Simple and versatile micro-cantilever sensors

• Published in: Sensor review 2009-01, Vol.29 (1), p.44-53
• Main Authors: Rinaldi, Gino, Packirisamy, Muthukumaran, Stiharu, Ion, Mrad, Nezih
• Format: Article
• Language: English
• Subjects: Boundary conditions; Eigenvalues; Electrons; Energy; Influence; Materials science; Mathematical models; Mechanical properties; Polynomials; R&D; Research & development; Sensors; Silicon; Statistical analysis; Stress state; Studies
• ISSN: 0260-2288; 1758-6828
• DOI: 10.1108/02602280910926841

Purpose - The purpose of this paper is to demonstrate the simplicity and versatility of micro-cantilever based sensors and to present the influence of added mass and stress on the frequency response of the sensor in order to determine the most suitable sensing domain for a given application.Design methodology approach - The frequency response of micro-cantilevers depends not only on the applied mass and surface stress, but also on the mass position. An interpretation of the theoretical frequency results of the 1st and 2nd natural frequencies, for added mass, identifies a nodal point for the 2nd natural frequency which demonstrates mass invariance. Hence, at this nodal point, the frequency response remains constant regardless of mass and may be used for identifying purely induced surface stress influences on the micro-cantilever's dynamic response. The Rayleigh-Ritz energy method is used for the theoretical analysis. Theoretical results are compared with experimental results.Findings - A graph of the 2nd natural frequency of micro-cantilevers with added mass demonstrates the variability of the frequency with mass position on the micro-cantilever. Of particular interest is the nodal point at which mass independence is revealed. This nodal point may be exploited to investigate purely stress-related influences on the dynamic characteristics of micro-cantilever sensors, thereby eliminating such effects as reactant evaporation from the micro-cantilever sensor surface. In this regard, the nodal point of the 2nd natural frequency response is used to decouple mass-stress influences.Research limitations implications - Owing to the micro-scale size of the micro-cantilevers, it may not be possible to apply mass or stress directly at the nodal point and to concentrate its influence there. Hence, a certain amount of influence due to mass-stress coupling may remain in the frequency responses observed.Practical implications - Silicon micro-cantilevers can be easily shaped and sensitized to a variety of influences. These qualities are highly regarded for sensor applications. The work presented herein, contributes to the optimization of micro-cantilever sensors' dynamic response as a function of mass and surface stress influences. The main criterion for choosing one or the other is based on the time for the surface reaction to take place between the sensing material and the target material. The results presented contribute to the performance optimization of micro-cantilever