Pen Lithography Research Articles

Large-Scale Direct Patterning of Aligned Single-Walled Carbon Nanotube Arrays Using Dip-Pen Nanolithography

The strength of dip-pen nanolithography (DPN) is the ability to create nano- or microarrays of organic compounds and nanomaterials in a nondestructive and direct-write manner. However, transporting large-sized ink materials, such as carbon nanotubes (CNTs), has been a significant challenge. We report a direct-write patterning of aligned single-walled carbon nanotube (SWNT) arrays on silicon oxide using DPN. The patterned SWNT arrays show a high degree of alignment and controllable width ranging from 2 μm down to 8 nm. Furthermore, field-effect transistors based on these SWNT arrays show p-type characteristic. High-throughput patterning of the aligned SWNTs over a large area was also achieved via polymer pen lithography (PPL). The reported technique will further expand the application of SWNTs to diverse nanoelectronic devices.

Click-Chemistry Based Allergen Arrays Generated by Polymer Pen Lithography for Mast Cell Activation Studies.

The profiling of allergic responses is a powerful tool in biomedical research and in judging therapeutic outcome in patients suffering from allergy. Novel insights into the signaling cascades and easier readouts can be achieved by shifting activation studies of bulk immune cells to the single cell level on patterned surfaces. The functionality of dinitrophenol (DNP) as a hapten in the induction of allergic reactions has allowed the activation process of single mast cells seeded on patterned surfaces to be studied following treatment with allergen specific Immunoglobulin E antibodies. Here, a click-chemistry approach is applied in combination with polymer pen lithography (PPL) to pattern DNP-azide on alkyne-terminated surfaces to generate arrays of allergen. The large area functionalization offered by PPL allows an easy incorporation of such arrays into microfluidic chips. In such a setup, easy handling of cell suspension, incubation process, and read-out by fluorescence microscopy will allow immune cell activation screening to be easily adapted for diagnostics and biomedical research.

Fabrication of Highly Transparent and Flexible NanoMesh Electrode via Self‐assembly of Ultrathin Gold Nanowires

Transparent electrodes simultaneously require high electrical conductivity and high optical transparency, which have been achieved with mesh metal structures. However, most currently fabricated micro‐ and nanoelectronic devices are produced via top‐down lithography methods. Here, a bottom‐up self‐assembly approach to fabricate mesh electrode using ultrathin gold nanowires (AuNWs) at the air/water interface is reported. Slow partial ligand removal during the aging process is the key for the formation of such self‐assembled mesh structures. The resulting mesh film has a typical mesh pore size of 8–52 μm, with a sheet resistance of ≈40 times smaller than our previously reported nonmeshed AuNWs electrodes under similar optical transmittance. Our self‐assembled mesh electrodes are mechanically flexible, easily transferrable to a variety of substrates, and also patternable by marker pen lithography or cutting machine lithography, and washable, and can be directly used for touch screen and flexible interconnects for light‐emitting devices. The entire fabrication process is under ambient conditions without the need for any special equipment. These attributes indicate the potential applications of self‐assembled gold mesh electrodes in flexible solar cells, touch screen displays, and wearable electronics.

Marker Pen Lithography for Flexible and Curvilinear on-Chip Energy Storage

On-Chip energy storage is currently on high demand as its potentiality for compatible integration with flexible and miniaturized functional electronic devices. Conventional microfabrication has been the widely employed technique in fabricating interdigitated microsupercapacitor devices in a reliable manner. However, developing unconventional lithography techniques can be attractive interms of simplicity with minimal sophistication while not compromising the performance. Here, we propose a simple and versatile strategy to fabricate on-chip microsupercapacitors (MSCs) employing hand-written sacrificial marker ink patterns, both in lift-off and etching modes. As a prototype, this technique is demonstrated for the fabrication of conducting polymer MSCs involving poly(3,4-ethylenedioxythiophene), polyaniline and metal oxide electrode materials. Typical values of energy density in the range of 5-11 mWh/cm3 at power densities of 1-6 W/cm3 are achieved, that are comparable to thin film batteries and superior to the carbon and metal oxide based microsupercapacitors reported in the literature. Fabrication of microsupercapacitor devices on curved surfaces and multi-stack designs are additional assets of this technique. This innovative strategy may be broadened for scalable fabrication of a wide variety of on-chip energy storage devices.

Hard Transparent Arrays for Polymer Pen Lithography.

Patterning nanoscale features across macroscopic areas is challenging due to the vast range of length scales that must be addressed. With polymer pen lithography, arrays of thousands of elastomeric pyramidal pens can be used to write features across centimeter-scales, but deformation of the soft pens limits resolution and minimum feature pitch, especially with polymeric inks. Here, we show that by coating polymer pen arrays with a ∼175 nm silica layer, the resulting hard transparent arrays exhibit a force-independent contact area that improves their patterning capability by reducing the minimum feature size (∼40 nm), minimum feature pitch (<200 nm for polymers), and pen to pen variation. With these new arrays, patterns with as many as 5.9 billion features in a 14.5 cm(2) area were written using a four hundred thousand pyramid pen array. Furthermore, a new method is demonstrated for patterning macroscopic feature size gradients that vary in feature diameter by a factor of 4. Ultimately, this form of polymer pen lithography allows for patterning with the resolution of dip-pen nanolithography across centimeter scales using simple and inexpensive pen arrays. The high resolution and density afforded by this technique position it as a broad-based discovery tool for the field of nanocombinatorics.

Liquid-Phase Beam Pen Lithography.

Beam pen lithography (BPL) in the liquid phase is evaluated. The effect of tip-substrate gap and aperture size on patterning performance is systematically investigated. As a proof-of-concept experiment, nanoarrays of nucleotides are synthesized using BPL in an organic medium, pointing toward the potential of using liquid phase BPL to perform localized photochemical reactions that require a liquid medium.

Ink transport modelling in Dip-Pen Nanolithography and Polymer Pen Lithography

AbstractDip-pen nanolithography (DPN) and Polymer pen lithography (PPL) are powerful lithography techniques being able to pattern a wide range of inks. Transport and surface spreading depend on the ink physicochemical properties, defining its diffusive and fluid character. Structure assembly on surface arises from a balance between the entanglement of the ink itself and the interaction with the substrate. According to the transport characteristics, different models have been proposed. In this article we review the common types of inks employed for patterning, the particular physicochemical characteristics that make them flow following different dynamics as well as the corresponding transport mechanisms and models that describe them.

Multi-color polymer pen lithography for oligonucleotide arrays.

Multi-color patterning by polymer pen lithography (PPL) was used to fabricate covalently immobilized fluorophore and oligonucleotide arrays with up to five different components. The oligonucleotide arrays offer a virtually unlimited inventory of orthogonal binding tags for self-assembly of proteins as demonstrated by use of the arrays to monitor cell-protein interactions of MCF7 cells.

Microfluidic Bioreactors for Cellular Microarrays

Living cell microarrays have been combined with microfluidic bioreactors, which provide multiple advantages for multiplex dynamic analyses and high-throughput screening. In the last decade, many developments in this new field have been introduced. The technology has evolved from fixed cell analysis towards living single-cell dynamic systems’ biology and high content analyses. The aim of this review is to provide an updated overview of the developments of living cellular microarrays in microfluidic bioreactors. Cell arrays in microfluidic bioreactors constructed with adherent mammalian cells are compared to non-adherent cells (mainly microbial cells). An overview is given on the design and construction of these microfluidic devices with a particular focus on cell patterning techniques. Cell patterning on adhesive micropatterns using techniques such as microcontact printing, microfluidic patterning, dip-pen nanolithography and polymer pen lithography as well as photo-patterning and laser-patterning strategies are discussed. Additionally, developments in mechanical cell patterning methods and robotic cell printing are reviewed. Two-dimensional (2D) as well as recently developed 3D cell arraying are discussed. Finally, cell array microfluidic setups and operation for single-cell types versus cell population variants are illustrated and compared on the basis of some illustrative examples in the field of drug screening, cytotoxicity evaluation, and basic cellular and microbiology research.

Flexible Lithography: Marker Pen Lithography for Flexible and Curvilinear On‐Chip Energy Storage (Adv. Funct. Mater. 31/2015)

Flexible Lithography: Marker Pen Lithography for Flexible and Curvilinear On‐Chip Energy Storage (Adv. Funct. Mater. 31/2015)

Marker Pen Lithography for Flexible and Curvilinear On‐Chip Energy Storage

On‐chip energy storage using microsupercapacitors can serve the dual role of supplementing batteries for pulse power delivery, and replacement of bulky electrolytic capacitors in ac‐line filtering applications. Despite complexity and processing costs, microfabrication techniques are being employed in fabricating a great variety of microsupercapacitor devices. Here, a simple, cost‐effective, and versatile strategy is proposed to fabricate flexible and curvilinear microsupercapacitors (MSCs). The protocol involves writing sacrificial ink patterns using commercial marker pens on rigid, flexible, and curvilinear substrates. It is shown that this process can be used in both lift‐off and etching modes, and the possibility of multistack design of active materials using simple pen lithography is demonstrated. As a prototype, this method is used to produce conducting polymer MSCs involving both poly(3,4‐ethylenedioxythiophene), polyaniline, and metal oxide (MnO2) electrode materials. Typical values of energy density in the range of 5–11 mWh cm−3 at power densities of 1–6 W cm−3 are achieved, which is comparable to thin film batteries and superior to the carbon and metal oxide based microsupercapacitors reported in the literature. The simplicity and broad scope of this innovative strategy can open up new avenues for easy and scalable fabrication of a wide variety of on‐chip energy storage devices.

"Multipoint Force Feedback" Leveling of Massively Parallel Tip Arrays in Scanning Probe Lithography.

Nanoscale patterning with massively parallel 2D array tips is of significant interest in scanning probe lithography. A challenging task for tip-based large area nanolithography is maintaining parallel tip arrays at the same contact point with a sample substrate in order to pattern a uniform array. Here, polymer pen lithography is demonstrated with a novel leveling method to account for the magnitude and direction of the total applied force of tip arrays by a multipoint force sensing structure integrated into the tip holder. This high-precision approach results in a 0.001° slope of feature edge length variation over 1 cm wide tip arrays. The position sensitive leveling operates in a fully automated manner and is applicable to recently developed scanning probe lithography techniques of various kinds which can enable "desktop nanofabrication."

Beam pen lithography based on focused laser diode beam with single microlens fabricated by excimer laser.

A method is proposed to minimize the focused spot size of an elliptically-diverging laser diode beam by means of a circular aperture and a single plano-convex aspherical microlens. The proposed microlens is fabricated using an excimer laser dragging method and has two different profiles in the x- and y-axis directions. The focused spot size of the beam is examined both numerically and experimentally. The feasibility of the proposed approach for beam pen lithography applications is demonstrated by patterning dotted, straight-line and spiral features on a photo resist layer followed by thin gold layer deposition and metal lift-off. The minimum feature size for dotted pattern is around 2.57 μm, while the minimum line-widths for straight-line and spiral pattern are 3.05 μm and 4.35 μm, respectively. Thus, the technique can be applied to write any arbitrary pattern for high-resolution lithography.

Patterning of Quantum Dots by Dip-Pen and Polymer Pen Nanolithography

AbstractWe present a direct way of patterning CdSe/ ZnS quantum dots by dip-pen nanolithography and polymer pen lithography. Mixtures of cholesterol and phospholipid 1,2-dioleoyl-sn-glycero-3 phosphocholine serve as biocompatible carrier inks to facilitate the transfer of quantum dots from the tips to the surface during lithography. While dip-pen nanolithography of quantum dots can be used to achieve higher resolution and smaller pattern features (approximately 1 μm), polymer pen lithography is able to address intermediate pattern scales in the low micrometre range. This allows us to combine the advantages of micro contact printing in large area and massive parallel patterning, with the added flexibility in pattern design inherent in the DPN technique.

Patterning via optical saturable transitions--fabrication and characterization.

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical Saturable Transitions (POST). In this technique the chemical properties of organic photochromic molecules that undergo single-photon reactions are exploited, enabling rapid top-down nanopatterning over large areas at low light intensities, thereby, allowing for the circumvention of the far-field diffraction barrier.(4) Simple, cost-effective, high throughput and resolution alternatives to nanopatterning are being explored, such as, two-photon polymerization(5,6), beam pen lithography (BPL)(7), scanning electron beam lithography (SEBL), and focused ion beam (FIB) patterning. However, multi-photon approaches require high light intensities, which limit their potential for high throughput and offer low image contrast. Although, electron and ion beam lithographic processes offer increased resolution, the serial nature of the process is limited to slow writing speeds, which also prevents patterning of features over large areas. Beam-pen lithography is an approach towards parallel near-field optical lithography. However, the gap between the source of the beam and the surface of the photoresist needs to be controlled extremely precisely for good pattern uniformity and this is very challenging to accomplish for large arrays of beams. Patterning via Optical Saturable Transitions (POST) is an alternative optical nanopatterning technique for patterning sub-wavelength features(1-3). Since this technique uses single photons instead of electrons, it is extremely fast and does not require high light intensities(1-3), opening the door to massive parallelization.

High throughput, high resolution enzymatic lithography process: effect of crystallite size, moisture, and enzyme concentration.

By bringing enzymes into contact with predefined regions of a surface, a polymer film can be selectively degraded to form desired patterns that find a variety of applications in biotechnology and electronics. This so-called "enzymatic lithography" is an environmentally friendly process as it does not require actinic radiation or synthetic chemicals to develop the patterns. A significant challenge to using enzymatic lithography has been the need to restrict the mobility of the enzyme in order to maintain control of feature sizes. Previous approaches have resulted in low throughput and were limited to polymer films only a few nanometers thick. In this paper, we demonstrate an enzymatic lithography system based on Candida antartica lipase B (CALB) and poly(ε-caprolactone) (PCL) that can resolve fine-scale features, (<1 μm across) in thick (0.1-2.0 μm) polymer films. A Polymer Pen Lithography (PPL) tool was developed to deposit an aqueous solution of CALB onto a spin-cast PCL film. Immobilization of the enzyme on the polymer surface was monitored using fluorescence microscopy by labeling CALB with FITC. The crystallite size in the PCL films was systematically varied; small crystallites resulted in significantly faster etch rates (20 nm/min) and the ability to resolve smaller features (as fine as 1 μm). The effect of printing conditions and relative humidity during incubation is also presented. Patterns formed in the PCL film were transferred to an underlying copper foil demonstrating a "Green" approach to the fabrication of printed circuit boards.

Colloidal pen lithography.

Colloidal pen lithography, a low-cost, high-throughput scanning probe contact printing method, has been developed, which is based on self-assembled colloidal arrays embedded in a soft elastomeric stamp. Patterned protein arrays are demonstrated using this method, with a feature size ranging from 100 nm to several micrometers. A brief study into the specificity reorganization of protein gives evidence for the feasibility of this method for writing protein chips.

Nanoscale resistive switching memory device composed of NiO nanodot and graphene nanoribbon nanogap electrodes

We report a nanoscale resistive random access memory (RRAM) device consisting of a NiO nanodot and graphene nanoribbon (GNR) nanogap electrodes. The GNR nanogap was established by an electroburning process induced by applying voltage ramp stress between the two ends of the GNR. A NiO nanodot was then deposited between the nanogapped GNR electrodes by an elaborately controllable dip pen lithography method using a nickel carbonate [Ni2(CO3)(OH)2] solution. The nanoscale GNR/NiO/GNR RRAM device exhibited reliable unipolar resistive switching characteristics with low SET/RESET voltages and currents, which might be the result of its miniaturized size and well-defined Ohmic contacts between the NiO nanodot and GNR electrodes.

Conductivity enhancement of stretchable PEDOT:PSS nanowire interconnect fabricated by fountain-pen lithography

We demonstrated an effective method for producing poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) arched nanowires, which are used as stretchable interconnects. Three-dimensional PEDOT:PSS arched wires with high stretchability were fabricated by a simple, inexpensive fountain pen lithography (FPL) technique. The grown PEDOT:PSS wires showed superior stretchable behavior: the wire conductance was only decreased by less than 0.5% when the horizontal strain increased by up to 80%. Using a steaming treatment with a co-solvent of ethanol and water, the wire conductivity was enhanced from 2 S m−1 to 1.57 × 103 S m−1, without undesirable deformation or collapse of the wires. The conductivity enhancement is attributed to enhancement in the inter-PEDOT chain charge transport, resulting from a conformational change of PEDOT and PSS chains by sequential solvation of PEDOT and PSS chains near the wire surface.

Apertureless beam pen lithography based on fully metal-coated polyurethane-acrylate (PUA) pyramidal microstructure array.

This work demonstrates a form of arrayed transmitting apertureless near-field photolithography, called apertureless beam pen lithography. An array of fully chromium-coated polyurethane acrylate (PUA) pyramidal microstructures was illuminated by a traditional Ultraviolet (UV) lamp to generate an array of massive UV beam pens for realizing apertureless beam pen lithography. Experimental results reveal that significant UV energy can pass through the apex of a fully metal-coated PUA pyramid even though the thickness of the metallic coating exceeded the penetration depth. The patterned photoresist profiles were 117 nm deep and the full-width-at-half-magnitude (FWHM) was 180 nm when the exposure dosage was 54 mJ/cm(2) and the wavelength was 365 nm. Both depth and FWHM increased with exposure dosage, implying that the profiles depended on exposure dosage rather than on physical imprinting. With the adjustment of the thickness of the photoresist layer and the exposure parameters, the lift-off process yields arrayed metal dots with a diameter of 300 nm. Finite-element simulation of the intensity distribution near the apex of the pyramid and within the photoresist layer was carried out to reveal that the energy concentration within the pyramids is increased by approximately an order of magnitude, significantly enhancing the UV energy that passes through the fully metal-coated apex. The contrast curve model of the photoresist was used to calculate the patterned photoresist profiles for various energies. Experimental results, theoretical analysis and potential improvements of the method are presented.