Lithography-Free Stress-Engineering of MEMS Structures Using Two-Photon Polymerization Masking

We present a lithography-free shadow masking technique for post-release metallization of Micro-Electromechanical System (MEMS) devices using Two-Photon Polymerization (2PP). High-resolution polymer masks are 3D printed and manually aligned to released MEMS structures with the aid of on-chip alignment features co-fabricated during the initial MEMS process. This approach enables precise, localized metal deposition without additional photolithography or wet processing steps. As a demonstration, 2PP-fabricated masks are used to selectively deposit chromium films onto electrostatic cantilevers, inducing controlled deflections through localized stress engineering. Custom-designed mask legs ensure a consistent standoff height and aid in lateral positioning. The resulting alignment accuracy is within$4~{\mathrm {\mu \text {m} }}$in both lateral dimensions, enabling reproducible and spatially targeted mechanical tuning of MEMS structures. This hybrid strategy offers a low-cost, flexible solution for post-release functionalization and stress modification in MEMS.[2025-0153]