Three-dimensional nanolithography using light scattering from colloidal particles.

The interaction between light and colloidal elements can result in a wealth of interesting near-field optical patterns. By examining the optical and colloidal properties, the intensity distribution can be tailored and harnessed for three-dimensional nanolithography. Here, we examine the use of light scattering from colloidal particles to fabricate complex hollow nanostructures. In this approach, a single colloidal sphere is illuminated to create a scattering pattern, which is captured by a photoresist in close proximity. No external optical elements are required, and the colloidal elements alone provide the modulation of the optical intensity pattern. The fabricated nanostructures can be designed to have multiple shells, confined volumes, and single top openings, resembling "nano-volcanoes." The geometry of such structures is dependent on the scattered light distribution and can be accurately modeled by examining the light-particle interaction. The hollow nanostructures can be used to trap nanomaterial, and we demonstrate their ability to trap 50 nm silica nanoparticles. These well-defined surface hollow structures can be further functionalized for applications in controlled drug delivery and biotrapping. Colloidal elements with different geometries and material compositions can also be incorporated to examine other light-colloid interactions.