Tools to Make Nanostructures “the challenge to Moore’s Law“ Scanning Probe Instruments Lithography Nanoscale Dip Pen E-Beam Nanosphere Liftoff Molecular Synthesis Self Assembly Nanoscale Crystal Growth Polymerization Nanobricks NanoCAD

The Return of Scanning Probe Instruments Assembling materials atom-by- atom or molecule-by-molecule Analogy – “bulldozer” or “crane” or “backhoe” Elegant but slow and expensive http://www.aip.org/mgr/png/html/abacus.htm A series of STM images showing the numbers 0 through 10 represented by single carbon-60 molecules (buckyballs) on a copper surface. The top row shows zero, with no molecules at the end of the row, and the successive rows provide representations of the numbers 1-10, with the appropriate numbers of molecules at the end of each row. (Image courtesy IBM Zurich Research Laboratory.)

Nanoscale Lithography “silk screen or rubber stamp concept” Micro-imprint lithography developed by George Whitesides (Harvard) Pattern inscribed onto a rubber surface (silicon/oxygen polymer) and the rubber surface is coated with molecular ink Complex but inexpensive and can make numerous copies Figure 15. Two examples of imprinting over a planarized surface. http://www.molecularimprints.com/NewsEvents/tech_articles/new _articles/MOT_SPIE2003_Imprint_Lith_review_paper.pdf

Dip Pen Lithography “fountain pen analogy”                                                                                                                                                                                                                                                                                                                                             http://chemgroups.northwestern.edu/mirkingroup/dpn.htm “fountain pen analogy” Developed by Chad Mirkin at Northwestern Univ. AFM tips are ideal nanopens Almost anything can be used as nanoink almost any surface can be written on Almost anystructure can be made no matter how detailed or complex Dip-Pen Nanolithography: Transport of molecules to the surface via water meniscus. Ultra-high resolution pattern of mercaptohexadecanoic acid on atomically-flat gold surface. B) DPN generated multi-component nanostructure with two aligned alkanethiol patterns. C) Richard Feynmann's historic speech written using the DPN nanoplotter

E-Beam Lithography Use of electron beam to make structures at nanoscale Applications in microelectronics http://brainsturbator.com/pdf/Prentice%20Hall%20Ptr%20%20Nanotechnology%20A%20Gentle%20Introduction%20To%20The%20Next%20Big%20Idea.pdf Figure 4.4. Two electrodes made using E-beam lithography. Thelight horizontal structure is a carbon nanotube. Courtesy of the Dekker Group, Delft Institute of Technology.

Nanosphere Liftoff Lithography Figure 4.5. Schematic of the nanosphere liftoff lithography process. Courtesy of the Van Duyne Group, Northwestern University. http://brainsturbator.com/pdf/Prentice%20Hall%20Ptr%20-%20Nanotechnology%20A%20Gentle%20Introduction%20To%20The%20Next%20Big%20Idea.pdf

Molecular Synthesis - making specific molecules for specific purposes - drug delivery techniques - extensive molecular synthetic work in drug companies (e.g. Lipitor, Penicillin, Taxol, Viagra) http://www.sigmaaldrich.com/img/assets/3760/Acta_37_2.pdf

Self Assembly Making nanostructures by letting the molecules sort themselves out Molecules will always seek the lowest energy available to them Molecules will align themselves into particular positions Use for large nanoscale arrays, different length scales, low cost, generality Electronic applications, coatings http://brainsturbator.com/pdf/Prentice%20Hall%20Ptr%20%20Nanotechnology%20A%20Gentle%20Introduction%20To%20The%20Next%20Big%20Idea.pdf Figure 4.6. Molecular model (top) of a self-assembled "mushroom" (more correctly a rodcoil polymer). The photograph (bottom) shows control of surface wetting by a layer of these mushrooms. Courtesy of the Stupp Group, Northwestern University.

Nanoscale Crystal Growth “seed crystal concept” Silicon Boules Manipulating seed crystals to grow to unusual shapes Charles Lieber (Harvard) http://brainsturbator.com/pdf/Prentice%20Hall%20Ptr%20%20Nanotechnology%20A%20Gentle%20Introduction%20To%20The%20Next%20Big%20Idea.pdf Figure 4.7. Two parallel nanowires. The light color is silicon, and the darker color is silicon/germanium. Courtesy of Yang Group, University of California at Berkeley.

Polymerization Controlled polymerization, in which one monomer at a time is added to the next, is very important for specific elegant structures. Robert Letsinger and his students at Northwestern University have developed a series of methods for preparing specific short DNA fragments. These are called oligonucleotides. The so-called gene machines use elegant reaction chemistry to construct specific DNA sequences. Figure 4.8. Schematic of the DNA hybridization process. The "matched" side shows how a DNA strand correctly binds to its complement and the "mismatched" side shows how errors can prevent binding. Courtesy of the Mirkin Group, Northwestern University.