FEM analysis of Microcantilever MEMS for measuring rheological properties of blood

Abstract

Microcantilever devices are widely used in biomedical because of its high sensitivity, better performance, low fabrication cost, robustness, and improved reliability over other equipment. The dynamic response of the device, in different medium i.e. air, water, gas, depends on the vibrational mode. Vibrational modes decide how effectively the cantilever is going to respond while operating in a particular medium. In this paper, microcantilever having length 60µm, width 6µm, and thickness 1.5µm has been designed for measuring density and viscosity of blood plasma. A finite element analysis (FEA) is adopted to obtain the eigenfrequencies of the microcantilever device for different beam lengths in the ‘vacuum’ medium. The model for fluid-structure interaction has been presented and analyzed. Since the properties of blood and glycerol are analogous to each other, thus different concentrations of glycerol have been taken to deduce the rheological properties of the fluid. The analytical results are found in close agreement with the FEA results. A comparative analysis of transverse and lateral vibrational modes is put forward to understand the behavior of the device. Also, after simulating the model, it is observed that the cantilever can measure viscosities from 0.86-3.02 centipoise. FEM analysis of microcantilevers vibrating in the vacuum has been presented. Resonant frequencies in the vacuum of laterally and transversally vibrating microcantilever are calculated through an eigenfrequency analysis using Comsol multiphysics software thus avoiding simulation time. A high degree of accuracy of the results is obtained. It is proved experimentally the advantages of lateral vibrations over transverse vibrations. Also, the Simulink model is proposed for measuring the rheological properties of blood. The design is capable of measuring the blood plasma viscosities range. Our study shows that FEM analysis is a suitable tool for designing and simulation of bioMEMS.