Contact Printing Research Articles

Microscale Patterning of Electrochromic Polymer Films via Soft Lithography

We present a direct fabrication technique of patterned polymeric electrochromic (EC) devices via soft lithography, enabling both negative patterning and positive patterning of the polymer. For this work, elastomeric polydimethylsiloxane (PDMS) molds were employed as not only stamps for direct contact printing of polymer inks but also templates for dewetting of polymer solutions under mild experimental conditions. We performed both negative patterning and positive patterning of a prototypical EC polymer and investigated the EC device characteristics according to solvents, solution concentrations, and pattern types. Eventually, the complex patterns, which cannot be realized by conventional shadow masking processes, and large-area structures were successfully demonstrated. We anticipate that these results will be applied to the development of various patterned devices and circuits, which may lead to further applications.

Programmable Contact Printing Using Ballpoint Pens with a Digital Plotter for Patterning Electrodes on Paper

A simple programmable contact printing method using ballpoint pens with silver nanoparticle (AgNP) and carbon nanotube (CNT) ink and a digital plotter were developed for quick patterning of electrodes on paper. This printing method enables sequential and programmable printing with two different inks and with ink consisting of high viscosity materials and is amenable to reproducibility of printed electrodes and customized designs. With this printing method, AgNP and CNT patterns with low electrical resistance and high density of the material can be printed. Using these AgNP and CNT inks, we fabricated disposable electrochemical sensors (ECSs) on paper. The ECSs were successfully used to detect glucose at various concentrations from 0 to 15 mM. The characteristics of the printed AgNP and CNT patterns, such as the printing resolution, surface morphology, and electrical properties, were also studied. The proposed contact printing method opens an avenue for printing paper-based electronics and devices.

Fabrication of Strain Gauges via Contact Printing: A Simple Route to Healthcare Sensors Based on Cross-Linked Gold Nanoparticles

In this study, we developed a novel and efficient process for the fabrication of resistive strain gauges for healthcare-related applications. First, 1,9-nonanedithiol cross-linked gold nanoparticle (GNP) films were prepared via layer-by-layer (LbL) spin-coating and subsequently transferred onto flexible polyimide foil by contact printing. Four-point bending tests revealed linear response characteristics with gauge factors of ∼14 for 4 nm GNPs and ∼26 for 7 nm GNPs. This dependency of strain sensitivity is attributed to the perturbation of charge carrier tunneling between neighboring GNPs, which becomes more efficient with increasing particle size. Fatigue tests revealed that the strain-resistance performance remained nearly the same after 10.000 strain/relaxation cycles. We demonstrate that these sensors are well suited to monitor muscle movements. Furthermore, we fabricated all-printed strain sensors by directly transferring cross-linked GNP films onto soft PDMS sheets equipped with interdigitated electrodes. Due to the low elastic modulus of poly(dimethylsiloxane) (PDMS), these sensors are easily deformed and, therefore, they respond sensitively to faint forces. When taped onto the skin above the radial artery, they enable the well-resolved and robust recording of pulse waves with diagnostically relevant details.

Hydrodynamic Layer-by-Layer Assembly of Transferable Enzymatic Conductive Nanonetworks for Enzyme-Sticker-Based Contact Printing of Electrochemical Biosensors.

Realizing high-performance electrochemical biosensors in a simple contact-printing-based approach significantly increases the applicability of integrated flexible biosensors. Herein, an enzyme-sticker-based approach that enables flexible and multielectrochemical sensors via simple contact-transfer printing is reported. The enzyme sticker consists of an enzymatic conductive network film and a polymeric support. The enzyme-incorporated nanostructured conductive network showing an efficient electrical coupling was assembled via the hydrodynamic layer-by-layer assembly of redox enzymes, polyelectrolytes, single-walled carbon nanotubes, and a biological glue material, M13 phage. The enzymatic conductive network on a polymeric membrane support was facilely wet contact-transfer printed onto integrated electrode systems by exploiting varying degrees of hydrophilicity displayed by the enzymatic electronic film, polymeric support, and receiving electrodes of the sensor system. The glucose sensors fabricated using the enzyme sticker detected glucose at a concentration of as low as 35 μM and showed high selectivity and stability. Furthermore, a flexible dual-sensor array capable of detecting both glucose and lactate was demonstrated using the versatile enzyme sticker concept. This work presents a new route toward assembling and integrating hybrid nanomaterials with efficient electrochemical coupling for high-performance biosensors and health-monitoring devices as well as for emerging bioelectronics and electrochemical devices.

Development of doctoring apparatus capable of measurement and control of doctoring angle and force in printing equipment for printed electronics

The quality of patterns that form printed electronic devices determines their performance and reliability. A doctoring process is necessary in contact printing, and directly affects the quality of the patterns. The doctoring angle and force are controllable parameters among doctoring conditions, in contrast to uncontrollable process-related parameters such as ink properties and printing speed. We developed a doctoring apparatus with a rotational motion-type blading unit that can exert a larger doctoring force to the plate than a linear motion-type blading unit by applying the bending moment to the blade. It can also control and measure the doctoring angle and force, whose values are provided without requiring additional measuring devices such as a camera and load cell. The doctoring angle decreases with increasing doctoring force; therefore, the doctoring angle is defined at the deformed state for more accurate measurement. An estimation method for the doctoring angle using a mathematical model based on the geometric relationships between the design parameters of the blade unit is developed and verified through comparison with direct measurements from photographs. To estimate the doctoring force, the torque feedback signal of the servo motor for the rotational motion of the blade unit is used and calibrated by a direct measurement device equipped with a load cell. The effect of the doctoring angle and force on the quality of the patterns is experimentally examined by assessing the printed patterns obtained in a roll-to-roll gravure printing process. The quality of the patterns is very sensitive to the combination of the doctoring force and angle, and can be enhanced by varying this combination. Therefore, the doctoring angle and force used in the printing process should be measured precisely and controlled appropriately to achieve high-quality printed patterns.

Lithography-free fabrication of field effect transistor channels with randomly contact-printed black phosphorus flakes

Black phosphorus (BP) has distinctive properties of tunable direct band gap as a semiconductor material, and both high carrier mobility and on/off switching performance for electronic devices, but has a significant drawback of material degradation in ambient atmosphere. Also, unlike graphene or MoS2, BP is only synthesized in bulk shapes limiting the fabrication of thin film-based devices. We demonstrated a contact printing process for BP field effect transistors (FET) with the steps of mechanical exfoliation of BP flakes and their randomized stamping in dry-transfer regime. The contact printing featured by fast, continuous and solvent-free process on the pre-patterned electrodes guarantees high process efficiency providing immunity against the chemical degradation of BP layers. With asymmetric I-V characteristics, the resultant BP-channelized FET shows the electrical properties of on/off current ratio, hole mobility, and subthreshold swing as > 102, ~ 130 cm2/Vs, and ~ 4.6 V/dec, respectively.

Investigation of Pulse electric field effect on HeLa cells alignment properties on extracellular matrix protein patterned surface

Cell behavior in terms of adhesion, orientation and guidance, on extracellular matrix (ECM) molecules including collagen, fibronectin and laminin can be examined using micro contact printing (MCP). These cell adhesion proteins can direct cellular adhesion, migration, differentiation and network formation in-vitro. This study investigates the effect of micro-contact printed ECM protein, namely fibronectin, on alignment and morphology of HeLa cells cultured in-vitro. Fibronectin was stamped on plain glass cover slips to create patterns of 25µm, 50µm and 100µm width. However, HeLa cells seeded on 50µm induced the best alignment on fibronectin pattern (7.66° ±1.55SD). As a consequence of this, 50µm wide fibronectin pattern was used to see how fibronectin induced cell guidance of HeLa cells was influenced by 100µs and single pulse electric fields (PEF) of 1kV/cm. The results indicates that cells aligned more under pulse electric field exposure (2.33° ±1.52SD) on fibronectin pattern substrate. Thus, PEF usage on biological cells would appear to enhance cell surface attachment and cell guidance. Understanding this further may have applications in enhancing tissue graft generation and potentially wound repair.

Thermal Healing of a Mixed-Thiol Monolayer at the Nanoscale

Using molecular dynamics simulation, we study the thermal healing of a mixed-thiol monolayer grown by contact printing. By simulating the monolayers with various compositions of octadecanethiol and decanethiol molecules, we show that a mixed-thiol monolayer grown by contact printing contains a significant portion of unbound molecules which fail to bind their sulfur atoms to the underlying gold surface. A subsequent thermal annealing (300–370 K) however removes the unbound thiol molecules and gives an ordered and compact monolayer. We uncover the molecular pathways behind the removal of the unbound molecules during thermal annealing.

Spatial patterning of the Notch ligand Dll4 controls endothelial sprouting in vitro

Angiogenesis, the formation of new blood vessels, is a vital process for tissue growth and development. The Notch cell-cell signalling pathway plays an important role in endothelial cell specification during angiogenesis. Dll4 - Notch1 signalling directs endothelial cells into migrating tip or proliferating stalk cells. We used the directing properties of Dll4 to spatially control endothelial cell fate and the direction of endothelial sprouts. We created linear arrays of immobilized Dll4 using micro contact printing. HUVECs were seeded perpendicular to these Dll4 patterns using removable microfluidic channels. The Notch activating properties of surface immobilized Dll4 were confirmed by qPCR. After induction of sprouting, microscopic images of fluorescently labelled endothelial sprouts were analysed to determine the direction and the efficiency of controlled sprouting (Ecs). Directionality analysis of the sprouts showed the Dll4 pattern changes sprout direction from random to unidirectional. This was confirmed by the increase of Ecs from 54.5 ± 3.1% for the control, to an average of 84.7 ± 1.86% on the Dll4 patterned surfaces. Our data demonstrates a surface-based method to spatially pattern Dll4 to gain control over endothelial sprout location and direction. This suggests that spatial ligand patterning can be used to provide control over (neo) vascularization.

High-power modular LED-based illumination systems for mask-aligner lithography.

Mask-aligner lithography is traditionally performed using mercury arc lamps with wavelengths ranging from 250 nm to 600 nm with intensity peaks at the i, g and h lines. Since mercury arc lamps present several disadvantages, it is of interest to replace them with high power light emitting diodes (LEDs), which recently appeared on the market at those wavelengths. In this contribution, we present a prototype of an LED-based mask-aligner illumination. An optical characterization is made and the prototype is tested in a mask-aligner. Very good performances are demonstrated. The measured uniformity in the mask plane is 2.59 ± 0.24 % which is within the uniformity of the standard lamp. Print tests show resolution of 1 micron in contact printing and of 3 microns in proximity printing with a proximity gap of 30 microns.

A Versatile Redox Responsive Nanoferrogels Based Sensor for Metabolics Analytics

Developed is an inexpensive label free redox responsive nanoferrogel molecular receptor integrated in a chemoresisistive sensor for rapid detection of Reactive Oxygen Species (ROS) such as H2O2 and H2O2 deriving metabolites, species are of interest in myriad applications including clinical, environmental, food, and plant physiology. Inexpensively fashioned by contact printing of redox responsive poly(N-isopropylacrylamide hydrogels herewith called ‘nanoferrogel’ on a conductive nanocellulose paper aerogel, the sensor is designed for specimen surface attachment as wearables, non-invasive transdermal sensors, and can be configured as microneedle sensor for in vivo analysis. Operating via ROS oxidation of the nanoferrogel trapped in the conductive aerogel film, the oxidized nanoferrogel volume change results in an overall change in conductivity, linearly proportional to ROS/ROS deriving metabolite concentration. In the presentation, the responsivity of the nanoferrogel to different ROS species such as H2O2, oxylipin, antioxidants will be demonstrated. The nanoferrogel based H2O2 sensor figures of merit, featuring, rapid (≤ 1min) H2O2 response, high selectivity, low limits of detection (≤ 0.01 µM),and broad linear dynamic range of (≤ 0.03 µM to ≥ 1.5M) will be highlighted. The nanoferrogel is perfectly recyclable, by electrochemical regeneration, affording ≥ 15 multiple usable cycles. Also showcased will be the adaptability of nanoferrogel for different sensor design configurations (e.g. micro/nanoelectrode systems), with some preliminary data attesting to the sensors utility for fundamental studies and detection of efflux of endogenous and exogenous H2O2 in single cells and other redox biomolecules, (e.g. glucose, choline). Preliminarily the sensor can be used for detection of bacterial (model used in our study Escherichia coli) autoinducers and metabolites, of importance in bacterial communication-quorum sensing. This would be a useful platform for understanding bacterial biofilm formation. Further, the nanoferrogel sensor fashioned for utility as a wearable device for detection of redox potential and inherent sweat metabolites will be demonstrated.

Manipulating Femtoliter to Picoliter Droplets by Pins for Single Cell Analysis and Quantitative Biological Assay.

Herein, we developed an automated and flexible system for performing miniaturized liquid-liquid reactions and assays in the femtoliter to picoliter range, by combining the contact printing and the droplet-based microfluidics techniques. The system mainly consisted of solid pins and an oil-covered hydrophilic micropillar array chip fixed on an automated x- y- z translation stage. A novel droplet manipulation mode called "dipping-depositing-moving" (DDM) was proposed, which was based on the programmable combination of three basic operations, dipping liquids and depositing liquids with the solid pins and moving the two-dimensional oil-covered hydrophilic pillar microchip. With the DDM mode, flexible generation and manipulation of small droplets with volumes down to 179 fL could be achieved. For overcoming the scale phenomenon specially appeared in picoliter-scale droplets, we used a design of water moat to protect the femtoliter to picoliter droplets from volume loss through the cover oil during the droplet generation, manipulation, reaction and assay processes. Moreover, we also developed a precise quantitative method, quantitative droplet dilution method, to accurately measure the volumes of femtoliter to picoliter droplets. To demonstrate its feasibility and adaptability, we applied the present system in the determination of kinetics parameter for matrix metalloproteinases (MMP-9) in 1.81 pL reactors and the measurement the activity of β-galactosidase in single cells (HepG2 cells) in picoliter droplet array. The ultrasmall volumes of the droplet reactors avoided the excessive dilution to the reaction solutions and enabled the highly sensitive measurement of enzyme activity in the single cell level.

Mask-aligner lithography using a continuous-wave diode laser frequency-quadrupled to 193 nm.

We present a mask-aligner lithographic system operated with a frequency-quadrupled continuous-wave diode laser emitting at 193 nm. For this purpose, a 772 nm diode laser is amplified by a tapered amplifier in the master-oscillator power-amplifier configuration. The emission wavelength is upconverted twice, using LBO and KBBF nonlinear crystals in second-harmonic generation enhancement cavities. An optical output power of 10 mW is achieved. As uniform exposure field illumination is crucial in mask-aligner lithography, beam shaping is realized with optical elements made from fused silica and CaF2 featuring a diffractive non-imaging homogenizer. A tandem setup of shaped random diffusers, one static and one rotating, is used to control speckle formation. We demonstrate first experimental soft contact and proximity prints for a field size of 1 cm2 with a standard binary photomask and proximity prints with a two-level phase mask, both printed into 120 nm layers of photoresist on unstructured silicon substrates.

Fabrication of Biomolecule Microarrays for Cell Immobilization Using Automated Microcontact Printing.

Biomolecule microarrays are generally produced by conventional microarrayer, i.e., by contact or inkjet printing. Microcontact printing represents an alternative way of deposition of biomolecules on solid supports but even if various biomolecules have been successfully microcontact printed, the production of biomolecule microarrays in routine by microcontact printing remains a challenging task and needs an effective, fast, robust, and low-cost automation process. Here, we describe the production of biomolecule microarrays composed of extracellular matrix protein for the fabrication of cell microarrays by using an automated microcontact printing device. Large scale cell microarrays can be reproducibly obtained by this method.

Improved Multiprotein Microcontact Printing on Plasma Immersion Ion Implanted Polystyrene.

Multiprotein micropatterning allows the creation of complex, controlled microenvironments for single cells that can be used for the study of the localized effects of various proteins and signals on cell survival, development, and functions. To enable analysis of cell interactions with microprinted proteins, the multiprotein micropattern must have low cross-contamination and high long-term stability in a cell culture medium. To achieve this, we employed an optimized plasma ion immersion implantation (PIII) treatment to provide polystyrene (PS) with the ability to covalently immobilize proteins on contact while retaining sufficient transparency and suitable surface properties for contact printing and retention of protein activity. The quality and long-term stability of the micropatterns on untreated and PIII treated PS were compared with those on glass using confocal microscopy. The protein micropattern on the PIII treated PS was more uniform and had a significantly higher contrast that was not affected by long-term incubation in cell culture media because the proteins were covalently bonded to PIII treated PS. The immunostaining of mouse pancreatic β cells interacting with E-cadherin and fibronectin striped surfaces showed phosphorylated paxillin concentrated on cell edges over the fibronectin stripes. This indicates that multiprotein micropatterns printed on PIII treated PS can be used for high-resolution studies of local influence on cell morphology and protein production.

Stable Wettability Control of Nanoporous Microstructures by iCVD Coating of Carbon Nanotubes.

Scalable manufacturing of structured materials with engineered nanoporosity is critical for applications in energy storage devices (i.e., batteries and supercapacitors) and in the wettability control of surfaces (i.e., superhydrophobic and superomniphobic surfaces). Patterns formed in arrays of vertically aligned carbon nanotubes (VA-CNTs) have been extensively studied for these applications. However, the as-deposited features are often undesirably altered upon liquid infiltration and evaporation because of capillarity-driven aggregation of low density CNT forests. Here, it is shown that an ultrathin, conformal, and low-surface-energy layer of poly perfluorodecyl acrylate, poly(1H,1H,2H,2H-perfluorodecyl acrylate) (pPFDA), makes the VA-CNTs robust against surface-tension-driven aggregation and densification. This single vapor-deposition step allows the fidelity of the as-deposited VA-CNT patterns to be retained during wet processing, such as inking, and subsequent drying. It is demonstrated how to establish omniphobicity or liquid infiltration by controlling the surface morphology. Retaining a crust of entangled CNTs and pPFDA aggregates on top of the patterned VA-CNTs produces micropillars with re-entrant features that prevent the infiltration of low-surface-tension liquids and thus gives rise to stable omniphobicity. Plasma treatments before and after polymer deposition remove the crust of entangled CNTs and pPFDA aggregates and attach hydroxyl groups to the CNT tips, enabling liquid infiltration yet preventing densification of the highly porous CNTs. The latter observation demonstrates the protective character of the pPFDA coating with the potential application of these surfaces for direct contact printing of microelectronic features.

A conductometric creatinine biosensor prepared through contact printing of polyvinyl alcohol/polyethyleneimine based enzymatic membrane

A conductometric creatinine biosensor was prepared through creatinine deaminase entrapped into a polyvinyl alcohol/polyethyleneimine/gold nanoparticles composite film, previously deposited on the surface of a PDMS stamp and then, after glutaraldehyde coupling, transferred on interdigitated microelectrodes by contact printing method. The detection of creatinine in a sucrose background solution, revealed a wide linear calibration plot (10–600μM creatinine concentration range), with a limit of detection of 2μM (S/N=3), a good repeatability. The resulting creatinine biosensor exhibits a drastic increase of detection range compared to that of the biosensor prepared by simple dropping: 10–300μM creatinine concentration range. The developed biosensor was validated by determining creatinine in spiked artificial blood serum.

Scanning probe microscopy of high-coercive iron garnet films

Mono-crystalline uniaxial anisotropy high-coercive garnet films are used for thermo-magnetic recording by laser beams or contact printing. High-coercive properties of garnet films are due to a significant mismatch between the lattice parameters of the film and the substrate. The mismatch leads to appearance of facet crystal structure in these films. In the work, the facet crystal and domain structures of high-coercive garnet films were established by methods of scanning probe microscopy.

Pitch Control of Hexagonal Non-Close-Packed Nanosphere Arrays Using Isotropic Deformation of an Elastomer.

Self-assembly of colloidal nanospheres combined with various nanofabrication techniques produces an ever-increasing range of two-dimensional (2D) ordered nanostructures, although the pattern periodicity is typically bound to the original interparticle spacing. Deformable soft lithography using controlled deformation of elastomeric substrates and subsequent contact printing transfer offer a versatile method to systematically control the lattice spacing and arrangements of the 2D nanosphere array. However, the anisotropic nature of uniaxial and biaxial stretching as well as the strain limit of solvent swelling makes it difficult to create well-separated, ordered 2D nanosphere arrays with large-area hexagonal arrangements. In this paper, we report a simple, facile approach to fabricate such arrays of polystyrene nanospheres using a custom-made radial stretching apparatus. The maximum stretchability and spatial uniformity of the poly(dimethylsiloxane) (PDMS) elastomeric substrate is systematically investigated. A pitch increase as large as 213% is demonstrated using a single stretching-and-transfer process, which is at least 3 times larger than the maximum pitch increase achievable using a single swelling-and-transfer process. Unlike the colloidal arrays generated by the uniaxial and biaxial stretching, the isotropic expansion of radial stretching allows the hexagonal array to retain its original structure across the entire substrate. Upon radial strain applied to the PDMS sheet, the nanosphere array with modified pitch is transferred to a variety of target substrates, exhibiting different optical behaviors and serving as an etch mask or a template for molding.

The Study on History of Photomontage and the Efficiency of Art Schools on it

Photomontage is a combination of several shots joined together for artistic effect or to show more of the subject than can be shown in a single artwork. Images were composed by cutting, gluing, arranging and overlapping two or more photos or reproductions of photos together, sometimes in combination with other non-photographic material such as text or other abstract shapes. The process of creating a collage photo can be traced back to the first darkroom printing attempts, when photographers experimented with direct contact printing of objects placed on photographic plates, or techniques such as double exposure and masking. Manipulation has a long history exactly as long as history of photography. With invention of photography, photomontage played an important role. It is interesting to say that also many years has passes that time, it is important as much as before. The question in this article is searching on the importance of photomontage and the important effect of other art schools on it. It is tired to conclude that with the invention of photography, photomontage was emerged and it was depended on photography. Moreover, the emergence of other art schools as Dadaism has had a positive effect on photomontage as well. This article is about the history of photomontage and the efficiency of other art schools like Dadaism on it.