Design criteria for bi-stable behavior in a buckled multi-layered MEMS bridge

Abstract

In this paper, the bi-stability of a buckled multi-layered micro-bridge with elastically constrained boundary conditions is studied theoretically and experimentally. The residual moment due to non-symmetric distribution of residual stress in the layers of the micro-bridge is taken into consideration. The buckled shape model, which characterizes the initial buckled deflection, is employed in this study. A systematic method of designing bi-stable buckled micro-bridges has been developed and applied to multi-layered structures. The method is tested against ANSYS simulation and shown to be in excellent agreement. Two multi-layer micro-bridges have been fabricated: (i) 2.5 µm thick low stress SiO2/1 µm thick high compressive stress SiO2/2 µm thick SCS Si; (ii) 1 µm thick high compressive stress SiO2/2 µm thick SCS Si. The fabricated bridges are tested for bi-stability by thermal actuation and the results agree well with the analysis. The intrinsic bi-stable nature of a buckled micro-bridge can only be guaranteed as long as the residual moment is within a certain threshold value.

Bistability of curved microbeams actuated by fringing electrostatic fields

“…whereP ,α are given in (13) and b 11 , s 11 are specified in (8). In the case when the exact fundamental buckling mode of the beam is used as a base function, i.e., when ϕ 1 = [1 − cos(2πx)]/2, we obtain…”

“…Bistable microstructures continue to attract attention of researchers working in the area of micro-and nano-electromechanical systems (MEMS/NEMS) design and analysis [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The reason for this interest is in functional advantages of this kind of devices in applications.…”

“…This is perhaps since these structures represent the simplest architectures employed in demonstrating a wide spectrum of complex phenomena typically exhibited in bistable devices. In addition to a small footprint of this device and a possibility of dimensional downscaling to the nanoscale regime, these devices provide attractive platforms in applications spanning non-volatile memory [17][18][19][20], switches [8] and sensors [21,22], wherein the use of other designs is precluded.…”

Determining pull-in curves with electromechanical FEM models

“…This type of behavior is not uncommon in MEMS due to the high levels of residual stress that can occur in Microsystems [19,20]. A very simple structure that will have this type of behavior is shown in figure 12.…”

Theoretical and Experimental Investigation of the Nonlinear Behavior of an Electrostatically Actuated In-Plane MEMS Arch

“…Consequently, the bistability of arches has been thoroughly studied in order to exploit them in useful applications [1][2][3][4][5][6][7][8][9][10]. For example, micro arches are used as microbridges [7], microvalves [11], microelectro switches or relays [12], logic memories [13], micromuscles [14], and micro-optical switches [15]. Micro arches were excited using various transduction methods including magnetic [6], electrostatic [10], and thermal methods [12].…”