part 4ii: dip pen nanolithography (dpn) after completing part 4i of this course you should have an...
TRANSCRIPT
Part 4ii:
Dip Pen Nanolithography(DPN)
After completing PART 4i of this course you should have an understanding of, and be
able to demonstrate, the following terms, ideas and methods.
(i) The DPN process,
(ii) The experimental factors that effect the DPN process (ink diffusion, ink-
surface interaction, tip dwell times and writing speeds, humidity.
(iii) Be aware of how DPN can be used.
Learning Objectives
Dip-Pen Nanolithography (DPN) is an new Atomic Force Microscope (AFM) based soft-lithography technique which was recently discovered in the labs of Prof Merkin.
DPN is a direct-write soft lithography technique which is used to create nanostructures on a substrate of interest by delivering collections of molecules (thiols) via capillary transport from an AFM tip to a surface (gold)
Dip-Pen Nanolithography
10 nm
http://www.chem.northwestern.edu/~mkngrp/
Scientific American
2001
AFM Friction image of an
ODT island recorded with a
dull tip under low load
500 nm
Diffusion of Ink from Tip to Substrate
Physisorbed thiols diffuse down the tip to the tip-surface
contact area and then diffuse out across the surface,
continuously increasing in range and concentration.
A SAM of “standing” thiols covers regions of sufficiently
high thiol concentration (radius r).
The contact radius, a, is defined as the distance at
which the tip-surface gap equals the height of the SAM.
Phys. Rev. Letts. 88 156104 (2002).
Ink: nC12H25-NH2
Surface: Mica
Ink: HO2C-C15H30-SH
Surface: Au
Phys. Rev. Letts. 90 115505 (2003).
Amine has weak interaction with Mica
Thiol has strong interaction with Au
Ink-Surface Interaction
The effect of dwell time on the size of
dots created by DPN of MHA dots on a
gold substrate.
Ink: HO2C-C15H30-SH
Surface: Au
Tip-Surface Dwell Time
Phys. Rev. Letts. 88 255505 (2002).
ESEM images of the effect on the meniscus
size as the relative humidity is increased from
40% to 99%
Water Meniscus and Humidity
Langmuir 21 8096 (2005).
Two gold electrodes connected by indium oxide deposited by thermal DPN.
Thermal DPN
Appl. Phys. Letts., 88 033104 (2006)
Indium Metal
Indium Metal
Indium Oxide
Indium Oxide
AFM image of a stretched strand of DNA modified with dots of Cy3-antibody.
Painting DNA!
Ultramicroscopy 105 312 (2005).
Growing Polymers of a DPN Written Surface
12
3
4
1. Write monomer thiol to Au surface with DPN.
2. Passivate exposed Au surface with decane thiol.
3. Expose surface to catalyst solution and rinse.
4. Expose surface to monomer solution
Height of polymer structures vs reaction time
Angew. Chem. Int. Ed. 2003, 42, 4785 –4789
Writing Monomers of a DPN Written Surface
Angew. Chem. Int. Ed. 2003, 42, 4785 –4789
1. Form a SAM of silane monomer2. Activate SAM with polymer catalyst3. Write monomers to the surface with DPN
a. write linesc,b write dots
3a3b3c
1 2
An Enzyme Ink for DPN
AddMg2+ ionsactivator
Write enzymes with DPN
J. AM. CHEM. SOC. 2004, 126, 4770-4771
Conclusions on DPN
DPN is a facile and versatile route to create nanostructured surfaces, with resolution
better than photolithography and almost equalling EBL.
It requires relatively cheap instrumentation and is carried out under ambient
conditions.
It is a serially process and hence relatively slow.
Summing Up Part 4
CP is a rapid parallel process, and utilises simple chemistry and processes for nanostructuring surfaces, usually under ambient conditions.
DPN is a slow serial process, but also uses simple chemistry and processes for nanostructuring surfaces, but requires an AFM (£100K).
Both processes utilise the well-established science and technology surrounding SAMs, and therefore for sure we have only begun to see the tip of the iceberg in terms of the chemistry that may be used with these lithographic processes.
SEM micrograph of a 32 probe array used for parallel DPN. The insert shows an enlarged view of the tip at the end of a beam.
Parallel DPN
Small, 1 924 (2005).Nanotechnology, 13 121 (2002).
upper left depicts misalignment between tips and substrate. By adjusting the substrate using a tilt-stage and applying a large setpoint (>10nN) all 26 tips can be engaged with the substrate (upper right).
When cantilevers make contact with the surface, their angle of reflection and subsequently their colorchanges, as observed by optical microscopy (compare lower left with lower right).
Centimeter scale patterning of nanometer scale features using parallel-DPN by patterning ODT on Au and then etching.