Self-Assembly of Nanoparticles

The lab is active in exploring novel type of “bottom-up” nanofabrication approach, where elementary components self-assemble to form functional structures.

Self-Assembled Ferrofluid Lithography: We have developed an active field-induced self-assembly process called self-assembled ferrofluid lithography (SAFLi), where magnetic nanoparticles are used as a tunable nanostructured mask for near-field lithography. In this approach, magnetic nanoparticles (~10 nm) in a carrier fluid, also known as ferrofluid, are used as fundamental building blocks. The particles, typically randomly dispersed in the solution, assemble to form ordered structures when external magnetic fields are applied. This technique allows the user to specify the particle assembly geometry, and therefore the shape of the “lithography mask,” by designing the external field.

Using the SAFLi process, we have demonstrated micro-dot array with controllable spacing and micro-ring structure with 250 nm feature sizes. The ring structures are especially interesting, and may have applications in nanomagnetics, micro-ring optical resonators, and biological cell confinement. This multiphase field-induced self-assembly process is versatile, as a single assembly system can pattern multiple geometries by simply controlling the external magnetic field. The process is also scalable and cost-effective, presenting itself as a promising nanomanufacturing tool.