Quasi-anisotropic wet etching of glass creates inclined microstructures for advanced optical and MEMS devices.

Glass is one of the most widely used functional materials in various fields, thus developing high-precision, on-demand and low-cost glass microstructuring technologies is essential for both academic and industry. Although numerous technological advancements in the past, it is still a challenge to fabricate microstructures with smooth inclined sidewalls on glass substrates, posing difficulties in fulfilling the advantages of glass material for many emerging applications, including optics and MEMS. In this paper, we establish a novel quasi-anisotropic wet etching strategy that expands the ability of glass micromachining and enables tunable inclined surface fabrication with high quality and low cost. By exploring the competitive effects of the etching induced by interface between glass and the mask layer, the quasi-anisotropic wet etching mechanism is systematically investigated. Through numerical simulations and experiments, the reproducibility and tunability are verified in fabrication of varied types of microstructures such as microprism, micro-pyramids and micro-cones. Furthermore, novel devices including diffusion plates, optical waveguide, VR/AR displays are designed and manufactured, with functions successfully demonstrated. The quasi-anisotropic wet etching strategy proposed in this paper not only offers a new path for precise and high-quality glass micromachining, but also enables significant application potentials in micro-optics, opto-MEMS and other related fields.