4D Printing of Silica Glass Microstructures Based on Capillary-Force-Assisted Assembly

Four-dimensional (4D) printing enables simple structures to undergo programmed and controlled morphological reconfiguration for fabricating more complex three-dimensional (3D) architectures, which has recently garnered considerable research interest. However, 4D printing of glass, particularly for glass microstructures, faces fundamental challenges due to the limited deformability of glass and the lack of reliable deformation mechanisms. Here, a capillary-force-assisted assembly approach is presented to realize the 4D printing of glass microstructures with programmable morphing capabilities. The precursor microstructures fabricated by two-photon polymerization are reconfigured into complex 3D microassemblies under postprinting capillary force, ultimately yielding transparent glass microstructures upon thermal sintering. Compared with conventional 3D printing approaches, our 4D printing approach enables the fabrication of geometrically sophisticated glass microstructures, particularly development-resistant geometries such as hollow microarchitectures, which are previously unattainable through additive manufacturing techniques. Furthermore, the fabricated glass-based chiroptical metamaterials demonstrate giant chiroptical responses and enhanced environmental stability when compared to conventional polymeric counterparts. Fully enclosed hollow microarchitectures successfully encapsulate a diversity of inorganic particles. This work provides a scalable platform for advanced glass microfabrication and allows for the 4D printing of functional inorganic devices.