Dip Pen Nanolithography Transport Mechanisms

NanoInk’s Dip Pen Nanolithography® (DPN®) platforms utilize two distinct deposition mechanisms to enable the patterning of a wide variety of materials.  The understanding of each mechanism is essential for successful DPN lithography processes.

Molecular Diffusion

• Ability to coat tips with solid-phase molecules
• High resolution
• No solvent
• 50 - 1,000 nm feature size

The deposition mechanism most commonly associated with Dip Pen Nanolithography is molecular diffusion and it involves the transfer of small molecules from a DPN tip to a surface.  With this mechanism, the molecular material is first coated and dried onto a DPN tip.  The subsequent transfer of molecules from tip to surface occurs through a water meniscus that forms spontaneously from the surrounding atmosphere.  The diffusion rate is molecule dependent.  The most common molecular diffusion materials are alkanethiols, but silanes and polymers also work well.  The molecular diffusion mechanism only applies to molecules that are in the solid phase on the tip.

The size of the features created from the molecular diffusion model are mostly dependent on the size of the water meniscus, allowing feature size to be controlled through the humidity (meniscus size) and the length of time the tip is held in contact with the surface.  Under the proper conditions, features as small as 50 nm and as large as 1000 nm can be reproducibly patterned.

Liquid Depositions

• Compatible with liquid-phase material
• Multiplexed deposition
• Feature size easily controlled via liquid/surface interactions
• 1 - 10 µm feature size

Liquids can be deposited using Dip Pen Nanolithography, but their deposition differs from that of molecular materials.  The most important difference is the absence of the water meniscus during liquid deposition.  While a meniscus does exist, it is composed of the actual liquid being deposited and not the water meniscus found in the molecular diffusion mechanism.  This small difference has profound implications on feature size resolution control methods, which need to take the liquid-tip and liquid-surface interactions into account.  As a general rule, the liquid must not have a surface affinity that is either too weak or too strong.  If surface affinity is too weak, the liquid deposition will not occur and if it is too strong, the liquid will transfer from tip to surface the instant the tip is brought into contact with the surface.  NanoInk has developed standard liquid carriers to which other molecules, like DNA or proteins, can be added to keep development time to a minimum. 

Molecular ink deposition

Close up view of the molecular transport mechanism in action

Multiplexed protein depositions with sub-cellular resolution and arbitrary shapes

Deposition of a liquid ink