Discover the most talked about and latest scientific content & concepts.

Concept: Printing press


Despite recent advances to control the spatial composition and dynamic functionalities of bacteria embedded in materials, bacterial localization into complex three-dimensional (3D) geometries remains a major challenge. We demonstrate a 3D printing approach to create bacteria-derived functional materials by combining the natural diverse metabolism of bacteria with the shape design freedom of additive manufacturing. To achieve this, we embedded bacteria in a biocompatible and functionalized 3D printing ink and printed two types of “living materials” capable of degrading pollutants and of producing medically relevant bacterial cellulose. With this versatile bacteria-printing platform, complex materials displaying spatially specific compositions, geometry, and properties not accessed by standard technologies can be assembled from bottom up for new biotechnological and biomedical applications.

Concepts: Bacteria, Microbiology, Cellulose, Microorganism, Printing, Inkjet printer, Ink, Printing press


Since its invention in ancient times, relief printing, commonly called flexography, has been used to mass-produce artifacts ranging from decorative graphics to printed media. Now, higher-resolution flexography is essential to manufacturing low-cost, large-area printed electronics. However, because of contact-mediated liquid instabilities and spreading, the resolution of flexographic printing using elastomeric stamps is limited to tens of micrometers. We introduce engineered nanoporous microstructures, comprising polymer-coated aligned carbon nanotubes (CNTs), as a next-generation stamp material. We design and engineer the highly porous microstructures to be wetted by colloidal inks and to transfer a thin layer to a target substrate upon brief contact. We demonstrate printing of diverse micrometer-scale patterns of a variety of functional nanoparticle inks, including Ag, ZnO, WO3, and CdSe/ZnS, onto both rigid and compliant substrates. The printed patterns have highly uniform nanoscale thickness (5 to 50 nm) and match the stamp features with high fidelity (edge roughness, ~0.2 μm). We derive conditions for uniform printing based on nanoscale contact mechanics, characterize printed Ag lines and transparent conductors, and achieve continuous printing at a speed of 0.2 m/s. The latter represents a combination of resolution and throughput that far surpasses industrial printing technologies.

Concepts: Liquid, Materials science, Printing, Printing press, Lithography, Printmaking, Flexography, Relief printing


Bioprinting is an emerging technique used to fabricate viable, 3D tissue constructs through the precise deposition of cells and hydrogels in a layer-by-layer fashion. Despite the ability to mimic the native properties of tissue, printed 3D constructs that are composed of naturally-derived biomaterials still lack structural integrity and adequate mechanical properties for use in vivo, thus limiting their development for use in load-bearing tissue engineering applications, such as cartilage. Fabrication of viable constructs using a novel multi-head deposition system provides the ability to combine synthetic polymers, which have higher mechanical strength than natural materials, with the favorable environment for cell growth provided by traditional naturally-derived hydrogels. However, the complexity and high cost associated with constructing the required robotic system hamper the widespread application of this approach. Moreover, the scaffolds fabricated by these robotic systems often lack flexibility, which further restrict their applications. To address these limitations, advanced fabrication techniques are necessary to generate complex constructs with controlled architectures and adequate mechanical properties. In this study, we describe the construction of a hybrid inkjet printing/electrospinning system that can be used to fabricate viable tissues for cartilage tissue engineering applications. Electrospinning of polycaprolactone fibers was alternated with inkjet printing of rabbit elastic chondrocytes suspended in a fibrin-collagen hydrogel in order to fabricate a five-layer tissue construct of 1 mm thickness. The chondrocytes survived within the printed hybrid construct with more than 80% viability one week after printing. In addition, the cells proliferated and maintained their basic biological properties within the printed layered constructs. Furthermore, the fabricated constructs formed cartilage-like tissues both in vitro and in vivo as evidenced by the deposition of type II collagen and glycosaminoglycans. Moreover, the printed hybrid scaffolds demonstrated enhanced mechanical properties compared to printed alginate or fibrin-collagen gels alone. This study demonstrates the feasibility of constructing a hybrid inkjet printing system using off-the-shelf components to produce cartilage constructs with improved biological and mechanical properties.

Concepts: Extracellular matrix, In vivo, In vitro, Printing, Inkjet printer, Paper, Ink, Printing press


The capability to print three-dimensional (3D) cellular tubes is not only a logical first step towards successful organ printing but also a critical indicator of the feasibility of the envisioned organ printing technology. A platform-assisted 3D inkjet bioprinting system has been proposed to fabricate 3D complex constructs such as zigzag tubes. Fibroblast (3T3 cell)-based tubes with an overhang structure have been successfully fabricated using the proposed bioprinting system. The post-printing 3T3 cell viability of printed cellular tubes has been found above 82% (or 93% with the control effect considered) even after a 72-h incubation period using the identified printing conditions for good droplet formation, indicating the promising application of the proposed bioprinting system. Particularly, it is proved that the tubular overhang structure can be scaffold-free fabricated using inkjetting, and the maximum achievable height depends on the inclination angle of the overhang structure. As a proof-of-concept study, the resulting fabrication knowledge helps print tissue-engineered blood vessels with complex geometry. Biotechnol. Bioeng. 2012; 109: 3152-3160. © 2012 Wiley Periodicals, Inc.

Concepts: Printing, Inkjet printer, Ink, Printing press, Lithography, Printmaking, Giclée, Old master print


We demonstrate plasmonic color printing with subwavelength resolution using circular gap-plasmon resonators (GPRs) arranged in 340-nm-period arrays of square unit cells and fabricated with single-step electron-beam lithography. We develop a printing procedure resulting in correct single-pixel color reproduction, high color uniformity of colored areas and high reproduction fidelity. Furthermore, we demonstrate that, due to inherent stability of GPRs with respect to surfactants, the fabricated color print can be protected with a transparent dielectric overlay for ambient use without destroying its coloring. Using finite-element simulations, we uncover the physical mechanisms responsible for color printing with GPR arrays and suggest the appropriate design procedure minimizing the influence of the protection layer.

Concepts: Color, Printing, Printing press, Lithography, Printmaking, Subtractive color, Color printing, Computer to plate


Gravure printing of graphene is demonstrated for the rapid production of conductive patterns on flexible substrates. Development of suitable inks and printing parameters enables the fabrication of patterns with a resolution down to 30 μm. A mild annealing step yields conductive lines with high reliability and uniformity, providing an efficient method for the integration of graphene into large-area printed and flexible electronics.

Concepts: Printing, Inkjet printer, Ink, Printing press, Electronic engineering, Rotogravure, Offset printing, Printed electronics


The development of printed electronics will require the ability to deposit a wide range of nano-materials using printing techniques. Here we demonstrate the controlled deposition of networks of silver nanowires in well-defined patterns by inkjet printing from an optimized isopropanol-diethylene glycol dispersion. We find that great care must be taken while producing the ink and during solvent evaporation. The resultant networks have good electrical properties, displaying sheet resistances as low as 8 Ohn/sq and conductivities as high as 105 S/m. Such optimised performances was achieved for line widths of 1-10 mm, and network thicknesses of 0.5-2 um deposited from ~10-20 passes while using processing temperatures of no more than 110 oC. Thin networks are semi-transparent with DC to optical conductivities of ~40.

Concepts: Nanowire, Liquid, Printing, Inkjet printer, Ink, Printing press, Ink cartridge, Printmaking


A major hurdle to the widespread application of light sheet microscopy is the lack of versatile and non-intrusive sample holders that are adaptable to a variety of biological samples for live imaging. To overcome this limitation, we present herein the application of 3D printing to the fabrication of a fully customizable casting kit. 3D printing enables facile preparation of hydrogel sample holders adaptable to any shape and number of specimen. As an example, we present the use of this device to produce a four-sample holder adapted to parallel live monitoring of multicellular tumor spheroid growth. To share our solution with the light sheet microscopy community, all files necessary to produce or customize sample holders are freely available online.

Concepts: Sample, Biology, Printing, Inkjet printer, Printing press, 3D printing, Holder


A silver molecular ink platform formulated for screen, inkjet and aerosol printing is presented. A simple formulation comprising silver neodecanoate, ethyl cellulose and solvent provides improved performance vs established inks yet with improved economics. Thin, screen printed traces with exceptional electrical (< 10 mΩ/□/mil or 12 μΩ·cm)) and mechanical properties are achieved following thermal or photonic sintering, the latter having never been demonstrated for silver salt based inks. Low surface roughness, sub-micron thicknesses and linewidths as narrow as 41 μm outperform commercial ink benchmarks based on flakes or nanoparticles. These traces are mechanically robust to flexing and creasing (less than 10% change in resistance) and bind strongly to epoxy-based adhesives. Thin traces are remarkably conformal, enabling fully printed metal-insulator-metal (MIM) band-pass filters. The versatility of the molecular ink platform enables an aerosol jet compatible ink that yields conductive features on glass with 2X bulk resistivity and strong adhesion to various plastic substrates. An inkjet formulation is also used to print top source/drain contacts and demonstrate printed high mobility thin film transistors (TFT) based on semiconducting single walled carbon nanotubes. TFTs with mobility values of ~25 cm(2)V(-1)sec(-1) and current on/off ratios > 10(4) were obtained, performance similar to evaporated metal contacts in analogous devices.

Concepts: Semiconductor, Materials science, Printing, Inkjet printer, Ink, Printing press, Thin-film transistor, Inks


3D printing has been intensively explored to fabricate customized structures of responsive materials including hydrogels, liquid-crystal elastomers, shape-memory polymers, and aqueous droplets. Herein, a new method and material system capable of 3D-printing hydrogel inks with programed bacterial cells as responsive components into large-scale (3 cm), high-resolution (30 μm) living materials, where the cells can communicate and process signals in a programmable manner, are reported. The design of 3D-printed living materials is guided by quantitative models that account for the responses of programed cells in printed microstructures of hydrogels. Novel living devices are further demonstrated, enabled by 3D printing of programed cells, including logic gates, spatiotemporally responsive patterning, and wearable devices.

Concepts: Scientific method, Bacteria, Materials science, Computer program, Printing, Inkjet printer, Paper, Printing press