Direct writing

Direct writing
Technology Details
Other Names	DPN, Ink Jet, 3D printing
Technology	Lithography
Equipment	Dimatix Inkjet Printer NanoInk DPN 5000 Heidelberg µPG 501 Mask Maker
Materials	inks

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Direct writing (also known as maskless lithography) There are several approaches to direct writing, i.e. ink jet printing, laser writing including gray-scale, dip pen nano-lithography (DPN), nanoimprinting, heat created structures with a sharp tip (NanoFrazor), Dynamic stencil lithography, oxidation and material displacement with AFM tip, etc. The common denominator in these techniques is that patterning can be done without the lithography steps. Ink jet printing uses a modified ink cartridge that can be filled with the material that needs to be deposited. The printer reproduces the designed pattern. While DPN uses an AFM cantilever dipped in the liquid that contains the atoms or molecules to be printed by using capillarity to be deposited where it is wanted. Dynamic( also "static') stencil uses a mask (stencil) through which atoms (i.e. as in deposition) or ions (i.e. as in FIB) go through to form a nano structure. Only the techniques available at LNF will be discussed in detail here.

Method of operation

Describe how the technology works.

Ink Jet Printing

A MEMS piezoelectric driven cartridge is used to generate drops of ink. By placing electrodes on the surface of the piezoelectric material, a section of the material can be made to move without affecting the surrounding material. By applying a voltage to the center electrode, an electric field is created between the center electrode and the ground electrodes. This creates the shear response in the piezoelectric material between the electrodes. By coupling the piezoelectric material to a pumping chamber that communicates with a nozzle, an ink drop is formed. This is also called drop on demand (DOD).The actual motion of the piezoelectric material is approximately one millionth of an inch.

Piezo DOD inkjet offers a variety of advantages over other materials deposition methods. As a non-contact deposition technology, it avoids contamination or damage of substrates. Rather than flooding a surface with functional fluids it is precise and purely additive, able to deposit the exact amount of material at the exact locations where it is needed without waste.

Dip Pen Nanolithography (DPN)

Dip Pen Nanolithography (DPN) is a direct write , tip-based lithography technique capable of multi-component deposition of a wide variety of materials with nanosclae registry. DPN allows the user to create user-defined patterns with feature size as small as 50nm and as large as 10um on substrates such as glass, plastic, gold and silicon, etc. DPN has the ability to design, deposit and characterize a wide variety of features and sizes on a benchtop, without the need of a clean room, master stamp or photomask.DPN was invented in 1999 by the Mirkin Group, and it can be used to deposit molecules and materials on surfaces with sub-50 nm resolution. This method employs an atomic force microscope (AFM) probe “pen” coated with a molecule- or materials-based “ink” that, upon contact with a surface, deposits the ink by diffusion through a water meniscus that forms under ambient conditions between the tip and substrate.

Parameters

Ink Jet Printing

The physical-chemical characteristics of the ink will or will not allow the jetting of fluids. For example, viscosity and surface tension will determine if the the fluid can flow through the micron size nozzle. If the ink has solid, the size of the particles should be less than 0.2 um to avoid clogging of the microchannels. In addition pH is also important.

Dip Pen Nanolithography

In this technique the chemical affinity between the ink and the substrate materials is critical. The technique is based on the transfer of material from tip (source) to the substrate via the meniscus formed between them. The local chemistry on the substrate must be such that allows the molecules transfer from the tip. For example, alkane thiolate inks (sulfur terminated hydrocarbons) can be easily deposited on gold surfaces as silanes (hydrogen-silicon compounds) can write on silicon. Therefore the surface chemistry of the substrate and the chemistry of the ink are the first two considerations.

Applications

Ink Jet Printing

This technique is convenient to use when a suitable ink needs to be deposited on a flat or relatively flat substrate and features larger that 30 microns are desired. This technique is not advisable for features less than 30 microns. There are two designs of jetting head available, one for pico liter size drop and another for um liter size drop. Smaller features can be obtained, with same materials from the smaller volume cartridge, but the size of the features that can be obtained, still depends on the surface chemistry of the substrate and the nature of the ink. In general it is recommended the ink physical characteristics (vapor pressure, viscosity) resembles that of water, though toluene is widely used as an ink.

The materials these unique systems can “print” range from UV-curable light-emitting polymers, liquid silver and conductive fluids to enzymes and DNA and other “organic inks” on all types of surfaces whose dimensions often must be controlled to within a few ten-millionths of a meter. The deposition of these fluids, from adhesives, masking inks, anti-scratch/ anti-glare compounds to UV-curable light-emitting polymers and conductive and electronics displays for life sciences, chemistry, 3-D mechanics, optics and photovoltaics, to name a few.

Dip Pen Nanolithography

This technique has been used to write with small organic molecules, such as alkanethiols (octadecanethiol (ODT) and mercaptohexadecanoic acid (MHA)) onto gold substrates. These molecules can form self-assembled monolayers (SAMs). It can also de used to write or template many different types of molecules and materials on a variety of surfaces (including metals, semiconductors and insulators) by controlling various experimental parameters such as ambient humidity, writing speed, and dwell time. These materials include polymers, colloidal nanoparticles (e.g. magnetic nanocrystals, carbon nanotubes), sol-gel precursors, small organic molecules, biomolecules (proteins and oligonucleotides) and even single virus particles and bacteria.

Materials

Optional description of materials that can be processed by technology. I think the best example of where this comes in handy would be with LPCVD describing the difference between HTO and LTO.

Equipment

All these techniques have dedicated equipment which is listed below

Complete tool list

Ink Jet Printing

Dimatix Inkjet Printer

• Dimatix DMP-2831

Gray Scale

Heidelberg μPG 501 Mask Maker

• Mask maker Heidelberg

Dip Pen Nanolithography (DPN)

NanoInk DPN 5000

• NanoInk DPN 5000

See also

Other related wiki pages

Further reading

How Dimatix works-a movie[1]

• External links (can be in another section below, if appropriate)

K. Salaita, Y. Wang, C. A. Mirkin, Nat. Nanotechnol. 2,145(2007).

"Top-down Nanomanufacturing", M. Imboden, D. Bishop, Physics Today,45,December(2014)