Amos Bardea and Ron Naaman

Department of Chemical Physics
Weizmann Institute of Science, Rehovot 76100, Israel

The new surface patterning method is based on Magneto Lithography (ML). ML is a "bottomup" method, but at the same time, it provides desired high throughput capabilities for mass production. It is based on applying a magnetic field on the substrate using paramagnetic metal masks that define the spatial distribution and shape of the applied field. The second component in ML is ferromagnetic nanoparticles (Fe3O4) that are assembled onto the substrate according to the field induced by the mask. ML can be used for applying either a positive or negative approach. In the positive approach, the magnetic NPs react chemically with the substrate. Hence, the magnetic NPs are immobilized on selective locations, where the mask induces a magnetic field, resulting in patterned substrates. In the negative approach, the magnetic NPs are inerted into the substrate. Hence, once they pattern the substrate, they block their binding site on the substrate from reacting with another reacting agent. After the adsorption of the reacting agent, the NPs are removed, resulting in a negatively patterned.
The ML method simplifies chemical surface patterning, since it does not require resist, which may contaminate the substrate, and it does not depend on the surface topography and planarity.
Since a mask is applied, it is possible to have high production throughput. Unlike other lithography methods, ML is a backside lithography, which has the advantage of ease in producing multilayers with high accuracy of alignment and with the same efficiency for all layers. ML can be applied to chemically patterning inside of tubes and to form a gradient of properties. Finally, ML allows one to form a multi-step process without removing the substrate from the solution. This feature may be of importance for bio-related applications when reactants have to be kept at controlled conditions

Reference
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d) Tatikonda A. K., Bardea A., Shai Y., Yoffe A., and Naaman R. Nano Lett. 10, 2262-2267
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e) Bardea, A. and Naaman, R., Magnetolithography. From the Bottom-Up Route to High
Throughput. Advances in Imaging and Electron Physics, Vol. 164, 1-27, (2010).