A Versatile Mass-Sensing Platform With Tunable Nonlinear Self-Excited Microcantilevers

• Published in: IEEE transactions on nanotechnology Vol. 17; no. 4; pp. 751 - 762
• Main Authors: Mouro, Joao, Tiribilli, Bruno, Paoletti, Paolo
• Format: Journal Article
• Language: English
• Published: IEEE 01.07.2018
• Subjects: Delays; Feedback loop; Frequency measurement; Mass-sensing; Microcavities; nonlinear oscillations; Oscillators; Piezoelectric polarization; Resonant frequency; self-excited microcantilever
• ISSN: 1536-125X; 1941-0085
• DOI: 10.1109/TNANO.2018.2829404

A versatile mass-sensing platform based on the nonlinear dynamical response of a microcantilever embedded in a self-excitation feedback loop is proposed. It is experimentally shown that the delay imposed in the feedback loop by an adjustable phase-shifter can be used to finely tune this system to work in three different modalities, according to the desired mass sensing application: 1) as a continuous mass sensor, where the oscillation frequency smoothly responds to changes in the mass added to the resonator; 2) as a threshold sensor, where a sudden change in the oscillation frequency is triggered by an arbitrarily small change of mass added to the cantilever; and 3) as a stable microresonator, whose oscillation frequency is almost not affected by environmental conditions, such as changes in added mass, or in density/viscosity of the surrounding fluid. This variety of dynamical responses was registered for a wide range of added masses, in the form of beads individually attached to the cantilever. A complete analytical model to explain the observed experimental results is derived and shows a strong agreement with the measured data. The high resolution and signal-to-noise ratio, as well as the threshold and stable sensing modalities obtained with this closed-loop technique, are not available in the current open-loop microcantilever-based mass sensors.