Magnetic nanocrystal modified epoxy photoresist for microfabrication of AFM probes

Nanocomposites based on an organic polymer and inorganic nanocrystals (NCs) represent a class of high impact functional materials able to convey the unique size and shape dependent properties of nano-objects to highly processable resists.[1] In this work, a novel magnetic nanocomposite based on a negative tone epoxy photoresist and magnetic colloidal Fe2O3 NCs has been manufactured for fabricating AFM probes. Epoxy-type photoresist grant superior lithographic performances when patterned by standard near- ultraviolet (UV) optical lithography, providing structures with high aspect-ratio and nearly vertical sidewalls. Such resists are at present employed in optical and micromechanical applications for the fabrication of optical waveguides, microfluidic systems and scanning probes.[2] However, these materials lack of any inherent functionality, e.g. electrical conductivity, luminescence, magnetism, piezoresistivity and dielectricity. Hence, the incorporation of NCs can confer them new properties maintaining the patterning resolutions required for the manufacturing of highly miniaturized devices. These added properties can be interesting for the fabrication of novel micro/nanoelectromechanical systems (MEMS/NEMS). The current challenge consists on incorporating NCs in the photoresist host matrix to add functionality preserving at the same time the polymer photostructurability. The NC addition has relied on the efficient dispersion of pre-synthesized functional nanosized fillers into the pre-made epoxy photoresist, by using a common solvent as recently reported by the authors in the incorporation of highly luminescent CdSe@ZnS NCs in the same epoxy photoresist.[3] Here, the magnetic properties, UV-photostructurability and mechanical characteristics of the nanocomposite have been investigated. The results show that, after the incorporation, the Fe2O3 NCs preserve their magnetism which is conveyed to the photoresist and retained after the UV-lithography process (Figure 1).