongation at break of any commercially available elastomer that is suitable for UV-curing-based 3D printing techniques."
Using high-resolution 3D printing with SUV elastomer compositions enables the direct creation of complex 3D lattices or hollow structures that exhibit extremely large deformation. "The new SUV elastomers enable us to directly print complicated geometric structures and devices, such as a 3D soft robotic gripper, within an hour. Compared to traditional molding and casting methods, using UV-curing-based 3D printing with the SUV elastomers significantly reduces the fabrication time from many hours, even days, to a few minutes or hours as the complicated and time-consuming fabrication steps, such as mold-building, molding/demolding, and part assembly, are replaced by a single 3D printing step," said Ge.
The SUV elastomers not only sustain large elastic deformation but also maintain good mechanical repeatability, which makes them good materials for fabricating flexible electronics. To demonstrate this, the researchers fabricated a 3D buckyball light switch that still works after being pressed for more than 1000 times.