Fabrication and analysis of awl-shaped serpentine microsprings for large out-of-plane displacement

Abstract

This work investigates a novel awl-shaped serpentine microspring for a suspension structure, with a lower spring constant under the same unit layout area in out-of-plane motion. Using Castigliano's theorem, the spring constant of the microspring was theoretically derived and simulations were performed using COMSOL Multiphysics to verify the theoretical results. The proposed awl-shaped serpentine microspring was successfully fabricated using siliconbased micromachining. Experiments were conducted to compare the theoretical and numerical results, which were in close agreement. In addition, a parameter of spring constant to layout area ratio (K/A) is defined to be used as the index for comparing spring constants under the same unit area. Accordingly, the awl-shaped serpentine microspring has a lower K/A value than the traditional serpentine microspring with the same total effective length and folds. With a greater taper angle, more folds, a smaller beam width, and lower beam thickness, the awl-shaped serpentine microspring has a smaller K/A value. Using the proposed mathematical model, the spring constants of microsprings of various sizes and geometric structures can be calculated in out-of-plane motion before the microstructure is fabricated. Thus, it saves time when designing a microspring with a proper spring constant.

A Whisker-inspired Fin Sensor for Multi-directional Airflow Sensing

“…This type of arrangement is a well-defined mechanical suspension system. By applying Castigliano's theorem to each beam element in the springs [15], the displacement of the center square plate in the spring system can be related to the total force and torque applied to the springs. Considering the mechanism of airflow sensing of the fin sensor, vertical translation of the center square plate becomes negligible compared to rotation, since the load from vertical direction is very low.…”

Archive of Mechanical Engineering

“…The mechanical spring is a key element in various micro-electro-mechanical systems (MEMS) devices such as micro-actuators, inertial switches, accelerometers, and so on [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. In these devices, mechanical springs are designed for single or multi-axis motion.…”

“…In these devices, mechanical springs are designed for single or multi-axis motion. Up to date, there are many types of springs introduced for applications in controlling in-plane motions [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The springs can be designed for compliance to the linear movements in 𝑥 and 𝑦 axes [1-4, 7, 9, 12].…”

Geometric Effect on the Nonlinear Force-Displacement Relationship of Awl-Shaped Serpentine Microsprings for In-Plane Deformation

“…Sharma and Gupta [32] designed a nonuniform serpentine spring for radio frequency MEMS switches; this design reduced actuating voltage. Chou, Lin, and Chen designed and analyzed the mechanical properties of awl-shaped serpentine microsprings (ASSMs) for in-plane and out-of-plane motion [33,34]. They found that under the same total effective lengths and folds, for the out-of-plane motion, the ASSMs had a smaller spring constant to layout area ratio than the traditional serpentine microsprings.…”