Micro-electro-mechanical systems (MEMS) by definition are coupled electrical and mechanical microsystems. Additionally, microfabrication tolerances, device geometry and thermal effects, for example, will further cloud the performance characteristics. Hence, the consolidation of these individual parameters into a single output based upon "forward-step" modeling will allow for a complete performance characterization in a manner where changes to the static and dynamic outputs are monitored in a step wise fashion through the addition of the individual parameters separately. This deterministic approach aims to synthesize the "parameter-matrix" under which the microsystem is constrained, both by device design and by the eventual operating conditions. The theoretical modeling of the synthesized parameters into an output determinant would be a valuable design tool especially when targeting specific performance characteristics at the design stage of the microsystem that are tied to both the device design and operating conditions. This paper presents a method for microsystem performance modeling based on the solution of a parameter-matrix into a deterministically synthesized output response. The mathematical modeling is based upon the Rayleigh-Ritz energy method using boundary characteristic orthogonal polynomials. The synthesized output models the static and dynamic response of the step-forward addition of individual microsystem parameters, which when they have been evaluated can be used to specify design criteria under a given set of operating conditions. This analysis method will not only allow the designers of microsystems to determine the influence of intrinsic and extrinsic limitations and conditions, but also to establish viable MEMS platforms based on predetermined output performance characteristics.
The static and dynamic characteristics of micro-electro-mechanical-systems (MEMS) can be influenced through the application of an electrostatic field or thermal gradient. Both of these mechanisms will affect the performance of the MEMS device significantly. The thermal effects manifest themselves by varying the structural characteristics, Young's modulus of elasticity of the waveguide structure, and the material properties. These types of influences will affect the mechanical integrity through an increase in the flexibility leading to variations in the static deflections and also to the dynamic frequency eigenvalues, and changes to the device geometry can lead to faulty measurements where capacitive sensing is employed. Hence, thermal variations in the operating environment can result in unwanted thermal noise and degradation of signal integrity.
Electrostatic fields or forces can be used to correct for thermal influences, for example, or as stand-alon microsystem performance tuners. The corrector characteristics can be achieved by the integration of a suspended electrode over the waveguide, for example where the induced electrostatic stiffness is aligned with the mechanical stiffness of the waveguide and are opposite in direction to the thermally induced "softening". The "stand-alone" characteristics of an applied electrostatic field can be used to selectively deflect the waveguide through an applied bias voltage and hence the static and dynamic performance can be trimmed or tuned by the application of an electrostatic field. This paper presents an experimental and theoretical investigation into coupled thermo-electrical influences on a microcantilever structure. These combined influences are typical of the operating characteristics and environments of microsystems currently in use.
Micro-electro-mechanical-systems (MEMS) offer many advantages for sensing a variety of physical parameters such as accceleration, pressure and temperature. Their small size allows them to operate in close proximity where conventional sensors cannot be introduced especially for thermal measurements. Temperature measurement and control is of fundamental importance to the optimal operating conditions of materials and machinery such as gas turbine engines, space exploration, etc. The temperature characterization will allow proper diagnosis of operating conditions and hence the optimization of controls and environment in order to augment performance and useful lifetime. MEMS based thermal measurements will be very useful as they are sensitive to small fluctuations in the operating conditions. Here, this paper proposes a novel MEMS based bimorph optical device as a thermal sensor. The paper includes the theoretical and experimental analysis on the thermal behavior of optical MEMS devices under different geometrical and parametric conditions. The paper also presents the static and dynamic behavior of optical MEMS based devices under different thermal environments. The results obtained verify the validity of the proposed designs for thermal sensing.
The control of environmental conditions, such as temperature, pressure, and humidity, are important in many applications ranging from bio-medical to space exploration. Proper humidity control is also important in the conservation of organic materials. Therefore an accurate and sensitive method to characterize the moisture content of the particular environment is of valuable importance.
This paper proposes a humidity sensitive polyimide material as a fiber optic sensor for humidity measurements. The spectral analysis and the intensity of transmitted light through the polyimide sensor will represent the humidity measure. The paper also presents the absorption characteristics of the proposed humidity sensitive material.
The experimental values on the spectral shift and light intensities are measured at different humidity conditions. This paper will also present the feasibility study for using the proposed fiber optic sensor for humidity measurements.
Modeling, manipulating and testing of the dynamic performances of micro-electro-mechanical systems (MEMS) devices are very important in building successful microsystems. However, MEMS devices pose several significant difficulties in characterization. The physical dimensions of MEMS devices are such that conventional measurement and characterization techniques cannot be used since the sensor would interfere with the measurement. Hence, non-contact sensing systems offer many advantages for MEMS characterization. One important issue in characterizing and troubleshooting MEMS devices is the differentiation between electrical and mechanical effects. By definition, MEMS devices are comprised of electrical and mechanical components forming integrated electro-mechanical systems. The dynamic response of these devices is often difficult to determine because of the coupled electro-mechanical behavior. It is also known that the dynamic response is influenced by the limitation of fabrication processes and the material conditions. Hence, this paper proposes a simpler method to verify the dynamic behavior of MEMS structures using Laser Doppler Velocimeter (LDV). Non-contact vibration measurements are thus possible with such a testing system that can lead to significant improvements in the accuracy and precision of MEMS testing. The dynamic experiments are conducted on different devices and the test results are compared with prediction.