Scanning probe-based fabrication of 3D nanostructures via affinity templates, functional RNA and meniscus-mediated surface remodeling

Developing generic platforms to organize discrete molecular elements and nanostructures into deterministic patterns at surfaces is one of the central challenges in the field of nanotechnology. Here we review three applications of the atomic force microscope (AFM) that address this challenge. In the first, we use two-step nanografting to create patterns of self-assembled monolayers (SAMs) to drive the organization of virus particles that have been either genetically or chemically modified to bind to the SAMs. Virus-SAM chemistries are described that provide irreversible and reversible binding, respectively. In the second, we use similar SAM patterns as affinity templates that have been designed to covalently bind oligonucleotides engineered to bind to the SAMs and selected for their ability to mediate the subsequent growth of metallic nanocrystals. In the final application, the liquid meniscus that condenses at the AFM tip-substrate contact is used as a physical tool to both modulate the surface topography of a water-soluble substrate and guide the hierarchical assembly of Au nanoparticles into nanowires. All three approaches can be generalized to meet the requirements of a wide variety of materials systems and thus provide a potential route towards development of a generic platform for molecular and materials organization.