Microcontact Printing Method Research Articles

Selective attachment of F-actin with controlled length for developing an intelligent nanodevice

Development of the nanodevice that myosin-coated beads “walk” on actin filaments (F-actin) tracks for in vitro nanotransportation was hindered due to the difficulty of assembling large-area well-orientated F-actin tracks on the surface. In this work, we present a selective attachment of F-actin with controlled length on a patterned surface by employing biotinylated capped protein gelsolin as intermediate anchoring bridge. A patterned streptavidin layer was formed via coupling with a biotin layer that photo-actively attached to an amine-functionalized glass surface. The patterned film was found stable and homogenous compared to that obtained by microcontact printing method, according to the profiling with fluorescence microscopy. By a secondary blocking process, non-specific binding of F-actin to the patterned surface through electrostatic adsorption can be resisted. The length variation of F-actin as a function of gelsolin concentration was also investigated, implying that F-actin is appropriately of 2.5 μm in average length once F-actin/gelsolin molar ratio is 4:1. Finally, the selective attachment of F-actin was well characterized with quantifying the number of attached F-actin per unit area in the patterned areas over that in blocked areas. The density of F-actin was estimated at c.a. 2 μm 2 per actin filament molecule so that the distance between one another actin filament is estimated as c.a. 1.41–1.97 μm. The unique properties of F-actin, e.g. well flexibility or electrical conductivity, make it feasible to lay them down and form unidirectional aligned tracks by fluidic flow or electrical field. This may open a possibility for the long-distant movement of myosin-coated beads, offering a novel discipline for the development of micro-biochip in vitro.

Facile patterning of genetically engineered M13 bacteriophage for directional growth of human fibroblast cells

We report a facile strategy for the patterning of cells that utilizes nanofibrous RGD-engineered phages in conjunction with microcontact printing methods to provide human fibroblast cells with specific biochemical and physical cues. This approach can be used for high-throughput screening assays as well as for energy and biosensor development.

Fabrication of an a-IGZO Thin Film Transistor Using Selective Deposition of Cobalt by the Self-Assembly Monolayer (SAM) Process

Interest in transparent oxide thin film transistors utilizing ZnO material has been on the rise for many years. Recently, however, IGZO has begun to draw more attention due to its higher stability and superior electric field mobility when compared to ZnO. In this work, we address an improved method for patterning an a-IGZO film using the SAM process, which employs a cost-efficient micro-contact printing method instead of the conventional lithography process. After a-IGZO film deposition on the surface of a SiO2-layered Si wafer, the wafer was illuminated with UV light; sources and drains were then patterned using n-octadecyltrichlorosilane (OTS) molecules by a printing method. Due to the low surface energy of OTS, cobalt was selectively deposited on the OTS-free a-IGZO surface. The selective deposition of cobalt electrodes was successful, as confirmed by an optical microscope. The a-IZGO TFT fabricated using the SAM process exhibited good transistor performance: electric field mobility (micro(FE)), threshold voltage (V(th)), subthreshold slope (SS) and on/off ratio were 2.1 cm2/Vs, 2.4 V, 0.35 V/dec and 2.9 x 10(6), respectively.

“Sandwich” Microcontact Printing as a Mild Route Towards Monodisperse Janus Particles with Tailored Bifunctionality

A “sandwich” microcontact printing method is reported. A monolayer of porous epoxy polymer microspheres is transformed into Janus particles with distinct functionality on each face by reaction with amine functional fluorescent dyes, carbohydrates, and magnetic nanoparticles.

Use of a gradient-generating microfluidic device to rapidly determine a suitable glucose concentration for cell viability test

We successfully determined a suitable glucose concentration for endothelial cells (ECs) using a gradient-generating microfluidic chip and a micro-stamper that were fabricated using micro-electro-mechanical systems (MEMS) technology. Our strategy was to generate a stable concentration gradient in the observation area based on a microfluidic network and micro-mixers, which produced a concentration gradient under various flow rates. The areas for cell adhesion were delineated on a glass slide with a micro-stamper using the micro-contact printing (μCP) method. We also discuss which glucose concentration gradients are suitable for cell viability test (i.e., 0–0.2%, 0.05–0.15%, and 0.06–0.17%). After examining various concentration gradients, the suitable glucose concentration for EC’s viability test was determined to range from 0.077% (4.2 mM) to 0.147% (8.16 mM). Higher or lower concentrations caused the ECs to atrophy or die. In this study, we describe a gradient-generating microfluidic chip that can be used to produce various drug concentrations for multi-concentration tests.

Effect of cell spot sizes on micropatterned cultures of rat hepatocytes

The effect of cell spot sizes (micropattern sizes) on the morphological and functional behaviors of micropatterned hepatocytes was investigated. Three similar cell chips with collagen spot sizes of 200 μm (chip 200), 500 μm (chip 500), and 800 μm (chip 800) were prepared by the microcontact printing method; the region outside the collagen spots was modified with polyethylene glycol to create the non-adhesion area. The total collagen area of these chips was kept similar. Although the morphology of rat hepatocytes on chips 500 and 800 showed an almost single-cell layer on the collagen spots similar to the random monolayer culture, hepatocytes on chip 200 gathered to the center of the collagen spot and formed multi-cell layers exhibiting a semi-spheroid form. The expression levels of cell–cell interaction molecules (cadherin and connexin-32) and cell function activities (albumin secretion and ammonia removal) were higher in the hepatocytes on chip 200 compared to those in other chip conditions and the random monolayer. These effects may relate to the boundary length obtained from spot size and spot number of collagen, and the cell chip with large boundary region may be superior in maintaining the functional expression of micropatterned hepatocytes.

Patterning of Hierarchically Aligned Single-Walled Carbon Nanotube Langmuir−Blodgett Films by Microcontact Printing

We present a patterning method for hierarchically aligned assembly of single-walled carbon nanotubes (SWNTs) using a combination of the Langmuir-Blodgett (LB) technique and soft lithography. The LB technique allows one to control the alignment and the surface density of SWNTs by adjusting surface pressure of the film at the air-water interface. The aligned SWNT Langmuir films are successfully transferred onto the polydimethylsiloxane (PDMS) or silicon substrate with unidirectional alignment, and SWNT patterns with various shapes are fabricated on silicon and flexible poly(ethylene terephthalate) (PET) substrates by contacting and peeling off the PDMS stamp from the substrates via microcontact printing or lift-up methods. The SWNT patterning technique using the combination of soft lithography and the LB method can be applied in various fields, such as flexible high-speed transistors, high-efficiency solar cells, and transparent electrodes.

Patterning Colloidal Crystals and Nanostructure Arrays by Soft Lithography

AbstractAs one of the most robust and versatile routes to fabricate ordered micro‐ and nanostructures, soft lithography has been extensively applied to pattern a variety of molecules, polymers, biomolecules, and nanomaterials. This paper provides an overview on recent developments employing soft lithography methods to pattern colloidal crystals and related nanostructure arrays. Lift‐up soft lithography and modified microcontact printing methods are applied to fabricate patterned and non‐close‐packed colloidal crystals with controllable lattice spacing and lattice structure. Combining selective etching, imprinting, and micromolding methods, these colloidal crystal arrays can be employed as templates for fabrication of nanostructure arrays. Realization of all these processes is favored by the solvent swelling, elasticity, thermodecomposition, and thermoplastic characteristics of polymer materials. Applications of these colloidal crystals and nanostructure arrays have also been explored, such as biomimetic antireflective surfaces, superhydrophobic coatings, surface‐enhanced Raman spectroscopy substrates, and so on.

Reactive Wet Stamping for Patterning of Polyelectrolyte Multilayers

Patterning of soft films, especially their bulk and not only their surface properties, presents a challenge. Several lithographic techniques do exist, but many of them are complex or limited in their ability to change properties. A few methods of patterning polyelectrolyte multilayers (PEM) have been reported, including microcontact printing and selectively growing layers on patterned self-assembled monolayers, but these all come with certain limitations. We present here the use of a modified microcontact printing method, reactive wet stamping (r-WETs), using a hydrogel stamp soaked in aqueous solutions to create patterns in PEMs. With this technique we are able to locally cause swelling and porosity changes in the PEM films and use our method to qualitatively study the evolution of the porous film morphology. This technique has the potential to locally control chemical functionality, film thickness, and mechanical properties, leading to a new ability to control film architectures both at the film surface and within the bulk of the film.

Patterning of polypyrrole using a fluoropolymer as an adsorption-protecting molecule

Patterning of the conducting polymer polypyrrole (PPy) was achieved using perfluoropolyether (PFPE) as a mask material. The fluoropolymer PFPE has both hydrophobic and oleophobic properties that allowed the generation of passivated patterns against PPy deposition. We exploited these properties to achieve the selective micropattern deposition of PPy, by simple chemical oxidation in an aqueous solution. Using a microcontact printing method, circle patterns with exposed carboxyl groups were prepared, while other region was protected by PFPE. Chemical oxidation of PPy on the patterned substrate resulted in selective deposition of PPy onto only the carboxylate-terminated regions, with little deposition on the PFPE layer. Cross-sectional analysis of the pattern revealed that the PFPE layer would form a hole-like structure around the carboxylate-terminated surfaces, with PPy deposition only in the holes. The PFPE layer had little influence on surface smoothness, compared to other self-assembled monolayers. These results suggest that PFPE can be used as a protective material for the surface modification and patterning of various materials.

Microfabrication of Patterns of Adherent Marine Bacterium Phaeobacter inhibens Using Soft Lithography and Scanning Probe Lithography

Two lithographic approaches have been explored for the microfabrication of cellular patterns based on the attachment of marine bacterium Phaeobacter inhibens strain T5. Strain T5 produces a new antibiotic that makes this bacterium potentially interesting for the pharmaceutical market and as a probiotic organism in aquacultures and in controlling biofouling. The microcontact printing (microCP) method is based on the micropatterning of self-assembled monolayers (SAMs) terminated with adhesive end groups such as CH(3) and COOH and nonadhesive groups (e.g., short oligomers of ethylene glycol (OEG)) to form micropatterned substrates for the adhesion of strain T5. The scanning probe lithographic method is based on the surface modification of OEG SAM by using a microelectrode, the probe of a scanning electrochemical microscope (SECM). Oxidizing agents (e.g., Br(2)) were electrogenerated in situ at the microelectrodes from Br(-) in aqueous solution to remove OEG SAMs locally, which allows the subsequent adsorption of bacteria. Various micropatterns of bacteria could be formed in situ on the substrate without a prefabricated template. The fabricated cellular patterns may be applied to a variety of marine biological studies that require the analysis of biofilm formation, cell-cell and cell-surface interactions, and cell-based biosensors and bioelectronics.

층상자기조립법을 이용한 나노구조체의 제조와 응용

층과 층 사이의 정전기적인력, 수소결합 또는 공유결합을 이용하여 층당 두께를 수 옹스트롱에서부터 수십 나노미터까지 제조할 수 있으며 박막의 표면 형태를 흡착시키고자 하는 물질 및 박막 후처리 공정을 통해 제어할 수 있으며 더 나아가, 삽입하는 물질의 특성에 따라 박막의 기능성을 집적화 및 다양화시킬 수 있다. 본 연구에서는 이러한 층상자기조립방법의 특성을 이용하여 반사방지막, 초소수성 필름 및 전기화학센서로의 응용가능성을 제시하였다. 반사방지막의 경우, 구형의 블록공중합체를 유리기판 위에 다층박막으로 적층시킴으로써 박막 굴절률을 1.25까지 감소시켰고 이를 통해 약 99.5%의 빛 투과도를 달성할 수 있었다. 더 나아가 바이오물질인 엔자임을 다층박막에 삽입시킬 경우, 활성 산소를 분해시키는 전기화학센서로의 제조가 가능함을 보인다. 본 연구는 본인이 이미 발표한 논문(J. Am. Chem. Soc. 128, 9935 (2006); Adv. Mater. 19, 4364 (2007); Electro. Mater. Lett. 3, 163 (2007))들을 정리하여 층상자기조립법에 관해 소개하는 논문이다. We introduce a novel and versatile approach for preparing self-assembled nanoporous multilayered films with antireflective properties. Protonated polystyrene-block-poly (4-vinylpyrine) (PS-b-P4VP) and anionic polystyrene-block-poly (acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were used as building blocks for the layer-by-layer assembly of BCM multilayer films. BCM film growth is governed by electrostatic and hydrogen-bonding interactions between the oppositely BCMs. Both film porosity and film thickness are dependent upon the charge density of the micelles, with the porosity of the film controlled by the solution pH and the molecular weight (Mw) of the constituents. PS7K-b-P4VP28K/PS2K-b-PAA8K films prepared at pH 4 (for PS7K-b-P4VP28K) and pH 6 (for PS2K-b-PAA8K) are highly nanoporous and antireflective. In contrast, PS7K-b-P4VP28K/PS2K-b-PAA8K films assembled at pH 4/4 show a relatively dense surface morphology due to the decreased charge density of PS2K-b-PAA8K. Films formed from BCMs with increased PS block and decreased hydrophilic block (P4VP or PAA) size (e.g., PS36K-b-P4VP12K/PS16K-b-PAA4K at pH 4/4) were also nanoporous. Furthermore, we demonstrate that the nanostructured electrochemical sensors based on patterning methods show the electrochemical activities. Anionic poly(styrene sulfonate) (PSS) layers were selectively and uniformly deposited onto the catalase (CAT)-coated surface using the micro-contact printing method. The pH-induced charge reversal of catalase can provide the selective deposition of consecutive PE multilayers onto patterned PSS layers by causing the electrostatic repulsion between next PE layer and catalase. Based on this patterning method, the hybrid patterned multilayers composed of platinum nanoparticles (PtNP) and catalase were prepared and then their electrochemical properties were investigated from sensing <TEX>$H_2O_2$</TEX> and NO gas. This study was based on the papers reported by our group. (J. Am. Chem. Soc. 128, 9935 (2006); Adv. Mater. 19, 4364 (2007); Electro. Mater. Lett. 3, 163 (2007)).

Self-assembly of Ag nanopowder on OTS-patterned glass

Ag ink was spontaneously patterned on glass substrate by using the surface energy difference of a pre-patterned octadecyltrichlorosilane (OTS) layer. Ag ink was confined into the hydrophilic area, where OTS layer was not formed. OTS layer was selectively transferred by micro-contact printing (μCP) method and significantly decreased surface energy. As a result, surface of glass substrate was separated as hydrophobic and hydrophilic with and without OTS layer, respectively. Ag line could be successfully patterned with the width of below 10 μm on the glass. The patterned Ag line was dense and abrupt on the edge and the thickness was about 0.25 μm. Ag film showed good adhesion on a glass substrate after anneal above 200 °C. The minimum resistivity was about 4 μΩ cm.

16.3: Polymer Network LCD Driven by Printed OTFTs on a Plastic Substrate

AbstractWe have prepared organic thin‐film‐transistor array with large area and high precision, 6 inch diameter and 200 ppi, by using microcontact printing method. And we have succeeded in driving a polymer network liquid crystal display (PNLCD).

Reversal μCP using hard stamps

In this work, we present a new method of Micro-Contact Printing (μCP) which we call reversal μCP using hard stamps which can be used for the fabrication of different structures like negative index materials, e.g., split ring resonators (SRRs), dots and squares made of gold. Typically soft stamps made of PDMS (polydimethylsiloxane) inked with thiols are used for μCP. The softness of the stamp material entails a lot of problems like deformation of the structures, sagging and pairing of the protruding features and reliability of the process. We use hard stamps which are spin coated with a thiol solution so that the thioles stay in the recessed areas of the stamp. In the following μCP process an EVG ®620 is used to bring the stamp and substrate into contact so that the thiols on the stamp diffuse and bind to the gold surface and serve as an etch mask for succeeding wet chemical etching. Using this method overcomes the disadvantage of a soft stamp material. Smallest feature sizes down to 100 nm are shown.

Site-Selective Deposition of Silver Nanoparticles Using Modified Silver Mirror Reaction and Surface Modification by Self-Assembled Monolayer

We developed a set of processes for depositing silver nanoparticles on a glass substrate that involves using a modifi ed silver mirror reaction, whereby dispersants are added to a conventional silver mirror solution. The whole set of processes was completed in 15 min in a nonvacuum environment, except the cleaning processes with oxygen plasma at 20 Pa, and at a low cost. The processes can be applied to the siteselective deposition of silver nanoparticles by modifying the surface characteristics of glass substrates using a self-assembled monolayer (SAM). We used a microcontact printing method that incorporated a non-photolithographic top-down process to pattern a SAM. The proposed processes are readily applicable to promising applications of metal nanoparticles, such as ultrasensitive sensors and catalysts.

A Negative-Type Photosensitive Poly(3-hexylthiophene) with Cross-Linker and Photoacid Generator

-Conjugated polymers ( CPs) have received great attention for their potential application to electronic devices derived from their semiconductive property. Among them, poly(3-hexylthiophene) (P3HT) is of great interest because of easy preparation, high charge mobility, and high processability. Based on these benefits, P3HT has been used in a wide variety of electronic devices, such as organic solar cells, organic fieldeffect transistors (OFETs), and sensors. Generally, a micro-patterned P3HT is fabricated by the microcontact printing (mCP) method with a poly(dimethylsiloxane) stamp. However, this method requires complicated operation resulting in low productivity. To overcome this problem, direct patterning onto polythiophenes based on a photolithographic method is highly required. Direct patterning onto P3HT was demonstrated when an exposed area became insoluble due to crosslinking of an alkyl chain under irradiation with UV light. However, the cross-linking of P3HT by irradiation required a huge exposure dose. Recently, efficient patterning methods of polythiophene derivatives were reported. These methods require multi-step reactions for the preparation of matrix polymers. In this paper we propose a new, simple patterning process of P3HT by combining hexamethoxymethylmelamine (CYMEL) as a cross-linker and diphenyliodonium-9,10-dimethoxyanthracene-2-sulfonate (DIAS) as a photoacid generator (PAG). The structures of the chemicals are shown in Figure 1. P3HT was easily synthesized by oxidation polymerization and a photosensitive P3HT was prepared from a mixture of each component. In the exposed area, the aromatic rings of P3HT react with a carbocation formed from CYMEL and cross-link with each other in the presence of acids from DIAS by irradiation. This eletrophilic substitution reaction is novel to the best of our knowledge, although the similar reaction based on arylene compounds has been reported. High-resolution patterns of CPs are expected from this approach.

Preparation and atomic force microscopy observation of lipid membranes on micro-patterned self-assembled monolayers

Using micro-contact printing (μCP) method, lipid membranes were deposited on the surface of micro-patterned self-assembled monolayers. Height and phase mode atomic force microscopy (AFM) images showed that the resulting deposited films were flat and that a micro-patterned composite bilayer system was constructed. It was also shown that the use of crystalline phase lipid membrane is effective for the preparation of the micro-patterned composite bilayer system of membranes with flat surface.

Nanoscale observation of local bound charges of patterned protein arrays by scanning forcemicroscopy

A protein patterned surface using micro-contact printing methods has been investigated byscanning force microscopy. Electrostatic force microscopy (EFM) was utilized for imaging thetopography and detecting the electrical properties such as the local bound charge distributionof the patterned proteins. It was found that the patterned IgG proteins are arranged down to1 µm, andthe 90° rotation of patterned anti-IgG proteins was successfully undertaken. Through theestimation of the effective areas, it was possible to determine the local boundcharges of patterned proteins which have opposite electrostatic force behaviors.Moreover, we studied the binding probability between IgG and anti-IgG in a1 µm2 MIMIC system by topographic and electrostatic signals for applicable label-free detections.We showed that the patterned proteins can be used for immunoassay of proteins on thefunctional substrate, and that they can also be used for bioelectronics device application,indicating distinct advantages with regard to accuracy and a label-free detection.

Distinct Chemical Contrast in Adhesion Force Images of Hydrophobic–Hydrophilic Patterned Surfaces Using Multiwalled Carbon Nanotube Probe Tips

In this paper, we describe a fabrication procedure for large-diameter carbon nanotube probe tips (CNT tips) for atomic force microscopy, the tip-end chemistry of the CNT tips, and their advantage drawn from the study of adhesion force imaging in an ambient atmosphere on a patterned hydrophobic and hydrophilic self-assembled monolayer, which has been prepared by a microcontact printing method. Force titration measurements in phosphate buffer solutions reveal that the CNT tip has retained carboxyl groups at its end. In adhesion force imaging, a distinct chemical contrast is obtained for the patterned surfaces as compared to a case using a silicon nitride tip. The origin of the distinct contrast is discussed in terms of the tip-end chemistry featured by carboxyl groups and a possible weakening of capillary forces of water caused at around the tip–sample interface because of the intrinsically hydrophobic nature of CNTs.