ABSTRACT
Direct patterning assembly techniques, especially SPLs, were usually dedicated to medical and biological research, which is aiming at the functional and structural study of biomolecular interactions and the fabrication of nanobiosensors and biocompatible materials. A variety of SPLs have been developed to locate nanoscale biomolecules and colloidal NPs. Among them, dip-pen nanolithography (DPN) [50, 63], is the most successful one. The main strategy is to use the tip of an atomic force microscope (AFM) cantilever as a “pen,” which is coated with a chemical compound or mixture acting as an “ink” and put in contact with a substrate, the “paper.” Thus the mechanism of the DPN technique is the diffusion of the molecular ink from a nanoscale tip to a surface through a water meniscus. In the last decade, DPN has emerged as a particularly attractive tool since it allows the direct transfer of biomolecules onto surfaces with a high registration and
resolution, while preserving their biological activity. Bellido et al. recently reported control of the number of ferritin protein NPs by adjusting the protein concentration used to coat the AFM tip and the dimensions of the dot-like features fabricated by DPN. The schematic illusion is shown in Fig. 7.1 [50].
