Advanced Flexure Design for Large-Stroke MEMS Comb-Drive Actuation

This paper introduces an advanced MEMS straight-guiding flexure system actuated by an electrostatic comb-drive mechanism, designed to achieve large, stable displacements. The proposed flexural suspension combines two types of beam structures including nested folded-beam flexures (NFF) and tilted folded-beam flexures (TFF), a unique configuration that enables large travel ranges at low actuation voltages. One of the key advantages of this design is its ability to significantly increase the bearing-direction stiffness while maintaining a low stroke-direction stiffness. This balance is critical for improving lateral stability and reducing the risk of side pull-in instability. In contrast to previous flexure designs aiming for displacements beyond 200 μm which often suffered from increased stroke stiffness, higher actuation voltage requirements, and early onset of pull-in instability, the proposed architecture effectively overcomes these drawbacks. The device has been successfully fabricated, and experimental results show strong agreement with both theoretical predictions and finite element method (FEM) simulations, confirming the practicality of the design for MEMS applications where large displacements are desirable and performance improves with increased stroke.