Dip-Pen Nanolithography (DPN)• DPN is a direct-write scanning-probe-based lithography in

which an AFM tip is used to deliver chemical reagents directly

to nanoscopic regions of a target substrate

• Components:

Pen: AFM scanning cantilever

Ink: the materials that bind to the surface

Paper: Substrate such as Au, SiOx, mica

Figure 1. Schematic representation of the DPN process. A watermeniscus forms between the AFM tip which is coated with “ink” moleculesand the solid substrate

Direct-Write DNP procedure

• Prepare the ink (Fe2O3nanoparticles hydrosol)

• Prepare the paper (mica & silicon, surface treatment by aqueous HF solution)

• Coat the cantilever with the ink

• Scan the area for patterning in the contact mode, with a slower scan rate, 1 µm s-1

• For AFM characterization, use the same AFM, scan it at higher scan rate, 10 µm s-1

Direct-Write DNP for protein array

• Prepare the ink (MHA: mercaptohexadecanoic acid)

• The paper (silicon slides) • Coat the cantilever with the ink• Scan the area for patterning in

the contact mode.• Protein adsorption (rabbit IgG ) • antibody recognition. • The resulting protein arrays we

re then characterized by AFM. B) Topography image of the protein array

Direct-Write DNP for protein array Height profiles of TM-AF

M images: rabbit IgG assembled on an MHA dot array generated by DPN before (A) and after (B) treatment with a solution containing lysozyme, goat/sheep anti-IgG, human anti-IgG, and rabbit anti-IgG; a control protein nanoarray before (C) and after (D) exposure to a solution containing lysozyme, retronectin, goat/sheep anti-IgG, and human anti-IgG.

Nanostructures patterned by DPN

A) Nanoscale dot arrays and B) nanoscale letters written on a Au surface C) TM-AFM image of 25- and 13-nm gold nanoparticles hybridized to surface DNA templat

es generated with DPN D) Fluorescence image of DPN patterns of fluorescently labeled IgG on SiOx

Nanostructures patterned by DPN

B) TM-AFM image of 60-nm gold nanolines C)12-nm gold nanogap on a Si/SiOx surface. D) 3D Si(100) nanostructures. TM-AFM image of DNA-modified line (E), features after hybridization with complementary DNA-modified nanoparticles; insert: high-resolution TM-AFM images

Advantages It might be the only lithographic technique that offers

• High resolution• High registration

• With direct-write printing capabilities

Limitation of the method

More efforts should be put in improving the speed and in transforming it into massively parallel process to be a powerful production tool in both the life science and the semiconductor industry.

Conclusions

• DPN is a unique scanning-probe-based lithographic tool for generating high-resolution patterns of chemical functionality on a nano range of surfaces.

• The combination of resolution, registration, and direct-write

capability offered by DPN distinguishes it from any alternative lithographic strategy and makes DPN a promising tool for patterning soft organic and biological nanostructures.