A laser-powered polymerization process for 3D-printing applications overcomes the need to build a 3D-printed object one layer at a time. A research team from France’s Fresnel Institute and École Centrale de Marseille introduced the method, using it to create miniature models of a bicycle and even the Eiffel Tower from silica glass. The approach is specifically based on multiphoton polymerization, which ensures that the polymerization process, which binds liquid monomer molecules into a polymer solid, occurs only at a precise laser focal point. From the method, users can directly fabricate 3D parts that range in size from several microns to tens of centimeters. The process also delivers a resolution that is theoretically limited only by optics used to shape the laser beam. Though multiphoton polymerization can bypass the need to build an object layer by layer, 3D-printing glass objects necessitates using a material that is transparent at the wavelength of the laser and remains such even after the completion of the polymerization process. The material must also absorb the laser light at one-half the wavelength of the laser to initiate the process. Researchers have developed a new laser-based process for 3D-printing intricate parts made of glass. It uses multiphoton polymerization to create an object directly in a 3D volume. Courtesy of Laurent Gallais, the Fresnel Institute and École Centrale de Marseille via OSA. In the new approach, the researchers mixed a photochemical initiator — to absorb the laser light — with a resin and high concentration of silica nanoparticles. The mixture’s high viscosity allowed the scientists to form a 3D part without any built-in deformations or supports to keep the focus object in place throughout the printing process. High-power ultrashort lasers — the researchers cited the chirped pulse amplification technology introduced by Donna Strickland Gerard Mourou that earned the duo the 2018 Nobel Prize in physics — further enabled the technique. “Only intense and very short pulses will create nonlinear photo polymerization with high precision and no thermal effects,” said Laurent Gallais, leader of the research team that introduced the method. The traditional layering process used to build 3D glass is limited, traditionally, due to the time it takes to construct individual layers. It can also be difficult to keep layers at a consistent thickness when using highly viscous resins in the process. Complex parts can also require added supports that must be precisely positioned and removed. The new approach can be used to make a variety of complex objects such as a bicycle and Eiffel Tower model. Courtesy of Laurent Gallais, the Fresnel Institute and École Centrale de Marseille via OSA. “Our approach could potentially be used to produce almost any type of 3D glass object,” Gallais said. The team is exploring the possibility of producing glass parts for watches or fragrance bottles, while also aiming to increase the practicality of the technique by reducing cost, testing with less expensive laser sources, and decreasing physical roughness. The research team additionally consists of Thomas Doualle and Jean-Claude Andre. The research was published in Optics Letters (www.doi.org/10.1364/OL.414848).