Material transport in dip-pen nanolithography

Dip-pen nanolithography (DPN) is a useful method for directly printing materials on surfaces with sub-50 nm resolution. Because it involves the physical transport of materials from a scanning probe tip to a surface and the subsequent chemical interaction of that material with the surface, there are many factors to consider when attempting to understand DPN. In this review, we overview the physical and chemical processes that are known to play a role in DPN. Through a detailed review of the literature, we classify inks into three general categories based on their transport properties, and highlight the myriad ways that DPN can be used to perform chemistry at the tip of a scanning probe.