Through-mask electrochemical micromachining (TMEMM) is a key technique for fabricating metal microstructures. However, manipulating the electric field to achieve various machining profiles remains a persistent challenge. To address this limitation, this paper introduces a sacrificial electrode into induction electrode TMEMM (IETMEMM) for the first time and proposes a novel method called sacrificial electrode-assisted IETMEMM (SE-IETMEMM). The sacrificial electrode is placed on the photoresist and is electrically connected to the workpiece through the regulating resistor. By adjusting the resistance, the potential of the sacrificial electrode is altered, enabling precise manipulation of the electric field distribution on the machined surface. Specifically, as the resistance increases, the electric field distribution evolves from center concentration to a uniform distribution and subsequently to edge concentration. This evolution is experimentally verified using the machining profiles of gear patterns. At a resistance of 0 Ω, the fabricated specimen exhibits a shallow edge and a deep center, indicating high localization with an etching factor ( EF ) of 10.3. At a resistance of 0.1 Ω, the profile becomes uniformly flat, with a non-uniformity ( Nu ) of only 12.2%. At a resistance of 1 Ω, the fabricated specimen exhibits an island-like profile. Compared with traditional TMEMM, SE-IETMEMM enhances localization by 836.4% at 0 Ω and improves uniformity by 78.1% at 0.1 Ω.

To improve the threshold accuracy of inertial switches, this study proposes a monolithic metal MEMS inertial switch with nonlinear springs. The switch uses two sets of inclined beams with asymmetric initial angles as suspension springs. Geometric nonlinearity produces low displacement sensitivity away from the design threshold and high sensitivity near the threshold. This response improves threshold discrimination and reduces the deviation between the actual and design thresholds. A nonlinear switch and a linear reference switch are designed with the same static threshold of 27.5 g. Their responses are compared using Abaqus static and explicit dynamic simulations. Both switches are monolithically fabricated from 50 μm thick 304 stainless steel by induction-electrode through-mask electrochemical micromachining (IETMEMM). Key dimensional deviations are below 2.5%. Drop-weight tests show measured nonlinear-switch thresholds of 27.8, 27.8, 26.9, and 25.4 g under half-sine shocks with pulse widths of 4, 6, 8, and 10 ms, respectively. The maximum threshold deviation is 2.1 g. The overall threshold accuracy is 92.4%, substantially higher than the 56.0% of the linear reference switch. This work combines a nonlinear threshold-regulation mechanism with monolithic IETMEMM fabrication and provides a new strategy for metal MEMS inertial switches with high threshold accuracy.