Resonant microcantilevers are widely spread for different applications, such as atomic force microscopy or biosensor
devices. The use of piezoelectric films on top of the cantilevers is a very promising technology due to the possibility of
implementing an all electrical actuation/detection scheme. Among the different piezoelectric materials, polycrystalline
aluminium nitride (AlN) is a very attractive material as, in contrast to typical alternatives such as lead zirconate titanate
or zinc oxide, it is fully compatible with standard silicon technology, what facilitates its integration in silicon-based
devices.
In this study, our objective is to use sputter-deposited polycrystalline AlN as the actuation material for cantilever-based
biosensors and to study the performance of high frequency modes for bio-detection in liquid media. Our results
demonstrate a limit of mass detection of 0.07 ng for a 300x200 μm2 cantilever in liquid media, which represents a value
below the mass of a monolayer of IgG on a 300x200 μm2 area.
Here we present a comparison between polycrystalline AlN and (100) silicon as a support for the development of an
immunosensor. A covalent approach was followed for the modification of the initially oxidized surfaces. First a layer of
epoxy-based silane organic molecules was deposited. Next, protein A was immobilized with the purpose of taking
advantage of its ability to properly orient the antigen binding sites of IgG antibody molecules. Finally the antibodyantigen
reaction was accomplished using rabbit IgG and a corresponding antigen, such as anti-rabbit goat IgG. The antirabbit
goat IgG was labelled with HRP. This allowed us to quantify the quantity of immobilized antigen. Our results
demonstrate the reliability of polycrystalline AlN as a platform for immunosensing, with results comparable to those of
silicon.
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