The goal of this research is to integrate electrothermal and electrostatic actuation in microelectromechanical systems (MEMS). We look at cases where these two types of actuation are intimately coupled and argue that such integrated electrothermomechanical microactuators have more advantages than pure electrothermal or electrostatic devices. We further propose a framework to model hybrid electrothermomechanical actuation to get a consistent solution for the coupled mechanical, thermal and electrical fields in the steady-state.Employing a Lagrangian approach, the inhomogeneous current conduction equation is used to describe the electric potential, while the thermal and displacement fields are obtained by solving the nonlinear heat conduction equation and by performing a large deformation mechanical analysis, respectively. To preserve numerical accuracy and reduce computational time, we also incorporate a boundary integral formulation to describe the electric potential in the medium surrounding the actuator. We show through the example of a hybrid double-beam actuator, that electrothermomechanical actuation results in low voltage, low power operation that could be used for switching applications in MEMS. We also extend the same device towards bidirectional actuation and demonstrate how it may be used to overcome common problems like stiction that occur in MEMS switches.ii
This paper presents a data-driven method of estimating stochastic models that describe spatial uncertainties. Relating these uncertainties to the spatial statistics literature, we describe a general framework that can handle heterogeneous random processes by providing a parameterization for the nonstationary covariance function in terms of a transformation function and then estimating the unknown hyperparameters from data using Bayesian inference. The transformation function is specified as a displacement that transforms the coordinate space to a deformed configuration in which the covariance between points can be represented by a stationary model. This approach is then used to model spatial uncertainties in microelectromechanical actuators, where the ground plate is assumed to have a spatially varying profile. We estimate the stochastic model corresponding to the random surface using synthetic profilometric data that simulate multiple experimental measurements of ground plate surface roughness. We then demonstrate the effect of the uncertainty on the displacement of the actuator as well as on other parameters, such as the pull-in voltage. We show that the nonstationarity is essential when performing uncertainty quantification in electrostatic microactuators.
SummaryExtensive substitution of Ni for Zn in hydrozincite from the Parc Mine, North Wales, has been observed. This is the first time that a substantial concentration of another transition metal in this mineral has been reported. The average composition of the nickeloan hydrozincite is Zn4.63Ni0.37(CO3)2(OH)6. The relationship of this new variety to other secondary carbonate-containing nickel minerals is discussed, as is the possibility of substitution of other transition metal ions into the hydrozincite lattice.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.