Contact Printing Research Articles

Low-voltage 2D materials-based printed field-effect transistors for integrated digital and analog electronics on paper

Paper is the ideal substrate for the development of flexible and environmentally sustainable ubiquitous electronic systems, which, combined with two-dimensional materials, could be exploited in many Internet-of-Things applications, ranging from wearable electronics to smart packaging. Here we report high-performance MoS2 field-effect transistors on paper fabricated with a “channel array” approach, combining the advantages of two large-area techniques: chemical vapor deposition and inkjet-printing. The first allows the pre-deposition of a pattern of MoS2; the second, the printing of dielectric layers, contacts, and connections to complete transistors and circuits fabrication. Average ION/IOFF of 8 × 103 (up to 5 × 104) and mobility of 5.5 cm2 V−1 s−1 (up to 26 cm2 V−1 s−1) are obtained. Fully functional integrated circuits of digital and analog building blocks, such as logic gates and current mirrors, are demonstrated, highlighting the potential of this approach for ubiquitous electronics on paper.

Fabrication of an imperceptible liquid metal electrode for triboelectric nanogenerator based on gallium alloys by contact printing

A simple method for fabricating a liquid metal (LM) pattern on a polydimethylsiloxane substrate through the process of contact printing is introduced in this paper. This material is easily oxidized when it is exposed to air; consequently, it is difficult to manipulate. Contact printing is a fabrication process based on an adhesive force between interfaces. Adhesion is enhanced by forming a new oxide layer; thus, the LM film on a flat mold is transferred to another mold by contact printing. Electrical conductivity of the transferred LM is 1.93 × 106 S/m, which is sufficiently high for its usage as an electrode in electric circuits. The resolution of the LM pattern can be controlled at ~20 μm and a complex pattern can be fabricated. Furthermore, the LM is semi-transparent and it is visually imperceptible when observed from a distance. Using the semi-transparent LM electrode, a LM triboelectric nanogenerator is fabricated. The device demonstrates normal performance as an energy harvesting system; consequently, the LM patterned by contact printing can be applied to wearable self-powered electronics.

Votos

An ex-voto is a votive offering to invisible forces, mainly given in fulfilment of a vow after being healed. It often takes form in the mold of the wounded member, a print that has been directly in contact with the body of the helped. This cyanotype was made with a radiography of my sick lungs, and plants I found dead in an exploited forest. In this photograph, I link the wounded wilderness – the French call forests “Earth lungs” – with my wounded lungs. Since Magic involves using analogies to weave links between a representation and its object in order to affect it, what kind of magic system is invoked when we summon action with contact prints? I tied this photograph to the terrible arsons devastating Amazonia, and more recently Australia, echoing with the disastrous impacts of global changes on the fragile balance of Earth life.

3D paper-based microfluidic device: a novel dual-detection platform of bisphenol A.

A novel platform of microfluidic paper-based analytical devices (μPADs) for dual detection of bisphenol A (BPA), a model analyte, was fabricated using an electronic digital plotter to create the stacked layer of μPADs and generate the lateral-flow channel without using an external pump. Two detection techniques, including electrochemical detection and laser desorption ionization mass spectrometric detection (LDI-MS), were used complementarily to improve the precision in the detection of BPA. The fluid sample was delivered to both detection zones by the capillary action, automatically generated from the fabricated microfluidic device. For an electrochemical sensor, two ballpoint pens filled with silver nanoparticles (AgNPs) and multiwall carbon nanotube (MWCNT) ink were used to print onto the paper with a contact printing method using a digital plotter. To further improve the sensitivity, zinc oxide (ZnO) was used to modify both electrochemical and LDI-MS detection zones. For BPA detection, high electrocatalytic properties and strong UV absorption of ZnO promote the electron transfer in the electrochemical sensor and ionization efficiency in LDI-MS with low interferences compared with a conventional organic matrix. Under optimal conditions, this platform showed a dual detection capability for BPA with a detection limit of 0.35 μM for electrochemical detection and with an ultralow detection limit of 0.01 pM for LDI-MS. This novel platform might be very useful for trace analyses requiring high precision detection of various analytes.

Iris spoofing detection using discrete orthogonal moments

Human iris being the most stable biometric modality suffers from presentation attacks like colored textured contact lenses and print attacks that obfuscate the natural iris texture. The paper presents discrete orthogonal moment-based invariant feature-set comprising of Tchebichef, Krawtchouk and Dual-Hahn moments which are extracted at localized iris regions to capture local intensity distributions of the iris texture. The orthogonal moment-based feature-set is made rotation, translation and scale-invariant in order to accommodate for geometric transformations when images are acquired in uncontrolled environment. The performance of the proposed techniques is evaluated using four publicly available iris spoofing databases: IIITD-Contact Lens Iris, IIITD Iris Spoofing, Clarkson LivDet 2015 and Warsaw LivDet 2015. The textured contact lens detection rate of 100% for IIITD-CLI and 99.48% for Clarkson datasets is achieved, respectively. Similarly, print+scan and print+capture attacks are detected with 99% and 98.93% accuracy for IIS datasets, respectively. The print attacks are detected with 99.63% and 98.89% accuracy for Clarkson and Warsaw datasets, respectively. The proposed techniques thus, prove to be effective in terms of contact lens and print attacks detection when acquired using multiple sensors.

Spatially selective biomolecules immobilization on silicon nitride waveguides through contact printing onto plasma treated photolithographic micropattern: Step-by-step analysis with TOF-SIMS chemical imaging

Time-of-flight secondary ion mass spectrometry has been employed to characterize micropatterning of aminosilane layer by photolithography and oxygen plasma treatment to achieve spatially selective biofunctionalization of Si3N4 waveguides surface corresponding to the sensing arm area of Mach-Zehnder interferometric biosensors integrated on silicon-chip. Si3N4 surface with (3-aminopropyl)triethoxysilane (APTES) layer was examined after photolithography, plasma treatment, photoresist removal, and after robotic spotting with biotinylated bovine serum albumin (BSA), blocking with BSA and specific binding of streptavidin. TOF-SIMS chemical imaging and microanalysis provided an inside view regarding the resolution and selectivity of surface modification after each step of both the APTES layer patterning and biofunctionalization procedures. More particular, the effective APTES removal and surface oxidization to create 20-µm wide APTES stripes through photolithography and oxygen plasma treatment was demonstrated. Exclusive adsorption of biotinylated-BSA on the APTES stripes through spotting of the patterned surface is then revealed, followed by a preferential but not exclusive BSA adsorption during the blocking step. The pattern was clearly developed through exclusive streptavidin binding to biotinylated-BSA only onto the APTES regions. The proposed spatially-selective biofunctionalization, performed with biotinylated-BSA, was demonstrated for the Si3N4 waveguide surface of an integrated on chip interferometric biosensor sensing arm for the detection of streptavidin.

Direct Patterning of Carbon Nanotube via Stamp Contact Printing Process for Stretchable and Sensitive Sensing Devices

HighlightsA dry transfer method for the mass production of transparent conductive carbon nanotube (CNT) films inspired by typography has been proposed.The strain sensors based on the CNT films have high stretchability and repeatability (gauge factor up to 9960 at 85% strain).These ultrathin strain sensors can detect human motion, sound, and pulse, suggesting promising application prospects in wearable devices.

A Low‐Cost Laser‐Based Nano‐3D Polymer Printer for Rapid Surface Patterning and Chemical Synthesis of Peptide and Glycan Microarrays

AbstractA low‐cost laser‐based printing setup is presented, which allows for the spot‐wise patterning of surfaces with defined polymer nanolayers. These nanolayer spots serve as a “solid solvent,” embedding different chemicals, chemical building blocks, materials, or precursors and can be stacked on top of each other. By melting the spot pattern, the polymer‐embedded molecules are released for chemical reaction. This enables researchers to quickly pattern a surface with different molecules and materials, mixing them directly on the surface for high‐throughput chemical synthesis to generate and screen diverse microarray libraries. In contrast to expensive ink‐jet or contact printing, this approach does not require premixing of inks, which enables in situ combinatorial mixing. Easy access and versatility of this patterning approach are shown by generating microarrays of various biomolecules, such as glycans for the first time, to screen interactions of antibodies and lectins. In addition, a layer‐by‐layer solid‐phase synthesis of peptides directly on the microarray is presented. Amino acid–containing nanolayers are repeatedly laser‐transferred and reacted with the functionalized acceptor surface in defined patterns. This simple system enables a reproducible array production, down to spot‐to‐spot distances of 100 µm, and offers a flexible and cheap alternative to expensive spotting robot technology.

Direct printing of metal contacts on 4H-SiC for radiation detection

Additive manufacturing (AM) has created the possibility of replacing traditional manufacturing techniques with faster, versatile, and cost-effective production options. In this study, we employed AM techniques to fabricate silicon carbide (SiC) radiation detectors based on commercial 4H-SiC wafers. Platinum (Pt) nanoparticle inks were synthesized and printed onto the surface of a 4H-SiC wafer using an aerosol jet printing technique to create Schottky diodes for radiation detection. The additive printed detectors were characterized for surface morphology through a scanning electron microscope (SEM) and atomic force microscope (AFM), and electronically by current-voltage (IV), capacitance-voltage (CV), and finally by alpha spectroscopy measurements. The printed detector achieved an energy resolution of 3.24% FWHM at 5.486 MeV, compared to 0.62% FWHM of a SiC detector fabricated by conventional cleanroom technologies and 0.3% FWHM of a commercially available Si detector.

Do-It-Yourself Pyramidal Mold for Nanotechnology.

The handcrafted fabrication of a pyramidal mold on a silicon wafer for nanopatterning was investigated. This process started with the manual delivery of an aqueous glycerol solution onto the SiO2/Si wafer using a micropipette and subsequent drying to form a hemisphere whose diameter is in the range of hundreds of micrometers. A coating of polystyrene (PS) onto this wafer generates a circular hole caused by dewetting. Subsequently, anisotropic wet-etching with the PS film as a mask produces a pyramidal trench, whose apex approaches hundreds of nanometers. Various elastomeric materials were casted into this pyramidal mold. A pyramidal tip mounted on a simple micropositioner was used for electrochemistry and patterning of a protein. First, an agarose hydrogel was cast with a hydrogel pen for the electrochemical reaction (HYPER). The redox reaction at the HYPER–electrode interface demonstrated the characteristics of an ultramicroelectrode or bulk electrode based on the contact area. Second, the pyramidal polydimethylsiloxane served as a polymer pen for the contact printing of silane on a glass substrate. After the successive immobilization of biotin and avidin with fluorescence labeling, the resulting fluorescence image demonstrated the successful patterning of the protein. This new process for the creation of a pyramidal mold, referred to as a “do-it-yourself” process, offers advantages to nonspecialists in nanotechnology compared to conventional lithography, specifically simplicity, rapidity, and low cost.

Metallized SU-8 thin film patterns on stretchable PDMS

We show how a rigid patterned SU-8 thin film in tandem with the mechanical Poisson effect can be used beneficially to enable robust metallization on stretchable polydimethylsiloxane (PDMS). Two generic planar processes used to form a thin, mechanically-robust strain-shielding photoresist on a soft substrate are developed to demonstrate these ideas. The first process is a self-aligned metallization of photolithographically patterned SU-8 features on PDMS. The second process is a fully photolithographic lift-off metallization of pre-patterned SU-8 features on PDMS. In both cases, the SU-8 has a sub-micrometre thickness (~800 nm)—supporting a thermally evaporated Ti/Au (5 nm/50 nm) thin film metallization. The resulting samples were characterized electromechanically—the results demonstrate that the electrical continuity of metal lines (width = 150 µm and length up to 1 cm) is maintained up to ~70% strain between the lines. The electrical resistance of such lines remains relatively stable: 35 Ω at zero-strain and 63 Ω at 69% average interline strain. The electrical resistivity of the evaporated gold is near to that of pure gold, and remains so even at high strains (49 nΩ m at 10% and 70 nΩ m at 41%)—this proves the absence strain-induced micro-cracking of the metal lines. Although a specific evaporated metal combination is used here to demonstrate a working prototype system, in principle, any thin-film material, which can be deposited by microfabrication, e.g. insulators, semiconductors…, could be integrated into the generic processes. The basic lithographic processes expounded here are also potentially extendible to encompass the integration of other microfabrication techniques, e.g. soft lithography, contact printing…, enabling more complex flexible systems to be envisaged and realized.

POLYMERIC SCAFFOLDS FOR TISSUE ENGINEERING APPLICATIONS

Polymeric materials are commonly used for many purposes in Tissue Engineering Applications. In particular, they are used as scaffolds which are specially prepared in cell growth studies as well as drug loading and release systems. In drug delivery and controlled release systems functional, scaffolds are widely used in order to send the drug to its target region. On the other hand, in cell growth systems patterned polymeric scaffolds are prepared and used to allow the cells to grow at a certain region with a particular form. For this purpose, different techniques are used for the adhesion of cells onto the material surfaces. In this study, patterned scaffolds from various polymers as Polymethylacrylate (PAM), Polystyrene (PS) and polyvinylchloride (PVC) were prepared using micro contact printing with the soft Lithographic Technique. The prepared materials were morphologically analyzed and cell growth was followed by using electron scanning microscope (SEM). Poly (dimethylsiloxane) (PDMS) molds were prepared in different shapes and used as stamp materials to transfer the designed patterns. The cell growth on these patterned surfaces was followed after seeding L929 mouse fibroblasts cells. Neutral Red Uptake Assay was applied to observe cell growth. The cell growth experiments showed that the cells were attached to the patterned surfaces and a significant increase in cell growth on the surfaces were observed.

Hybrid Polyphosphazene–Organosilicon Polymers as Useful Elastomers

Six high molecular weight, soluble, and stable elastomers were prepared derived from −O(CH2)3Si(CH3)3/–OCH2CF3 cosubstituted polyphosphazenes with 1–92 mol % of the organosilicon component. The surface and morphological properties are appropriate for biomaterials, soft contact printing, or other elastomeric applications. Full substitution by either side group yields thermoplastics. The syntheses were facilitated by small molecule model reactions to establish appropriate reaction conditions.

Metallo‐Hydrogel‐Assisted Synthesis and Direct Writing of Transition Metal Dichalcogenides

AbstractTwo dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted interest for their compelling nanoscale new properties and numerous potential applications including fast optoelectronic devices, ultrathin photovoltaics, and high‐performance catalysts. Large‐scale growth of uniform TMDC materials is essential for investigating their physics and for their integration into devices. However, the wafer scale deposition of TMDCs on arbitrary nonselective substrates is still beyond the current state‐of‐the‐art. In this article, a method to synthesize layered TMDCs (MoS2 and WS2) at the wafer‐scale by sulfurization of transition metal ions (Mo5+ and W6+) in a gelatin template (metallo‐hydrogel) is reported. This process is adaptable to versatile substrates, including amorphous silicon oxide, high‐temperature quartz, and silicon. Although the products are nominally few layer materials, direct band photoluminescent (≈1.8 eV), similar to single‐ or decoupled multilayer MoS2 is observed. Finally, the solution‐based deposition enables contact printing of TMDC channels to be useable for device applications including thin film transistors with printed silver contacts using the same process.

Multi-Responsive Hydrogel Based Flexible Sensors for Plants/Animals Metabolic Stress Analytics

Versatile and non-invasive multiresponsive flexible sensor platforms developed in our research group will be demonstrated in this talk. The sensor platforms are fabricated by contact printing on a composite carbon nanotubes/polyaniline conductive flexible films, embedded with multi-responsive (redox, ionic strength, pH) molecularly imprinted responsive polymer hydrogels, highly selective biomimetric molecular receptors. In this presentation, data highlighting the sensor platforms when applied for dosimetric and real-time monitoring of metabolic stress biomarkers in plants and animals will be discussed. With standout customization and versatility, the flexible wearable sensors are interfaced to Bluetooth, which transmits data wirelessly to a mobile device, demonstrating their utility for autonomous deployment in health/wellness diagnostics and precision agriculture.

Blister-Actuated LIFT Printing for Multiparametric Functionalization of Paper-Like Biosensors.

Laser induced forward transfer (LIFT) is a flexible digital printing process for maskless, selective pattern transfer, which uses single laser pulses focused through a transparent carrier substrate onto a donor layer to eject a tiny volume of the donor material towards a receiver substrate. Here, we present an advanced method for the high-resolution micro printing of bio-active detection chemicals diluted in a viscous buffer solution by transferring droplets with precisely controllable volumes using blister-actuated LIFT (BA-LIFT). This variant of the LIFT process makes use of an intermediate polyimide layer partially ablated by the laser pulses. The expanding gaseous ablation products lead to blisters in the polyimide and ejection of droplets from the subjacent viscous solution layer. A relative movement of donor and receiver substrates for the transfer of partially overlapping pixels is realized with a custom-made positioning system. Using a specially developed donor ink containing bio-active components presented method allows to transfer droplets with well controllable volumes between 20 fL and 6 pL, which is far more precise than other methods like inkjet or contact printing. The usefulness of the process is demonstrated by locally functionalizing laser-structured nitrocellulose paper-like membranes to form a multiparametric lateral flow test. The recognition zones localized within parallel micro channels exhibit a well-defined and homogeneous color change free of coffee-ring patterns, which is of utmost importance for reliable optical readout in miniature multiparametric test systems.

Printed silver contacts to CVD diamond detectors

Abstract Novel, printed contacts for single crystal CVD grown diamond particle detectors are reported. Silver contacts with guard-rings were formed by three-dimensional metal printing. The resulting devices exhibit similar properties to the current state-of-the-art diamond detectors employing carbide layer contacts, yet detectors with the printed contacts retain high charge collection efficiency even after exposure to 450 °C (unlike aluminum contact devices for instance). The printed silver contacts do not require high temperature annealing steps as carbide based contacts. The contact printing process is performed within a few minutes in ambient conditions. The novel printed contact method enables contact deposition without expensive vacuum equipment; furthermore, contact patterning can be designed and performed instantaneously, without design and fabrication of expensive photolithography masks and without the need for clean room facilities.

Development of a Bacterial Macroarray for the Rapid Screening of Targeted Antibody-Secreted Hybridomas

Hybridoma screening is a key step for the successful generation of high-affinity analyte-specific monoclonal antibodies (MAbs). This work presents an innovative screening method, known as a bacterial macroarray, generated by contact printing of hybridoma cell supernatant samples on a nitrocellulose (NC) membrane initially coated with fluorescein isothiocyanate (FITC)–labeled bacteria. Given that bacterial fixation will be influenced by complex bacterial surface structures, we selected both gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes) and gram-negative bacteria (Escherichia coli O157:H7 and Cronobacter sakazakii) to optimize the fixation conditions for binding to the NC membrane, such as the aperture of the NC membrane, the concentration of bacteria, the dosage of glycerin in the spotting buffer, and the fixation time and temperature. As a result, we found that a better bacterial macroarray could be developed when the spotting buffer, containing 1011 CFU mL–1 of FITC-labeled bacteria and 15% (V/V) glycerol, was spotted onto a 0.45 µm NC membrane with an incubation of 2 h at 37 °C. Finally, we verified the stability and specificity of the prepared bacterial macroarray by detecting cell cultures with the addition of two MAbs (Escherichia coli O157:H7 MAb E7 and Cronobacter sakazakii MAb 1E9) to simulate the screening experiments. Here, we describe a bacterial macroarray to efficiently screen the targeted antibody-secreted hybridomas.

A Fast and Simple Contact Printing Approach to Generate 2D Protein Nanopatterns.

Protein micropatterning has become an important tool for many biomedical applications as well as in academic research. Current techniques that allow to reduce the feature size of patterns below 1 μm are, however, often costly and require sophisticated equipment. We present here a straightforward and convenient method to generate highly condensed nanopatterns of proteins without the need for clean room facilities or expensive equipment. Our approach is based on nanocontact printing and allows for the fabrication of protein patterns with feature sizes of 80 nm and periodicities down to 140 nm. This was made possible by the use of the material X-poly(dimethylsiloxane) (X-PDMS) in a two-layer stamp layout for protein printing. In a proof of principle, different proteins at various scales were printed and the pattern quality was evaluated by atomic force microscopy (AFM) and super-resolution fluorescence microscopy.

A shape-shifting composite hydrogel sheet with spatially patterned plasmonic nanoparticles.

We report a simple and reliable approach to fabricate composite hydrogel sheets with spatially patterned regions of plasmonic gold nanoparticles using a combination of contact printing and diffusion-controlled galvanic replacement reaction. In response to near-infrared laser irradiation, the localized increase in temperature induced the controlled shape deformation of the composite hydrogels, due to the combined effect of photothermal heating of the loaded gold nanoparticles and the thermal responsiveness of the hydrogel matrix. The same hydrogel can be designed to exhibit different modes of shape deformation depending on the direction of light irradiation, which has rarely been reported previously. The composite hydrogels may find applications in biomedicine and soft robots.