Micro-scale Realization of Compliant Mechanisms: Manufacturing Processes and Constituent Materials—A Review

Abstract

Compliant micromechanisms (CMMs) acquire mobility from the deflection of elastic members and have been proven to be robust by millions of silicon MEMS devices. However, the limited deflection of silicon impedes the realization of more sophisticated CMMs, which often require larger deflections. Recently, some novel manufacturing processes have emerged but are not well known by the community. In this paper, the realization of CMMs is reviewed, aiming to provide help to mechanical designers to quickly find the proper realization method for their CMM designs. To this end, the literature surveyed was classified and statistically analyzed, and representative processes were summarized individually to reflect the state of the art of CMM manufacturing. Furthermore, the features of each process were collected into tables to facilitate the reference of readers, and the guidelines for process selection were discussed. The review results indicate that, even though the silicon process remains dominant, great progress has been made in the development of polymer-related and composite-related processes, such as micromolding, SU-8 process, laser ablation, 3D printing, and the CNT frameworking. These processes result in constituent materials with a lower Young’s modulus and larger maximum allowable strain than silicon, and therefore allow larger deflection. The geometrical capabilities (e.g., aspect ratio) of the realization methods should also be considered, because different types of CMMs have different requirements. We conclude that the SU-8 process, 3D printing, and carbon nanotube frameworking will play more important roles in the future owing to their excellent comprehensive capabilities.

A miniaturized statically balanced compliant mechanism for on-chip ultralow wide-bandwidth vibrational energy harvesting

“…Bistable CMs present benefits in three different ways. Firstly, bistable CMs have good adaptability to MEMS techniques (Wilcox and Howell, 2005;Wang et al, 2021). Secondly, the switch between preloading and unloading on the negative-stiffness beams can be easily achieved by the reversible snapping-through behaviour of bistable CMs.…”

Design and Development of a Hair-like Sensor with Bridge-Type Flexible Amplification Mechanisms

“…It is also proved that the elastic modulus of the silicon beam specimen does not show a size effect. And the linear elastic theory is still applicable to the micro flexible mechanism presented based on silicon material in some works of literature [28,29]. The amplification ratio of the amplification mechanism is defined as the ratio of the output displacement to the input displacement.…”