Ultralow Shrinkage 3D Transparent Nanoporous Glass Printing through Low-Temperature Sintering for Micro-Optical Applications.

Current glass additive manufacturing relies on high-temperature processing to achieve optical transparency accompanied by significant structural shrinkage. These factors significantly restrict the micro-optical applications of three-dimensional (3D) glass microstructures in microsystems. Here, a low-temperature, low-shrinkage 3D printing strategy for transparent nanoporous glass microstructures is presented using a molecular cross-linker-free resin containing methacrylic acid-functionalized nanoparticles (MAA-NPs). The MAA-NPs serve dual roles as photopolymerizable units and silica precursors, enabling the creation of 3D microarchitectures with a 78 wt % solid loading through two-photon polymerization. In stark contrast to conventional particle-loaded composites, uniform nanoparticle dispersion eliminates wavelength-scale pores in the microstructure after sintering at 650 °C, achieving 97% visible-light transmittance. Most importantly, the combination of MAA cross-linking, which enables small interparticle spacing, and low-temperature sintering results in nanoporous glass 3D microarchitectures with low linear shrinkage (∼5%), thereby enabling high-fidelity fabrication of complex micro-optics. Crucially, our strategy enables direct in situ integration of glass microlenses on optical fibers at low temperatures, achieving high alignment precision without assembly steps. This strategy exhibits potential across multiple domains, including micro-optics, photonics, biomedical devices, and integrated optics.