טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentSalinas Gal
SubjectA Novel Bi-Stable Mechanism for MEMS Applications
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Josef Givli
Full Thesis textFull thesis text - English Version


Abstract

A bi-stable mechanism is a structure which has two stable equilibrium configurations that are separated by an unstable equilibrium configuration. Bi-stable mechanisms are very useful in MEMS applications, such as relays, valves, clips, threshold switches and memory cells. One advantage of such mechanisms is that they can apply a contact force without the need for continued actuation power.


If a bi-stable structure is actuated under force-control conditions (soft device), it “snaps” to its secondary stable position, when the force reaches a critical level. If designed correctly, this position is maintained even after the external force is removed. Thus, in order to return the mechanism to its original (stress-free) configuration one needs to apply a negative (restoring) force. This work aims at developing a bi-stale beam for which the restoring force is higher than the snap (forward) force. This unique feature has several advantages with respect to MEMS applications. To achieve this goal the post-buckling response of curved beams with various geometries is studied using non-linear finite element analysis (FEA). The FEA was verified by comparing to analytical solutions for curved beams with cosine-like shapes. Based on the FEA, a family of beam geometries for which the restoring force is significantly higher than the snapping force has been found.


In order to validate the theoretical analysis, we performed experiments with models manufactured by rapid prototyping technique. In this work the novel design developed for this research will be presented, as well as the finite element analysis, analytical solutions for specific beam geometries, experimental observations and the implications of the experimental results.