Dip-pen nanolithography technique

Nano-scale polymer patterning was reported to be fabricated by the enzymatic oxidative polymerization of caffeic acid on 4-aminothiolphenol-functionalized gold surface with dip-pen nanolithography technique [74],... 

EW has also been successfully employed for handling tiny amounts of liquid in biotechnological applications (see Fig. 5). For instance, using the EW-based dip-pen nanolithography technique, droplets in femtoliter to picoliter range have been successfully spotted onto surfaces, to form DNA and protein fluorescence-labeled arrays. 

The dip-pen nanolithography technique allows directly printing a wide variety of biomaterials including DNA, phospholipids, and proteins with a resolution below 50 nm (94-96). 

For direct patterning on the nanometer scale, scanning probe microscopy (SPM) based techniques such as dip-pen-nanolithography (DPN), [112-114] nanograftingf, nanoshaving or scanning tunneling microscopy (STM) based techniques such as electron induced diffusion or evaporation have recently been developed (Fig. 9.14) [115, 116]. The SPM based methods, allows the deposition of as-sembhes into restricted areas with 15 nm linewidths and 5 nm spatial resolution. Current capabihties and future applications of DPN are discussed in Ref. [117]. 

DNA arrays have been also generated by Dip-Pen Nanolithography (DPN) [80]. DPN involves the transfer of NAs directly from a coated Atomic Force Microscope (AFM) tip to the substrate of interest by virtue of direct molecular diffusion. Using this technique, thiol-modified ONDs have been patterned onto gold substrates and acrylamide-modified ONDs onto glass sHdes that were previously modified with mercaptopropyltrimethoxysilane. Feature sizes ranging from many micrometers to less than 100 nanometers could be obtained. The deposition of two different OND sequences onto the same substrate has also been reported [80], but the appHcation of this principle to the fabrication of high-density arrays remains to be addressed. 

Controlled delivery of collections of molecules onto a substrate with nanometre resolution can be achieved with the tip of an AFM. This positive printing mode technique is called dip-pen nanolithography (DPN) and its working principle is illustrated in Fig. 3.27. DPN uses an AFM tip as a nanopencil, a substrate as the paper and molecules with a chemical affinity for the substrate as the ink. Capillary transport of molecules from the AFM tip to the solid substrate is used in DPN to directly write patterns consisting of a relatively small collection of molecules in submicrometre dimensions. The hrst example introducing the technique was the transfer of octadecanethiol onto gold surfaces (Piner et al, 1999). 

Dip-pen nanolithography (Jiang and Stupp 2005) and soft lithography (Hung and Stupp 2007) have been used to control the placement and orientation of PA nanofibers on two-dimensional substrates. The soft lithographic technique is the more... 

The application of scanning probe lithography (SPL) has been widespread owing to its ability to modify substrates with very high resolution and ultimate pattern flexibility.96 Dip-pen nanolithography (DPN),97 high contact force AFM,98 and constructive nanolithography99 are some of the most commonly employed techniques, all of which aim to control the position and directed assembly of molecules and nanoparticles. 

The so-called dip-pen nanolithography is one of these promising novel techniques. It has been developed by Ch. Mirkin etal. and is based on the use of Atomic Force Microscopy (AFM) tips to deposit functionalized molecules on appropriate surfaces. The molecules are first deposited in solid state on the tip. The transport to the surface happens by means of the water meniscus between the tip and the surface that is present in air of usual humidity. Gold surfaces are preferably used to deposit thiol molecules forming strong Au-S bonds. The places were thiol molecules are deposited simply depend on the software moving the AFM tip on the surface. Figure 13 explains in a simplified manner the process. 

One of the innovative applications of scanning probe microscopy for nanolithography is dip pen nanolithography (DPN). In this special technique the water meniscus formed between the tip and the substrate acts as a medium for molecular transport. The technique depends on the key phenomenon that the molecule to be deposited on the substrate (which is referred as the ink ) can be transported in a controlled way from the tip (which is initially coated with the ink) to the substrate. The molecule (the ink) to be deposited on the substrate should interact with the substrate to form a chemical bond, leading to a stable structure [82]. 

Pattern fabrication is an important issue in many fields ranging from microelectronics to biological microarray production and nanotechnology.64 Soft and probe lithography techniques such as microcontact printing (pCP) and dip-pen nanolithography (DPN) are frequently used to pattern surfaces.65 Conventional pCP is an efficient and... 

Dip-pen nanolithography is a high resolution patterning technique that enables the creation of patterns from the sub lOOnm to many micrometers length scale.76 This technique uses an ink-coated AFM (atomic force microscopy) tip as a nanopen. The ink molecules are transported from the tip to a substrate, normally by capillary forces when the tip is in contact with the surface of the substrate.77 The driving force for such transport is chemisorption of the ink to the underlying substrate due to a chemical78 or electrochemical force.79... 

---