Microengineering glass substrates: techniques and applications

The rapid advancement of Micro-Electro-Mechanical Systems (MEMS) and microfluidic technologies has established glass as an indispensable substrate material, effectively overcoming the limitations of traditional silicon in applications requiring high optical transparency, chemical inertness, and superior electrical insulation. However, the amorphous network structure and inherent brittleness of glass pose significant barriers to the high-precision fabrication of deep microstructures. This review provides a systematic and rigorous overview of contemporary subtractive microengineering techniques. Fabrication methods are systematically categorized into five primary groups: mechanical (micro-grinding, sandblasting, and ultrasonic machining), thermal (reflow, microwave, and laser ablation), chemical/electrochemical (wet etching and electrochemical discharge machining), plasma-based (Reactive Ion Etching), and hybrid strategies such as Laser and Ultrasonic Assisted Electrochemical Discharge Machining. We analyze the critical relationships between material properties and removal mechanisms, emphasizing the brittle-to-ductile transition in mechanical machining and the pivotal role of gas film stabilization in discharge-based processes. Through representative demonstrations of chip-level hermetic packaging, through-glass via (TGV) arrays, and high-resolution bio-analytical platforms, this paper highlights the transformative role of microengineered glass in enhancing device performance and reliability. Finally, the core challenges regarding precision-throughput-cost trade-offs and emerging trends are discussed to provide a foundational roadmap for next-generation glass-based microsystems. This review offers a comprehensive framework for navigating the selection and innovation of glass materials and fabrication strategies, ensuring application-oriented precision and throughput for advanced MEMS and microfluidic platforms.