Nonlinear thermomechanical design of microfabricated thin plate devices in the post-buckling regime

Abstract

A design approach for thermomechanically stable sub-micron plates is developed utilizing the post-buckling regime via a nonlinear plate analysis. Based on the analysis results and experimental observations, local stresses are observed to have maxima in the near-post-bifurcation regime, but then to decrease significantly in the post-buckling regime. This effect is more significant with plates of larger sidelength and smaller thickness structures, enabling microfabrication of numerous plate and membrane structures that are typically considered susceptible to failure due to buckling. Using a stress-based failure criterion, rather than the typical buckling criterion, an expanded design space for thin plates beyond the traditional pre-buckling regime is revealed. A device class that benefits in both power and efficiency from thin, large-area freestanding plates is microfabricated fuel cells, particularly high-temperature solid oxide fuel cells (µSOFCs). As a demonstration of the expanded design space, µSOFCs of submicron (450 nm) layer thickness are designed, fabricated and operated in the far postbuckled regime, verifying thermomechanical stability (up to 625 °C) and functional operation. The design approach introduced here can be applied to a range of microfabricated devices such as purification membranes, electrolysis cells and biochemical sensors.