(351g) Design and Fabrication of Micron-Scale Magnetic, Amphiphilic, Janus Structures

We present techniques we have developed for the design and fabrication of micron-scale structures with ferromagnetic or paramagnetic properties (as desired), whose surface chemistry can be controlled to impart solubility or interfacial activity. Using photolithography, we microfabricate structures with specified geometry, incorporating layers of magnetic metals (e.g. Nickel, Cobalt, Permalloy) to provide different magnetic properties as well as a gold layer which enables us to tune surface chemistry using versatile gold-thiol chemistry. Particle shape, size, and thickness can easily be tuned in addition to surface and magnetic properties. We describe the mechanisms that give rise to ferro- or para-magnetic structures, giving basic design rules for these novel structures. While our main purpose for synthesizing these structures is for use as probes for interfacial rheology, we describe more generally some novel feaures and potential applications involving these structures, including interfaces whose properties can be externally tuned, as well as the static and dynamic configurations adopted at fluid/fluid interfaces under applied magnetic fields.