Dip Pen Nanolithography: a "Desktop Nanofab" approach using high-throughput flexible nanopatterning

Large-Area Patterning of Metal Nanostructures by Dip-Pen Nanodisplacement Lithography for Optical Applications

Au nanostructures are remarkably important in a wide variety of fields for decades. The fabrication of Au nanostructures typically requires time-consuming and expensive electron-beam lithography (EBL) that operates in vacuum. To address this challenge, this paper reports the development of massive dip-pen nanodisplacement lithography (DNL) as a desktop fabrication tool, which allows high-throughput and rational design of arbitrary Au nanopatterns in ambient condition. Large-area (1 cm² ) and uniform (<10% variation) Au nanostructures as small as 70 nm are readily fabricated, with a throughput 100-fold higher than that of conventional EBL. As a proof-of-concept of the applications in the opitcal field, we fabricate discrete Au nanorod arrays that show significant plasmonic resonance in the visible range, and interconnected Au nanomeshes that are used for transparent conductive electrode of solar cells.

Large-area scanning probe nanolithography facilitated by automated alignment of probe arrays

A method for the automated alignment of scanning probe polymer pen arrays is reported. This system enables nanolithography over large (cm²) areas with high uniformity, with any misalignment being ≤0.0003°.

Generation of plasmonic Au nanostructures in the visible wavelength using two-dimensional parallel dip-pen nanolithography

The fabrication and characterization of over millimeter (mm)-scale Au plasmonic structures are reported. Fishnet structures of Au are fabricated by the "bottom-up (direct deposition of alkanethiol)" and "top-down (wet-etching of Au)" combined approach using massively parallel dip-pen nanolithography (DPN). An array of two-dimensional (2D) parallel 55,000 pens was used for the DPN writing of 1-octadecanethiol (ODT) on an Au film in an area of 10 mm × 10 mm. The plasmonic resonance of the over millimeter-scale Au fishnet structures is shown at the visible region around 500 nm, which is measured by ellipsometrical experiments and theoretical finite-difference time-domain (FDTD) calculation. It was demonstrated that massive metal plasmonic structures can be conveniently obtained by using DPN, complementary with both e-beam lithography and nanoimprint lithography.

Challenging material patterning: fine lithography on coarse substrates

Precise patterning of inorganic materials is important for many technological applications. Often lithography processes are required on challenging substrates with respect to topography, flexibility, and surface adhesion. Here we show the fabrication of artificial gunshot residues (GSR) on adhesive tape samples by means of dip-pen lithography as an example for fine lithography on coarse substrates. We deposited lead-, barium-, and antimony-containing inks on SEM adhesive tape by direct writing with a fine tip. Single as well as multiple element structures with dimensions in the range of 10-75 µm were fabricated.

Reagents in microfluidics: an 'in' and 'out' challenge

Microfluidic devices are excellent at downscaling chemical and biochemical reactions and thereby can make reactions faster, better and more efficient. It is therefore understandable that we are seeing these devices being developed and used for many applications and research areas. However, microfluidic devices are more complex than test tubes or microtitre plates and the integration of reagents into them is a real challenge. This review looks at state-of-the-art methods and strategies for integrating various classes of reagents inside microfluidics and similarly surveys how reagents can be released inside microfluidics. The number of methods used for integrating and releasing reagents is surprisingly large and involves reagents in dry and liquid forms, directly-integrated reagents or reagents linked to carriers, as well as active, passive and hybrid release methods. We also made a brief excursion into the field of drug release and delivery. With this review, we hope to provide a large number of examples of integrating and releasing reagents that can be used by developers and users of microfluidics for their specific needs.

Multifunctional lipid multilayer stamping

Nanostructured lipid multilayers on surfaces are a promising biofunctional nanomaterial. For example, surface-supported lipid multilayer diffraction gratings with optical properties that depend on the microscale spacing of the grating lines and the nanometer thickness of the lipid multilayers have been fabricated previously by dip-pen nanolithography (DPN), with immediate applications as label-free biosensors. The innate biocompatibility of such gratings makes them promising as biological sensor elements, model cellular systems, and construction materials for nanotechnology. Here a method is described that combines the lateral patterning capabilities and scalability of microcontact printing with the topographical control of nanoimprint lithography and the multimaterial integration aspects of dip-pen nanolithography in order to create nanostructured lipid multilayer arrays. This approach is denoted multilayer stamping. The distinguishing characteristic of this method is that it allows control of the lipid multilayer thickness, which is a crucial nanoscale dimension that determines the optical properties of lipid multilayer nanostructures. The ability to integrate multiple lipid materials on the same surface is also demonstrated by multi-ink spotting onto a polydimethoxysilane stamp, as well as higher-throughput patterning (on the order of 2 cm(2) s(-1) for grating fabrication) and the ability to pattern lipid materials that could not previously be patterned with high resolution by lipid DPN, for example, the gel-phase phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or the steroid cholesterol.

High-throughput optical quality control of lipid multilayers fabricated by dip-pen nanolithography

Surface supported phospholipid multilayers are promising materials for nanotechnology because of their tendency to self-organize, their innate biocompatibility, the possibility to encapsulate other materials within the multilayers, and the ability to control the multilayer thickness between ∼ 2 and 100 nm during fabrication. Dip-pen nanolithography (DPN) is an atomic force microscopy (AFM) based fabrication method that allows high-throughput fabrication and integration of a variety of micro- and nanostructured materials including lipid multilayers, with areal throughputs on the scale of cm(2) min(-1). Although multilayer thickness is a critical feature that determines the functionality of the lipid multilayer structures (for instance as carriers for other materials as well as optical scattering properties), reliable height characterization by AFM is slow (on the order of µm(2) min(-1)) and a bottleneck in the lithographic process. Here we describe a novel optical method to reliably measure the height of fluorescent multilayers with thicknesses above 10 nm, and widths above the optical diffraction limit based on calibrating the fluorescence intensity using one-time AFM height measurements. This allows large surface areas to be rapidly and quantitatively characterized using a standard fluorescence microscope. Importantly, different pattern dimensions (0D dots, 1D lines or 2D squares) require different calibration parameters, indicating that shape influences the optical properties of the structured lipid multilayers. This method has general implications in the systematic and high-throughput optical characterization of nanostructure-function relationships.

Strategies for patterning biomolecules with dip-pen nanolithography

Dip-pen nanolithography (DPN) is an atomic force microscopy (AFM)-based lithography technique, which has the ability to fabricate patterns with a feature size down to approximately 15 nm using both top-down and bottom-up approaches. DPN utilizes the water meniscus formed between an AFM tip and a substrate to transfer ink molecules onto surfaces. A major application of this technique is the fabrication of micro- and nano-arrays of patterned biomolecules. To achieve this goal, a variety of chemical approaches has been used. This review concisely describes the development of DPN in the past decade and presents the related chemical strategies that have been reported to fabricate biomolecular patterns with DPN at micrometer and nanometer scale, classified into direct- and indirect DPN methodologies, discussing tip-functionalization strategies as well.

Effects of probe pollutants on morphological and mechanical measurements of muscle and collagen fibers using atomic force microscopy

Because of the interaction between probes and samples, pollutants in buffer solution or in the air would easily bind to probes and make the probe polluted, which might influence the morphological and mechanical measurements with atomic force microscopy. The polluted probes might transfer the pollutants onto the samples and thus change the surface ultrastructure of samples, or collect the deviated feedback signals to make the phantasm images. The former process is irreversible even if a new probe is employed, and the latter one is a reversible process as long as changing the used/polluted probe. Effects of polluted probes on morphological and mechanical characteristics of insect flight muscle and rat tail tendon collagen I fibers had been discussed in this study, in which, we constructed a series of methods to avoid/reduce the collecting of phantasm images and deviated mechanical information, such as changing the scanning direction and scanning force, replacing the new probes, or cleaning the polluted probes.

Self-leveling two-dimensional probe arrays for Dip Pen Nanolithography

Scanning probe lithography (SPL) has witnessed a dramatic transformation with the advent of two-dimensional (2D) probe arrays. Although early work with single probes was justifiably assessed as being too slow to practically apply in a nanomanufacturing context, we have recently demonstrated throughputs up to 3x10(7) microm(2)/h--in some cases exceeding e-beam lithography--using centimeter square arrays of 55,000 tips tailored for Dip Pen Nanolithography (DPN). Parallelizing DPN has been critical because there exists a need for a lithographic process that is not only high throughput, but also high resolution (DPN has shown line widths down to 14 nm) with massive multiplexing capabilities. Although previous methods required non-trivial user manipulation to bring the 2D array level to the substrate, we now demonstrate a self-leveling fixture for NanoInk's 2D nano PrintArray. When mounted on NanoInk's NLP 2000, the 55,000 tip array can achieve a planarity of <0.1 degrees with respect to the substrate in a matter of seconds, with no user manipulation required. Additional fine-leveling routines (<2 min of user interaction) can improve this planarity to <0.002 degrees with respect to the substrate-a Z-difference of less than 600 nm across 1 cm(2) of surface area. We herein show highly homogeneous etch-resist nanostructure results patterned from a self-leveled array of DPN pens, with feature size standard deviation of <6% across a centimeter square sample. We illustrate the mechanisms and methods of the self-leveling fixture, and detail the advantages thereof. Finally, we emphasize that this methodology brings us closer to the goal of true nanomanufacturing by automating the leveling process, reducing setup time by at least a factor of 10, enhancing the ease of the overall printing process, and ultimately ensuring a more level device with subsequently homogeneous nanostructures.

Site-specific dual ink dip pen nanolithography

The ability to deposit different materials with nanoscale precision at user-specified locations is a very important attribute of dip pen nanolithography (DPN). However, the potential of DPN goes beyond simple deposition since DPN used in conjunction with lateral force microscopy (LFM) allows site-specific investigations of nanoscale properties. In this work, we use two different inks, 16-mercaptohexadecanoic acid (MHA) and 1-octadecanethiol (ODT) to show site-specific dual ink DPN enabled exclusively by our proprietary software. A diamond-dot pattern was created by using a layer-to-layer alignment (LLA) algorithm, which enables a MHA pattern (diamond) to be written concentric with another ODT (central dot) pattern. This simple demonstration of multi-ink DPN is not specific to alkanethiol ink systems, but is also applicable to other multi-material patterning, interaction, and exchange studies.

Gloss phenomena and image analysis of atomic force microscopy in molecular and cell biology

Proper sample preparation, scan setup, data collection and image analysis are key factors in successful atomic force microscopy (AFM), which can avoid gloss phenomena effectively from unreasonable manipulations or instrumental defaults. Fresh cleaved mica and newly treated glass cover were checked first as the substrates for all of the sample preparation for AFM. Then, crystals contamination from buffer was studied separately or combined with several biologic samples, and the influence of scanner, scan mode and cantilever to data collection was also discussed intensively using molecular and cellular samples. At last, images treatment and analysis with off-line software had been focused on standard and biologic samples, and artificial glosses were highly considered for their high probability. SCANNING 31: 49-58, 2009. (c) 2009 Wiley Periodicals, Inc.