Compact models for micromechanical squeezed-film dampers with gap sizes comparable to the surface dimensions are presented. Two different models considering both the border flow and non-uniform pressure distribution effects are first derived for small squeeze numbers. In the first 'surface extension' model the border effects are considered simply by calculating the damping with extended surface dimensions, and in the second 'border flow channel' model an additional short fictitious flow channel is placed at the damper borders. Utilizing a large amount of two-dimensional (2D) FEM simulation results by varying the damper dimensions, mainly the ratio a/ h between the surface length and the air gap height, surface elongations are extracted using both elongation models. Both linear and torsional modes of motion are considered at the continuum flow regime. These results show that the 'surface extension' model is superior, since the extracted elongation a is almost constant ( a = 1.3h), leading to a very simple model. Next, the rare gas effects are included in the 'surface extension' model in the slip flow regime (Knudsen number 0 < Kn < 0.13). Considering slip boundary conditions, 2D FEM simulations are repeated and the elongations, now functions of the Knudsen number, are extracted from the results. A simple fitted equation for calculating the surface extension a finally results. The maximum relative errors of the models are smaller than 10% for a/ h > 4 in the linear motion and for a/ h > 10 in the torsional motion. The model assumes incompressible flow and thus the maximum frequency where the models are valid is limited. In typical MEMS topologies where the elongations must be considered, this means that the models are valid below frequencies of 500 kHz. To also model rectangular 2D squeezed-film dampers, these elongations are applied directly in the surface length and width used in the compact models. Comparison with three-dimensional (3D) FEM simulations shows that the new model gives excellent results, and it extends the validity range of existing compact models. The maximum relative error of the models is smaller than 10% for a/ h > 16 in the linear motion and for a/ h > 16 in the torsional motion. The new surface extension model is useful in simulating both the circuit level and the system level behavior of gas-damped microelectromechanical devices with aspect ratios greater than 2 in the time and frequency domains.

This work presents experimental [infrared (IR) thermography] and computational (finite element model) results of temperature distributions of an electrokinetic separation chip. Thermal characteristics of both the electrolyte solution and the polymer chip (SU-8) are taken into account in modeling temperature distributions during electrokinetic flow. Multiphysics and multiscale simulation couples electrostatics, heat transfer, and fluid dynamics. The accompanying IR thermography is a non-contact method, which can measure fractional temperature differences with sub-second time resolution. Any structures or temperature marker molecules interfering with the experiment are not needed. Nominal spot size in the IR measurements is 30 lm with a field of view of several millimeters enabling both local and chip-scale temperature monitoring simultaneously. As a result, we present a computer model for electrokinetic chips, which enables simulation of fractional temperature changes during electrophoresis under real operating conditions. The accuracy of the model is within ±1°C when the deviation in electrochemical processes is taken into account. The simulation results also suggest that the temperature on the chip surface qualitatively reflects the temperature inside the microchannel with an average offset of 1-2°C.

Actuation or sensing in microdevices is often achieved through electro-mechanical coupling. In practice though, the electro-mechanical system is complicated by the effects influenced by the gas surrounding the system. The gas damping may be of the same order of magnitude as the electric and mechanical forces, and thus it needs to be accounted for in the design of the devices. Notably in microsensor design, controlling the amount of damping is crucial in achieving the desired measurement accuracy and sensitivity. A certain amount of damping is required to filter out high frequency oscillations, but too heavy damping reduces the sensitivity of the device. In this paper we present a modelling method based on the finite element method to simulate the behaviour of a planar gas-damped microdevice under electrostatic loading. The transient model takes into account the true nonlinear behaviour of the damping and includes effects from non-uniform gap height. The computational cost of the simulations has been significantly reduced by various reduced-order and reduced-dimensional methods utilized in the model development. The method is used to simulate an accelerometer prototype under voltage ramp loading, up to the pull-in. The results of the simulation are compared to capacitance measurements of the real device. The method is also suitable for other types of planar microdevices, such as pressure sensors, micromirrors or microswitches.

E-Infrastructures play an increasingly important part in the provision of digital services to environmental researchers and other users. The availability of reliable networks, storage facilities, high performance and high throughput computers and associated middleware and services to ease their utilisation all contribute to enabling research and its exploitation. Their relevance, possible use and utilisation to date are described.

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