Electromechanical analysis of a piezoresistive pressure microsensor for low–pressure biomedical applications
A.L. Herrera–Maya , d, B.S. Soto–Cruzb, F. López–Huertac, and L.A. Aguilera Cortésd
ª Centro de Investigación en Micro y Nanotecnología, Universidad Veracruzana, Boca del Río, Ver, México.
b Centro de Investigación en Dispositivos Semiconductores, Benemérita Universidad Autónoma de Puebla, Puebla, Pue., México.
c Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla, Puebla, Pue., México.
d Departamento Ingeniería Mecánica, Campus Irapuato–Salamanca, Universidad de Guanajuato, Salamanca, Gto. México.
]]> Recibido el 9 de junio de 2008
Aceptado el 12 de enero de 2009
Abstract
The electromechanical analysis of a piezoresistive pressure microsensor with a square–shaped diaphragm for low–pressure biomedical applications is presented. This analysis is developed through a novel polynomial model and a finite element method (FEM) model. A microsensor with a diaphragm 1000 µm length and with three different thicknesses (10, 15, and 20 µm) is studied. The electric response of this microsensor is obtained with a Wheatstone bridge of four p–type piezoresistors located on the diaphragm surface. The diaphragm that is 10 µm thick exhibits a maximum deflection of 3.74 µm using the polynomial model, which has a relative difference of 5.14 and 0.92% with respect to the Timoshenko model and the FEM model, respectively. The maximum sensitivity and normal stress calculated using the polynomial model are 1.64 mV/V/kPa and 102.1 MPa, respectively. The results of the polynomial model agree well with the Timoshenko model and FEM model for small deflections. In addition, the polynomial model can be easily used to predict the deflection, normal stress, electric response and sensitivity of a piezoresistive pressure microsensor with a square–shaped diaphragm under small deflections.
Keywords: Finite element model; piezoresistors; polynomial model; pressure microsensor.
Resumen
El analisis electromecánico de un microsensor de presión piezoresistivo con un diafragma de sección cuadrada para aplicaciones biomédicas de baja presión es presentado. Este análisis es desarrollado mediante un nuevo modelo polinomial y un modelo con el método elemento finito (FEM). Un microsensor con un diafragma de 1000 µm de longitud y tres diferentes espesores (10, 15 y 20 µm) es estudiado. La respuesta electrica de éste microsensor es obtenida mediante un puente de Wheatstone con cuatro piezoresistores tipo p localizados sobre la superficie del diafragma. El diafragma con 10 µm de espesor presenta una deflexion máxima de 3.74 µm utilizando el modelo polinomial, el cual tiene una diferencia relativa de 5.14 and 0.92% con respecto al modelo de Timoshenko y al modelo FEM, respectivamente. La máxima sensibilidad y esfuerzo normal calculado con el modelo polinomial son 1.64 mV/V/kPa and 102.1 MPa, respectivamente. Los resultados del modelo polinomial concuerdan bien con el modelo de Timoshenko y el modelo FEM para pequeñas deflexiones. Además, el modelo polinomial puede ser utilizado fácilmente para predecir la deflexión, esfuerzo normal, respuesta eléctrica y sensibilidad de un microsensor de presión piezoresistivo con un diafragma de sección cuadrada sujeto a pequeñas deflexiones.
]]> Descriptores: Modelo de elemento finito; piezoresistores; modelo polinomial; microsensor de presión.
PACS: 07.10.Cm;07.07.Df;47.11.Fg
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Acknowledgements
This work was supported by the University of Guanajuato (UG DINPO project 099/2008) and CONACYT through project 84605. We would also like to thank Prof. Jerry Hemmye of Western Michigan University for useful discussions and suggestions.
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