1/27/2015 Authors: Matteo Verotti; Rocco Crescenzi; Marco Balucani; Nicola P. Belfiore
J. Mech. Des.. 137(1), 012301 (2015); doi:10.1115/1.4028791

Compliant mechanisms may change their configuration thanks to their flexible parts, generally called flexures. They present some significant advantages with respect to rigid body mechanisms: no backlash and friction, no need for lubrication and maintenance reduction, and, mainly, the possibility of being crafted by means of planar construction technology, as a unique block of material. For this reason, MEMS can be developed by using the same principles adopted for the design of compliant mechanisms.

However, flexures are characterized by some disadvantages, such as limited capability in terms of motion and force transmission, deformations highly dependent on the applied loads, limited resistance to yielding, variable position of the center of relative rotation.

In this paper, a new flexure hinge is introduced, with the aim of overcoming some of such limitations. The Conjugate Surfaces Flexure Hinge (CSFH) combines a curved beam, as flexible element, and a pair of conjugate surfaces, whose contact depends upon the load conditions. The contact between the conjugate surfaces can reduce the stress in the curved beam and limit the variations of the position of the relative rotations center.

This paper discloses how to simulate (both theoretically and with finite element analysis), construct (by means of a single step lithography and Reactive–Ion Etching, RIE), process and test (by means of in-SEM observation and manipulation) a new concept silicon CSFH prototype. 

Conjugate Surfaces Flexure Hinge for MEMS applications (geometric layout (a) and test of the silicon prototype (b)) and for macro scale applications (geometric layout (c) and PVC prototype in neutral and deformed configurations (d)).