So far, the impact of biomineralization processes on lithographic and microelectronic production processes has not yet been explored. Indeed, as an example, the controlled realization of silica patterns by parallel, low-cost, gentle biomineralization processes would be a feasible and powerful method for producing nano- and microstructures and for realizing electrically-insulating patterns for microelectronic devices. As opposed to conventional anthropogenic and industrial manufacturing, the biological synthesis of silica occurs under mild physiological conditions of low temperatures and pressures and near-neutral pH, with clear advantages in terms of cost-effectiveness, parallel production, and impact on the environment. The integration of nature-mimic biomineralization processes with micro- and nanofabrication to be accomplished within BIO-LITHO will be a unique route to make them usable in the medium-long term for industrial application and production, thus giving actual socio-economic development perspectives to this very innovative field of science.
In particular, some peculiar proteins of sponges (silicateins) catalyze the reaction of silica polymerization to give ordered structures. In such sponges, the siliceous spicules contain a proteinaceous axial filament of silicatein. To date, several isoforms of silicatein have been cloned from the marine sponges and freshwater sponges. These proteins are very similar to cathepsins, a well-known cysteine protease family and they are able to coordinate the deposition of silica. At neutral pH, the silicatein filaments and their constituent subunits catalyze the "in vitro" polymerization of silica and silesquioxanes from tetraethoxysilane and organically-modified silicon triethoxides, respectively. The catalytic activity is based on the polymerisation of the organosilica compounds by means of a protease-like active site, in which the cysteine is replaced by serine. Besides this catalytic activity, when the proteins are assembled into mesoscopic filaments (of diameter in the µm range and up to a few millimetres in length), they serve as scaffolds that spatially direct the synthesis of polysiloxanes over the surface of the protein filaments. Hence, these biomolecules present the combined characteristics of: (1) chemical action (catalysis) for the formation of silica and (2) patterning action, by driving the silica on the surface of the filaments.
We plan to exploit this unique combination within a novel technology that allows the realization of patterned, aligned assembly of silica fibers, and their employment as insulating layers for new transistor devices.
Soft lithography techniques, including replica molding, micromolding in capillaries, capillary force lithography, nanoimprinting and solvent-assisted approaches will be used for the controlled patterned deposition of molecules. These flexible methods will be strategic for the fabrication of biomolecular patterns, by virtue of the wide range of usable target surfaces and solvents, including aqueous solutions, and of the very low operation cost, which makes them affordable for bio-organic laboratories. Particular attention will be paid to approaches entirely operating at room temperature. A number of techniques employing imprinting processes and microfluidic networks will be used for the precise fabrication onto soft matter, including polymers and biomolecules and onto inorganic substrates. High-aspect-ratio photolithography will be employed for the optimized fabrication of µm-scale master templates to be used in the selective functionalization of surfaces. Specific approaches will be designed and implemented, for the hierarchical assembly of silicatein fibers into functional networks. Controlled parallel and crossed arrays will be realized by fluidic alignment.
