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Dip-pen Nanolithography and Nanoprinting


Dip-pen Nanolithography and Nanoprinting


  Dip-Pen Nanolithography(DPN) is a new scanning-probe based direct-write tool for generating such surface-patterned chemical functionality on the sub-100nm length-scale, and it is a technique that is accessible to any researcher who can use an atomic force microscope(AFM). It utilizes an (AFM) tip as a nanoscale pen, molecular substrates as ink, and solid substrates as paper. When the molecule-coated tip is in contact with the substrate, molecules diffuse out onto the substrate, chemically anchor to the surface, and form well-ordered self-assembly monolayer (SAM) patterns. Like macroscale quill pens. the molecular ink coating on the tip surface works as an ink reservoir. A number of variables including relative humidity, temperature, and the tip speed can be adjusted to control the ink transport rate, feature size, and linewidth.

Molecular Ink


Molecular Ink


  Various types of organic molecules have been used for DPN ink experiments. Most commonly used organic molecules form SAMs on substrates. These molecules are comprised of three different parts: (1) a chemisorbing group, (2) and end group, and (3) a spacer(iner part). When these molecules are deposited on to a proper substrate, they chemically anchor to the substrate and form a well-ordered stable crystalline monolayer film with a thickness ranging from 1 to 10 nm.



Nanoscale Pen


Nanoscale Pen


  AFM tips with various shapes and chemical surfaces have been utilized as nanopens for the DPN process. Most common materials for the AFM tips are Si3N4. Tips usually have a pyramid shape and the heights about 3- 10um.



Phase of molecular ink



Phase of molecular ink


  We studied a "double molecular layer" model of DPN to interpret three different molecular transport processes such as "Surface Melting", "Surface Wetting", and "Binary Diffusion". A diffusion equation approach was used for theoretical method, and the result could point out the qualitative explanation for the dependence of the pattern growth rate on solvent and adsorbed water as well as on temperature.This results can be an important guide to the precise control of nanoscale molecular transport for direct deposition processes.



Surface Liquid Formation



Surface Liquid Formation


  ODT is the surface melting case because it has a low melting point and hydrophobic properties. MHA is complex case of surface wetting and binary diffusion phenomena because it has hydrophilic properties and it is coated from ink solution.