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Jozwiak G.,Wydzial Elektroniki Mikrosystemow | Zawierucha P.,Wydzial Elektroniki Mikrosystemow | Kopiec D.,Wydzial Elektroniki Mikrosystemow | Woszczyna M.,Wydzial Elektroniki Mikrosystemow | And 3 more authors.
Przeglad Elektrotechniczny | Year: 2010

Micromechanical resonant sensors are widely applied to measurements of low forces, masses and viscosity. After surface functionalization they might be used as biochemical sensors for intermolecular force detection. The noise existing in those devices is the main factor limiting the device sensitivity and the measurement resolution. Furthermore, the analysis of mechanical thermal noise of the microcantilever can play main role in a calibration process of sensor mechanical properties. In the paper the mathematical models for 1/f noise, Johnson-Nyquist noise and thermal oscillations noise in frequency domain are presented. The special attention is paid on mechanical thermal noise and its connections with mechanical properties of the system. It is shown that only thermal noise analysis is able to determine system spring constant and that the methods based on the system transmittance analysis fail due to inseparability of the system effective mass and the system spring constant or due to the lack of calibrated excitation source. The measurement system for investigation of noise in piezoresistive cantilevers is presented. The system was utilized for examination of piezoresistive microcantilever made at Warsaw Institute of Electron Technology. The power spectrum of the cantilever noise was estimated and the sensitivity of the piezoresistive bridge of the cantilever was measured. After that the analysis of obtained power spectra was performed. As a result the resonance frequency, the resonance quality factor, the cantilever mean thermal deflection and the cantilever spring constant were calculated. Obtained results confirm that system is able to detect a mean thermal deflection that is less than 1 angstrom.

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