MEMS technology combines micromachining and integrated circuit fabrication technologies to produce highly reliable
MEMS transducers. This paper presents an overview of MEMS transducers applications, particularly in automotive and
aerospace industries, which includes inertia sensors for safety, navigation, and guidance control, thermal anemometer for
temperature and heat-flux sensors in engine applications, MEMS atomizers for fuel injection, and micromachined
actuators for flow control applications. Design examples for the devices in above mentioned applications are also
presented and test results are given.
This paper describes a systematic shape tuning procedure of adaptive structures for MEMS actuator applications. Due to fabrication process variations, MEMS devices can have different shapes with varied deflections. Such shape variations should be corrected for specific applications. As a result, it is necessary to establish a shape tuning procedure. Finite element modeling and optimization approach were used to minimize the shape variations. The procedure integrated Python programming, ABAQUS, and optimization algorithm for engineering applications. It used the powerful Python scripts programming, the vast library of ABAQUS functions, and a robust preexisting optimization algorithm, NLPQL, which provides more efficient, flexible, and systematic tools for optimization problems. Optimization was used in the adaptive structural designs and the shape tuning procedure after the assembly. Using this approach, three bimorph, gold-on-polysilicon, samples with different initial shapes were studied for shape tuning. The shape was characterized by maximum tip deflection resulting from thermo-mechanical deformations. The standard deviation of the shape variations was reduced from 1.21 to 0.05 μm after tuning. This reduction was verified by experimental data. Another case with ten devices was studied to confirm the effectiveness of the procedure. The standard deviation of the deflections was reduced from 0.81 to 0.02 μm after tuning. These results demonstrated the effectiveness of the optimum procedure for shape tuning. This general-purpose systematic methodology can be applied to adaptive structures for a variety of aerospace applications.
Comb-finger structure has been widely used in MEMS device as actuator and capacitive sensing unit. We can quite often find that the capacitance of and electrostatic force between a pair of the fingers are calculated by parallel plate model. This is certainly the simplest and the easiest solution, but with very low accuracy. The analytic method with reasonable accuracy is generally necessary for design engineers because it can give a quick estimation of the design and correct insight into the performance of the design. In this paper, the long comb-finger structure is analyzed. The multi-body-system, e.g., comb-finger above the ground, has been simplified. The fringe field effect is taken into account. Applying semi-empirical equations, we have developed analytic models for calculating capacitance and electrostatic force for various comb-finger structures. The results from the analytic models are compared with simulation results from commercial simulation software.
We describe the design of novel fuel atomizers with a unique internal spiral-conical structure for turbine engines and other propulsion systems. The atomizers are developed using a unique combination of two recently developed technologies: polymer-derived ceramics and an invert microstereolithography process. The polymer-derived ceramics are stable up to high temperatures (1500~1800ºC) and have excellent mechanical and thermal properties. Thus, fuel atomizers made from these materials can be used at high temperatures and have higher corrosion resistance. Invert microstereolithography is a recently developed 3-D microfabrication process that enables complex 3-D structures to be built with high dimensional precision (1µm). The resulting atomizers have many advantages, including stability at high temperatures, high resistance to corrosion, a unique structure for efficient sprays, low cost and amenability to batch manufacturing. With the success of our earlier investigation and recent development, we are able to develop novel atomizers that will fill an immediate need for propulsion systems and many other high-temperature applications. In the future, we will integrate the atomizers into combustion systems and perform physical demonstration of the complete fuel injection system on a representative engine platform for a range of operating conditions.
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