Design and Electro-Thermo-Mechanical Behavior Analysis of Au/Si3N4 Bimorph Microcantilevers for Static Mode Sensing

Abstract

This paper presents a design optimization method based on theoretical analysis and numerical calculations, using a commercial multi-physics solver (e.g., ANSYS and ESI CFD-ACE+), for a 3D continuous model, to analyze the bending characteristics of an electrically heated bimorph microcantilever. The results from the theoretical calculation and numerical analysis are compared with those measured using a CCD camera and magnification lenses for a chip level microcantilever array fabricated in this study. The bimorph microcantilevers are thermally actuated by joule heating generated by a 0.4 μm thin-film Au heater deposited on 0.6 μm Si3N4 microcantilevers. The initial deflections caused by residual stress resulting from the thermal bonding of two metallic layers with different coefficients of thermal expansion (CTEs) are additionally considered, to find the exact deflected position. The numerically calculated total deflections caused by electrical actuation show differences of 10%, on average, with experimental measurements in the operating current region (i.e., ~25 mA) to prevent deterioration by overheating. Bimorph microcantilevers are promising components for use in various MEMS (Micro-Electro-Mechanical System) sensing applications, and their deflection characteristics in static mode sensing are essential for detecting changes in thermal stress on the surface of microcantilevers.

Performance of molecular crystals in conversion of light to mechanical work

“…The bending crystal can be modeled as a cantilever with two layers, where the actuation relies on the mismatch between the photoinduced strain in the active layer (isomerized cis layer) and the inactivity of the second layer (nonisomerized trans layer). The maximum displacement can then be determined by using the Stoney equation ( 46 ) and can be expressed as: where κ is the curvature of the crystal, L is the length of the crystal, ε max is the maximum photoinduced surface strain, E is the Young’s modulus, t is the thickness, and the subscripts t and c denote the trans substrate and the cis isomerized layer, respectively. The effective Young’s modulus of an irradiated crystal, which is essential to understand the effect of the actuation on the flexibility of the crystal, can also be calculated while accounting for the isomerized layer and its mechanical properties ( 46 ): where t is the total thickness of the crystal.…”

Modelling and Analysis of Thermomechanical Behaviour in Composite Bimorph Actuator

“…The differences in strains of two limbs tend to create displacement. The transverse displacement of the bi-layer beam is achieved by varying temperature and thickness of the actuator [5]. Bimorphs of composite materials are also used to harness photo-thermo-mechanical actuation.…”