Microcontact Printing Method Research Articles

Deposition behaviors and patterning of TiO 2 thin films on different SAMs surfaces from titanium sulfate aqueous solution

Patterning of TiO 2 thin films was successfully obtained on different self-assembled monolayers (SAMs) in aqueous solution by micro-contact printing (μCP) method. The substrates were immersed in an aqueous solution containing titanium sulfate (Ti(SO 4) 2) and hydrogen peroxide for deposition at 80 °C. The growth rates on various surfaces were as follows: sulfonic (–SO 3H) > amino (–NH 2) > methyl (–CH 3) > hydroxyl (–OH). According to the XPS results, SAMs with the terminal groups of –SO 3H and –NH 2 were favorable for the deposition. The TiO 2 film deposited on the SAM with the terminal group of –CH 3 could be easily peeled off. Clearly, TiO 2 patterns were obtained on the prepatterned surfaces of –SO 3H/–CH 3 and –NH 2/–CH 3 SAMs. The deposition mechanism might be relevant to electrostatic interaction, Stern layer, lone pair electrons and Van der Vaals forces. The TiO 2 film was anatase after annealing at 500 °C and comprised particles with an average diameter of ca. 10 nm.

Study of selective deposition of TaN thin films on OTS patterned Si(100) substrates

Cubic TaN thin films have been selectively deposited on Si(100) substrates in the temperature range of 400 - 500 °C by combination of micro-contact printing (μCP) and metalorganic chemical vapour deposition (MOCVD) methods. The patterned Si(100) substrates were initially fabricated with the self-assembled monolayers (SAMs) using an organic molecule of octadecyltrichlorosilane (OTS) by μCP method. Ta(N(MeEt))3(NtBu) and NH3 were used for the growth of TaN thin film. For a selective growth study, we characterized the as-grown films with optical microscopy (OM), micro-Raman spectrometer and atomic force microscopy (AFM). In the beginning of film deposition TaN thin film preferred to grow on silicon surface area rather than OTS printed area due to hydrophilicity of silicon surface, however, the selectivity of TaN thin film deposition was depended on the deposition time in the deposition temperature range.

Application to Mechanically Stable Flexible Liquid Crystal Displays Using Surface Induced Anisotropic Phase Separation

We investigated the effect of surface wetting on the 2-dimensional anisotropic phase separation. The surface conditions were spatially modulated by laminating several types of alignment materials on the ITO substrate in a periodic square pattern using micro-contact printing methods. 2-dimensional phase separation was obtained without/with UV irradiation and the relative wettability of LC and polymer on alignment layer and ITO surface determined the diffusion direction of each material during phase separation. Furthermore the polymerized wall structures are different for different LC monomer mixing ratio. This technology can be applied to flexible liquid displays.

Preparation and Characterization of Micro-patterned Hybrid Bilayer Membrane

Bio-mimetic membrane, hybrid bilayer membrane (HBM), was prepared on solid substrate using Self-Assemly and Vesicle Fusion (VF) methods. The HBM films were composed of self-assembled monolayer (SAM) of alkanthiol and phosphatidylcholine. Micro-patterned composite membranes of lipids were made on solid substrate with micro-patterned SAM by a micro-contact printing (CP) method. AFM and Kelvin probe force microscopy (KFM) observation was conducted under height and phase modes, and surface potential, respectively. The height imaging showed that the flat surface was formed by the CP method. Furthermore, the phase imaging and surface potential imaging revealed the micro-pattern formation. These results show that an artificial bilayer was successfully prepared on the surface without SAM, and lipid monolayer on the surface with SAM. These results were supported by the cyclic-voltammetry (CV) and surface potential.

Selective deposition of metal oxide thin films on Si(100) surfaces by combination of metal-organic chemical vapour deposition and microcontact printing methods

TiO2, ZrO2 and HfO2 thin films have been deposited selectively using metal-organic chemical vapour deposition (MOCVD) technique with various single molecular precursors on Si(100) substrates which were patterned with octadecyltrichlorosilane (OTS) applied by microcontact printing (μ CP). Titanium (IV) isopropoxide [Ti(OiPr)4], bis-isopropoxy-bis-tertiarybutyl- acetoacetate zirconium [Zr(OiPr)2 (tbaoac)2 ] and hafnium tert-butoxide [Hf(OtBu)4 ] were used for titanium dioxide (TiO2), hafnium and zirconium oxide (ZrO2 and HfO2) thin films, respectively. Selective depositions were successfully carried out in a home-made MOCVD system. All the deposited thin films had higher reactivity on bare silicon surfaces than OTS self-assembled monolayers (SAMs) deposited area. However, there was slightly different selective growth tendency on OTS deposited Si(100) surfaces. The selectivity tendency of the deposited thin films was revealed in order of TiO2, HfO2 and ZrO2. This tendency was explained by means of film growth rate, structures and molecular weight of precursors and acidity of transition metal of precursors.

Microcontact printed diaphorase monolayer on glass characterized by atomic force microscopy and scanning electrochemical microscopy

Micropatterns of diaphorase (Dp) were fabricated on glass substrates by the microcontact printing (μCP) method and characterized with atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM). AFM images of the printed samples revealed that the mean height of the Dp patterns was 3–5 nm, indicating the formation of a monolayer pattern. The Dp molecules on the surface organized themselves into two-dimensional arrays. We used two kinds of inking solutions: Dp–phosphate buffer solution (PBS) (pH 7.0) and Dp–PBS (pH 7.0) with glutaraldehyde (GA, 1% v/v) as a cross-linking reagent. Although the AFM imaging showed high-quality Dp monolayer patterns in both cases, SECM measurements indicated that the enzymatic activity of Dp was almost lost when Dp–PBS with GA was used as the inking solution, whereas clear enzymatic activity was found when Dp–PBS was used.

Micropatterning of Electrodes by Microcontact Printing Method and Application to Thin Film Transistor Devices

Electrode micropatterning without etching was successfully achieved by the microcontact printing (µCP) method. We used a conductive polymer poly(3,4-ethylenedioxythiophene)/poly(4-stylenesulfonate) (PEDOT/PSS) as an electrode material. We controlled the surface free energy of poly(dimethylsiloxane) (PDMS) by exposure to vacuum ultraviolet (VUV) light with a wavelength of 172 nm using an excimer lamp. Consequently, we established an inking technique for PEDOT/PSS aqueous dispersion on a PDMS elastomer stamp. The micropatterns of PEDOT/PSS thin films of 1 µm width were fabricated by transferring the PEDOT/PSS aqueous dispersion on the PDMS elastomer stamp to another substrate by the µCP method. Furthermore, we fabricated top contact (TC) organic thin film transistors (OTFTs) with PEDOT/PSS as source and drain electrodes. We demonstrated the successful operation of the fabricated OTFTs with a channel length of 5 µm and an electrode width of 8 µm. Results show that the µCP method is promising for application to various devices that require micropatterning.

Selective MOCVD of titanium oxide and zirconium oxide thin films using single molecular precursors on Si(1 0 0) substrates

Titanium oxide (TiO 2) and zirconium oxide (ZrO 2) thin films have been deposited on modified Si(1 0 0) substrates selectively by metal-organic chemical vapor deposition (MOCVD) method using new single molecular precursor of [M(O i Pr) 2(tbaoac) 2] (M=Ti, Zr; tbaoac=tertiarybutyl-acetoacetate). For changing the characteristic of the Si(1 0 0) surface, micro-contact printing (μCP) method was adapted to make self-assembled monolayers (SAMs) using an octadecyltrichlorosilane (OTS) organic molecule which has –CH 3 terminal group. The single molecular precursors were prepared using metal (Ti, Zr) isopropoxide and tert-butylacetoacetate (tbaoacH) by modifying standard synthetic procedures. Selective depositions of TiO 2 and ZrO 2 were achieved in a home-built horizontal MOCVD reactor in the temperature range of 300–500 °C and deposition pressure of 1×10 −3–3×10 −2 Torr. N 2 gas (5 sccm) was used as a carrier gas during film depositions. TiO 2 and ZrO 2 thin films were able to deposit on the hydrophilic area selectively. The difference in surface characteristics (hydrophobic/hydrophilic) between the OTS SAMs area and the SiO 2 or Si–OH layer on the Si(1 0 0) substrate led to the site-selectivity of oxide thin film growth.

Selective growth of iron oxide thin films using the combined method of metal-organic chemical vapor deposition and microcontact printing

The authors have carried out the selective deposition of magnetite iron oxide (Fe3O4) thin films with about 50nm thickness on Si(100) surfaces which were patterned by octadecyltrichlorosilane (OTS) using microcontact printing (μCP) method. The μCP method showed that hydrophobic patterns with microdimension were able to be formed on hydrophilic area such as silicon surface. Iron oxide thin films were deposited on the Si(100) substrates by thermal metal-organic chemical vapor deposition (MOCVD) method using single molecular organometallic precursor of iron pentacarbonly [Fe(CO)5] with high purity (99.999%) oxygen gas. The deposition was performed in the range of 250–350°C substrate temperature for 2–10min under 1×10−2Torr in a homemade MOCVD system. In order to check the selectivity of as-deposited thin films optical microscopy, scanning electron microscopy, and atomic force microscopy analyses were performed. To confirm the crystallinity of deposited thin films, x-ray diffraction patterns and micro-Raman were studied. Also energy dispersive x-ray and x-ray photoelectron spectrometry results showed the composition of the as-grown iron oxide thin films. By means of these results, the authors can suggest the selective deposition mechanisms and tendencies of iron oxide thin films onto the OTS patterned Si(100) surfaces.

Fabrication and Micropatterning of Conducting Polymer Nano-Films for Electronic Displays

We investigate the electrical conductive poly(3,4-ethylenedioxythiophene) (PEDOT) nanofilms and micropatterning prepared by vapor-phase polymerization method using self-assembling teacnique. The thin conductive films were uniformly fabricated between 20 and 100 nm, there surface resistance wasenhanced until to 102 /square, and the light-transmittance were also increased as up to 95 %. We report a fabrication of electrically conducting PEDOT pattern on a electrically insulating substrate using a microcontact printing method. Then, patterns are successfully obtained with line widths down to 3 .

Site selective micro-patterned rutile TiO 2 film through a seed layer deposition

Micro-patterned films obtained from micro-contact printing (μCP) method are often challenged by site selectivity limitation. For applications site-selectivity requires improvements. In this paper a site-selective deposition of the rutile TiO 2 thin films on patterned SnO 2 film, which was formed on the patterned octadecyltrichlorosilane (OTS) SAMs through μCP is described. The depositions proceeded in an environmentally friendly aqueous solution (SnCl 4 and peroxotitanium acidic solution) at a lower temperature (80 °C). It is shown that the OTS SAMs has a good selectivity deposition for SnO 2 particles, which was mainly dominated by the heterogeneous nucleation mechanism. The SnO 2 layer had a structure-directing effect for growth of the rutile TiO 2, which was usually formed above 600 °C. The patterned films were characterized by a variety of techniques, including ellipsometry, optical microscopy, SEM, AFM, XPS, and DLS to determine the thicknesses, topologies, microstructures, chemical compositions of the films, particle sizes and zeta potentials of the titanium particles.

Surface-Grafting of Polyglutamate on Si Wafer Using Micro Contact Printing

Surface-grafting of poly(γ-benzyl-α, L-glutamate) (PBLG) on the 3-aminopropyl triethoxysilane (APS) pretreated silicone substrates was conducted by the monomer, γ-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) which was synthesized through the phosgenation procedure. PBLG, one of liquid crystalline polymers, micro-patterns were fabricated by micro-contact printing (μCP) and surface-grafting method. Then, PBLG patterns were characterized with electron microscopy (SEM), atomic force microscopy (AFM), infrared spectroscopy (FT-IR), Raman spectroscopy and polarized optical microscopy. α-helix conformation of PBLG was dominated on the patterned surface which was confirmed by FT-IR spectroscopy. From the polarizing microscope images, lyotropic liquid crystalline properties of the patterned surfaces were observed. The SEM and AFM images show that the height of PBLG patterns was 300 nm and line width was 15 μm. The interval between lines was about 5 μm.

A Novel Method for Fabricating Chemically Defined Patterns as Standard Samples for Surface Chemical Imaging

Abstract To produce micrometer scale chemical patterns, a new method is developed. In this method, silica beads are used as a mask of an underneath substrate. We produced the patterns with CH3- and COOH-terminated regions and compared them with similar patterns prepared by the microcontact printing (μCP) method. The advantage of this technique over μCP is that monolayers with higher chemical purity can be patterned: thus it provides ideal and well-defined standard samples for surface chemical imaging such as chemical force microscopy.

Ordered Silica Microspheres Unsymmetrically Coated with Ag Nanoparticles, and Ag‐Nanoparticle‐Doped Polymer Voids Fabricated by Microcontact Printing and Chemical Reduction

Colloid particles usually have charges or nanoparticles uniformly distributed over their surface. The design and preparation of unsymmetrically coated colloid particles have been a long-standing challenge in surface and colloid science. These particles would remedy some limitations of their spherical counterparts for potential applications in modeling the behaviors of highly irregular colloids that are more commonly found in industrial products, in the fields that require lattices with lower symmetries and high complexities, and as potential building blocks in generating three-dimensional (3D) photonic crystals with complete bandgaps. However, due to the thermodynamic limitations of the reaction, there have been only a few reports about the preparation of microspheres unsymmetrically coated with nanoparticles, which typically involve Langmuir–Blodgett techniques, the evaporation of metals on colloidal particles, controlled phase separation, and using the gas/liquid and liquid/solid interface action. Although some of these methods are effective to fabricate unsymmetrically coated particles, challenges in this field still exist. For example, the assembly of these particles into ordered arrays, enhancement of the unsymmetrical coating density, and precise control of the tropism of these particles have not been well developed. Two-dimensional (2D) structured arrays and patterns are also important due to their potential applications in engineering microelectronic and optoelectronic devices, the fabrication of biological and chemical sensors, and for controlled crystallization. Existing, elegant approaches that involve lithography, imprinting, and soft lithography techniques have been successfully applied to create patterned surfaces in microelectronic and plastic electronics. Among them, soft lithography encompasses a set of flexible methods for patterning materials. As a branch of soft lithography, microcontact printing (lcp) has also been used to modify solid surfaces with different properties, such as charge nature and wettability, to direct the deposition of colloidal microspheres on special regions of substrates. Recently, lift-up soft lithography and modified microcontact printing methods have been developed to pattern colloidal crystals. In this communication, the fabrication of ordered silica microspheres unsymmetrically coated with Ag nanoparticles using lift-up soft lithography and chemical reduction is reported. Taking advantage of the flexibility of lcp, these microspheres are easily transferred onto polymer-coated solid substrates and precisely realize a tropism conversion. By etching away the silica microspheres, ordered Ag-nanoparticle-doped polymer voids are obtained. These silica microspheres unsymmetrically coated with Ag nanoparticles and Ag-nanoparticle-doped polymer voids can also be used as templates to fabricate ordered Ag-nanoparticle-doped polymer and gold composite voids with different morphologies. Compared with previous methods, it is believed that some progress in preparing ordered microspheres unsymmetrically coated with nanoparticles and nanoparticle-doped composite voids has been made, in that: a) the unsymmetrical coating density on the microspheres is increased, b) the ordered array of these unsymmetrically coated microspheres has been realized, c) the tropism of these ordered unsymmetrically coated microspheres can be well controlled, and d) ordered nanoparticle-doped polymer or polymer and metal composite voids with different morphologies can be easily obtained. Due to this progress, this method will provide a powerful platform for fabricating ordered, versatile, colloidal microspheres unsymmetrically coated with nanoparticles, and hybrid patterns. Figure 1 outlines the procedure for preparing ordered silica microspheres unsymmetrically coated with Ag nanoparticles and Ag-nanoparticle-doped polymer voids. First, monodisperse silica microspheres are assembled into colloidal crystals on a silicon wafer. Using the lift-up soft lithography technique, a single layer of close-packed silica microspheres are then transferred onto the surface of a poly(dimethylsiloxane) (PDMS) stamp. After depositing Ag nanoparticles on these microspheres by chemical reduction and spin-coating a thin C O M M U N IC A TI O N S

Multi-colour micro-contact printing based on microfluidic network inking

We report on a simple method of multi-colour micro-contact printing (MCμCP) that can be applied for monolayer molecular patterning of different types of molecules at the same time. Soft lithography has been used to fabricate specially designed microfluidic channel structures (top layer) and stamps for micro-contact printing (bottom layer). We have taken advantage of the spatial resolution of microfluidics networks and their numerous channels to bring into contact the solutions of molecules and the micro-contact printing stamp on a very precise and defined surface. Thus, we can vary the type of molecules deposited as well as the shape of the deposition by varying the number and design of microfluidic channels. This particular use of the microfluidic networks has been enabled by tightly but reversibly sealing the microfluidic networks on the stamp by using succion around the channels to prevent any leakage. After the molecules deposition and the peeling off of microfluidic channels, the micro-contact printing stamp can be used for micro-contact printing in a traditional manner. Our results show that the established MCμCP method enables precise protein deposition numerous in types, shapes and proportions, thereby allowing one to develop a variety of bio-applications.

P-172: Micro-Contact Printing Method for Multi-Domain Liquid Crystal Alignment

We proposed a simple method for patterning alignment layers to produce multi-domain liquid crystal (LC) alignment. By micro-contact printing method, we produced multi-directional easy axis on the alignment layer using conventional LC alignment materials. Our printing method would be a very useful tool for designing a LC mode in wide-viewing LCDs or transflective LCDs.

Rapid Fabrication and Chemical Patterning of Polymer Microstructures and their Applications as a Platform for Cell Cultures

Much of the current knowledge regarding biological processes has been obtained through in-vitro studies in bulk aqueous solutions or in conventional Petri-dishes, with neither methodology accurately duplicating the actual in-vivo biological processes. Recently, a number of innovative approaches have attempted to address these shortcomings by providing substrates with controlled features. In particular, tunable surface chemistries and topographical micro and nanostructures have been used as model systems to study the complex biological processes. We herein report a versatile and rapid fabrication method to produce a variety of microstructured polymer substrates with precise control and tailoring of their surface chemistries. A poly(dimethylsiloxane) (PDMS) substrate, produced by replication over a master mold with specific microstructures, is modified by a fluoro siloxane derivative to enhance its anti-adhesion characteristics and used as a secondary replication mold. A curable material, deposited by spin coating on various substrates, is stamped with the secondary mold and crosslinked. The removal of the secondary mold produces a microstructured surface with the same topographical features as the initial master mold. The facile chemical patterning of the microstructured substrates is demonstrated through the use of microcontact printing methods and these materials are tested as a platform to guide cell attachment, growth and proliferation. The master mold and flexible fluorinated PDMS stamps can be used in a repeated manner without any degradation of the anti-adhesion characteristics opening the way to the development of high-throughput fabrication methods that can yield reliable and inexpensive microstructured and chemically patterned substrates.

Direct microcontact printing of oligonucleotides for biochip applications

BackgroundA critical step in the fabrication of biochips is the controlled placement of probes molecules on solid surfaces. This is currently performed by sequential deposition of probes on a target surface with split or solid pins. In this article, we present a cost-effective procedure namely microcontact printing using stamps, for a parallel deposition of probes applicable for manufacturing biochips.ResultsContrary to a previous work, we showed that the stamps tailored with an elastomeric poly(dimethylsiloxane) material did not require any surface modification to be able to adsorb oligonucleotides or PCR products. The adsorbed DNA molecules are subsequently printed efficiently on a target surface with high sub-micron resolution. Secondly, we showed that successive stamping is characterized by an exponential decay of the amount of transferred DNA molecules to the surface up the 4th print, then followed by a second regime of transfer that was dependent on the contact time and which resulted in reduced quality of the features. Thus, while consecutive stamping was possible, this procedure turned out to be less reproducible and more time consuming than simply re-inking the stamps between each print. Thirdly, we showed that the hybridization signals on arrays made by microcontact printing were 5 to 10-times higher than those made by conventional spotting methods. Finally, we demonstrated the validity of this microcontact printing method in manufacturing oligonucleotides arrays for mutations recognition in a yeast gene.ConclusionThe microcontact printing can be considered as a new potential technology platform to pattern DNA microarrays that may have significant advantages over the conventional spotting technologies as it is easy to implement, it uses low cost material to make the stamp, and the arrays made by this technology are 10-times more sensitive in term of hybridization signals than those manufactured by conventional spotting technology.

An inverted microcontact printing method on topographically structured polystyrene chips for arrayed micro-3-D culturing of single cells

With the goal to investigate the relation of shape and function of single cells or clusters of cells in a 3-dimensional (3-D) microenvironment, we present a novel platform technology to create arrays of microwells on polystyrene (PS) chips for hosting cells in a local microenvironment characterized by controlled shape and surface chemistry. The micro-3-D cell culturing combines 2-dimensional chemical patterning with topographical microstructuring presenting to the cells a local 3-D host structure. Microwells of controlled dimensions were produced by a two-step replication process, based on standard microfabrication of Si, replica molding into poly(dimethylsiloxane), and hot embossing of PS. This allowed the production of large numbers of microstructured surfaces with high reproducibility and fidelity of replication. Using inverted micro contact printing, the plateau surface between the microwells was successfully passivated to block adsorption of proteins and prevent cell attachment by transfer of a graft-copolymer, poly( l-lysine)- g-poly(ethylene glycol). The surface inside the microwells was subsequently modified by spontaneous adsorption of proteins or functionalized PLL- g-PEG/PEG-X (X=biotin or specific, cell-interactive peptide) to elicit specific responses inside the wells. Preliminary cell experiments demonstrated the functionality of such a device to host single epithelial cells (MDCK II) inside the functionalized microwells and thus to control their 3-D shape. This novel platform is useful for fundamental cell-biological studies and applications in the area of cell-based sensing.

Monolayer assembly and striped architecture of Co nanoparticles on organic functionalized Si surfaces

We present a new strategy to fabricate a monolayer assembly of Br-terminated Co nanoparticles on functionalized Si surfaces by using chemical covalent bonding and microcontact printing method. Self-assembled monolayers (SAMs) of the Co nanoparticles formed on the hydroxyl-terminated Si surface exhibit two-dimensional island networks with locally ordered arrays via covalent linkage between nanoparticles and surface. On the other hand, SAMs of the nanoparticles on the aminopropyl-terminated Si surface show an individual and random distribution over an entire surface. Furthermore, we have fabricated striped architectures of Co nanoparticles using a combination of microcontact printing and covalent linkage. Microcontact printing of octadecyltrichlorosilane and selective covalent linkage between nanoparticles and functionalized Si surfaces lead to a hybrid nanostructure with selectively assembled nanoparticles stripes on the patterned functionalized Si surfaces.