L. Bellon, Journal of Applied Physics 104, 104906 (2008)
doi: 10.1063/1.3021102
We present a simple theoretical framework to describe the thermal noise of a microscopic mechanical beam in a viscous fluid: we use the Sader approach to describe the effect of thesurrounding fluid (added mass and viscous drag) and the fluctuation dissipation theorem for each flexural modes of the system to derive a general expression for the power spectrum density offluctuations. This prediction is compared with an experimental measurement on a commercial atomic force microscopy cantilever in a frequency range covering the two first resonances. A very good agreement is found on the whole spectrum, with no adjustable parameters but the thickness of the cantilever.