The Electron Beam Lithography (EBL) technique has been employed for the development of various research topics dealing with nanotechnology, such as nanodevices fabrication and nanomachining. Exploiting our previous experience with EBL, we succeeded in achieving high-resolution nano-patterns useful for sensing applications, such as nano-gap electrodes (left image). On the other hand, the use of EBL in some innovative non-standard ways led to nice results on Si nanomachining and on direct-writing methods applied to different molecules and biomolecules, as shown in the SEM image on the right. Left: High-resolution nanogap of Au electrodes obtained by standard EBL and lift-off Right: Si nanostructures in relief obtained by a non-standard EBL method, involving photoresist irradiation at very high dose and electro-chemical etching.___________________________________________________________________________
Research and development of silicon nanosensors
Our group fabricates and characterizes gas sensors based on nanostructured silicon. We have studied the IV curves of mesoporous silicon devices both in vacuum and in presence of NO2 traces. By the use of different electrode configurations, the longitudinal (parallel to the sample surface) and transverse (perpendicular to the sample surface) components of the electrical conductance have been independently measured and compared, in order to optimize the sensor responsivity. This way, we succeeded in fabricating highly sensitive devices, and we observed a correlation between the sensors responsivity and the morphology of nanostructured siliconTowards nano-biopatterning for electronics and sensing applications.
Selective localization of active proteins into patterns or specific sites is important for the develop-ment of biosensors, bioMEMS, tissue engineering, and basic proteomic research. By improving the resolution of the protein features, it is possible to enhance many properties of the patterned bio-molecules. Smaller feature sizes enable the fabrication of high-density protein arrays for biosensors or proteomic screening, or allow studies of cellular interactions with small and precisely located clusters of extracellular matrix proteins. We present a technique for selectively patterning bioactive proteins with nanoscale resolution using direct writing methods based on EBL. A 3D nanopatterning process has been developed, based on the local activation of porous Si by electron beam irradiation. Proteins bind to irradiated regions, and the depth of biomolecule patterns is controlled by varying the electron energy. 3D protein nanopatterning: (top) schematic view of the process, (left) optical image of selective binding of proteins to irradiated PS regions with sub-?m resolution.
The e-beam is able to locally activate the material, so that proteins selectively bind to the irradiated regions. We have found that the process can be serially repeated, allowing the fabrication of biochips where various types of biomolecules are immobilized in different regions. Thus, the technique is suitable for the production of innovative biodevices. Left: Fluorescence microscopy image of a porous silicon biochip with different proteins (Glucose-Galactose Binding Protein (GGBP) and Glutamine Binding Protein (GlnBP)) immobilized on adjacent microspots.
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