A piezoelectric cantilever with a non-piezoelectric, or piezoelectric tip
useful as mass and viscosity sensors. The change in the cantilever mass
can be accurately quantified by monitoring a resonance frequency shift of
the cantilever. For bio-detection, antibodies or other specific receptors
of target antigens may be immobilized on the cantilever surface,
preferably on the non-piezoelectric tip. For chemical detection, high
surface-area selective absorbent materials are coated on the cantilever
tip. Binding of the target antigens or analytes to the cantilever surface
increases the cantilever mass. Detection of target antigens or analytes
is achieved by monitoring the cantilever's resonance frequency and
determining the resonance frequency shift that is due to the mass of the
adsorbed target antigens on the cantilever surface. The use of a
piezoelectric unimorph cantilever allows both electrical actuation and
electrical sensing. Incorporating a non-piezoelectric tip (14) enhances
the sensitivity of the sensor. In addition, the piezoelectric cantilever
can withstand damping in highly viscous liquids and can be used as a
viscosity sensor in wide viscosity range.