Mechanical structural design of a MEMS-based piezoresistive accelerometer for head injuries monitoring: a computational analysis by increments of the sensor mass moment of inertia.

Messina, Marco; Njuguna, James; Palas, Chrysovalantis

Abstract

This work focuses on the proof-mass mechanical structural design improvement of a tri-axial piezoresistive accelerometer specifically designed for head injuries monitoring where medium-G impacts are common; for example, in sports such as racing cars or American Football. The device requires the highest sensitivity achievable with a single proof-mass approach, and a very low error ( < 1%) as the accuracy for these types of applications is paramount. The optimization method differs from previous work as it is based on the progressive increment of the sensor proof-mass mass moment of inertia (MMI) in all three axes. Three different designs are presented in this study, where at each step of design evolution, the MMI of the sensor proof-mass gradually increases in all axes. The work numerically demonstrates that an increment of MMI determines an increment of device sensitivity with a simultaneous reduction of cross-axis sensitivity in the particular axis under study. This is due to the linkage between the external applied stress and the distribution of mass (of the proof-mass), and therefore of its mass moment of inertia. Progressively concentrating the mass on the axes where the piezoresistors are located (i.e. x- and y-axis) by increasing the MMI in the x- and y-axis, will undoubtedly increase the longitudinal stresses applied in that areas for a given external acceleration, therefore increasing the piezoresistors fractional resistance change and eventually positively affecting the sensor sensitivity. The final device shows a sensitivity increase of about 80% in the z-axis and a reduction of cross-axis sensitivity of 18% respect to state-of-art sensors available in the literature from a previous work of the authors. Sensor design, modelling, and optimization are presented, concluding the work with results, discussion, and conclusion. The paper is an extension of Messina, M.; Njuguna, J.; Palas, C. Design and Optimization of a MEMS-Based Piezoresistive Accelerometer for Head Injuries Monitoring: A Computational Analysis. In Proceedings of the 5th International Symposium on Sensor Science (I3S 2017), Barcelona, Spain, 27-29 September 2017.

Citation

MESSINA, M., NJUGUNA, J. and PALAS, C. 2018. Mechanical structural design of a MEMS-based piezoresistive accelerometer for head injuries monitoring: a computational analysis by increments of the sensor mass moment of inertia. Sensors [online], 18(1), article number 289. Available from: https://doi.org/10.3390/s18010289

• Journal Article Type: Article
• Acceptance Date: Jan 18, 2018
• Online Publication Date: Jan 19, 2018
• Publication Date: Jan 31, 2018
• Deposit Date: Feb 1, 2018
• Publicly Available Date: Feb 1, 2018
• Journal: Sensors
• Print ISSN: 1424-3210
• Electronic ISSN: 1424-8220
• Publisher: MDPI
• Peer Reviewed: Peer Reviewed
• Volume: 18
• Issue: 1
• Article Number: 289
• DOI: https://doi.org/10.3390/s18010289
• Keywords: Piezo resistive accelerometer; Sensor design; Biomechanical device; Head injuries monitoring; TBI
• Public URL: http://hdl.handle.net/10059/2706
• Contract Date: Feb 1, 2018