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Abstract
Cantilever based mass sensors utilize that a change in vibrating mass will cause
a change in the resonant frequency. This can be used for very accurate sensing
of adsorption and desorption processes on the cantilever surface. The change in
resonant frequency caused by a single molecule depends on various parameters
including the vibrating mass of the cantilever and the frequency at which it vibrates.
The minimum amount of molecules detectable is highly dependent on the
noise of the system as well as the method of readout.
The aim of this Ph.D. thesis has been twofold: To develop a readout method
suitable for a portable device and to investigate the possibility of enhancing the
functionality and sensitivity of cantilever based mass sensors.
A readout method based on the hard contact between the cantilever and a biased
electrode placed in close proximity to the cantilever is proposed. The viability of
the method is shown theoretically, and the output signal is shown to scale very
well with the dimensions of the cantilever, and hence should be applicable to
nano-scale cantilevers.
The hard contact method is proven to work on cantilevers on the micro- and nanoscale
with measured resonant frequencies up to 11MHz. Values of the reciprocal
frequency resolution as high as 80000 are obtained together with a signal to noise
ratio of 108. The result is an almost digital readout, which in turn simplifies the
detection of the resonant frequency considerably.
An analytical expression is derived relating the mass and position of a particle
attached to a cantilever to the resonant frequency. It is shown theoretical possible
to find the mass and position of a particle by measurements of the resonant
frequency of several bending modes.
In the measurements the sensitivity of the cantilever based mass sensor is improved
when operated at higher bending modes. By measuring the resonant frequency
of several bending modes both the mass and position of an attached gold
bead are determined.
Original language | English |
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Number of pages | 155 |
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Publication status | Published - Mar 2007 |
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Dive into the research topics of 'Cantilever Based Mass Sensing: Alternative Readout and Operation Schemes'. Together they form a unique fingerprint.Projects
- 1 Finished
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Investigation of Nano-resonators for Mass Detection
Dohn, S. (PhD Student), Boisen, A. (Main Supervisor), Sigmund, O. (Examiner), Bouwstra, S. (Examiner), Hansen, O. (Supervisor) & Laegsgaard, E. (Examiner)
01/09/2003 → 30/03/2007
Project: PhD