Highly Stretchable and UV Curable Elastomers for Digital Light Processing Based 3D Printing (original) (raw)

centimeters. However, so far the studies on developing DLP compatible high-performance, multifunctional materials are comparatively very limited. Elastomers, due to their excellent material properties of elasticity, resilience, and electrical and thermal insulation, have been used in myriad of applications including automotive bumpers, rubber seals, flexible electronics, energy absorbers, and many others. In addition, elastomers are also considered as ideal materials for fabricating soft robots and smart biomedical devices which require soft and deformable material properties to establish safe and smooth interactions with humans, externally and internally. The most widely used elastomers in these applications are silicon rubber, that is, Ecoflex (Smooth-On), SE 1700 (Dow Corning), and Sylgard (Dow Corning). However, the thermal curing process of these silicon rubbers constrains the fabrication of objects to only traditional ways, such as cutting, molding/casting, spin-coating, etc. In order to enrich the design and fabrication flexibility, researchers have developed a few direct ink writing (DIW) based methods to 3D print silicon rubbers by developing printing inks which are composed of two parts of a silicone elastomer, that is, base and cross-linker with an expensive platinum-based catalyst. However, after printing out the two parts, a few hours curing process is still needed at room temperature. In addition, the lateral resolution of the DIW technique is determined by the size of the printing nozzle which is at hundreds micrometer scale, and the requirement of support materials in the case of printing overhanging structures significantly constrains the structure complexity. In addition to the thermal curable silicon rubbers, there are a few commercially available UV curable elastomers that are suitable for UV curing related 3D printing techniques such as digital light processing (DLP), stereolithography (SLA), and Polyjet. These UV curable elastomers include Carbon EPU 40, Stratasys TangoPlus, Formlab Flexible, and Spot-A Elastic. However, compared to silicon rubbers, those UV curable elastomers still have very significant limitations. First, the highest elongation at break of these elastomers is about 170-220%, which is not sufficient for certain advanced applications. Second, as they are commercial product, users are not able to tune the mechanical properties, that is, the Young's modulus. In addition, in order to guarantee the printing resolution, light absorbing dyes are usually added to these commercial resins, which results in opaque printed objects and therefore are not applicable in applications requiring good light transmittance.