Finite Element Analysis Simulations of Micro and Nano-Electromechanical Sensors for Design Optimization

Micro and Nano-electromechanical sensors (MEMS and NEMS) provide a means of actively sensing minute changes in the surrounding environment. Small changes in temperature, momentum, and strain may be sensed in passive modes while greater sensing possibilities exist in active modes. Theoretical femto-gram resolution mass detection and heated element sensing methods may be used while volatile organic compound (VOC) sensing may be achieved when combined with a functionalization layer or device heating. These devices offer a great reduction in cost and offer increased mobility by allowing a lab-on-chip solution for the prospective user while also greatly reducing the amount of energy consumed by current sensor designs and equipment set-ups. Work has been done in our lab on AlGaN/GaN MEMS cantilevers and InN NEMS nanowire sensors for use as NOx and VOC sensing applications. Research and development of optimal mechanical designs for these proposed sensors can be a very iterative, and therefore an expensive process. The devices must be grown (in the case of NEMS) etched, and characterized; a process taking several weeks or months and often involving the use of advanced facilities. Because of this great time and material cost methods are needed to reduce the number of iterations to optimal design and streamline the research and development process to achieve a faster time to end-product. Finite element analysis (FEA) simulations allow the researcher to test hundreds of proposed designs within weeks. Allowing a research and development team to reduce the number of proposed design configurations as well as propose and test the feasibility of new sensor designs for future works. Using full-featured simulation packages such as COMSOL Multiphysics allows a researcher to not only model the mechanical properties of the proposed MEMS/NEMS sensors, but also provides the ability to couple together other attributes of the complete device model such as environmental losses, joule heating effects, and polarization. This can be done either within the simulation software itself, or through coupling with external packages such as MATLAB. Here COMSOL simulations, as well as the simulation methodology, will be presented for the cases of the AlGaN/GaN resonant cantilever sensor as well as the InN nanowire based design. In the case of the AlGaN/GaN MEMS sensor some simulation results will be compared to experimental measurements to show the feasibility of this research step for micro-scale and nanoscale mechanical sensor design