By employing a transparent inert liquid as the constraining surface, this stereolithography 3D printing system can fabricate even large-scale and ultra-high-aspect features continuously without a need for scaffolding or support. Stereolithography uses photopolymerization to create solid objects. Exposing liquid resin to UV light in specific locations creates a solid object defined by the patterned UV light. In conventional stereolithography approaches, the polymerization of resin occurs at a solid interface (transparent window). The solid interface is needed in order to constrain the liquid resin into a predefined layer thickness. A major disadvantage of polymerization at a solid interface is the adhesion (stiction) of the solid object to the solid window interface. As a consequence, large peel forces must be applied to separate the solid object from the solid window interface. The peel force is proportional to area of the 3D object. These peel forces lead to poor process reliability, failed or defective objects, and a need for support or scaffolding structures to prevent the object from breaking during the fabrication process. In addition, because of the requirement for the peeling process, the object must be grown in discrete layers.
Researchers at the University of Florida have developed a stereolithography 3D printing system that enables polymerization at a liquid interface. This system employs a transparent inert liquid used as a constraining surface during the stereolithography process, in contrast to the solid interface used in conventional approaches. Due to the inherent deformability of the inert liquid, the peel forces of the photopolymerized object from the interface are negligible. In addition, polymerization at a liquid interface allows 3D objects to grow continuously (layer-less) as opposed to layer-by-layer (discrete layers) thus reducing total fabrication time. This system has the advantages of being able to fabricate objects with large-area and ultra-high-aspect features, and it also improves process reliability without a need for support or scaffolding. Fabrication of 3D objects both on the macro and micro scale benefits from photopolymerization at the liquid interface.
Continuous, UV-curing, 3D printer that produces large and ultra-high-aspect ratio layer-less objects
The transparent inert liquid forms a layer adjacent to the liquid resin interface. The inert liquid constrains the liquid resin between the previously polymerized layer. During UV polymerization, the inert liquid remains in its liquid state and prevents a finite thickness of resin directly at the inert liquid-resin interface from being polymerized. Thus, researchers can grow 3D objects continuously without stiction. Minimal stiction during separation from the liquid interface facilitates layer-by-layer printing of an object, resulting in a layer-by-layer growth of the 3D object.
